Pioneer SX 750 Repair & Restore - Part 1

Hi everyone! I have to admit that the time got away from me on this one! There are a lot of interesting things (I think, anyway) in this video, so I decided to leave it as is. Grab some popcorn (or a five course meal with this length) and follow along if you dare. If some of this stuff is just review for you, feel free to skip ahead! Hopefully, part 2 will be shorter!! This video was perfect when I uploaded it. After KZbin got gone with it, it looks choppy and faded. You never know anymore what it will look like when you upload something!

[@geraldbowling2973]

You are an Excellent teacher, very well done!

[@nenesundog]

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. :)

[@peterhiggins479]

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.

[@Beexzz]

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!

[@lornespry]

@ 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.

[@bennyandersson2437]

Best repair video of vintage receiver on youtube. Thanks

[@erikharrie3477]

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.

[@brianchisnell1548]

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

[@PhutureprimitiveRulz]

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.

[@xraytonyb]

I'll have to check that out. Thanks for the tip! So far , the two transistor solution is working great as well.

[@anthonyrose1391]

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

[@juanpablosoto7357]

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

[@daveb5041]

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.

[@Zestypanda]

Grrrr. How could you?!

[@j.t.cooper2963]

👍🏻😎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.

[@ashleycox432]

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.

[@xraytonyb]

Thanks for the kind words! I'll try to do a video on power supplies later on. That sounds like a good idea!

[@RectifiedMetals]

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….

[@karljarl3010]

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.

[@pflores3186]

I first want to say I really like this video. It talks about and shows more detail than others of this type on KZbin. As to the BC117's, I would first check the electrical conductivity of the case(s). You want to be sure the case is isolated. I never assume anything, I have been surprised to many times. Then I would also look to thermally tie the two cases together. Perhaps with some non-conductive glue or as Karl stated a common heatsink. Something that encapsulates them both and evens out the thermal gradients. That is basically what the originals are, two matched pair of PNP's in the same epoxy case, to get the same Theta JC, (thermal junction to case).

[@kouroshjahanshahi97]

Are you in Minneapolis? What’s the best number to contact you?

[@richardkelsch3640]

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

[@elcheapouno]

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 :-)

[@bretspangler8717]

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 ?

[@cdanielh128]

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.

[@mwilsonojai]

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

[@johnbeckham1483]

The Pioneer SX650 is not the easiest receiver of the vintage era to work on!

[@jimmysjamin1]

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 !

[@reginaldmorton2162]

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

[@jb678901]

Even less. I modified an $8 plastic power strip (which has 4 sockets and a power on/off lighted switch). Opened it up (6 screws) to put the DIM bulb socket (closest to switch) in series with the load (furthest socket from switch). Works like a charm. Requires metal shears to clip the heavier gage socket conductors and a soldering iron to solder the wires to form the series circuit. Took me less than a half hour to do the job.

[@donnyhilliard8177]

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

[@tommybewick]

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

[@rvsteve583]

here in "merika we have 60 hz.

[@taknmybeatings7036]

Kinda what I was thinking...

[@JLinnooxs]

OK I stand corrected thanks.

[@Denvermorgan2000]

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

[@sordello51]

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.

[@sirjammer]

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

[@mangist]

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

[@BlankBrain]

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.

[@MichaelMartin-xb7tc]

I used to date a 4 gang tuner. Now I'm married to one

[@bryansmalley]

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

[@thattubesound2214]

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

[@The.Home.Cinema.Engineer]

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

[@saarike]

Wonderful video!

[@briancampbell7712]

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?

[@florenciomendez5529]

What’s your eBay store

[@ulrichschwenk6164]

ULTRA-LOW-NOISE 🤣 Now it's Ultra-High-Noise!

[@sijumathew9193]

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...

[@corneliosison7787]

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?

[@neilmartins9630]

did you chek the soder joints .

[@erdemkaya5503]

It might also be dirty contacts on the speaker relay. Try tapping the relay area a bit to see if sound cuts in and out.

[@Royalbigness]

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.

[@Royalbigness]

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

[@scottdrake5159]

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.

[@fredfabris7187]

I’ve zip tied 2 together with some thermal compound between. Not pretty but probably better than doing nothing

[@enchantededition6879]

@@fredfabris7187Old comment I know, I think thermal compound is designed for heat sink impurities it probably wouldn’t make much difference on those.

[@nycitalianess7825]

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.

[@Hawkrvo]

I have that model I bought new in 1977. Switch contacts look worn. I hear it’s a poorly designed switch. Too many contacts. I like a plain up down switch but the an and b speaker deal.

