Pioneer SX 750 Repair & Restore - Part 1 

Dear Tony. For me, a wannabe audio electronics guy and a knowledge thirst person your channel is a gold mine. Your way of explaining things is second to none. There are quite a number of these types of channels dedicated to audio gear repair and restoration but your teaching and detail orientated approach is amazing. Thank you very much for all kind words and time invested in shooting these videos as well as for your willingness of sharing invaluable information. Keep this channel running! Thank you!

I inherited my father-in-law's SX 750. I brought it home and enjoyed it until the crackle in the pots worsened and the lighting would flicker and it made a sizzle noise. It sat dormant for a year or two. With a burst of confidence from this video, I opened it up and did a quick cleaning of the pots. Problem solved. It is now playing flawlessly. I am sure I speak for myself and others when I say THANK YOU for taking the time to post an informative and helpful video.

Awesome video. But, please never say "why did I waste your time..." Those details and long winded break downs and explanations are as important as the schematics themselves. The details make the difference and prove to me that you know what you're talking about. Thanks for the video. I might send you my SX-750 to get repaired. :)

Best repair video of vintage receiver on youtube. Thanks

You are an Excellent teacher, very well done!

You are the best teacher in the world !!! Thanks for your work !!

Wow. To find a repair tech that is as thorough as you would be amazing. Thank you for this video. I have this receiver from my grandparents. I spent years growing up laying in front of this watching the needles bounce and tuning between stations. Beautiful amber glow and velvet sounds filling my imagination. I salvaged it and it needs to be serviced but if I cannot find anyone to do this I will attempt myself. I work on basic electronics and am a A/C tech so will need to research but THANK YOU for this walk through on a beautiful machine.

Great video, few comments - Almost 3 hours !, with some preparation could be condensed into an hour or so..... - As other suggest, thermally coupling the 2 new transistors a good idea. - Why change out the transistor pair on the good working channel ? - I would do more left / right comparisons to more quickly trouble shoot the bad side. - No rectification of the US 60Hz supply would result in 60Hz flicker - right ? - Nice idea to sand the straw hat LEDs for a more diffused output. - I have seen Pioneer display lamps replaced with blue LEDs - very nice. - Looks like the current limiting resistor was missed in the PCB layout - a simple quick proto board would have been adequate, and 100 Ohms better, as 10 Ohms is providing almost no current limiting - shortening the LEDs life expectancy. - The rectification and then reservoir coupling of the LED supply does provide a nice soft start effect. - You can get unobtanium devices from the ubiquitous semiconductor company, San Jose I think.... - a joke ! nice job.

Compliments for the effort and explanations. Keep up the very good works and keep those great machines up and running forever!

Your videos are amazing, thank you for the great work and clear explanations!

Hi! Very nice and helpfull vídeo. Thanks a Lot for that. I'm in Rio de Janeiro, Brazil and just trying to reform my Sx750 that has problems on FM. I was just looking for a clarification on this problem and your video saved me! Thanks a Lot for that. Nice work!

Great video, you really do put an incredible amount of effort into these and it is much appreciated. I'd be interested to see a video discussing power supply design, showing, for example, how you go about selecting and sizing a power transformer, appropriate filter capacitors etc.

You have the credentials of a great teacher Tony, I just today picked up my own sx750 haven’t accessed anything on it yet , thanks for the heads up on this unit

Very awesome video. For someone that has a hobbyist level of electronics and to be able to watch somebody go through schematics and explain things very nicely and detailed is awesome. I like how you went and detail through the schematic to troubleshoot the issue. Also, very cool to see you make the rectifier circuit. Keep up the great vids man, you have a new subscriber :-)

WOW! What a battle! Quite a bit of a challenge for sure. Difficult to find parts, uncooperative protection circuit, multiple problems scattered through the amp, tuner, power supply. I wish I'd taken some notes on the times here and there. And next you'll have to use equipment on hand instead of what Pioneer recommends. This is a great sharing of how it's done! Thanks X-Ray! Can't wait to see part two.

