Heathkit GC-1005 Panaplex Clock Troubleshoot

Bam! Nice find David.

I have been concerned about the suspected "blowing" of the clock chip, because I have very little CMOS experience. I am currently using a CD4017 on a breadboard, and have accidentally touched some pins from time to time, while at others making sure to ground myself. I wondered "could it really be that easy?" I am sure a single hit when you are charged could in fact blow a chip, but I happy to hear that the chip is not fried - both for you and generally . Maybe a display will pop up. You probably like retaining the original design - but I would repeat the suggestion of using the smaller display for seconds if you don't have plans for it - which you may.

I didn't want to comment on the previous video because I'm not a tube expert, but I remember thinking: Hmmm didn't the clock show 88 (88) 88 when you powered it up the first time, too? You had to flick a switch (presumably to adjust the time) to bring the chip out of the initial state. And you didn't try that after you touched the chip and thought it was bad. I don't even think the grounding wire to the back panel has anything to do with it; I reckon that high voltage multiplexer generates much more RF interference than any Wifi networks in your house. Besides, I've never seen a chip go bad from touching it while it was in a circuit. Again, I'm no expert but as I understand, the reason why static electricity and CMOS don't go together well is that the high voltage causes a brief but strong current that goes through the transistors because it has nowhere else to go, but when the chip is in a circuit, the electrons of a minor static discharge through your fingers just go into the circuit, where there is plenty of capacitance to absorb them. Anyway, I'm glad there's hope for this one. Would be great to find some new displays!

Jac Goudsmit

Fran, the GC-1005 has a flicker issue. I built mine in 1974 and the seconds digit pretty well flickered out of the box. It is most noticeable with the number 1 and it comes and goes. Heathkit issued an advisory in 1973 and recommended changing the time constant parts that control the digit multiplex. These were already incorporated in my version and should be in yours as well. Some users have replaced the displays and that solves the problem. I will point out that I had brand new displays in 1974 and it still did it. However, a clock we had at work was fine for its whole life. Old neon gets finicky as it ages and voltages that used to make it fire just don't anymore.I highly doubt that you have an RF issue. Unfortunately, you have a GC-1005 display issue. One of these days, I plan to look at the high voltage waveform at the display and make sure it is clean. As you can see from the schematic, this voltage is multiplexed to one digit at a time. Oh yes, I have been getting around to this for the last 30 years or so. Good luck and thank you.

Hi Fran. Great to see the chip didn't get zapped. Found this info about the clock. Has something about the flicker that might be useful. Thanks! <a href="http://www.decodesystems.com/heathkit-clocks.html" rel="nofollow noopener" target="_blank">http://www.decodesystems.com/heathkit-clocks.html</a>

David Blake

I noticed that the first time I fired it up, but it has not responded with throwing the setting switches since. But I'll try a few other things before giving up on that chip entirely.

Fran Blanche

A great display for its time, just not built to last.

Fran Blanche

The neon/atmosphere often leaks through the pins also. And cmos can be the devil, or ahead of it's time... Jk, keep up the good work.

Ross Johnson

Thanks for the video and I enjoyed the explanation of how the displays work starting at 5:30.

Wait! Your mostek chip might not be damaged. I have the very same clock (built it in 1975). When you power on the clock, it displays all "8"s. Slide the time setting switch on the bottom to set the time. It should then go to the familiar 12:00:00. Return the switch to off and the clock should keep time. YOu can find the panaplex displays on ebay...but hold your wallet.

thinks variable frequency drive...wait that's not right, searching google...finds a fran video explaining them. must be kismet.

CloneRanger

Ooh, those panaplex seals seem like they must be terrible compared to conventional tubes... I can see why most modern VFDs stick to a more conventional glass construction.

Jamie Magin

Almost seemed like some cathode poisoning on the centre digits.

Vaughn B.

You could modify the seconds to be the smaller display.... good luck with the chip you bought.