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Old 26th Jun 2022, 7:16 pm   #185
Alan Bain
Triode
 
Join Date: Jan 2012
Location: Amersham, Buckinghamshire, UK.
Posts: 24
Default Re: Spectrum Analyser TR4172

Here is the repaired first IF bias board (after and before pictures!). I have to admit that it was tricky. The board material conducts heat away very effectively and the gold layer appears to be pure gold (so no nickel in the alloy) and doesn't wet with solder. I found I had to use a powerful iron to be able to work quickly. The resistive layer underneath does wet with difficulty. I was very reluctant to use anything corrosive to clean the surfaces given the comments in this thread about glue cure by products damaging trace adhesion. New parts deliberately not straight to avoid the damaged trace sections. One trace to decoupling 10n cap replaced by a wire (single strand of 7/0.2 hookup wire).

Afterwards now drawing 13mA instead of 22mA+ and voltages look sane. Time for more analyser testing.
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