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Copyright © 1994-2007
Reproduction of this document in whole or in part is permitted if both of the
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1. This notice is included in its entirety at the beginning.
There are two kinds of problems with remotes:
1. They seem to have legs of their own and disappear at the most
inconvenient times.
2. They get abused by being dropped, dunked in Coke or beer, chewed on
by the pet tiger, or left alone to develop dead leaky batteries.
While there are some remotes that will respond to a whistle and beep back
to identify their location, most are the ordinary deaf, dumb, and blind
variety. I cannot help you locate your missing remotes. If you have
disappearing remote syndrome, a well designed universal remote - on a
tether - may make a good investment. However, the following was too good to
pass up:
(From: Bill Samuel (phantom@isoc.net).)
"In '89, a Customer brings in their VCR for me to fix. (Zenith VRE-200) It
won't accept tapes, plus their kids misplaced their remote, so they wanted
a price on a new one.
Well, after taking the unit apart, I called them and said, "Sir, I've found
the problem with your VCR. BTW, you don't need a new remote.""
Most actual problems with remotes can be solved relatively easily. They
are often of a physical nature. Since remotes operate on low voltages
under non-stressful conditions, spontaneous electronic failure is relatively
uncommon. The following are not good for remotes: Sitting or stepping on
them, using them as drink stirrers, door stops, projectiles for target
practice, substitutes for dog bones, or depositories for your old leaky
batteries.
However, if you go inside the TV, VCR, or other controlled device, see the
respective repair guide for that equipment for essential SAFETY information.
To narrow down the problem, use an IR detector to determine if the remote
is emitting an IR signal when each button is pressed. While this does not
guarantee that the signal is correct, it eliminates most common problems from
consideration. An IR detector card or an IR detector circuit like one of those
described in the section: IR Detector and Related
Circuits are very handy for testing remote controls and other IR emitters.
Some camcorders, video cameras, and digital cameras (those that do not
incorporate an IR-blocking filter) are sensitive to IR as well and will
show a bright spot of light if aimed at a working source of IR. However,
since there might be an IR-blocking filter, a negative response
is not definitive unless you confirm that the camera
responds to a known working remote. And, PCs and PDAs with IR links and
suitable software (e.g., OmniRemote for the Palm III) may be useful for
remote testing. See the section: Some Alternative
'Quick and Dirty' Remote Testers for additional options.
MCM Electronics, Centerville, Ohio/1-800-543-4330, list 2 different shaped
cards for $7.29 each (#72-005/3.5 x 2.5" card & 72-003 /4.75 x 0.75" probe.
Radio Shack, Edmund Scientific, and others offer similar detectors.
The salvaged IR sensor module from a TV or VCR may also be used as an IR
detector. These usually operate from a single supply (12 V typical) and output
a clean demodulated signal - you will not see the carrier, only the 1s and 0s.
This will be true of an IR detector circuit as well unless you are careful to
position the remote and photodiode just so as the circuit acts as somewhat of
a low pass filter due to the B-E capacitance of the transistor. Radio Shack
and Digikey (among other) also sell inexpensive IR receiver modules (under
$5) which would also provide a demodulated signal for your viewing pleasure.
However, note that some may be tuned for a particular carrier frequency like
40 kHz and therefore may not respond to all remotes. (Note, I have heard of
spurious pickup issues with some of the Radio Shack units - they are not the
same as those sold a while ago.)
(From: Brett Walach (bwalach@dpg.devry.edu).)
For anyone needing a great IR receiver at a reasonable price, try Radio Shack's
MOD1. It's an IR receiver that demodulates the data for 40Khz x-mitters. The
output can then be viewed on a scope or used to drive a small transistor which
would in turn drive a speaker! The output from the MOD1 is the inverse of the
code sent. That is, the TTL logic level from the MOD1 is high when no IR is
present. If by chance you need an IR receiver that operates on a different
carrier, try DigiKey (1-800-DIGI-KEY). I know that they have the other two
types for sure.
CAUTION: You can easily turn a simple repair (e.g., bad solder connections)
into an expensive mess if you use inappropriate soldering equipment and/or
lack the soldering skills to go along with it. If in doubt, find someone else
to do the soldering or at least practice, practice, practice, soldering and
desoldering on a junk circuit board first! See the document: "Troubleshooting
and Repair of Consumer Electronic Equipment" for additional info on soldering
and rework techniques.
Test equipment beyond a good eye and maybe a multimeter is rarely needed.
The most challenging part of repairing a remote hand unit may be just getting
inside! Manufacturers seem to pride themselves on the extent to which this
is becoming more nearly impossible without dynamite:
The following are the most common types of problems and suggested solutions.
As noted, most are physical in nature: dead batteries, gunk, bad connections.
For all but the first two, disassembly will be required. Manufacturers
seem to be using more and more creative (read: obscure and difficult to
open) methods of fastening the two halves of the remote shell together.
There may be a screw or two and/or the case may simply 'crack' in half by
gently prying with a knife or small screwdriver along the seam or sliding
the two halves a fraction of an inch to unlock some catches. Look
for screws on the back (possibly under a not-so-easy to peel off label)
and inside the battery compartment, as well as hidden snap fasteners.
Make sure that all the batteries point in the correct direction as marked
inside the battery compartment or under its cover. If it uses more than
2 batteries, getting one in backwards could also result in weak or erratic
operation.
In addition, check selector, power, or enable) switches for proper
operation. Remove the batteries and use an ohmmeter to test across
the contacts with the switch(es) in all positions. These switches can
be easily damaged as a result of dropping or squashing the remote. The
contacts may become dirty, gunked up, corrode, or simply wear out as
well. Locating a replacement may prove challenging. Disassembling the
switch may allow you to clean or restore the contacts in some cases.
