[time-nuts] Embarrassing stuff...
Burt I. Weiner
biwa at att.net
Thu May 16 11:11:35 EDT 2013
Since you fessed up I'll tell you my story. About 25 years ago I had
a Singer/Gertsch FM-10CS synthesized signal generator / Service
Monitor, the big rack mounted one that I used as a heterodyne signal
generator, externally reference, as part of my off-air frequency
measurement service. It had developed some hum so I figured it was
probably time to replace the filters. That didn't help. After a
little deeper investigation I discovered that the full wave bridge
rectifier block was cracked and smelled funny, so on to replace
that. Being the responsible type, but young and foolish, I pulled
the plug out of the wall and proceeded to un-mount the power supply
circuit board, which was still connected by a plethora of pendant
wires. Well, when I laid the circuit board over to get to the
rectifier that was just below it, there was this strange sound that
came out of the FM-10CS. Imagine the sound of Godzilla stuffed and
trapped into a sealed beer can and trying to relieve himself of a
little stomach pressure, that's exactly the sound that came out of
the FM-10CS. Well, I had pulled the wrong plug out of the wall,
obviously leaving 120 VAC on the FM-10CS's line cord. When I laid
the circuit board over, I laid it on top of the primary A.C. mains
wires thereby thrusting 120 VAC onto the 5 volt buss. After about a
months hard work, many oaths, 600 or so parts later, I had it working
again. I still have him and he works fine, but the position has been
taken over by some more modern stuffs. I kept all the smithereens in
a cigar box that now resides on my bench, kinda like a shrine, as
reminder. What can I say. I hope you don't feel so embarrassed now.
This MV89 is mounted on a PCB with SMA connectors for the EFC, REF and
10MHz. I connected the EFC from the TB to the REF out of the oscillator,
not for very long, and things haven't been quite right since then.
I should not play in the workshop after drinking wine with dinner!
It'll be interesting to see how Trimble designed the DAC. There doesn't
seem to be much more than a 4V reference, a quad opamp and a bunch of
RCs. I guess that as long as it's monotonic, accuracy is not overly
> Fess up David. Tell the story.
> > David,
> > I'm sure it's nothing compared to what I did many years ago to my
> > Singer FM-10C Synthesizer. You tell us your story and I'll tell you
> > mine. You're among friends. Every time my life flashes before my
> > eyes it's mostly embarrassing stuff.
> > Burt, K6OQK
> >> From: David Hooke <dhooke-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org>
> >> Subject: Re: [time-nuts] three cornered comparison tools
> >> Hi All,
> >> I've managed to blow up the DAC output on my TBOLT; it now has about
> >> 0.5V 42kHz ripple on it. I think I know how I did this, but it's too
> >> embarrassing to share in public.
Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
biwa at att.net
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