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Hi everybody. Just wanted to share something. I recently restored sx780. Well, I thought I did it because when I plugged my TT in I was able to hear nothing but buzzing noise. I totally recaped this unit. Replaced 3 transistors, add 3 heatsinks to these transistors. Installed custom power packs...

Spark, thank you for your help. Transistors from East Point work perfectly. Bias adjusted to 8mv again. Unit sounds amazing. Time to clean up the case, put it together and enjoy it

What's DBT? If that's a dimbulb tester, yes i do have it.

I'll get some. They not expensive. Thanks again for your help

I'll order mica insulators from the same guy. Thermal compound i have. Question, why can't I use the old mica insulators?

Awesome. Thank you

Digikey has MJ21193G. The MJ21194G will be harder to find. Digikey, Mouser , Newark got non in stock. Can you recommend a good place to buy it from?

Looks like only Q614 is bad. Plus the 82 ohm resistor. Is MJ21193G good replacement? Or should I buy a new "original" pair of 2SB541 from eBay?

Hey guys. So i replaced all e caps in power and amp boards. I've tested it and it sounds really good. I adjusted bias. And when i was double checking the voltages, disaster happened. I accidentally touched the MM probe to the radiator while checking the V (Stupid stupid stupid, i know) I saw...

I'll put them up for sale on ebay just to see if there's any interest...

I found 12000uf 63V made by Kemet. 22.5mm lead spacing, dia 35mm. Perfect fit. Little shorter the original ones. 52mm tall. But i think it should be tall enough to be held by the original bracket.

I've read another thread about sa-600. Many people been saying to upgrade the original caps with 12000uf ones with slightly higher voltage. Original 10000uf. Any thoughts on that?

Hey everyone. I'm about to start another project. This time it's Technics SA-500. I have a question about power supply caps. They look original and they tested good. How is it possible for 45 y/o capacitor to be as good as new? The DC offset is a bit to high for my tase. -30mv + 35mv. And...

How do you know so much about sa-300? Did you fix a lot of them? I was looking at the service manual for SA-500. It shows how to adjust bias only. Nothing about DC offset. It would be really nice to install trim pots like i did on sa300. You think it is possible to do?

Yup. You were pretty close. I'm wondering, how come the factory never installed the trim pots instead of the resistors?

210 and 217 ohms

Success. Both R613 and R614 replaced with nice blue trim pots I was able to adjust the DC offset to almost 0V. Ecluser, thank you again for all the informations. I learned a lot here. I just bought another Technics. But this time it's SA-500. Can wait to put in on my bench

Like this one?

Trim pot?

I gotta say that after replacing all e caps (except for the tuner board) and 8 transistors SA-300 sounds sweet. Especially low tones. And it's pretty loud compared to SA-80 And i love the way the green caps looks.

That's what I got. C600s and C700s. I always (4 times so far) get the good stuff. Nichicon. And for audio path i got bi-polal MUSE also by Nichicon

Yes, both are positive

Quick update. Caps and transistors finally came last night. 2SA798 got replaced with matching pair of KSA992 (hFE 432 and 433. Another pair hFE 428 and 429) DC offset changed. It's 95mV on right channel and 105mV on left. But the good news is , that there's no buzzing sound from the speakers...

T That's the plan. I wanted to do it last night but package from didikey never arrived. Hopefully it'll be delivered today.

So i tested some resistors R621 - R634. They all good. Then i removed and tested: Q601 hFE 257 and 357 Q602 hFE 360 and 368 Also i put Q601 back the way it was. I still can barley hear left channel. (Fuse is good) But now the DC offset in left channel is 18mv not 33V like yesterday. Could it be...