Hoyle Quartz LCD Projection Clock Model # 7770
Oh, where do I begin? I might as well admit it at this point...

William: Hello. I'm William and I have a clock fixation.

Others: Hi, William.

. . . .

I've never pictured myself as any sort of a clock collector, and most clocks really are not that interesting at all. Still, I've come across a few, and like I said before, a few of them are interesting enough that I felt it prudent to grab them. And then, after finding next to no information on the World Wide Web about them, I've created pages like this one. Not that you or anyone else cares, but now you know. And maybe you're here because you have this very clock and need some information about it? Stay tuned, it's all here.

Here are the clocks I found moldering in my grandparents' basement.

Two Hoyle Quartz LCD Projection Clocks Model # 7770

Yes, it really was midnight when I took the picture. You'll also notice that the clocks are "beating against" one another here, as one has its colons illuminated while the other is turning them off.

As you can see, the unit on the left has had much more use than the one on the right, or at least has been subjected to a lot more wear and tear. However, both are interesting because they are projection clocks, and can display the time of day on your ceiling at night or when the room is only dimly lit. As for the brand, Hoyle Products is still around as a maker of card games (you will notice that their logo on these clocks and on the products they sell today is--as of this writing in November 2009--identical) despite their not having a web site. However, at the time these clocks were made, Hoyle was a division of a company known as Brown & Bigelow.

Brown & Bigelow is still around today and they do have a web site. They make (or, probably more accurately, distribute) promotional items. And it would appear that they have made more than a few projection clocks over time, some of which were branded "Hoyle".

I removed the dead batteries and slapped good ones into both units. The one on the right tried to run and fell over on its face. The one on the left was lifeless and there was a huge battery mess inside it.

Both of them, particularly the one on the left, would clearly need repairs to run again. I really didn't know if I could repair them. The first problem that I had to clean up was that of battery leakage. People have a bad habit of putting portable items aside for months (or longer!) at a time with the batteries in place. This is a big mistake. Batteries contain fairly nasty chemicals and will leak if given the chance to do so. Do yourself a favor and remove them before that happens.

Once I'd cleaned the battery terminals up, both clocks were a lot happier and able to run. However, the projection can only run on a constant basis when the power adapter is plugged in. Without external power, it can only run intermittently when the snooze bar is pressed. Both were plugged in to a live outlet, and the power supplies appeared to be working, but both clocks had burned out light bulbs and therefore could not project the time. The one on the left had a hot case corner and a very unhappy (hot) wall wart power supply. So I'd have to crack the cases to see what was inside and if I could repair it. Both plugs were loose in the casing and would barely hold the power adapter's connector when it was pushed in.

Printed in the corner of the display is the word "JAPAN", and it would lead you to believe that the clock "movement" itself was sourced from a Japanese manufacturer while the clock itself was put together in Hong Kong. That's not entirely true. Both clocks were fully assembled in Hong Kong, right down to the printboard inside. The clock on the left in the picture above is driven by an NEC uPD833 "8-channel digital liquid crystal display timepiece and timer circuit with 4MHz or 32kHz crystal oscillator operation" as per the rather breathless datasheet title. You and I would probably call it a digital clock controller IC. And I suppose it qualifies as being a Japanese clock "movement" of sorts.

Whatever the case, the NEC uPD833 is capable of numerous functions:
The main display in these Hoyle clocks is capable of displaying 24 hour time, and the projection display should be able to do so as well. Whoever built these clocks did not take advantage of this, nor did they make use of everything the NEC part is capable of. More on that later.

As for the clock on the right, it is driven by a no-name controller IC and fully assembled in Hong Kong, while it too bears the word "JAPAN" in the lower corner of the display window. I really suspected that this IC was nothing more than a low-cost knockoff of the NEC uPD833 part, but such is not (quite) the case. The behavior of both ICs is similar, but the second clock has a circuit board with fewer interesting modification opportunities. The NEC part starts keeping time at 1:00 AM when batteries are put in while the no-name part starts at 12:00 AM. Some of the symbols in the displays are different, though both retain the ability to display 24-hour time if it were possible to enable such a display. Finally, the alarm tones are different. The NEC uPD833
beeps several times in a row followed by a period of silence, while the no-name part beeps constantly when the alarm goes off. NEC goes a little breathless on us again by describing the alarm tone generated by the uPD833 as being a "fine alarm tone".

Oh, and the no-name/knockoff controller peeps on every hour. Sometimes it also has a beeping alarm fit when the batteries are first installed. The NEC IC is much more "well behaved" -- it remains silent on the arrival of each hour as well as when batteries are installed.

Where most clocks reset their seconds count to zero every time you advance a minute or hour with the setting buttons, these clocks do not do so. If you want to synchronize them, insert the topmost battery to start the clock the moment your time source strikes a new minute and zero seconds.


