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Sansui 1000A Problem

K

KMozart

New Member
Hi,

This is my first post here, so excuse me if I make a typo and my English. Been messing with electronics, made bunch of DIY stuff, repaired bunch of gear, (Luck! LOL! ) Re-cappesd and mod-ed some few large recording consoles. I can follow directions very well, but I have no experience with Sansui at all, so decided to ask here first before attacking it and making it worse.

I got my Sansui 1000A of "Evil"buy restored. Sounds amazing for the first 5 min, when left side starts to lose the low end (bass). Swapped preamp tubes, power tubes, it is always the left side. Any suggestion where to start looking?

Thank You!

Kosta
 
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Welcome,,, You can start by comparing voltages from the good channel to teh bad(Left) one... something should be different if it isn't a tube,,,
 
I would suspect the bass control circuitry of the left channel. Maybe the wiper loses contact inside the bass pot or there could be something wrong with one of the capacitors around that pot (the 0.003 uF and the 0.03 uF). What happens to the sound of the left channel when you turn the bass up and down?
 
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I'll start checking the voltages, Thank you for the suggestion.


It is strange that right when I turn it on, works fine for about 5 min, then bass starts fading on the left side. Not sure what happens to the left when I turn the bass up, I'll pay attention to that, but the right one has way too much, when I turn the bass pot up... I'll check the suggested capacitors as well. Thank you!
 
Sounds very much like something is heating up and throwing off the frequency response. Have you checked the output tube biasing?
 
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