Got this for free, previous owner said when he connected speakers on amplifier he heard very loud cracking noises and immediately disconnected it to avoid damaging speakers and he was going to throw it away.
When I opened the case I didn't notice anything visibly burn/bulging.
Then I connected some suicidal speakers and turned on amp. Nothing.
Then played with volume control and heard noises that could be due to dry/dirty potentiometer.
Then connected audio input and retried. Left channel was working but the right channel was dead and when cranking up volume, it would make terrible noises indeed, now I get why previous owner got scared.
I checked every cap and found 1 cap that has gone short circuit (0uF capacitance , 5-15 ohm resistance).
I also found some caps that have started to go high esr.
Caps had date codes of 1982, so I proceeded to preemptively replace most of them including the bad ones, using exclusively good Japanese brands 105c and entry level low esr.
Unfortunately the amp uses the dreaded STK IC Here it is STK2038B (not to be confused with STK2038II , they are totally incompatible!) and the right channel is dead.
Sanyo has stopped producing them since late 90s, so it is nearly impossible to find original ones. I was lucky to find some probably fake Chinese clone. Costed me around 10 euros and when it finally arrived, checked it and found it noticeably lighter than the original broken one
So, I replaced faylty STK with good working one and also cleaned the switches and pots with CRC contact cleaner and the amp is working again!
I attach some pictures that I took during repair, unfortunately I forgot to take an overall photo of the amp before putting back the metal cover.
Here are 2 photos from the internet:
http://nvivo.free.fr/Site/Technics_SU-Z45_files/3_1.jpg
https://www.avsite.gr/forum/proxy.ph...f9819d9d5638a6
I also replaced the 2x 6800uF main caps with 2x 10000uF 50V Nichicon GU 105C
When I opened the case I didn't notice anything visibly burn/bulging.
Then I connected some suicidal speakers and turned on amp. Nothing.
Then played with volume control and heard noises that could be due to dry/dirty potentiometer.
Then connected audio input and retried. Left channel was working but the right channel was dead and when cranking up volume, it would make terrible noises indeed, now I get why previous owner got scared.
I checked every cap and found 1 cap that has gone short circuit (0uF capacitance , 5-15 ohm resistance).
I also found some caps that have started to go high esr.
Caps had date codes of 1982, so I proceeded to preemptively replace most of them including the bad ones, using exclusively good Japanese brands 105c and entry level low esr.
Unfortunately the amp uses the dreaded STK IC Here it is STK2038B (not to be confused with STK2038II , they are totally incompatible!) and the right channel is dead.
Sanyo has stopped producing them since late 90s, so it is nearly impossible to find original ones. I was lucky to find some probably fake Chinese clone. Costed me around 10 euros and when it finally arrived, checked it and found it noticeably lighter than the original broken one

So, I replaced faylty STK with good working one and also cleaned the switches and pots with CRC contact cleaner and the amp is working again!
I attach some pictures that I took during repair, unfortunately I forgot to take an overall photo of the amp before putting back the metal cover.
Here are 2 photos from the internet:
http://nvivo.free.fr/Site/Technics_SU-Z45_files/3_1.jpg
https://www.avsite.gr/forum/proxy.ph...f9819d9d5638a6
I also replaced the 2x 6800uF main caps with 2x 10000uF 50V Nichicon GU 105C
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