[time-nuts] Embarrassing stuff...

Burt I. Weiner biwa at att.net
Thu May 16 11:11:35 EDT 2013


David,

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.

Burt, K6OQK


OK.

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
important.

Cheers.

david

 > Fess up David. Tell the story.
 >
 > LOL,
 > Tom


> > 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
www.biwa.cc
K6OQK  



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