[@ZachLauterbach]

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

[@keithnelson5605]

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!!!

[@jlmalta7873]

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!

[@SkitaEkul]

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.

[@26Jorgeb]

Hello, I'm a subscriber.May I know where you are at? Is it possible to have my equipment serviced by you?I hooe you'll accept my request.Thank you so much. Enrique Jorge

[@ralph7585]

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

[@HiFilover168]

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.

[@mikemurphy5336]

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

[@Cavemannspace]

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.

[@lloydparks4974]

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

[@cmj20002]

Straw hat LED.

[@jeffm2787]

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.

[@tmackinator]

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

[@coreyfellows9420]

Why would a sx450 have no back light display . Fuses + Bulbs + No continuity or power to the bulbs.

[@justincase3880]

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

[@thomaselliott4562]

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?

[@whstark]

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.

[@peteschreiber9517]

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

[@MrPageplayer]

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

[@richardkelsch3640]

Those LEDs will fry if left to operate over current. Sure they work now, but they are being over stressed beyond their rated limits and their lives will be greatly reduced. Granted, it's been almost four years now, but I wonder if one has died already. A 10 ohm resistor is not an acceptable substitute for a 68 ohm. 100 ohm is.

[@TY-ob7fz]

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 !!!

[@CofeeAuLait]

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.

[@roymoss9178]

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

[@Gmusic101]

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.

[@Barry7777777]

First thing to check is the internal fuses, the use an ohm meter to check that the main power switch is making contact when turned on. If the fuses and switch are good, measure outputs of the power supply. If power supply is okay, then repair is probably outside the skills of most DIY'ers and the receiver may need to be sent off for repair.

[@flyguy456thetechnicsking3]

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

[@crazytiger630]

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.

[@michaelbussert6375]

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

[@timbolei5482]

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 ?

[@josephsirois2353]

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

[@1stcontact590]

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.

[@williambradfordbaldwin4386]

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

[@bretspangler8717]

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

[@cukedaddy]

You'll have to get lucky to get the schematics he has

[@moustafadadou9260]

Can I contact you i have amplifier pioneer sa508 Noise when operating

[@lloydparks4974]

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

[@splicetape9435]

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

[@julianwest4030]

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.

[@int53185]

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

[@greedo2660]

Excellent video! Thanks for sharing.

[@larryshaver3568]

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

[@jasonthejawman5442]

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

[@justincase3880]

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

[@justincase3880]

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

[@jim...792]

Gold dust! Many thanks from a newbie.

[@IAmSamuelCharpentier]

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!

[@kens7746]

In place of the tantalum can you use bipolar electrolytic?

[@JLinnooxs]

Hi I know this is a old video but I have say your Dim bulb explanations wrong . The bulb and switch are in series not parallel . It should go ac in to the switch then the bulb then out.leave the neutral straight in and out. the switch and bulb are on the hot leg. no ground leg. also use an Isolation transformer on the stereo or DUT. Double check you don't have any ground loops or common grounds between your scope and DUT. Safety FIRST.

[@xraytonyb]

Thank you for the comment. I will try to explain how the explanation is not wrong. First, the switch IS wired in parallel with the bulb. This is to allow the current limiting bulb to be by-passed, in order to allow direct power to the DUT, after it is determined safe to do so. You can also add a switch in series with this, if you want to be able to switch the power off to the DUT, but this can also be achieved by unplugging the device or switching it off at the power switch. As for the isolation transformer, it is not needed on the device in this video, as the power transformer provides the electrical isolation to the device. I think where you got this from is where you watched some videos where someone was working on a transformerless "hot chassis" radio, in which case you need to have the isolation transformer. I have done multiple videos explaining this concept, but in a nutshell, this is how the current limiting bulb is normally used. Thanks for watching!

[@peterb4312]

Ok, we are now looking inside the transistor....

[@Royalbigness]

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.

[@xraytonyb]

Thank you for the kind words!

[@hughesjr1959]

Tony, Love watching your videos!

[@2574mcu]

Looks quite similar to a realistic brand receiver.

[@TY-ob7fz]

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

[@xraytonyb]

Thanks for the comment! The problem with the dual transistor pack was not the fact that they were unmatched, but that the pinout was different, with respect to emitter, collector and base. It is a 5 pin device, so two of the elements are tied together internally. In the original device, I think the emitters are tied together and in the replacement device, the collectors were tied together (or something to that effect, I can't quite remember). Thanks for watching!