The frequency is often 455 kHz (I assume since they are widely used as
filters in the IF section of AM radios and are thus inexpensive.)
If you have an oscilloscope, check for signals on the IC when buttons
are pressed - if there is no action on any pin, then you may have a bad
resonator (or bad IC, etc.). Monitoring on one lead of the ceramic
resonator should produce a signal at its resonant frequency when a button
is pressed. A typical waveform may have an amplitude of a few tenths of
a volt.
If you do not have a scope, one possible indication of a bad resonator
(aside from it being smashed) would be a steady output from the IR LED
for all button presses - normally the output would be visibly pulsating.
Of course, this could indicate a bad IC as well.
A ceramic resonator usually is a small blue or orange object that looks
similar to a plastic (sharp edges) or dipped (smooth edges) capacitor.
The circuit board marking will be X1 or CR1 or something like that.
Replacements may be available from places like MCM Electronics or
other electronics distributors. Or, consider an organ donation from
a remote for equipment that has long since gone to that entertainment
center in the sky if the frequency of its resonator is the same.
However, the frequency may be fairly critical for proper operation (within
5 percent or better may be required for some) and while not a common failure,
I've heard of the resonator frequency changing (probably from a trauma) by
enough to cause problems.
(From: Lewin A.R.W. Edwards (sysadm@zws.com).)
If your resonator has 3 pins instead of 2, and you can't find a replacement,
you can use a 2-pin resonator, but you'll need to add two small caps (perhaps
33 pF?) between the legs of your resonator and ground.
Once you think you got it all, do it again - and with soap and water as
well - both the rubber and circuit board.
This goo may originate from a number of sources (no one seems to know
for sure) including: body oils, spills, plasticizers from the flexible
keypad, protective grease, etc. Unless you had dunked the remote in a
vat of motor oil to create this problem there may be no sure way to
prevent it from returning in the future. More below.
I have one (1) data point to suggest that cleaning the rubber pad with a soft
pencil eraser may be better than washing. However, this may also
remove the conductive material in some units.
(From: Steve Lenaghan (tamerica@prairie.ca).)
We do a ton of cordless phones and I have never had to repair a conductive pad
in my career (35 years). We soak them in scalding water and dish soap for 30
minutes. I clean the PC boards with alcohol and a rough cloth. Works every
time.
(From: Michael Shell (mikes1987@yahoo.com).)
People have noticed that the keys (and remotes) that are used more often, tend
to have more oil problems. This is in agreement with my observations.
One thing I have to make clear is that I *KNOW* that whatever is going on
is NOT due to spillage or other external contamination. If I had not seen it
with my own eyes, I would not believe it either! Sometimes the keys that are
used most often (and have the most oil) are in the center - this is a LONG way
for an external contaminant to have to travel!
The oil behaves a bit differently from most normal household (and hand) oils.
I would not have noticed these fine points except for the fact that I have
worked with Silicone (DOT 5) brake fluid which, except for an added purple
dye, behaves in the same way.
So, it seems the silicone keypad manufacturers have been keeping a dirty
little secret all these years!
I guess we all have to look forward to our 3 year cleaning ritual. I suppose a
hardcore hardware hacker could do his own keypad baking and post some before
and after weight measurements to tell us how many grams of oil these things
hold! (WARNING: you may have to do the baking in an oxygen free atmosphere!)
If the plating has worn off and cleaning the contacts doesn't last for more
than a few days or weeks, tinning them with a thin coating of solder should
help.
MCM Electronics at 1-800-543-4330 lists a Rubber Keypad Repair Kit
for $24.95. It is supposed to contain enough material to repair 400
contacts (2 containers each good for 200 contacts). Their part number
is 20-2070. Not cheap but 400 contacts covers quite a few typical
remotes. Note: I do not know whether it is easy to mix only enough
material for just 1 or 2 contacts - it would be worth confirming that
this is possible before ordering. Or else, invite a few dozen friends
(and their flakey keypads) over for a remote repair party. :-)
For a similar price, Remote Control
Keypad Repair also has a kit for coating the worn out rubber. It consists
of a little bottle of some conductive paint which doesn't appear to need
mixing.
There is also a material called 'resistive coating' or something like
that that goes on like paint. It may be available from an electronics
distributor. Or, if you are friendly with your local repair shop, they
may be willing to spare a few drops.
Occasionally, the conductive material is not actually worn off entirely
only on the surface and there may still be some beneath surface. Light
sanding may help.
Unfortunately, there is no single best solution since the material used
for the conductive rubber pads in remotes is not all the same.
(From: Paul Weber (webpa@aol.com).)
As for as repairing conductive rubber keypads: I've not used the metal
tape method, but will probably try it. I've had great success with a
thorough cleaning and light buffing of the contact area with very find
(1000 grit) wet/dry sandpaper."
(From: Rufus (Pink@Floyd.Edu).)
(From: Wes Hilterbrand (replayelectronics@usa.net).)
BTW, this is just my opinion. I CANNOT be held responsible for any damage
incurred due to following this procedure. Try this AT YOUR OWN RISK!
Remember, if you mess up your working remote, there is no recourse."
(From: Keith Craig (kcraig@mlode.com).)
(From: Mark Saterfield (kc4tzn@webtv.net).)
(From: Mike Harrison (wwl@netcomuk.co.uk).)
(From Rodney A Schmidt (rschmidt@iastate.edu).)
(From: Luis Ortega (imagremlin@hotmail.com).)
Different buttons my remote have been repaired using these techniques (for
the sake of experiment!)."
