[Test-Equipment] re: Does my 141T have a terminal illness?

[Chris Trask]

    There's one in particular on the board on the bottom side of the
mainframe.  It's a 47.5K (I think) 1% 1/2W wirewound resistor that's
actually dissipating over 0.6W.  I had one burn out and replaced it with a
47K 5% 1W.  It's been working fine ever since.  I seem to recall that the
symptoms of the failure were similar to what you described.

    I also had one blow out a 68V zener on that board when we had a power
mains surge.  It was harder to find the zener than it was to replace it.

Chris

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----- Original Message -----
From: "Alan Melia" <alan.melia at btinternet.com>
To: <test-equipment at mailman.qth.net>
Sent: Tuesday, July 31, 2007 2:40 AM
Subject: [Test-Equipment] re: Does my 141T have a terminal illness?


> Hi Carl dont panic too quickly  :-))
> The sweep is quite dependent on the correct psu voltages. The 141 frame
has
> a habit of cooking some of the resistors which drift high. You will need a
> 141T manual from one of the several free sites and then before doing
> anything else check and re-adjust the 4 power rails to spec. They must be
> done in the correct order, as in the manual. I suspect the -12v rail as
this
> provides a reference for the schmidt that trips the sweep. I had a similar
> effect on one of my frames which would not sweep below 10ms.
>
> Good Luck with it
> Cheers de Alan G3NYK
>
>
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