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9090 Lamps Dim After Warm Up

JJCalvillo

JJCalvillo

AK Subscriber
Subscriber
Have a buddy's 9090 working fine minus one quirk I'm trying to reproduce. He says after spinning a few records the dial lamps dim.

So far I've tried listening to FM figuring the lights would eventually dim, but they didn't. So I'll try a few records next.

Thinking this is a light circuit problem, probably a transistor starting to fail when it gets warm, but haven't looked at the schematic yet.

Anyone see something like this before?
 
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I know the lamps will dim if that selector switch isn't clean? I had one switch that took a quarter of the can of Deoxit until the lights all slowly started to come back after vigorously rotating the knob.They were completely out mind you..
 
Don't think it's the solder joints, when he got this I went through it for him. Have to look through my notes but I'm sure I put in LEDs and reflowed the joints. Made the connection switch so the dial stays lit.

I'll DeOx the switch once I get it to dim, while checking the voltage.
 
Look the switch contacts over good.
I had one switch where the contact that supplies the 6.5VAC to the disc that distributes it to the various functions had come away from the disc.

IMG_20220818_153941629.jpg
 
@kwayde thanks for posting the photo. You posted this for me when I was working on another 9090 and couldn't get the lights to work. It turned out someone had taken the switch apart and not bothered to put two of the five rotating discs back in. Ended up finding a modern switch designed by a guy in FL on the auction site.

The lights work and it takes a good amount of play before they dim (haven't gotten it to do so yet), so it seems like something is getting warm and fritzing out. Isn't actually on the bench yet.
 
JJCalvillo said:
@kwayde thanks for posting the photo. You posted this for me when I was working on another 9090 and couldn't get the lights to work. It turned out someone had taken the switch apart and not bothered to put two of the five rotating discs back in. Ended up finding a modern switch designed by a guy in FL on the auction site.

The lights work and it takes a good amount of play before they dim (haven't gotten it to do so yet), so it seems like something is getting warm and fritzing out. Isn't actually on the bench yet.
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Things warm up/cool down and expand/contract. Could be the contacts or could be a bad solder joint. I'd go over those lamp solder joints again.

Hoping you don't have something like this going on:

1789992202877.png
 
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