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Tuner Transistors how likely could they be the cause of no FM

Ric Harris

Ric Harris

Active Member
I've got no less than 3 receivers that the FM doesn't work on. I've recapped 2 of them and it had no effect. I can't find a short or a cold solder joint and the variable capacitors have no gunk or dust in them and no I didn't spray Deoxit on them LOL! Ones a HK 330 the other is an early 70's Sony the 3rd is a Nikko but it has some reception but poor at best. I just seem to have a knack for finding ones with FM issues.
I'm running of idea's.
 
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First , the best way to act is not to "recap" a unit if it is not working .
Second , doing a "recap" is not doing a repair
third, repair your tuner and then do your "recap" if you think that the sound would be "magic" after that .
Question : do you have noise at the output like "white noise " ?
Check all voltages and if you are not successfull give them to a tech for service, he will have all the necessary tools for that .
 
Biggest single failures I remember are: local oscillator not workin due to tuning cap not clean, or op amp in IF strip died.

Cheers,

David
 
Ric, check to see if you are getting voltage to the FM sections on the 2 dead tuners. Usually the power to the tuner board is switched by the function selector.

A scope is useful here. It will let you know where the signal is being lost if it's not a power issue.

And I have to agree with clinic-audio; recapping is something best done after repair. There's too much chance of introducing new troubles if you don't. Logical troubleshooting is far better than blind parts replacement.
 
tell me what it is first, and do you have the SM?

I have resurrected tuners, but it took work.

and even if the tuner works, there are 2-4 transistors typically that amplify its output to 'line levels' to hit the preamp next. they can go bad but more info is needed.

and while you CAN recap the e-caps on a tuner, many are very small value units (or a local filter) that are there to keep DC off something. they will inhibit performance, not delete it.
 
quaddriver said:
tell me what it is first, and do you have the SM?

I have resurrected tuners, but it took work.

and even if the tuner works, there are 2-4 transistors typically that amplify its output to 'line levels' to hit the preamp next. they can go bad but more info is needed.

and while you CAN recap the e-caps on a tuner, many are very small value units (or a local filter) that are there to keep DC off something. they will inhibit performance, not delete it.
Click to expand...
A SM as in signal meter? I use to be a Direct TV installer but I think I chucked it when I got a Bird Dog. If I found it where would I be checking pre capacitor or post?
 
Ray Gianelli said:
Ric, check to see if you are getting voltage to the FM sections on the 2 dead tuners. Usually the power to the tuner board is switched by the function selector.

A scope is useful here. It will let you know where the signal is being lost if it's not a power issue.

And I have to agree with clinic-audio; recapping is something best done after repair. There's too much chance of introducing new troubles if you don't. Logical troubleshooting is far better than blind parts replacement.
Click to expand...
Yeah I'm not real big on swapping out everything in hopes of hitting the lottery. It never works for me and its time and money wasted. I've learned to recognize amp issues but tuners are a mystery to me. I know a Ham Radio Geek from high school who could figure it out but he's and odd duck and that's my last resort unless I want to drive 80 miles 4 times and pay someone else to figure it out. Problem with that is I don't learn anything that way. .
 
ok I was peeking at the SCM (OM = owners manual, SM = service manual, SCM = schemtatic) - The 330 A, B, C and a few addendum are on hifiengine. google it, join, then you can get many for free.

does you machine have no AM OR FM? or both are out? they use separate boards after the front end, and if you were swapping caps, its unlikely you went in side that....

there are a couple pins for the front end you need to find B+ voltage, and on the FM board a couple for different voltages.

lets see if we cannot make it make noise, the heck with stereo lock for now....
 
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