Wow A to Z Receiver 101 talk about instructional very cool ! I have this exact receiver that needs a tune up this video is going to be beyond useful ! Thanks so much for taking the time out to post Bravo Bravo extremely Awsome !

I just want to thank you for taking the time to upload your videos and sharing your wealth of Knowledge. I am an amatuer but have some nice vintage gear which I'd like to restore myself. You explain things simply enough to make sense to us novice people. You are a good man.

Wow !!! You are Very knowledgeable About your subject and a wonderful teacher !

Thank you for doing this series! I am into restoring tube radios, mostly Pre- and just post-war American. I have been getting more and more interested in '60s and '70s Japanese gear. I have an SX-750 that I want to restore. I am not afraid of the mechanical complications but I do not have experience in solid state. I look forward to using your vids as a guide through my own project. I also have a clean Eico ST-70 that I want to go through properly. I will be watching your series on that set, as well. Much like you, I have so many customer projects that I have trouble getting to my own. I recently purchased a couple of Elekit amp kits that I really want to get to but..... Cheers! Michael

Originally, I am just replace the bad cap on my Sansui AU517. After watching this series, I am going to follow Tong's guide to do a complete restoration. Thank you Tony.

Thanks for the memories. At the time these came out I hated all things Pioneer. Although I did make a lot of money working on them. Sansui was my favorite.

I restored a Pioneer SA-7100 some time ago and it's performing great to this day. I have 2 SX-750s. One an American model and one a multi voltage. Both earmarked for a recap etc. i also have an SX-1250 on it's way from the U.S. I love Pioneer stuff.

Tony, Love watching your videos!

You are awesome! Thanks for the great lessons. Thanks!

What a tome of an instruction video. Well done.

Excellent video! Thanks for sharing.

You will notice that volume does not drop off when you switch on speakers B. Great gear!

👍🏻😎Some of my gear is 40 years old now and it still performs like it did when it came out of the box back in 1983. I've kept it cool and clean the whole way and it all still looks like new as well. I'm not changing anything until I have to. It aint broke, so no need to fix it yet. I'll cross that bridge when necessary.

Wonderful video!

Thank you for the many informative videos and sharing invaluable knowledge and experience. Sometimes we don't realize how much time and work it takes to put these together. Perhaps it be an idea to splice a series together on a couple of cd's and post for sale ? You'll have a sale right here !!!

Gold dust! Many thanks from a newbie.

Amazing video...came here as i scored the same amp....the heat sink on one channel is hot, but i probably should adjust the idle current......thanks , i learned a lot...

Awesome video Tony as always :) I have the same amp and im looking for the power switch cause mine is toast ….cant seem to find one anywhere . anyways keep them coming . thank you

very informative . thank you .

Boy, you’re not joking about audio manufacturers have more priority of making the best then, over making it more profitable now. Glad you mention the lack of need of replacing main filters. It’s a waste. If it ain’t broke….

They used to make S-shaped heatsinks that just slid down on a transistor pair using heatsink compound. It would be very easy to fabricate using a strip of aluminum, a drill bit and pliers.

most excellent. thanks

I have the same receiver and bought it new in the 70s !

OK I stand corrected thanks.

Love watching your videos. By the way, I just did a refurb on a Pioneer SX-650. I purchased replacement 2SA798's through eBay as well. Not sure who you bought from but I purchased through Dalbanicorp and the transistors just dropped right in. No issues whatsoever. Just thought I would share that with you.

Definitely not wasting my time...measuring those main filter caps very interesting...im curious about if you did have to change the big caps in some amps like the one im about to do something with , for aesthetics im wondering if i can get two that 50v 15000uf that are the same size as the originals ?

Very nice! As a novice getting into the hobby your videos are very informative. Some of the most detailed videos out there. As you are using parts, like the poly caps, can you tell us what they are? Thanks!!!

thanks for your videos! i just reclaimed a pioneer sx 6000 after decades of estrangement. it's an awesome little system from long ago and it still sounds great except for one problem... the left channel doesn't work on any of the speaker selections. ... I tested the ground to the spkr output and its grounded so im sure its along the hot side. would you be willing to guide me a bit in order to get this dinosaur sining in full concert again? thank you for your consideration.

