[time-nuts] GC-1000 Clock Cap Choice?

Bill Hawkins bill at iaxs.net
Mon Jan 17 04:46:49 UTC 2011

Thanks, I needed that (wiping off the cold water [I hope] from the
deluge delivered).

Indeed, there is nothing special about 60 Hz (even though Hertz
never resonated anything at 60 cycles per second) filter capacitors.

There is nothing special about 100 and 1000 cps PLLs either. A good
plastic cap should be fine. I'd be more worried about the resistors,
unless the PLL caps were electrolytics. The output filters should be
low pass, which are not particularly critical.

Disclaimer: I don't have a GC-1000 manual or schematic. Most of this
is based on the outcome of shotgunning the caps in an R-390 class
receiver. Brooke's tables of marked versus measured capacities sure
do indicate the need for replacement, but not with anything exotic.

Bill Hawkins

P.S. You don't know that he'll be dead in 20 years, but there is a
high probability that he'll be beyond caring. I mean, if an interviewer
asked you what was the most important thing that happened to you during
your life, the one that you would like to live over before you die,
would you name the day you got your GC-1000 working?

Was this a troll? You decide . . .

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of WB6BNQ
Sent: Sunday, January 16, 2011 7:41 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GC-1000 Clock Cap Choice?


WTF !  Just replace them with the same type as was in there.  That will give
another 20 or so years and by then you will be dead and won't give a damn.

The only "critical" (for that time) component would be the TC loop
capacitors for
the 567 PLL's.  They should be silver mica types (good enough tempco for the
567's), but knowing heathkit they might have just used common disk ceramic
(bad for tempco).

All these other people going crazy with all the {RE} engineering crack me
up.  No
thought as to what is really needed to fix the item.  All they truly do is
a given level of noise that exceeds the original expectations of this list.

Well, one other thought . . . . . but I would hate to accuse you of


Brooke Clarke wrote:

> Hi:
> More than half the electrolytic caps in this Heathkit GC-1000 Most
> Accurate Clock are bad and I'm trying to come up with modern replacements.
> http://www.prc68.com/I/HeathkitGC1000.shtml#Rx
> The Tone Decoder board uses a couple of NE567 PLL ICs to capture the 100
> Hz and 1000 Hz WWV tones.  Heathkit used Tantalum caps for the PLL
> output filter.  I'd think something like a low loss electrolytic or
> plastic cap would be better.
> http://www.prc68.com/I/HeathkitGC1000.shtml#TB
> Also how about using Aluminum Organic Polymer caps (where there are
> replacements) instead of the plain electrolytic caps?
> The plan is to replace all the electrolytic and tantalum caps since the
> ones that are now OK may fail in the near future.
> Any thoughts?
> --
> Have Fun,
> Brooke Clarke
> http://www.PRC68.com

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