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SX-780 bass distortion

schmikka

schmikka

AK Member
Subscriber
Hi all - SX-780 fell into my lap and this is the lowdown. Sounds nice, maybe a bit less robust than the last one I ran across, with headphones on no issues at all. But through the speakers I get some distortion just in the bass on the right channel. Fairly thoroughly deoxited. Did not check fuses beyond eyeballing. Any quick ideas? I have no skills at all with a multimeter - if it requires that kind of checking it may just need to go into the shop. Thanks in advance!
 
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Thanks - they appear to be the original Darlingtons. Does my description sound like a problem with one of them?
 
I did pick up some replacement Darlington power packs but thought I'd ask a couple more quick questions before installing them. Do the power packs ever degrade over time, or do they just fail? Also, if there isn't distortion through headphones - only through speakers - would that suggest it could still be a power pack? I have the two NOS replacements and the heat sink compound ready to go, and I even ordered the replacement .22 resistors that I read often fail when the power packs fail. My problem - noted above - is that I still haven't learned how to check readings with a multimeter aside from DC offset. Is there a good video on YouTube someone would recommend?
 
Well it did turn out to be a blown right power pack. I tried a new speaker relay first, but that didn't fix it. After trying a couple of power packs off eBay that proved to be duds, I finally got a genuine article, and the SX-780 is back sounding sweet! I'm pretty proud of myself because this is my first significant soldering aside from speaker crossovers, and it went a long way toward building my confidence for other repairs. This is a great hobby!
 
Sounds like you did particularly well with this repair.

Congratulations and well done :thmbsp:
 
schmikka said:
Well it did turn out to be a blown right power pack. I tried a new speaker relay first, but that didn't fix it. After trying a couple of power packs off eBay that proved to be duds, I finally got a genuine article, and the SX-780 is back sounding sweet! I'm pretty proud of myself because this is my first significant soldering aside from speaker crossovers, and it went a long way toward building my confidence for other repairs. This is a great hobby!
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Where did you get the good Darlington power pack?:scratch2:
 
Bookmarked, might have to grab a pair at that price. Good insurance, and if I never need them, they would probably be easily liquidated via ebay
 
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