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Old 17th Sep 2021, 3:39 pm   #1
mrrstrat
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Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 159
Default Hallicrafters SX-17 Advice on repair.

I was able to snag this set from a guy who bought it new and was the 1 owner. He used it until about 35 or so years ago and stored it rather well - nice set and he has the distinction of being one of the developers of the Cray Computer here is the USA. So this set is doubly cool

I did the normal thing with a nice condition set: careful DeOxit on switches, check and replace tubes, look for evidence of issues.

The crayon capacitors looked particularly bad so I carefully replaced them and weak looking dog bone resistors. I recently completely restored a SX-16 and that set was fantastic so I was hoping the same from this one.

I normally do not have a non-working set from the start in sets in this condition, but on slow power I had a resistor smoke and die. I am very certain my soldering is solid and did each one at a time to prevent confusion - and did so on a few different sittings as to not get 'fatigue restore syndrome' and rush it.

My set is a later model SX17 - evidenced by the 6H6. I do have the original manual and schematic - even still some things to not appear to exactly match from what I have seen inside and the original owner assured me he never worked on it.

I have some pix and circled the resistor in question - I looked at the schematic located the resistor - I believe it is the only 1K the SX17 has and is R39. The place it couples to ground is a coupled 10K/10K and a 25uF/400. I do not seen any evidence of the 10uF and am not absolutely sure where this cluster of parts is in my set. Point-2-point always stimeys me as I like PC board layout with its orderly and easy to follow layout.

I am not sure why with just the 5Z3 (rectifier) in the set this resistor still wants to glow and burn out. Previous trials I had all tubes and would replace the 1K so I could do some measurement of voltage to see what is going on.

Perhaps someone has been down this path? Any assist is most greatly appreciated.
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