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Reference 180r

V

vmedia

Active Member
Hello. I am working on a Reference (by Quadraflex) 180r that is in fantastic cosmetic shape and works just fine except for no FM stereo/no stereo light (the light was blown, I have replaced with an 8V30mv lamp)
I have cleaned the mono/stereo/MPX toggle as well as variable resistors on the FM board - adjusting each back and forth when on a strong station with very little change in signal (if any) and still no stereo. I suspect the LA3350 multiplex ic chip, but since no service manual or schematic are available, I have no way of confirming. I'm happy to track one down and try, but they are a bit rare and take time to receive. I actually pulled one from a parts unit, only to discover that the leg on pin one is broken. Voltage measurement on lamp leads is around 9 vdc - both legs - which never varies regardless of tuning.
Any thoughts would be most appreciated.
 
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Just in case someone else has a similar issue, here's the conclusion to this fix.
Despite my certainty that I had thoroughly cleaned and exercised the variable resistor that effects the FM Stereo/Stereo light circuits in the LA3350ic - VR104 (I traced the connections from pin 6 on the ic) - I tried again, this time using concentrated Deoxit D5 and making sure to get to the back side of the VR.
Sure enough! As soon as I moved the resistor - Stereo from one end of the dial to the other and stereo light blazing!
I've relearned an important lesson - always make sure you REALLY clean things before moving on to replacing components.
 
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