Note that strictly speaking, these IR emitters should perhaps be called
Infra Red Emitting Diodes or IREDs since they produce no visible light.
However, we will use the term IR LED throughout this document since its
meaning is understood by the vast majority of readers.
(From: Duane P Mantick).
WARNING: DON'T replace the memory capacitor with a battery as it is charged
from the main battery when present. While the remote may appear to work
this way, attempting to charge non-rechargeable batteries can result in
unpleasant behavior. Although the risk of fire or explosion is probably
low, why take chances?
However, some of the One-For-All (and probably others as well) remotes do
have capabilities not listed on the package (or web site). Check with the
manufacturer (in the case of Universal, this can be via email) to determine
whether any of their products have what is needed for your model(s).
Universal 'learning' remotes are available at slightly higher cost (perhaps,
$25-100). The better ones are capable of memorizing all of the actual signals
sent by your original remotes by viewing the IR transmission directly. Of
course, your existing remotes must be working properly for teaching purposes.
Make sure you get a money back guarantee with these as some may not be
compatible with all equipment. The advantage of a learning remote is that it
can be taught to perform setup, adjustment, and programming functions as well
as those for normal operation. However the teaching process is likely to be
tedious and time consuming and you will have to keep track of which buttons do
what - possibly not worth the effort in the end. If the backup batteries
should ever go dead, the entire learning process will need to be repeated.
(From: Michael Schuster (schuster@panix.com).)
These definitely =behave= as though they have EEPROMS; i.e. learned
functions are retained indefinitely without power.
Also the upgradable one-for-all remotes from Universal Electronics (i.e.
the ones with the 'magic' key) almost certainly have EEPROM since they can
be customized by moving buttons around and assigning straight binary
functions to keys not in the original pre programmed arrangement. Such
customizations are also retained if power is lost."
(From: Dakuhajda (dakuhajda@aol.com).)
By the way the most expensive RCA universal remote that Wal-Mart sells I use in
our shop for almost all but the very newest RCA TV sets. Last 2 years models.
(From: techman@niobiumfive.co.uk.)
Some universal remotes are better than others. I recently bought
(here in the UK) one called "Wizard" made by Philex (a big manufacturer
of replacement remotes). It has several levels of programming:
All this can be setup for 8 different devices. Settings are saved in FLASH
memory so you don't lose any programming when the batteries die. :-)
It does has a few undocumented quirks, like setting a new manufacturer
code seems to clear all existing "learned" codes. :-(
I bought it from Grandata (UK 0208-900-2329, international +44-208-900-2329)
for GBP 16.50 + tax and postage.
I have also wired a phototransistor and an IR LED to the serial port
on an old laptop, and experimented with turning that into a learning
remote. I must say I was surprised at how many different coding schemes
seem to be in use, just running through a) above and observing the
waveforms I documented about 20 variations before I got bored.
I got it working with my UK satellite "digibox" and with a JVC
VCR, but haven't taken it much further. I was particularly interested
that the VCR (HR-S4700EK) responds to two quite different coding
schemes, presumably it was designed to be backward-compatible with some
old code of theirs, but the newer code is required to get all the
functions to work. A few codes do functions for which there is no
button on the official remote (and are normally only accessible from
buttons on the front panel!) One code wipes out all ones timer recording
settings! :-(
Panasonic has a web site you can enter your model number and get a parts
list with list prices and part descriptions:
This site includes support for Panasonic, Technics, and Quasar consumer
electronics. However, my quick visit only showed accessory type items
(e.g., replacement original remote controls, cables, etc.). Encrypted
credit card protection presumably makes it possible to order parts directly.
They will also attempt to locate hard to find remotes.
Test by removing the front panel if possible and direct the remote at the
sensor directly. Inspect and clean the sensor window thoroughly with mild
detergent and water.
Borrow a replacement or universal remote to determine if the device responds
with a known good unit. Check demodulated waveforms with an oscilloscope
to confirm proper signal levels and reliable operation. See the section:
Diagnosing the Problem as well.
And, there could be a design or manufacturing problem with your set....
While the IR-receiver module inside that TV may be a mature component and may
function well on the test bench, it is entirely possible that the TV
manufacturer has made a (design) fault in applying it. An IR-receiver is a
very sensitive device, and a television is a very dirty environment. This
may be a case of an EMC problem, not an optical problem. Under the right
conditions, with this type of IR-transmitters and IR-receivers, distances
of 100 feet or better may be crossed...
But, this should not be the customer's problem. The service organization of
the TV manufacturer is the proper place to obtain a fix. The complaint is
valid and it should be cured.
These are likely possibilities if you have just changed your room layout or
added something to it:
A neighborhood kid (or adult with the maturity of a kid) may be playing
tricks on you from outside your window or even across the street. It
doesn't take much (a lens) to extend the effective distance over which
a universal remote will operate reliably.
Cover the sensor of the misbehaving equipment with a piece of black tape
to see if the problem goes away. Then round up your other remotes (and/or
other animate objects) and discipline them!
Turn off all fluorescent lamps to see if the problem goes away. A cardboard
baffle can be taped to the sensor to block the interfering light. Try a
different brand of compact fluorescent as not all cause interference.
Turn off the lamps or move the Sun
Turn off suspect devices. If the problem goes away, they will need to be
moved to another location. Shielding is probably not a viable option.
There are three ways to solve this problem: changing the wavelength of
the light, the modulation frequency, or coding used by the remote. Only
the first of these is likely to be realistically possible without major
effort and would involve replacing the IR LED(s) in the hand unit with
visible ones (red, yellow, or green) and replacing the IR passing filter
on the controlled equipment with one selective for the visible wavelength.
