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Message

Not getting -5V?

2008-01-13 by Jon

Hi!

I just got myself another broken Poly-800. (The first one I got is now beyond repair. As I was 
offered a second one. I thought: Two minus makes a plus..). But now, after picking the new 
one appart. It seems like the -5V circuit is broken. I've replaced Q18. But the only reading i 
get is +0.9V where it should be -5V.

Could it be that small transformer that's busted? (KD-4? xD-4? It's hard to read the name on 
the schematics. And it says T1 on the circuitboard). The output of it is +0.45V (Measured at 
leg 1 of D10), I asume it shoudl be -2.50V instead?

Any ideas on how to replace it?

The long way, I guess, is to replace the entire circuit with a AC-DC converter that takes 9VAC 
in and with a 7805 and a 7905 regulates it.. But it seems like to much trouble right now.. Or?

Thanks!

//Jon

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