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Sansui 9090DB FM issues

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degdug

New Member
Hey all,

I just finished a recap of the 9090DB, fixing of the Dolby board, and LED upgrade. All was well until yesterday when FM radio started jumping around. It was working fine for hours previously.

The issue is only present on FM radio. I've tried with antenna and without. No change.

Contacts have been cleaned generously.

Wondering if anybody has experienced this in any receiver.

Thanks!

FM Issues
 
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degdug said:
umping around
Click to expand...

Welcome to AK. It might be helpful if you gave a little more detail about the symptom, perhaps including what you see on the tuning meters.

I know you said FM only, but have you checked AM? If there are also symptoms on AM, then a likely suspect is failing solder joints on the little tuner power supply regulator board that's at the end of the tuner subchassis - the opposite end from the tuning flywheel.
 
chazix said:
Welcome to AK. It might be helpful if you gave a little more detail about the symptom, perhaps including what you see on the tuning meters.

I know you said FM only, but have you checked AM? If there are also symptoms on AM, then a likely suspect is failing solder joints on the little tuner power supply regulator board that's at the end of the tuner subchassis - the opposite end from the tuning flywheel.
Click to expand...
Added deoxit to the tuner shaft and that did the trick! Still need an alignment though. Most of my FM channels are being muted unless I turn FM muting off. Adjusting the trimpot doesn't seem to do much of a difference.
 
degdug said:
Added deoxit to the tuner shaft and that did the trick! Still need an alignment though. Most of my FM channels are being muted unless I turn FM muting off. Adjusting the trimpot doesn't seem to do much of a difference.
Click to expand...
What kind of levels are you seeing on the FM signal strength meter. You could have a weak or failed IF amplifier. A lot of them will still pass a signal even if not working.
 
mrk229 said:
What kind of levels are you seeing on the FM signal strength meter. You could have a weak or failed IF amplifier. A lot of them will still pass a signal even if not working.
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Max I've seen is 4/5 most radio stations that I'm getting sound out of don't even really move the signal meter.
 
degdug said:
Max I've seen is 4/5 most radio stations that I'm getting sound out of don't even really move the signal meter.
Click to expand...
I am assuming you live near several strong stations and are using an antenna of some kind. Does the strong 4/5 signal automatically open up the muting if it is turned on?

Barely moving the meter is a sure sign that something is wrong, question is what? If you look there seem to quite a few 9090DB tuner issue threads. I have fixed several 8080/9090 FM problems.

What trimpot were you adjusting for muting?
 
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The 9090 tuner picks off a portion of the meter signal before the majority of the IF amplification. The orange lines lead to the signal meter circuit.
The blue ovals are the IF amp IC's. You can see the muting signal is picked off (blue lines) after IC01. It also contributes to the signal meter via D3 & D4.

Please don't mess with VR02, we will assume it has not been messed with. VR03 (also blue oval) is the muting sensitivity adjustment.

Does the tuning needle swing back and forth at all?

9090if.jpg
 
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