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Fisher 600 silver mica disease possibly?

gadget73

gadget73

junk junkie
Subscriber
Pretty sure I know the answer to this already but I'm hoping someone is going to tell me what I want to hear instead

Hauled the TA-600 to work for reasons. For the past week its been absolutely fine. This morning suddenly the FM signal dropped to nothing and it would randomly pop in and out, sometimes at full strength, sometimes weakly. The eye tube goes full open when the station drops out. No amount of tube wiggling, cable fiddling, or chassis tapping would reliably reproduce the issue.

Is this one of the types that are prone to SM issues? These transformers are 119 EIA code, Automatic Manufacturing Division of General Instrument. They look like the ones I'm familiar with that have this problem.
 
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Since you want to hear what you want to hear, couldn't it just be bad tube. In case you hadn't noticed, they do fail every now and then. Also, could the oscillator be dropping out?
 
possible the oscillator is dropping but sometimes the station kicks back in weakly, sometimes at full strength. Its happening across the band too, when I've had oscillator problems it would drop above or below a certain point but not cut in and out at random anywhere on the band. When it drops it drops totally dead, no hiss from the IF stage.

Could be a tube going whacky too, I couldn't even tell you where most of these came from. Probably either in it when I got it, or from the parts donor that came with it. Certainly all old/used and I don't specifically remember even testing them. Entirely possible I decided it was working so the tube tester's opinion didn't matter any. I've had this thing for years, it hasn't been in climate controlled storage and has never been used regularly during my ownership so a problem developing after running 8+ hours a day for a week or so isn't too surprising.

I can see if I've got spares and try swapping them tomorrow.

I guess if it is a bum transformer I have an excuse to put in that wide band detector i've had sitting around for years to give me better FM stereo performance with the decoder. I'll have to align it anyway.
 
Pretty much what I figured. Was really sort of hoping to hear that these transformers were not prone to it and it was more likely a bad cable from the antenna. A guy can hope ya know?

Annoying, the Fisher went to work because the Allied 495 / Pioneer SX1500td that normally does work stereo duty hasn't been working well, and I wasn't sure if it was the antenna or the tuner. Hooked the Fisher up and it was pulling in stations well until this morning when it cut out. Almost afraid to see if my Sherwood S-7000 still works, I don't need yet another thing in the repair queue but its the only other receiver I own.
 
and it ran all day today with no issues whatsoever. Now I'm back to wondering if it was the rain Monday night causing problems with the antenna cable, the humidity making the transformers act up, or some other random glitch.

I replaced the antenna about a year ago because it was falling apart but left the cable. That cable has been outside close to 20 years, so its entirely possible its not awesome.
 
No worries, we've got a nice Rubber apartment reserved for ya, and it floats too! :naughty: :naughty: :naughty:
 
well its been fine since I posted about it acting funny, so if all it takes to "fix" it is to ask a question on the internet I'm fine with it.

I guess this is the vintage electronics version of taking the car to the mechanic and suddenly that noise goes away.
 
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