When I was a kid I had one of those. Unfortunately being a kid we disassembled it using using a high air pressure sub millisecond total disassembling technique.Quite loud and quite a waste. We thought it was junk because modern (year 2000's) pioneer was/is junk. I have since learned that some old electronics are much better then today's. Although I currently use a modern Mirantz. They still only produce 50 watts, really all you need.

Nice LED retrofit .. BTW, You get V drop thru the diode bridge .. needing less drop resistance ...

Ya gotta listen to all these videos to totally understand and learn. I thought I would need to spend a lot of money to troubleshoot electronics. But $20 bucks for light bulb test I can do.thanks

On the two transistors that you installed in place of the single part, could you possibly use some mechanical connection between the cases to tie them together thermally ? maybe just epoxy them together ?

I just found your CH. You are amazing. Great teacher. Thanks. Where abouts are you located and are you taking in any more work?

Hi, I would suggest you take out transistors with black leads and clean by droping in some tarnoff to clean them, it gets off the masterious wiskers that grow between the transistor at the base of the transistor, causing noise and instablity, As for the matched pair you can glue them together with super glue, but Id clean and test the old one.

Tony you cover it well, how do figure out the table shooting and what's wrong?

Great videos Tony. I have a SX-750 and want to replace the Power Supply's two large electrolytics. I cannot find any recommended replacements listed anywhere. Do you have a suggestion for source and part number for these?

Its good to see an into the nitty-gritty details vid, thanks! Might I offer something to consider with the bc117's, I would suggest to tie them together. I have used copper or alu strips or blocks to build custom and relatively high mass heat-sink for discrete mirrors. These metal cans are excellent because of high heat conductivity. Just by taking a small block of alu and drilling in the right holes to sit the cans into with thermal compound and thereby having these thermally tied (mind if isolation is req'd). Thermal is critical for this application, especially for discrete matching even if the betas appear identical at first. Also, did you use a curve tracer or smu's to trace these betas? Just using a single beta reading from that atlas tester won't really qualify as matching, unfortunately. I'm often measuring a difference in the 10's of dB of THD when cutting corners during matching. Would be interested in observing this matching process, this is, lets just call it an interesting topic for yours truly at the moment. Regards.

You may want to heat sink the two transistor together to help keep the temp constant between the pairs

Just found you! Really appreciate your work & expert amazing knowledge of my favorite Vintage Audio! I'm looking to buy a true Hi-Fi Stereo System just like the ones I listened to in the 1960s and '70s when I was growing up.... Can you please reach out to me so that I can contact you to make a purchase? Love what you're doing with the Pioneers! I grew up with those and they are phenomenal! Exceptional! You really know what you're talking about and you seem very trustworthy. In My World...... Analog = Integrity. Thank you so much! Please let me know how I can communicate with you. Looking forward to warming all of my Nostalgic Good Senses and my yearning Heart & Soul, with my Lifetime Collection (since the age of 4) of 400 Vinyl Masterpiece Gems! Thank you, Sir!! May GOD Bless You.

learned a lot, thanks, prepping to restore my sx 650, this helped a lot, tons of detail, shopping for an inexpensive esr meter too. Where did you source your schematics ? I have the pdf service manual, but the drawings are cut up, a paper version would be nice

Was wondering whether they put the package together haphazardly or honest mistake. Thank you for reply. Hope all is well. Miss your videos though the ones you have out already is terrific to watch over and over again.

Hi and thanks for your great reviews...on my speaker crossovers I have 2, 20uf x 100wv that someone added a Wima 1.0uf next to, that was not originally on the crossover...do techs do this for a performance boost - equating in better sound from the speakers?

I have one of these and the sound started to cut on left or right speaker... It belonged to my Gran so I hope I can save it!

