Pioneer SX-1280 Part 3 - Power Amp Boards

[@M-P-X]

Finally someone who understands why you shouldn't replace electrolytic capacitors in the signal path with film caps 👍

[@frankgeeraerts6243]

YES ...I fully agree with you !

[@chaber6419]

Unfortunately my intro into audio repair was Audiokarma and not you Tony. Although after 7 years struggling to understand circuit design you’ve made one thing clear to my brain. Think about those “recommended” capacitor and transistor replacements. How many Wimas and Kemets have I swapped for orange UCCs? A lot. How THD tests post signal transistor change. None. And quite a few refurbed units that sounded not magical afterwards despite looking ok on limited bench testing. Hope my ramble makes some sense. You’re an inspiration Tony. Much love for you being you. Keep it up.

[@ohmbug10]

Yep, there's a lot of good and bad advice on AK. I take the trust but verify approach. The two hardest parts of audio repair is that I'm new to it and parts are hard to come by.

[@jdmccorful]

@@ohmbug10 Ditto!

[@SkyhawkSteve]

It's great when your tools have stories behind them.😊

[@atelier_HiFi]

You make too much sense with your reasoning and explanations of cap replacements. I enjoyed your video.

[@craigm.9070]

Happy New Year Tony & family!

[@nanocamp-audio]

New year, fresh roll of solder.💪

[@PrimeHiFi]

Happy new year, Tony! Happy to see such frequent uploads from you. You and your videos are an incredible source of information for the community and I can’t thank you enough for posting them. Can’t wait to see how the 1280 comes out. Wishing you a happy and healthy 2024!

[@Tron1731]

I think your referencing the sparkling high frequency and yes when capacitors get old the magic sparkling treble goes away ✨️ but now its back

[@bobmulhiemer7564]

Thank you so much Tony! I am very excited to see how you do this beautiful electronic work!

[@TurntableGuy]

There's going to be a lot of members at AK jumping off bridges considering the practice of replacing those orange low-leakage/noise caps with Wima films has been THE thing to do for the last little while. I haven't done it because I'm not paying the outrageous prices for the Wimas.

[@scrappy7571]

I've read over there, that many have removed the wima's and installed 'lytics to get the sound back. The past few amps I've done, did not use wima's and have been happy with the results.

[@g.fortin3228]

Sweet ! I was almost expecting little bigger heatsinks but maybe they don't fit well. Nice job and this beast of a receiver will be roaring again after.

[@FireandFrostHVAC]

I agree with you 100% about replacing electrolytics with electrolytics and not film capacitors, different frequencies pass from different capacitor types. You might be inadvertently creating a high pass filter with different caps.

[@alexw890]

Damn it! I’ve been doing this on the past 7 units I’ve done!

[@FireandFrostHVAC]

@@alexw890I’m not saying it can’t be done and work, I’m saying that I’m not 100% certain that I’m changing the frequency range from one type of capacitor to another, so I’ve always tried to replace electrolytics with electrolytics.

[@Alex.M.S.]

For signal path I found that Nichicon UES series, bi-polar Muse sound absolutely brilliant. They are design to be used like that. Happy New Year!

[@Uraim]

I used loctate glue to hold the transistors together and it worked very well :))) My SA7800 amplifier board became happy again after replacing leaky 2sc2291 & 2sa979 pair :)))

[@aminbjt5843]

Hello Thank you for your interesting and informative videos. It is better to use local feedbacks in power amplifiers. This will reduce the open loop gain of the circuit and when the negative feedback is connected, the circuit will need a smaller compensation capacitor. Also, the task of reducing the distortion will not be given only to the global feedback. In the input differential circuit, to make the transistors more similar, it is better to use the resistance in the emitter of the transistors. (See Douglas Self) ​RE>10re re=25mV/IC

[@scrappy7571]

I recall the Marantz 2285 that Tony chased down a distortion problem. Removed 2 Kemet film caps in the pre amp signal path and some of the distortion was gone.

[@t1d100]

I am very much looking forward to your explanation of the current mirror compensation circuit thingy.

[@alexw890]

Damn I’ve been using tons of film caps in the signal path! Shoot.

[@808v1]

great video - thank you

[@frankgeeraerts6243]

I wound a copper foil and thermal glue on the pair , the foil winded arround....heat shrink to finish and clamp the pair.

[@jeditoto3441]

Hi Tony, could you show on the curve tracer how a noisy transistor looks like? You seem to have a list of usual suspect transistors that you systematically replace - could you share it with the replacements you typically use? and Happy New Year !! and thanks again for all the great videos - I have learned so much from you !

[@zambrano966]

Hola Tony, que raro que no remplazaste el Q10 y Q12 (2SC1904A y 2SA899A), Se que hay un sustituto actual que le va muy bien el KSC3503 y KSA1381 😊

[@brettbarnett9823]

Do you have a list of common problem transistors and what you replace them with? I would like mostly the ones that Pioneer uses if you have something. Thanks!! Also, instead of the plastic washer isolating the heatsinks, could I just use a plastic screw and nut?

[@josephbruggeman8962]

What Pot did you use? I'm working on a SX980 now so the video couldn't have been timed better. Thanks Tony!

[@leearft8605]

Happy New Year Tony! I can't wrap my head around C3 being a polarized rather than non-polar cap in the signal path, could you elaborate on that subject?

[@viol999]

Hi Tony, Happy new year! Been following your channel for a few years now. I'm a noob to this hobby and just picked up a sx-1280 in nice condition. I'd like to do a restoration of it but cannot find any high definition schematics like you have there. I've looked through AudioKarma and hifi engine but cannot find any hi def schematics. can you possibly lead me to a source of hi def schematics for the sx-1280.

[@Calimero-1980]

I got a question for you, I'm having an issue with my SX-1080 left amp, I replace Q2 and Q8 with KSC1845 on both boards, is it required to also replace Q1? or should be ok to keep it original on Q1? Thanks!

[@jedi-mic]

What was the original code for the power transistors q11 q13 ? Happy New Year would they be in the Pioneer SX 650 there's one somebody said I can have it's not working I think they're quite good amps. black gate become a make audio note capacitors I think KT series

[@RickMahoney2013]

How do you test the board before you put it back in the receiver ?

[@SacreDro]

Are SIlmic Elna the best caps for audio amps?

[@frankgeeraerts6243]

Nothing is ever the best .........but when used in the right position of duty >....those Silmic realy do souind smooth and musical, they lack the harshness in the treble ( silky and well defined ) and do have a very nice bass response ....( living bass ....on a track with steam locomotive engines you can hear the engine breathing alive ) They need about one hundred hours run in time to fully letting hear and show their beauty... OUT OFF PRODUCTION today ...

[@jdmccorful]

Good stuff! Lets keep rolling. Thanks for your time and Happy New Year!