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

[jeremy-ca]

Both fuses on the 6552B IF section are blown, they are for -10 and -12.6V. 
Replacing them gave the same results. The small power transistors next to 
them test OK. Thats as far as Ive got so far.

Im getting nowhere trying to dl a manual from BAMA or the edebris mirror. 
All dl's come up with 0 bytes. This happens on 2 different PC's

Any ideas before I dig in and make it worse?

Carl
KM1H

----- Original Message ----- 
From: "Chris Trask" <christrask at earthlink.net>
To: "Alan Melia" <alan.melia at btinternet.com>; 
<test-equipment at mailman.qth.net>
Sent: Tuesday, July 31, 2007 9:02 AM
Subject: Re: [Test-Equipment] re: Does my 141T have a terminal illness?


>    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
>
>     ,----------------------.       High Performance Mixers and
>    /    What's all this     \    Amplifiers for RF Communications
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>   \  _______,--------------'           Chris Trask / N7ZWY
>  _ |/                                  Principal Engineer
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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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>>
>
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