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Sony STR-DE435 repair issues

 
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pelekkk
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PostPosted: Thu Aug 16, 2007 3:24 pm    Post subject: Sony STR-DE435 repair issues Reply with quote

Hi,
my brother damaged this amp by accidentally connecting speaker cables. I already found that MN2488 and MP1640 transistors blown (output, darlingtons) and that one double-resistor (0.22 ohm, 5W) is open. From what a friend told me, preamplifier IC (uPC2581V) can be blown. Is there a way to check if it's any good? I'm not a pro, just know basic of electronics Smile
Cheeers
pelekkk
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Thu Aug 16, 2007 8:49 pm    Post subject: Reply with quote

That rings a bell.... While the UPC may or may not be bad, there is no concrete way of testing other than standard check for shorts between pins. (as a rule, you can use one of the other UPC's from a known good channel to use as sort of reference without having to pull it)

If/when those UPC's are damaged, you'd read a dead short between pins & most of the time they'd crack open.
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pelekkk
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PostPosted: Sun Sep 16, 2007 12:07 am    Post subject: some other issues Reply with quote

OK, so I fixed what I could. There was no shortage between legs in this IC, so I assumed it's good.
I've put everything together, screw all the screws and this is what I've got:
When I plug the power chord, amp turns on (and it should go to sleep mode, wright?), on display there is "ALL CLEAR" and after 2-3 secs everything is on. Seems like amp is working, but none of the buttons in front is working (except for two: power buttun and that knob that has A-B-AB-OFF speaker selection).
What can be wrong? I checked all the connections, all relay are clicking, just those darn buttons...
Cheers!
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Sun Sep 16, 2007 3:07 am    Post subject: Reply with quote

The "all clear" should come up when the unit is being reset! So if you are absolutely sure nothing is left unplugged/etc., then sounds like there may be a system control problem also which means more troubleshooting preferably with a scope. ----just make sure none of the pushbuttons are accidently jammed?
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