The silicon sensor in the remote receiver probably will work just fine for
visible light. A colored piece of cellophane or plastic may be adequate
for the filter. Using a green LED may be best since its wavelength is
furthest away from the IR wavelength making the filtering easier.
I have not actually tried this stunt but there is no fundamental reason why
it shouldn't work. However, some experimentation may be required to find a
suitable high brightness LED and to match it to driver in the hand unit
since the LED's voltage drop will be different and may require changing a
resistor. And yes, with care, it should be possible to extend this approach
to 3, maybe even 4 devices. Multicolored remotes might be kind of cool. :)
The manufacturer of the remote control is the next likely source (after the
instruction manual) for the codes and other information. However, there is
a good chance that one of the following web sites may be able to help you:
But they suggest using the technical support line (800-636-8352) for remote
control programming and other Memorex consumer electronics questions.
There is complete info on programming and special functions for many
models. Since other universal remotes may be rebranded One-For-Alls,
this information may be useful for those as well.
There are complete specifications and setup instructions for most of their
products (with the rest coming soon).
And here is another one:
Next time, make copies of the instruction manual(s) and put them in obvious
places like taped to the back of the TV or inside the entertainment cabinet.
Better yet, print the specific instructions and/or codes on a slip of paper and
stuff it into the battery compartment of the remote. Or tape the info to the
back and then cover with clear tape to protect it from wear.
One of the primary axioms of life is that you will lose those instruction
manuals. :-)
I know this procedure works for models 3 and 4+ and assume it to be similar for
the others.
(From: Larry Sabo (sabo@storm.ca).)
If extra distance or sensitivity is needed in the same room, it may not be
too hard to replace the IR LEDs in the hand unit with more and/or higher
power devices (though the IR LEDs used originally are generally quite powerful)
but this would require some circuit hacking and possibly some reverse
engineering of the design to determine what is possible. A small convex
lens over the IR window on the receiver will help as well but will reduce the
angle to the receiver over which response will be reliable. This would be
suitable if you always use the equipment from a fixed location like a couch
at the opposite end of the room.
Where the transmitter and receiver are both in restricted locations, a short
focal length convex collimating lens can be added to the transmitter as well
as the receiver. The angular coverage of both receiver and transmitter will
be reduced but the range will increase. Reducing the beam divergence by a
factor of 2 at the transmitter will increase the range by approximately a
factor of 2. Doing this at the receiver as well will add another factor of 2.
Several hundred feet should be possible with very inexpensive lenses. I would
suggest a lens of around 1 inch diameter with a 1 inch focal length. This is
not critical but an IR detector circuit or card should be used to help set up
the proper distance to the transmitter IR LED and receiver photodiode.
There are a number of ways of implementing this:
Where at least one video cable exists between the two rooms, a variation on
this theme uses a combination of the coax shield and earth ground to send
the signal between the rooms.
(From: Robert Scott (Robert.Scott@ncl.ac.uk).)
One of these circuits exists at:
(From: Francis VE2FGS (sonytech@videotron.ca).)
I personally have small pyramids called "Powermid" made by X-10 which work
fine.
Those come by pair, one transmitter and one receptor. You plug them in 120 VAC
wall outlet and it transmit signals between the two pyramids with FM signals.
It work very fine and I think it's the most practical, cheap, and fast way to
transmit IR signals from one room to another.
I paid about $40 (Canadian) for the pair.
I know of 1 link to such devices. Try:
The carrier frequency and coding schemes (these are even more varied than the
table above would indicate) have apparently not been standardized. They may
also vary quite a bit even different models of equipment from the same
manufacturer. Therefore, it is beyond the scope of this document to enumerate
them all. It is possible to see these types of waveforms with an oscilloscope
by monitoring internal signals of the remote including certain pins on the
controller IC as well as the IR LED or its driver or across the transistor of
the IR detector circuit (see the section: IR Detector and
Related Circuits).
Check out ZipLabel.com Computerized
Infrared Remote. They have a very cheap and cheerful method of obtaining
IR codes. DOS software is provided for textual or binary capture of remote
control codes. Windows software for the device is also linked to the site. The
Windows software "Monster Clicker" allows you to create any number of virtual
remote control functions. This software also has full Macro facilities. It
is well worth a visit for the small amount of construction required this is an
excellent option.
Here is an even more extensive list:
(From: Joe Krantz (joed.krantz@symbios.com).)
Almost all you can find free from the net you can find linked from
Finally, here is a site that appears to have a lot of more or less
non-commercial info on medium to high end (they say) remote controls from
various manufacturers including detailed coding and other technical details:
IR radiation falling on the photodiode causes current to flow through R1
to the base of Q1 switching it and LED1 on.
Component values are not critical. Purchase photodiode sensitive to near
IR - 750-900 um or salvage from optocoupler or photosensor. Dead computer
mice, not the furry kind, usually contain IR sensitive photodiodes. For
convenience, use a 9V battery for power. Even a weak one will work fine.
Construct the circuit so that the LED does not illuminate the photodiode!
The detected signal may be monitored across the transistor with an
oscilloscope.
The IR receiver module from a TV, VCR, or purchased from Radio Shack or
elsewhere, drives the base of Q1 through R1. It may even be possible to
eliminate the transistor circuit entirely and connect the LED directly to the
module's output (in series with a current limiting resistor to Vcc or Gnd) but
that depends on the drive capabilities of the module. You can use whatever
Vcc is required for the IR receiver module for the LED circuit as well but may
need to change the value of R2 to limit the current to the LED to less than
its maximum rating.
The specific case where Vcc is +5 V is shown.