Hi! I have a question about that blue electrolytic cap in the video. I am in the beginning stages of a Pioneer restoration right now. Its an SX535 and it seems like my output power transistors went towards the light and they are not coming back. I have replacements but iv been reading that those blue caps have a real tendency to go resistor on you. Also the 2sa726 and 2sa725 are said to often go bad so I got some replacements for those as well just in case. I am planing a total recap on my project and my plan was to get it going first and then do the recap. My problem seems to be that I don't want to damage the replacement transistors or any other component in the process. Any thoughts on this will be much appreciated. Realy nice video by the way. Thanks fore charing and taking the time to do this (I know how much time it takes to make a nice video.) PS If anybody else have any thoughts on this feel free to give me some advice.

@ xraytonyb: at about 11:23, don't you mean to say 60Hz - not 50Hz. Japan where I live, common supply is 100VAC at either 50 or 60Hz depending on region. I have an old American tube preamp here that was designed to run on 60Hz only. Because I live in a 50Hz region, I have the power supply not only on a step-down transformer, but also run a large fan to keep the the prepamp's power supply from overheating. All domestic appliances are designed to run on both frequencies. I enjoy all of your presentations.

Hi Tony. Did you ever check the gain on the A798 dual transistors to see if they were matched. Perhaps a manufacture error or someone producing these replacements to satisfy customer demand but missing these finer details. Also in replacing with the four new transistors, could you tie the pair together with epoxy to prevent temperature drift. Love your videos and patience in explanation. Brings me back to electronics 101

I have a question regarding the LCR meter, sorry if it's a trivial one but won't one of those huge capacitors behave different under full load? What i mean is if there is, by any chance, the possibility that the capacitor passes the LCR meter check but behaves improperly under stress or amp load.

What do you suggest when restoring the chassis. I have a Pioneer SX780. There are some minor scratches on the brushed aluminum.

Have you ever done a 650? I believe it was 35 watts per channel. Good sound.

Damn Ray...I have A 650 I wanted you to Work on.......Sheesh!

I wasn't going to comment, since I saw this was from December 27, 2016. But then I saw that people are still commenting, so I thought I would offer my first comment/question for you. Btw, I do love your style, speaking to comments to comments you've made more recently; as far as I'm concerned, don't change a thing! I very much enjoy your videos, and besides, as you say, your play time. The question: Regarding the "double" transistors that were originally in one package (but had the extra PCB hole), did you ever think it would have been advantageous to "thermally couple" the two replacements with a common heatsink? It would have been slightly harder with the TO-3s from your X-ray work, but I remember you mentioning the merits of matched transistors sharing thermal variations.

Tony, can you explain the type of connection on the 8657a (N-type?) and is the 300ohm balun a standard 75-300ohm type?

for the dual transistor package what about 2 singles transistors that you gang together in a custom alum heat sink wrapped around both transistors rather than 7 bucks each, also sometimes they are fakes and have wrong polarity pinouts also

It is based on a cheap parts that they put into the Pioneer receiver amplifier section Sansui makes better parts

i have the sx-750 receiver I'm going to have it recapped i want to have it all recapped like you do in this video how many caps are there if i get it all recapped i just want to make sure guy I'm have doing it does it all and how much should a recapping and cleaning cost just a price range could someone please answer my question thank you

Hi Tony , great job on this receiver:)) I’m currently looking for the power switch for this receiver 😳 if you could steer me in the right direction I’d appreciate it :) anyways keep the videos coming ! Thank you

I've got a Pioneer SX636 receiver that is giving me problems. I turn it on and i get static pop-ing noise and the volume isn't turn up at all. I have taken it apart and cleaned it thoroughly and still the same thing.

Do you suppose that the 6 holes in the transistor sockets were used early on in the production of this amp? Maybe Pioneer originally used two separate transistors, changed the design and decided not to do anything different with their printed circuit boards for cost reasons.

I often feel that some of the new caps will never have the same service life as the old ones did. Not talking capacitor plaque of the 90's and early 2000's of course. The old caps from the 70's and 80's perhaps early 90's just worked well. I've also ran into a couple cases where lower ESR actually causes some circuits to no longer function. Old switch mode supplies tend to fall into this category. Poor design if you ask me, but none the less a problem.

Looks quite similar to a realistic brand receiver.