Both clocks have different internals. The NEC-based unit has a circuit board with several interesting areas, including a number of what would appear to be  "option selects" that govern the controller's behavior. Those areas have been bridged with solder that connects two circuit board pads. There is also a trimpot control that probably should not be played with unless you enjoy getting your clock back to the point of being accurate. A few resistors, diodes, dipped capacitors and the clock oscillator round out the parts present on each board.

Then there is the wiring. These clocks have a lot of point-to-point wiring consisting of thin wire that is very easy to break or separate from the soldered points on the circuit board. As the ceiling projection is handled by a separate display unit, the display wiring is multiplexed by simply connecting both displays together, in parallel. This assembly consists of tinned wiring grouped together in an insulated jacket with space between each conductor. It looks like a very low grade ribbon cable, because that's basically what it is.

You must have batteries in place to allow these clocks to operate. The power adapter is for constant time projection only.

The battery and power wiring is very interesting. There are three wires coming from the battery compartment. Tracing the circuit reveals two power planes are present in both clocks.  The NEC datasheet states that a second power plane (VDD) is needed to set the state of some of the IC's functions. Interestingly, both clocks will operate satisfactorily when a battery is present only in the topmost position of the battery holder. I take this to mean that the absence of the VDD power plane is not a crtical problem The second connection is used to provide the VDD power plane.

Both clocks, particularly the one based around the no-name IC, have more than a passing resemblance to the internals of the Micronta 63-753 clock I talk about elsewhere. The no-name IC based clock also has the text "no (0) jewels - unadjusted" printed on its circuit board, just as the Micronta clock does. There are, of course, no jewels to worry about in a digital clock!

Hacking / Modifications

The presence of numerous "option selects" on the NEC-based clock's circuit board open up some possibilities for circuit modification. In particular, the presence of a "2" shaped character in the rightmost numeral position suggests that these clocks can keep 24-hour time, which might be a nice feature for some applications. It would have been even nicer if Hoyle had implemented a switch to allow the user to choose which timekeeping method they wanted.

With the face of the clock laying down and the back cover removed, it's possible to see four bridged solder connections. Studying the NEC datasheet shows these as being connected to various "mode select" pins of the IC. In particular, one of the solder bridges connects the 12/24 hour select to the VSS power plane, forcing the IC into the 12 hour timekeeping mode. I tried to force the clock into the 24 hour mode. As I have two of them, setting one to the 24 hour method of timekeeping could come in handy.

This didn't really work, mainly because I didn't feel like going to the trouble of connecting the VDD power plane to the (assumed) VDD connection in the battery area. To do so would have required lots of messing around with very fine wire and the very real possibility of breaking it. The NEC IC would not behave reliably as a 24-hour clock when I tried setting it to that mode by breaking the connection and leaving it "floating". It would attempt to function as a 24-hour clock, but the IC tended to reset itself whenever a time value requiring the display of a leading "2" in the hours position was requested. Considering that the 12/24 hour selection pin was floating, this behavior is not suprising.

If someone wanted to go the trouble, a single-pole, double throw switch could be added to the clock circuit to select between VSS and VDD power going to the 12/24 selection pin on the IC. This should reliably set the 12 or 24 hour timekeeping mode.

For now I've undone the changes and have been using the clock as a twelve hour unit. I may revisit this in the future, if I feel inclined to do so.

Sadly, the clock based on the no-name IC does not appear to have any of these "option select" solder bridges on its circuit board. Without a datasheet for the IC in use (which is larger and has more pins than the NEC uPD833) I doubt it would prove very useful to attempt modifications on this type of clock.


Both of these clocks required repairs.

The first problem had to do with the corrosion caused by leaking dead batteries. The corrosion had to be cleaned off the terminals, and careful work with an icepick proved effective in removing it. Many times, though, the outcome isn't this good as the terminals have been consumed to the point where there is no more metal left or whatever is left is so brittle that the terminal breaks while being cleaned. Take the batteries out of stuff before putting it away, people! This sort of thing is PREVENTABLE.

Both clocks use the rather odd (for this application) miniplug connector to accept power from an external power supply as opposed to a barrel plug. Over time, this connector has worked itself loose, allowing the female portion of the connector (the one inside the clock) to twist around and around until the wiring broke in one clock and shorted itself out in the other. This sort of plug is used in audio equipment more often than it is used in power delivery applications.

Fortunately, the "wall warts" supplied with these clocks appear to be robust and the one that was shorted did not seem to be permanently harmed by this. The only noticeable effect of the short was excessive heat being produced both at the power adapter "wall wart" and where the wiring was shorted together in the one clock.

The other clock simply failed to project at all as the wires had simply been ripped free of the connector...well, this and a burned out light bulb kept it from projecting.