IR receiver diode (from scrap Penney's unit) attached to 18" single pair
wires-passed through heavy-gauge straw (from some unknown latte drink in the
early A.M.). RTV the tip to maintain rigidity. Positive end to plus end of
9 V battery. Negative end to 330 ohm 1/4 W resistor, and from there to display
LED (I chose a pretty red one from the scrap box), and then back to negative
of battery.
Time consumed: 2 hours. (1 hour to make sure the RTV was cured properly.)
Application to numerous remote control sources and to a couple of CD pickups
provided nice glow from the indicator LED.
I just received a Fisher 25 disc unit for repair, and the above tester was
instrumental in determining that over 12 IR emitters were functional. (Some
of these were in locations otherwise very difficult to access.)
(From: Raydon Berry (rayberry@pt.lu).)
Measure the current consumption from the batteries. Put the multimeter
on a range of about 25 mA and when you press each button, the code being
sent will show up as a wagging needle on a VOM or an average current for a
DMM. If the ceramic filter or the IR diodes have failed, the current
remains very low, but if OK, you should see pulses of 5 to 10 mA.
(From Malik (M.dad@mmu.ac.uk).)
Simply couple the output of the IR receiver (in the TV) to the input of the
audio output stage. Use a low value ceramic cap and a high value resistor,
this should be possible on all remote TV's and will cost you next to nothing."
(From: ShyGuy4Yu (shyguy4yu@aol.com).)
(From: Sam).
What a nice idea! The only concern I would have is that not all IR
transmitters use the same modulation frequency so I don't know how
forgiving the demodulator in the IR receiver would be. Thus, you might
think a remote control is bad when in fact it is just incompatible.
You could probably learn to recognize the codes by ear after a while
as well! :-)
(From: Paul Grohe (grohe@galaxy.nsc.com).)
Clip a *glass* encased diode (1N34, 1N914, 1N4148, etc.) between your
scope probe tip and ground clip. Crank the scope sensitivity up to about
20 tp 50mV/div. Hold the diode by the grounded lead (to reduce noise pickup).
Point the "business" end of the remote directly at the clear part of the
diode body. The IR packets will now be visible on the scope.
You may have to move the remote around to find the "hot spot" in the window.
The more of the diodes junction that is exposed, the better the response.
A Sony remote generates about 50mVpp with a typical 1N4148/1N914 and more
than 200mVpp with a "wide open" 1N34A point-contact Germanium (at 1 cm).
BTW, the time constant of this setup may mask the actual 40kHz
carrier pulses. Place a 100k resistor in parallel with the diode
to see the individual pulses clearly (sensitivity *is* reduced).
Or just simply hold the remote against an AM radio for a quick test."
(From: Sam)
And, Filip also suggested that last one so I will honor him as well. :-)
Almost any sensitive amplifier may pick up some clicks from a working
remote. A guitar or microphone amp may work for this. However, none of these
indirect methods actually test the IR output but probably are accurate
enough in most cases.
(From: Filip M Gieszczykiewicz (filipg@repairfaq.org).)
(From: Bob Quackenbush (quackenb@heidelberg-emh11.army.mil).)
(From: David C. Brink (db@mcs.com).)
(From: Sam)
Note: Since the voltage drop across an IR LED is usually less than that
across a visible LED, this may not work unless the remote uses two LEDs in
series. In that case, substitution may be needed.
-- end V2.99 --
All Rights Reserved
2. There is no charge except to cover the costs of copying.
DISCLAIMER
While it is hard to imagine any catastrophic consequences resulting from
attempting to repair a remote control, we will not be responsible for such
consequences or collateral damage should it occur! :)
Introduction
Remotes, Remotes, and More Remotes
Twenty years ago, a wireless remote control was a $50 or $100 option (in 1980
dollars) to a TV or VCR. Early remote controls used ultrasound or radio
frequency analog transmission and could perform only limited functions -
you were lucky to get anything beyond on/off, volume, and channel up/down.
Today, a remote control is standard with even the lowest cost basic
electronic equipment. Nearly all modern remote controls use Infra Red (IR)
light for digital data transmission. Some have more buttons and functions
than a personal computer! Unfortunately, many have row upon row of tiny
identical size buttons with no logical layout of functions. Others are a
masterpiece of ergonomic engineering almost operating by themselves.
IR Remote Diagnosis and Repair
SAFETY
There isn't anything dangerous inside a remote hand unit. Even staring
point blank into the IR emitter isn't likely to harm anything. The worst that
will happen if you make a mistake is that the circuit will be damaged beyond
beyond repair and a new remote control will be in your future! :)
Testing of Remotes
Unless your remote hand unit has been run over by a bulldozer and is flat as a
pancake, don't immediately assume it is actually broken.
Diagnosing the Problem
The following assumes that there is no response to the hand-unit even if up
close to the TV, VCR, or other controlled equipment. Where the remote works
but only over a shorter distance than when new, see the section:
Reduced Operating Range.
Reduced Operating Range
With proper design, there really shouldn't be anything in a remote control
(or the receiver) that degrades with reasonable use (at least in terms of
operating distance). However, not all remote controls are properly designed
(or manufactured) and there can be other causes for a remote that used to
operate reliably from the other end of the house or bounced off the far wall
but now won't even respond directly from a few feet away:
Remote Repair
Most problems can be remedied without any special skills. However, where
bad connections or component replacement is involved, you will have to be
able to do just a bit of fine soldering. In this case, a low power (e.g.,
25 W) fine tip soldering iron and fine rosin core solder will be needed.
Fortunately, the circuit boards in remotes are generally constructed using
features sizes (pads and lines) that are state-of-the-art from the 1950s.
