Sony STR-DE435 repair issues

[pelekkk]

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
Cheeers
pelekkk

[vtech]

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.

[pelekkk]

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!

[vtech]

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?