FM?

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philipt95

Member (SA)
Hey guys,
I have a simple problem here.
My sharp functions well - radio works, but only on AM +SW1/2.
However, when I switch it onto FM mode, all I get is a constant fuzz sound, and it doesnt tune to any stations. :sad:
If anyone knows what possible reasons to this are, please let me know.
And even better if you could give me a heads up on how to restore the FM. :yes:

Cheers
 
blu_fuz

blu_fuz

Well-Known Member
Staff member
My TRC-935 doesn't have FM eiher :annoyed: .

This should be an easy fix, right guys :w00t: :yes:
 
baddboybill

baddboybill

Boomus Fidelis
Could be a dirty band selector switch :hmmm: But like these guys said not a simple fix when no station at all comes in :thumbsdown:
 
docs

docs

Member (SA)
Some continuity tests and checking of capacitors would be a good place to start.
 
Superduper

Superduper

Moderator
Staff member
Strānj-Bōōmbŏks said:
baddboybill said:
Could be a dirty band selector switch :hmmm: But like these guys said not a simple fix when no station at all comes in :thumbsdown:
Click to expand...
Not. :lol:
Click to expand...

I agree with Stranj. No stations is usually "easier" fix than some stations. Relatively speaking.
Docs: Dead FM issues are seldom related to caps. More than likely, either the RF amp, one of the IF amps or the oscillator or mixer amps has failed.

Anyone notice that the OP never even bothered to identify what model he's talking about. Maybe this is on a Coby. Doesn't matter I guess since all boombox tuners are identical. ;-)
 
docs

docs

Member (SA)
Yeh I do agree SD, just I had a similar issue with just fuzzy noise on the TEC and it was a cap but it more likely be something tougher to solve.
 
Superduper

Superduper

Moderator
Staff member
Just commenting from experience here Docs. Most of the tuner receiving stages makes use of ceramic or polystyrene capacitors which are very reliable. The caps that are failure prone are the electrolytic ones, but those are usually found in the audio circuitry of the tuner and because AM/SW are working, that stage is presumed fine. Not saying that a bad cap is not the cause, just saying that it's probably not the first thing I would look for. Tuner transistors operate in the VHF and UHF range so they do seem to fail more regularly than audio transistors which operate at far lower bandwidths.

My first suspicion in this particular case is the FM RF amp, although like I said, a failure in the oscillator or mixer stages, or the 3rd IF can also cause the issue. The middle stages are shared with AM so although possible, not the first place to consider.

Because no FM usually involves go/no-go type of troubleshooting, it is easier to diagnose.

Generally speaking, when a tuner receives poorly and captures only some stations, the issue could be weakness in any of the stages and could also involve FM alignment issues which is probably the hardest area of FM troubleshooting to understand and correct.
 
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