Therefore, rework isn't nearly as challenging as, say, on your 500 MHz PC!
Even if the case is slightly damaged after disassembly (e.g., a snap or two
break off), the sparing use of a semi-permanent adhesive like windshield
sealer will probably be able to fasten it all back together in such a way that
little evidence remains of its traumatic experience.
Problems with Remotes
Most problems occur in the hand units due to the abuse inflicted on them by
kids, pets, and even otherwise well behaved adults. However, the equipment
or even outside interference can also be at fault. Therefore, also see the
sections: Problems with the Equipment and
Problems Due to Interference.
Dead Batteries or Batteries Inserted Incorrectly
Solution obvious. If batteries tend to go dead quickly - the batteries
in a remote typically last years - then you may have a stuck button,
some conductive grime under one of the buttons, or a defective IC - or
you may be using cheap batteries.
Corroded Battery Contacts
Clean off the chemical deposits - first dust out the dried material with
a soft brush and then remove the remainder with a damp lint free cloth
or paper towel. Polish the contacts with a Fiberglass brush and/or pencil
eraser and/or very fine sandpaper or a nail file. If there is evidence
that the battery juice made its way inside the case, you will need to open
the remote and thoroughly clean the interior. Additional repairs may be
needed if damage to wiring, components, or circuit board traces is evident.
Broken or Intermittent Contacts
There are most often between the battery connections and the circuit
board. Carefully resolder and reinforce them if necessary. There
could also be cracked solder joints on various component pins
(particularly those that get abused like switches) as well. Reflow
the solder on any suspect joints.
Broken Ceramic Resonator
These may fail from shock when remotes are dropped.
Dirt, Spills, Gunk, Oily Buildup Inside
This may cause circuit problems preventing keys from operating reliably
or physical problems resulting in keys being just plain stuck or sticky.
Unreliable or erratic operation from these causes is probably the most
common remote control problem after dead batteries.
CAUTION: In some cases, the conductive black material may be soluble in
alcohol - carefully test first on the pad of a key you don't care much
about. If black material comes off on your cloth or swab, use only the
water and detergent. Putting the black stuff back on is much more
difficult than removing it. :-)
Worn or Corroded Pads on Circuit Board
These may be interdigitated or semi-circular patterns and suffer from
both wear and corrosion. Conductive Epoxy or other similar conductive
paint (like that used for rear window defogger repair) or ink may be used
for repair. A piece of thin copper foil can be glued to the circuit board
and soldered to the appropriate circuit trace. (Gold foil would be better
as it will not corrode but might be just a tad pricey for a $10 remote!)
Worn Conductive Material on Rubber Buttons
Compare the bottoms of frequently used keys with those that are rarely
pushed. If you can see the rubber through the conductive material after
cleaning, the pad is likely worn to the point of being non-functional.
This may be repaired with conductive Epoxy or other similar conductive
paint or ink. A sliver of aluminum foil can sometimes be glued to the
rubber surface. 3M makes EMI/RFI foil shielding tape, type 1181, that
should work very well for this. Another source for small quantities of
metal tape would be a shop that makes stained glass or sells supplies for
making it. Pencil lead (graphite) may also work
though for how long is unknown (though some have reported good success
with this readily available material).
"If you're looking for aluminum or copper foil tape with adhesive on it,
visit your local hardware store, in the plumbing and/or roof rain gutter
sections. Alternatively, try an auto parts store. I've found a variety
of adhesive foils (including stainless steel) in these kinds of
establishments.
"If you can find similar pads on another remote's membrane, trim them
off square and use them to replace the defective pads. You can use
silicone glue to attach them. Be careful to trim off the same amount
from each pad so the buttons throw will be the same, and don't trim
too deep as to damage the rubber dome."
"About the best way I have found is to take an old remote (trash or have
absolutely no need for) with the same type of conductive pads. Look for a
little used pad (such as a record button), add some skillful maneuvering
with an exacto knife, and some SuperGlue, and you can sometimes replace
the bad pad(s) on your remote with better pads. The way I have done this
is to cut the pad about halfway down from the sheet it's connected to
(around the pad's circumference, a little ways under the conductive
surface). This should probably be done only as a last resort, and WATCH
YOUR FINGERS!
"I use a can of 'TV TUBE COAT' (GC Electronics), a conductive paint used
for picture-tube aquadag (black paint on outside of picture tube used
for ground). Squirt a tiny amount on a piece of paper and use a Q-tip
(cotton swab) to drop on the pad."
"Pens are available that come preloaded with conductive ink at local
electronics stores though apparently not Radio Shack."
"It isn't the same as the silver stuff used for car screen heaters, etc.,
which I'd guess probably dries too hard and cracks off. It's made by
Circuit Works, who also do conductive epoxies. Their part number is
CW2610 for a repair kit, UK supplier is Farnell, price is UKP 22.33."
"What I used to remedy it was to use the stainless steel tape that is sold
to seal ducting insulation, use a paper hole punch, and super glue the
punched stainless onto the pad. I have had extremely good luck using
this, and since the stainless is adhesive anyway, it stays in place while
the super glue is drying."
"I tried using Permatex Quick Grid Rear Window Defogger Repair Kit (part
number: 15067), which is easily available through the Internet and auto
parts stores. My early attempts failed, they worked for a couple of
days, and then the conductive paint would crack, peel off and make
permanent contacts. Eventually I found three ways of making it work:
Cracked Circuit Board
These can be repaired easily as the circuit boards are usually very
simple, single sided, and have wide traces. Use Epoxy or an adhesive
like Duco Cement(tm) or windshield sealer to repair and reinforce the
circuit board. Scrape off any insulating coating and jumper breaks with
fine wire and solder. Do not just bridge the gaps with solder as cracks
and future problems are a certainty.
