TEK 475: Dead on Start Up.


Redguuz
 

Hello Specialists,

Maybe you could give me some advice how to "debug" my broken TEK 475.

It had worked the hour before and I switched it off.
Realized that I might need it later, I repowered it again, but the Fan started and stopped immediately and the graticule lighting was off. No trace.

I have the ARTEK manuals and the Repair manuals of the US Military. (I have not opened the scope yet).
I concluded that at least the +15V Power Supply has failed but I understand (from the SM manual P172/240), that there is a "hierachy" of power supplies and that, if a PS "higher" in the hierarchy fails, it will influence the lower ones.
Apparently to protect circuits from unbalanced voltages. (is this correct?).

Questions;
1) I understand that I should start with checking the +50V (UNREG) and then 50V (REG)\, next the+ 110V, +15V, and then +5V, -8V and finally -15V.

Is this correct?.

3) Are the composed PS Buffer electrolytic capacitors still available as New Old Stock?
4) I understand that TEK used a way too low margin in Voltage rating for the Tantum capacitors on power rails.
- Are there any which particularly have a bad reputation and should ALWAYS be replaced?.
or
5) Should I eventually replace ALL those tantalum caps on the various power rails with 105 deg. C electrolytic capacitors?
- or are there "solid aluminum" alternatives to the tantalums used in that era (mid 1970's - mid 1980 's ?

Appreciate your advice, before I will be embarking on a repair attempt.

NB.
I have a HAMEG HM-605 (60 MHz) which I had to repair (broken Bridge rectifier (1 diode interrupted) in a -12V supply rail) , before I could trying to repair the TEK.
The HAMEG suits me well, but the TEK 475 has a much higher bandwidth (200 MHz).

So I like to resurrect the TEK 475.

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