I know you know this, but the USA line frequency is 60Hz. You said 50Hz more than once. You got the rectified frequency right with 120Hz, but in Europe it would be 100Hz full wave rectified. You're forgiven :D

Ah, the pioneer SX-750. First let me get the complaints out of the way. I really liked the blue dial lights of the 30 series (SX-737) much better, but have to admit there's something sexy about the silver face plate. The biggest problem, in my opinion, was with the power switch on a rotary knob with the speakers. The SX-750 had no muting delay (at least I think it doesn't) when powered up, this COULD lead to switching noise. A separate push button or toggle switch would have been better. Speaking of toggles, the front panel toggle switches had a very positive feel (and sound) when flipped on or off, nice touch! Good things about the SX-750? You bet. It offered 50 wpc and in 1977 that was neat. Also had a very good FM front end for a unit in its price range. Two tape monitors and an aux input plus high filter (only 6db/oct but helpful). Two way dubbing was possible, but hey some other 50 watt receivers only had one monitor. Not many had a mic input like the SX-750. Got my SX-750 in 1978 at Crazy Eddie's in NYC. When I added a pair of Ohm Acoustics Model L speakers my Bay Ridge, Brooklyn apartment really came alive, WOW. Enough output to impress if not annoy the neighbors! Don't be fooled by its age, the SX-750 is still a formidable unit. If you don't agree check out the prices on e-bay. Not my main amp anymore, but there's nothing to apologize for with the SX-750. Thanks for letting me rant.

In place of the tantalum can you use bipolar electrolytic?

What awg unwrap tools do I need to work on one of these?

this video is extremely compressed even at 1080p but other then that this was very helpful!

Watch Out! when Tony says “kind of a little bit” ..

Do you repair stereo receivers for anyone or just your own

I always heard tanalum was noisy too.

Question. I have a SX750 that when recently playing, it just died. No warning, no noise, just dead. I have a turntable and eq plugged into the switched and unswitched outlets on unit and they operate just as they should, however the receiver itself will not power on. What part should I be looking at as to being the problem? Thank you.

Enjoyed the video! I'm in the market for a vintage receiver..... you mention about getting rid of a few items, Do you have an online store or can I contact you about for sale items?....cheers

Hello Tony, looking forward to your restoration of the 1050! In the video, when talking about your ESR meter, you mentioned that in the USA, or North America, our mains frequency runs at 50 Hz. I thought our main frequency ran at 60 Hz? I do know that in Europe, they run 50 Hz. Please correct me if I'm wrong sir.

Do you buy many in bulk? I wouldn't i've been burned a few times doing that

Can you help me with a Pioneer SX-750? The audio keeps cutting out and two lamps are out

Hello. I got a kenwood kr4600. Mono only and bad bass control and maybe more. Trying to find someone to make it better.

Ignore the naysayers, personally I wish you still made 3 hour videos 😁

So... In order to provide the LEDs upgrade with enough voltage and avoid potential flickering, you made use of the FULL BRIDGE RECTIFIER!!!

In the untied states there is a 60 cycle current not a 50 cycle thats europe and other places not usa.

The static sound, sounds like is cross between an acetylene torch and a HV arc ...

I love that term "Unobtainium".... NOT !! Hey, I noticed the buldging filter caps on the power supply. Are they ok ?

My SX-750 has a chip on the defuser in the exact same spot. Kind of weird.

I have the sx750. After 20 years, I powered it up. However the sound sometimes cuts out by itself. When I toggle the switches, the sound comes back suggesting maybe loose contact. I tried spraying contact cleaner but it didn’t seem to work. Anybody know where to get replacement toggle switches or suggest a fix?

Radio shack? Thanks to parts express there hasn't been a Radio shack around here in years...

Haven't saw you much on u tube lately do you still make videos ?

the sx-x50 series of receivers were probably the pinnacle of Pioneers consumer line. Excellent sound quality and real world power ratings with fairly low distortion specs. light years better than today's fully integrated, infinitely over sampled, completely digitized, plastic crap.

Straw hat LED.