Bad IR LED
Test the IR LED(s) with an external power supply (with current limiting
resistor) and IR detector and/or monitor voltage across them while
operating. Substitute a visible LED and see if it lights up when keys
are pressed. Use a scope to monitor the drive to the LED. You should
see the pulse code modulated carrier. If faulty, replace with a readily
available high intensity IR LED.
Bad IC
If the remote uses a custom chip, throw it away! However, a failed chip
is usually quite unlikely unless struck by lightening (now how would that
happen?). Even accidentally inserting the batteries backwards (though
definitely not recommended!) - which tends to kill many devices - may not
cause any harm to a remote. Check each pin on the IC with a scope to
determine if it is at least alive.
"An awful lot of IR remotes use IC's from the same or similar series. A
common series comes from NEC and is the uPD1986C which, incidentally is
called out in the NTE replacements book as an NTE1758. A lot of these
chips are cheap and not too difficult to find, and are made in
easy-to-work-with 14 or 16 pin DIP packages. Unless you have no soldering
or desoldering skills, replacement isn't difficult."
Dead Memory Capacitor
Some hand units have some type of device to hold the internal settings during
the period when the batteries are removed for replacement. This may be a large
conventional electrolytic capacitor or "supercap". The PCB marking will
probably be a "C" number but who knows? If this device fails, any sort of
behavior is possible. Simply check across it with a multimeter - there
should be some voltage on it, probably equal or slightly less than that of
the main battery, though a lower value is possible as long as it's not
near 0 V. Replacements should be available.
Alternatives to Repair
There are a large variety of preprogrammed universal remotes available starting
at $10. These are set up by inputting a code number for each type of equipment
you will be using - TV, VCR, Cable box, etc. Don't loose the instruction
manual or you will not know what codes to use if the batteries go dead or
the remote looses its memory for any reason! Record the codes in pen on a
label on the back of the remote and inside the battery compartment. For
general TV/VCR/cable use, the $10 variety are fine. However, many will not
provide special functions like programming of a TV or VCR or access to other
model specific menu functions.
"You can get most of the Zenith OEM remotes from MCM Electronics. These
include some that were sold under the Gemini name as consumer items; their
4-device learning/preprogrammed remote was particularly nice).
"Unfortunately RCA remotes cannot be repaired on any made after 1986. The
circuit board is molded to the plastic case, only way to get the darn thing
apart and you break it beyond being able to put it back together. Rca sells a
universal remote control system link 5 that even has the pip feature. Usually
$25. If you really want an exact match look inside the battery cover you can
get the part number for the remote control, six digits, usually 221000 or
similar. You can call any RCA authorized servicer and they can order it for
you, or you can contact MCM electronics, Excel electronics, or any other
authorized Thomson parts distributor. "
Original Replacement Remotes
In some cases, the only realistic option is to obtain an original replacement
remote control. This might be the case where special functions need to be
easily accessible or you have fallen in love with the button layout, style, or
decorator colors! If you need to access special functions on your equipment,
a learning remote might be an alternative if you have access to a working
remote control so you can teach it. However, learning remotes are rarely as
convenient as the original. As for color, there is always spray paint!
Problems Not Due to a Defective Hand Unit
Problems with the Equipment
While circuit problems with the hand unit discussed in the section:
Problems with Remotes are most likely, the following
causes should not be overlooked if the remote does not work or has limited
range:
Note that if this is a problem with new equipment (or if it has always been
this way), don't neglect the obvious: Has the protective plastic film been
removed? This is often present to prevent damage during manufacturing and
shipping. It is amazing how many people neglect to remove this - I have gotten
10 year old TVs and VCRs at garage sales with this ugly film still in place!
Problems Due to Interference
Symptoms for the following may range from no, intermittent, or incorrect
response or greatly reduced range to the equipment being possessed - a TV
changing channels, volume, or powering itself on and off as though being
controlled by a poltergeist. (Where the problem is due to more than one
piece of equipment interacting, see the next section.)
Where Multiple Pieces of Equipment Use the Same
Codes
It sometimes happens: A second VCR or TV, even if from a different
manufacturer, may use exactly the same remote coding. Where there is no
unit select switch on the device and hand unit, only careful aiming (possibly
with a set of blinders!) will allow control of one at a time.
Forgot Your Universal Remote Setup?
Hopefully, you saved the instruction manual. No? Some universal remotes
like the Zenith Allegro have an 'auto search function' which will sequence
through all possible codes. You then push a button to lock in the proper
settings when the TV or VCR's channel or power status changes. Of course,
since you don't have the instruction manual, you likely don't know how to
use this feature either!
Code search Programming of RCA SystemLINK Remote
Controls
Perhaps this is your lucky day and this is the type of remote you have that is
in search of an instruction manual.
(From: Aldrich TV, Inc. (aldrichtv@centuryinter.net).)
"I find it works better if you have the unit on and watch for it to go off.
It is easy to miss it coming on and then you have already passed the proper
code and have to start over."
IR Items of Interest
Increasing the Range of a Remote Control or IR Data
Link
For operation between rooms, a repeater is best - an IR receiver that sends
the data over a cable to an IR transmitter in the other location. This would
require an IR receiver module similar to the one found in a TV or VCR, buffer
to drive the cable, and a IR transmitter modulated at the appropriate carrier
frequency (around 40 kHz typically).
