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Heathkit GC-1197 Chimes Off Tone and Skipping Beats

snappyapple632

Oct 21, 2021
3
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Hello engineers and hobbyists, Over the past few weeks, I have been making attempts at repairing a Heathkit GC-1197 with a GCA-1195-1 chime module installed. I bought it in "For Parts/Repair" condition, assuming that the burnt-out incandescent segments were the only issue. When the clock arrived in the mail, I plugged it in to discover there was no sound. The three original electrolytic capacitors on the chime board were immediate suspects, to which I promptly replaced (with 67V of the same capacity, the originals were 25V) and could now hear the chimes properly. However, this was only the start of a battle with an electronic Hydra, as two new problems reared their ugly heads: the chime board was skipping beats at random and the chimes sounded waaay too deep, even with the pitch all the way to the max. Here is what I've probed into thus far using the module's built-in test probe:

  • Running through the testing instructions in the manual, I find the signal from D304 and D305 is at full intensity. Per the cause chart's recommendation, I tested D304, D305, and R322 with a multimeter. They all work fine and their solder joints are good.
  • The clock signal coming from the IC305 (the time decoder) seems normal with no signs of noise that would cause the beat to skip. However, IC314 and IC315 show a pattern with random irregularities that reflect the skipping of beats heard in the chimes. I tried swapping IC314 and IC309 (both the same CD4013BE chip) which did not see any improvements.
  • All other tests in the manual passed fine with the built-in probe.
Here is a sound file detailing the chimes and the skipping beat (it skips once at 00:31 on the file): https://drive.google.com/file/d/1AGSqt1lWC72Cqysc6UjjvHkfKbiTxLpc/view?usp=sharing

And here is a digital copy of the manual that I was referencing, featuring all the parts used and instructions with troubleshooting steps: https://elektrotanya.com/heathkit_gca-1195-1_chimes_for_gc-1195-1187_clocks_sm.pdf/download.html

At this point, I am very stumped. I'm hoping I can find some other GC-1195/1197 owners here that could have an idea of what's wrong. Thank you for your help in advance!
 

bertus

Moderator
Nov 8, 2019
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Messages
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Hello,

On the chimes board there is a potmeter (R324) to adjust the frequency of the chimes:
GCA-1195_frequency generation.png
Here you can find the potmeter on the board:
GCA1195-1B_reduced.jpg
I have also added a PDF with the full schematic of the chimes.

More heathkit manuals and schematics can be found here:
https://www.vintage-radio.info/heathkit/

Bertus
 

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  • Heathkit GCA-1195-1 Electronic Clock Chimes Schematic.pdf
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snappyapple632

Oct 21, 2021
3
Joined
Oct 21, 2021
Messages
3
Hello,

On the chimes board there is a potmeter (R324) to adjust the frequency of the chimes:
View attachment 53187
Here you can find the potmeter on the board:
View attachment 53188
I have also added a PDF with the full schematic of the chimes.

More heathkit manuals and schematics can be found here:
https://www.vintage-radio.info/heathkit/

Bertus
Hi,
I have already tried setting the pitch at the highest setting, the recording I provided was also with it set at max. Thanks for the schematics, I'll take a look when I get the chance.
 

73's de Edd

Aug 21, 2015
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3,658
HEY ! . . . . .Appy Snapple . . . and with you being the 632nd of same . . . .

After listening to that . . . . .
WHAT ? . . .I say WHAT do the power supply outputs of the units look like . . . .ripple wise.
By the sound produced by the unit, one would think that one or more of the systems PS sections is putting out pure unadulterated PULSATING DC instead of a PURE-PURE-PURE DC supply voltage.
Thus relating to having a SEVERE decline in the units filter capacitors effectiveness , since that units original 1976 build date.
Confirm by either using a scope for observation of the DC power rails . . . . . OR . . . . . if U no havee scoppee ? or expertise.
Utilize a DVM, placed in its in its AC voltage function and have the + probe connected into 1 lead of a ***** 1 ufd or so PAPER / POLY cap***** (NOT electrolytic) and probe with that caps free end lead.
Then scale down ranges to the most readable one . . . . . if that meter is not being auto ranging.

***** BECAUSE some DVM's can act REAL squirrelly on their readings when having a DC component additionally being present / riding with the normally expected AC voltage input.

I'm expecting AC ripple in the millivolts decades . . . . . .but, if you're finding multi volts instead . . . .! ! ! !
You can bridge across a cap with a like value, if wanting for a quick evaluation. Then discharge it before moving on to make another test.

After ve done bin gettink der chimes soundink guuds, den ve be lookink at der chimes timing . . . .

Thaaaaaaaaassit . . . . .

73's de Edd . . . . .

Now, I don't mean to brag, but I just finished my 14-day supply of diet food, in 3 hours and 20 minutes. . . . . flat !

.
 
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