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5000a lighting issues

wmgwizard

wmgwizard

Addicted Member
Just picked up a very clean 5000a and proceeded with the whole clean n tweak procedure.

I was able to find and replace most of the bulbs, but there are two that are giving me fits.

There is one single screw in bulb in the top left corner beside the tuning weight. I believe it is supposed to illuminate the Sansui script on the faceplate.
I have checked the bulb and it's ok. I measured 24.3 volts between the lamp positive post and chassis ground. I tried a jumper from the ground of the lamp to chassis ground and the bulb lit very brightly then settled down to normal brightness within a second. When I did this though I got a loud pop through the speakers and the sound went away. As soon as I removed the jumper the sound came back but the bulb went dark. What gives?

The other bulb is the FM Stereo indicator. The screw in bulb tests ok, I am only measuring 1.3v between the positive post in the socket and chassis ground. The signal is definitely in stereo but the lamp wont light. Any ideas?

Thanks in advance for all of your help

also posted in vintage solid state......
 
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The lamp by the tuner wheel is probably the over load lamp.

The stereo light problem is probably the transistor that drives the lamp.

Edit: Just checked the schematics, which you can get from HiFI Engine, and PL001 is the protector lamp, 25v 90ma.

The stereo lamp is 8v 150ma. Looks like TR408 drives it. The collector goes to ground when a stereo signal is tuned.
It's a place to start.


Rob
 
Last edited:
Thanks Rob.

Since this unit is new to me and I dont have an owners manual is it safe to assume the lamp by the tuning dial is indeed the protection light.
 
Shine a flashlight into the dial from the front to see if you see anything in the dial that my confirm it is the protector lamp. Then try shining it from inside where the lamp is and look at the front to see what it looks like.

I am 95% certain that it IS the protector lamp.

You could pull it out and see if it has the voltage rating on it. 25v. Or the current rating. 90ma.

Do not replace this lamp with a 6.5v lamp, it must be 25v.

Rob
 
IIRC that red dot being the protector lamp. I have a 5000a. Nice receiver and shakes the house. :D
 
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