Remote Remotes (Remote Extenders)
In some situations, it is desirable to be able to operate a remote controlled
piece of equipment from another room - where a direct line-of-site path does
not exist. One example of this would be to control a stereo receiver in the
living room (which has speakers wired all over the house) from a bedroom.
In all cases, the IR receiver should be a module that includes automatic
level control and generates a logic level output. If possible, it should NOT
demodulate the IR signal so that the frequency of the carrier is maintained.
The IR transmitter then only needs to convert this logic level to on-off IR
pulses. Widgets based on all of these schemes are available commercially.
Controlling TVs, VCRs, CDs, etc., From a PC
(From: Donald Hoffman (dhoffman@epix.net).)
IR Signal Transmission and Coding
Modern remotes use a pulse code modulated carrier to send the command. Typical
carrier frequencies vary between roughly 36 and 56 kHz (although rumor has it
that Bang and Olefsun remotes may use 455 kHz for the actual IR carrier - I
have not been able to confirm this). Each pulse or bit consists of multiple
cycles (e.g., 32) of this carrier. Here are approximate measurements made of
the general characteristics of some typical remotes:
Model Carrier Cycles/bit Repeat rate
------------------------------------------------------------------
Emerson VCR 36 kHz 32 10 Hz
Mitsubishi VCR 38 kHz 10 20 Hz
Panasonic VCR 56 kHz 48 10 Hz
RCA TV 56 kHz 28 16 Hz
Sony CD 40 kHz 24/48 20 Hz
Sylvania TV 36 kHz 32 10 Hz
Technics CD 56 kHz 48 10 Hz
Toshiba VCR 38 kHz 20/320* 9 Hz
Yamaha receiver 38 kHz 20/320* 9 Hz
For buttons that repeat, typical rates are 10 to 20 Hz and the entire code may
actually be sent only when the button is first pressed with only a 'repeat'
code sent while it is held down. (* This extra length 'bit' was evident in
the repeat code for the Toshiba VCR and Yamaha receiver - which both seemed
to use very similar coding schemes. Repeat for all keys used a 320 cycle bit
followed by an 80 cycle gap and a 20 cycle bit.) It would appear that various
combinations of NRZ, RZ, PWM, and others are used depending on manufacturer
and model. Think of the challenges involved in designing a universal remote!
Capturing Remote Control Codes
(From: Dez Ellis (dezellis@lineone.net).)
Links to IR Related Web Sites
The sites below have quite a bit of information on IR remote data transmission,
coding schemes, various circuits. There are even tables of formats for the
remotes from a number of manufacturers:
(From: Tomi Holger Engdahl.)
IR Detector and Related Circuits
IR Detector Circuits
Two approaches are shown below.
IR Detector Circuit Using Bare Photodiode
This IR Detector may be used for testing of IR remote controls, CD player
laser diodes, and other low level near IR emitters. It will not have the
sensitivity or dynamic range of the approach described in the section:
IR Detector Circuit Using IR Receiver Module but will
respond to all sources of IR falling within the wavelength range of the
photodiode used since there is not demodulation or coupling circuitry to get
in the way.
Vcc (+9 V) o-------+---------+
| |
| \
/ / R3
\ R1 \ 500
/ 3.3K /
\ __|__
| _\_/_ LED1 Visible LED
__|__ |
IR ----> _/_\_ PD1 +--------o Scope monitor point
Sensor | | (low active)
Photodiode | B |/ C
+-------| Q1 2N3904
| |\ E
\ |
/ R2 |
\ 27K |
/ |
| |
Gnd o--------+---------+--------o Gnd
_|_
-
IR Detector Circuit Using IR Receiver Module
This one uses an entire IR receiver module as the IR sensor. Its sensitivity
and dynamic range will be much better than the circuit described in the
section: IR Detector Circuit Using Bare Photodiode since
these modules have automatic gain control circuitry built in. However, some
modules are tuned to a particular modulation frequency and/or are AC coupled
and will not respond to all remotes or other pulsed or continuous IR sources.
R2
Vcc (+5) o------+-----------/\/\--------+
| 220 __|__
| _\_/_ LED1 Visible LED
| |
|+ +--------o Scope monitor point
+----------+ | (low active)
-| IR |out R1 B |/ C
IR ---> : Receiver |------/\/\-----| Q1 2N3904
-| Module | 10K |\ E
+----------+ |
|- |
Gnd o------+-----------------------+--------o Gnd
Steve's Instant IR Tester
(From: Steve Rice (punky@efortress.com).)
Some Alternative 'Quick and Dirty' Remote Testers
In addition to the IR detector circuits, IR detector card, and camcorder,
video camera, or digital camera here are a few other options:
"If you have a IR remote TV in the workshop for testing VCRs and other video
equipment, you can modify this so that audio can heard from the speaker which
represents the IR signal.
"Take a known good IR receiver from an old set. Supply proper DC to it. Feed
the output into an audio amplifier. You can hear intermittent operation
really well without squinting at test equipment. Put one on the counter for
demo to customers.. Great!!"
"Here is a another "quick" and "very dirty" test of the IR emitter I have used:
"Simply hold a pocket AM radio or Walkman set on AM and push the buttons. This
works for all the remotes I have.... except the ultrasonic one. :-)"
"Tune an AM radio to a quiet area of the band, hold the remote near the
(normally internal) antenna, press and hold any key on the remote. The sound
will be a quiet fluttering, so listen carefully. Be careful with your
interpretation of the results. "No flutter" may NOT mean that the transmitter
isn't working."
"Just dissect the remote far enough to get access to the IR LED(s) leads (if
the remote has been through the moving bits of the Lazy-Boy a few times, such
disassembly might not even be necessary). Hold a LED in parallel with it and
see if it lights when you press the remote buttons."