Repairs in both cases consisted of cleaning up (untwisting) the wiring and resoldering it to the receptacle plug. Although the wire proved to be very fine, it took solder well and the repair appears to be robust as compared to the factory soldering job. Soldering the wires back on is a little tricky due to their thin nature. The plastic body of the power connection means that care in soldering is required or you will melt and deform the connector.

Tightening the connector was also required as it had backed out and almost fallen into the case. In this case, the outer ring of the connector screws onto the connector body inside the clock, thusly holding everything together tighlty. Two notches in the outer ring allow it to be tightened or loosened as though it were a screw. A very small side cutters served as an effective device to fasten or loosen the outer ring. While it may loosen again, the ring was fastened very tightly. At least the little outer ring hadn't disappeared entirely.

If you need a new connector, it is important that the replacement connector contains a sping-loaded disconnect that severs the connection between battery and power adapter ground. This probably isn't crucial, but the designers included it for a reason...so you should do so as well.

Replacement Projection Bulb

There is no helpful legend to tell you what kind of bulb should be used for a replacement in these clocks. If you're lucky, the correct-but-burned-out bulb will still be in your clock, and you may simply buy another of the same type.

I was not that lucky. One of my clocks didn't have a bulb at all, and the other had a PR30 bulb. And I assumed that its previous owners hadn't messed with it! Silly me, making such an assumption and getting a PR30 bulb for this clock!

The PR30 is completely unsuitable for this application. Although the voltage rating for this bulb (3.75 volts) strikes a fair balance between what the power adapter puts out and what the batteries can supply (ensuring that--in theory--the bulb will light reasonably well on either power source) it pulls some 860mA per its rating. You'll blow away most batteries with this kind of current draw if you request a time projection for anything beyond the shortest possible interval. This also makes the little Hoyle wall-wart power adapter very unhappy. In addition to getting VERY hot, the power adapter didn't have to oomph to light the PR30 bulb to nearly enough intensity to make the projection usable. I really thought the wall-wart was bad until I noticed that it didn't get anywhere near as hot without the clock plugged in. Oops.

The clock based on the knock-off IC also tended to reset itself whenever the snooze bar was pushed. This is not surprising considering what probably happened to the IC's supply voltage whenever the bulb lit up!

It seems that what you really want is a PR17 bulb. This bulb comes about as close as you can to the 4.5 volt, 300mA rating of the Hoyle power adapter, with the bulb having a 4.9 volt rating and current draw of 300mA. The projection is entirely readable in even a moderately lit room, and this bulb still shines brightly enough with the batteries in place that you can still use the temporary projection function that is built into the snooze bar. Since the bulb will be spending a lot of time turned on, the slightly higher voltage rating should prolong its life in this application.

If you know of a better replacement bulb, please let me know. I wrote Brown & Bigelow and never got a reply from them.

There is also a "grain of sand" bulb (maybe two of them) in the main display to light it up at the edges. It too comes on when the snooze bar is pressed.

The "Wall Wart" (or plug-in power supply)

These clocks utilize a 4.5 volt DC, outer tip positive power adapter with a connector just like that of an audio miniplug, rated at 300 milliamps. (If you needed to find a replacement, a monophonic earphone jack would probably work fine. Just try to get one that will disconnect the negative battery lead when the connection is made.

You might have to "assemble" your own wall wart if you need one.

The regulation on the original Hoyle power adapter is not particularly good when unloaded--I tested the unloaded adapter and got voltage readings well in excess of eight volts DC.


Both of these neat clocks are running again, and they project the time perfectly with their new light bulbs. If you've read down this far, I appreciate your taking the time do so, and would like to hear what you have to think about this page.

Also, if you know approximately how old these clocks are, I'd certainly like to know. All I can say with regard to their age is that my grandparents had them for as long as I can remember. The only clue I've seen is printed on one of the power adapters--the numbers "81 13" appear on it. I take them to mean the 13th week of the year 1981.

Thank you for listening today. Now, if you'll pardon me, I have to go find another clock!

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Copyright 2009-10 William R. Walsh. All Rights Reserved. Written 11/09/2009. Updated 12/03/2009 and again on 02/27/2010. Permission is granted to mirror this page in its unedited entirety as long as a link back to this site and credit for the material is provided. You may not charge a fee or exchange items of value to provide access to this page or its content, other than an amount reasonably necessary to cover the cost of connection time, data transfer or printing supplies. Content from this page may not be displayed alongside advertising content of any type. You may use portions of this page in other products only if you provide credit and a link back to this page and only if the finished product is freely accessible to anyone interested in having a copy. If you use this material in work of your own, you may not charge or exchange items of value to provide access (other than as reasonably necessary to cover connection time, data transfer fees, or to cover printing supply costs) nor may you display advertising materials alongside any content you use from this page. Images may not be edited other than to resize them or to provide for faster downloading.