Hello. I've found a Technics sa-160 receiver/amp in the attic and tried turning it on. It sometimes works a little(distorted audio coming from the speakers), sometimes not really(VERY quiet sound coming). Sometimes when I turn up the volume there's helicopter sound(soi...soi...soi...soi).
When opened up I've immediately noticed a blown cap(actually only it's plates were left in the pcb) so I replaced it with a 1uF 50v cap since I have no idea what cap there was before. Though the problem persisted.
Then I've cleaned the pots, then used a vacuum cleaner inside. Same. Then I let it play some music for like 15 minutes, come back and right in my eyes a cap started smoking and bulged. I immediately turned it off, and replaced that 100 uF 16v cap with 100 uF 50v. Now that cap was near that part on the pcb where it said 15v, but when I measured it I got 35v! Then I measured the part where it said 5v and it was 6.28v(not much of a problem I guess?). Also 1 transistor somewhere near gets burning hot, I can't hold my finger on it for 1 sec. I guess that's because of 35v.
It does same crap even with no input. Same crap with headphones in. I'm pretty sure it's not the speakers, not the input or pots. Also there's no relay click (maybe there's no relay at all?).
Sometimes it amplifies the signal, sometimes it feels like it's sending input straight to the output...Maybe a little weaker...If it amplifies then, there's a pretty loud background hum/buzz. In the beginning there's pretty clean sound coming with background hum/buzz but after a min or 2 it gets distorted more and more and I turn off the amp to not damage it more. I guess some part gets too hot.
HALP? 😕
When opened up I've immediately noticed a blown cap(actually only it's plates were left in the pcb) so I replaced it with a 1uF 50v cap since I have no idea what cap there was before. Though the problem persisted.
Then I've cleaned the pots, then used a vacuum cleaner inside. Same. Then I let it play some music for like 15 minutes, come back and right in my eyes a cap started smoking and bulged. I immediately turned it off, and replaced that 100 uF 16v cap with 100 uF 50v. Now that cap was near that part on the pcb where it said 15v, but when I measured it I got 35v! Then I measured the part where it said 5v and it was 6.28v(not much of a problem I guess?). Also 1 transistor somewhere near gets burning hot, I can't hold my finger on it for 1 sec. I guess that's because of 35v.
It does same crap even with no input. Same crap with headphones in. I'm pretty sure it's not the speakers, not the input or pots. Also there's no relay click (maybe there's no relay at all?).
Sometimes it amplifies the signal, sometimes it feels like it's sending input straight to the output...Maybe a little weaker...If it amplifies then, there's a pretty loud background hum/buzz. In the beginning there's pretty clean sound coming with background hum/buzz but after a min or 2 it gets distorted more and more and I turn off the amp to not damage it more. I guess some part gets too hot.
HALP? 😕
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That doesn't sound good. With +15 V (I assume?) that far over spec, everything supplied by this voltage may well be fried now, including the tuner section and the phono preamp. She may have ended up on the attic for good reason!
Here's the service docs.
First off you must find out why the +15V regulator isn't working properly (with power off). I can only imagine bad solder joints on some of the transistors, a bad ground connection or a dead transistor (you can perform a rough check in-circuit with the diode test function - a transistor contains two back-to-back pn junctions after all and should measure as such when checking B-E or B-C, so if you find either a dead short or no indications for a 600-700 mV forward drop the part is probably toast).
It looks like you may be in over your head with this one. You could still learn a lot though!
Here's the service docs.
First off you must find out why the +15V regulator isn't working properly (with power off). I can only imagine bad solder joints on some of the transistors, a bad ground connection or a dead transistor (you can perform a rough check in-circuit with the diode test function - a transistor contains two back-to-back pn junctions after all and should measure as such when checking B-E or B-C, so if you find either a dead short or no indications for a 600-700 mV forward drop the part is probably toast).
It looks like you may be in over your head with this one. You could still learn a lot though!
Tried to find bad solder joints but everything seemed fine. Then I took out them power transistors (2 2sb1185 and 1 d1762). Checked them with mm resistance test method. 1st 2sb1185 reads around 1350 kohms, 2nd 1300 kohms and d1762 gives 1500 kohms. I have no idea. Also 2 traces on the pcb peeled of a little because of the heat from the soldering iron so I'll have to get a less powerful tool with a proper tip (5mm wide is not easy to handle in such delicate situations)..
Okay, so I've solved high voltage problem, but there's constant white noise in speakers and audio from input to output does not pass through. What to look for?
EDIT: Removed receiver module and now white noise is gone. Audio from input to output does pass through but it's not getting amplified and at higher volume gets distorted.
EDIT: Removed receiver module and now white noise is gone. Audio from input to output does pass through but it's not getting amplified and at higher volume gets distorted.
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My SA 160 just wont power on...im not really good at this..but I'd be jazzed if I actually learned to fix it...the glass fuse x look blown.. but that is all Ive checked.
Failures of those SA-160's are mostly because of solder joints to the SVI amp chip and the two power regulator transistors mounting on the heatsink.
The PC board must be pulled and completely gone over.
Additionally, the interconnects connecting the front panel and main board must be checked and resoldered, as well as any rear panel jacks.
Been there, done that..... many times.
The PC board must be pulled and completely gone over.
Additionally, the interconnects connecting the front panel and main board must be checked and resoldered, as well as any rear panel jacks.
Been there, done that..... many times.