Servicing a Pioneer SX-1250 for a Friend

[@xraytonyb]

0:00 Intro 2:39 Initial audio test 3:25 First look inside 4:59 ASMR 6:26 Looking at the underside of the receiver & the soft start circuit 14:05 Servicing the flat & tone amp sections 18:09 Removal, cleaning & testing of the the volume and balance controls 33:43 Cleaning of the lever switches 35:02 Replacement of the 2SA725 transistors on the flat amp board 38:41 Flat amp board service is complete 39:12 Servicing the tone amp board 45:09 Cleaning the pushbutton switches - some helpful tips 52:19 Servicing the stabilizer board (a.k.a. regulated power supply board) 1:08:22 Testing the receiver after servicing the flat amp, tone amp and stabilizer boards 1:10:06 Audio test - still getting some distortion! ( at 1:10:25 you can really hear it) 1:12:01 Servicing the protect board - some tips on the protect relay testing/replacing & care 1:24:39 Some comments about the soft-start relay 1:27:07 Final test & closing comments

[@2packs4sure]

Everybody stand by while I attempt to gaslight Tony into believing we're old friends.....

[@g.fortin3228]

Rewatched for a refresher..and glad I did. It's great to have these videos up, helps save the units from improper maint and keep them alive. Really sweet receiver.

[@jasonneubold7570]

Careful with that thing. It's worth 1.2 million dollars! 🤪 Really enjoy your videos!

[@repairfreak]

Very nice old beast! I just love the quality they built into these older units. I serviced about 25+ years ago what I believe was the SX1980 model “the biggest one.” This thing had so many dials and switches it was amazing. I weeded out a handful of bad transistors and caps. I documented and itemized every part I replaced for the owner. Needless to say the owner was ecstatic to have it fixed. I was very proud with my accomplishment as well. It was a huge amount of work all in all. Now at age 55 I’m not even sure if I would have the level of patience or time to do this kind of in-depth repair again, lol. Thanks for your very nice video, bravo! 😎👍

[@kev-the-windsurfer.]

I had a good one on a SX1250 Stabilizer board, the -65V regualted supply was intermittently going unstable, C4 82pf ceramic cap was intermittently shorting. It took some diagnosing, you'd not normally suspect a ceramic cap doing that. I suspect its the heat in there contributing to that. I put some modern heatsinks on the TO220 pass transistors.... SX1250 is an excellent beast!! Its a big job restoring one, I have done 3 of them now and enjoy the journey every time.

[@unclefrogy743]

like your videos and watching you do all the fiddly stuff which I would have never thought were doable!! a tip I have found for cleaning hands that get real sticky stuff on them that is difficult to remove. Instead of reaching for ever more powerful solvents I use "baby oil". It takes advantage of the structure of the skin it does not dissolve the sticky stuff and just thin it out and allow the solvent to take deeper but helps to lift the dead cells that the stuff is stuck to then plane dish-soap washes off everything. Works on epoxy, paint, grease and should do well on flux. works especially well on concrete without activating the alkali in the cement and "burning" and drying the skin.

[@jeremiahchamberlin4499]

I always learn something from your videos, Tony. Today I learned (1) why my boards always come out gray from wiping down with ‘hydrous’ alcohol, (2) that a little bit of corrosion on a protect relay can cause BIG problems with sound quality, (3) one needs to know how a switch is put together in every detail in order to properly service it [spring detents & step potentiometers], and (3) watch out for painted and/or tarnished leads on transistors. It seems to me that you have made good use of your prior work on these units, you know right where to go to check for problems and do some preventive maintenance (the best kind of maintenance). I wish I shared your love for cleaning the controls; I know it is necessary, but to me it seems like drudgery.

[@robertmatheson9542]

I used to own a Pioneer 1050, the matching cassette deck, the phono, and four large speakers years ago to have a quad stereo system. It was used extensively, and one day years later one of the channels went out on the receiver. I took the receiver in several times and they never could fix it. I was very frustrated at not finding someone who could fix it so I sold the whole system for 100.00 to a friend. He was happy I was upset. Now that I have seen your videos I wish I never have sold and kept it as I now know that it could have been easily repaired. I am looking at replacing the whole system. I originally bought the entire system speakers and all for 1500.00 in 1976 now a rebuilt one is 2000 to 3000 dollars just for the receiver. The inflation is terrible.

[@zulumax1]

I have used an ESR meter to measure the resistance of relay and switch contacts. I have two of them, a Capacitor Wizard that measures to 0.1 ohms, and a MESR-100 that will measure down to 0.001 ohms. Thanks for all the great work on this video, I enjoyed it very much Tony.

[@douglashoff95]

I have one of these which a friend gave me. He upgraded to a surround sound system. He purchased it new from me when I worked at a local tv/stereo shop.

[@unclefrogy743]

without using a micovolt dmm could you find the source of the distortion using something like an oscilloscope or a signal tracer to find bad component or the circuit fault . a side note it pretty hard to hear what equipment sounds like online when it has to go through all of the processing used by youtube it it not as bad a old landline telephone but it ain't like being there either. I appreciate time and effort you put into going into the depth of what is happening and why thanks a lot

[@mikepxg6406]

Excellent video. Thank you Tony for sharing. 👍

[@wedoshotz6645]

Another great video. I always learn something. Thanks Tony.

[@henkefrangbg6156]

Thank you sir for god video! I am a happy owner of a Pioneer sx 1250 Mvh Henry Johansson Göteborg Sweden 🇸🇪🇺🇲🇸🇪

[@xray111xxx]

Wow I love the older SX series receivers. I grew up with them. Later I got to sell them. They were beasts.

[@davet3804]

Thanks for advice on latch spring on push switch.VERY useful.

[@g.fortin3228]

Man this is valuable stuff here ! Tony..Sir! .. you have helped so many of us and we are thankful !! I would have never thought of it being the relay on this, lesson learned not to overlook, and to think about the path.

[@philipslighting8240]

So good. Thanks Tony.

[@ptronix]

A beautiful receiver Tony, wish I still had my pioneer catalogue from that era. I used to drool over things I couldn't afford. Wonder how many thousands that would cost today, if they still made them. I had to make do with the humble sa606 & tx606 tuner. But they were great at the time for me, best wishes nick

[@Digital-Dan]

Great mics! Amazing the bass reaches my ears (from computer speakers) with booming bass.

[@jdmccorful]

Great masterclass on upkeep of audio equipment.

[@excentor]

Love to see you working on Pioneer equipment!!!! come on! I have some stuff to be entertained while I work ;) thank you tony! as usual

[@erikdenhouter]

Well done showing the effect of resistance of contacts in series with the speaker. Generally speaking, when the contacts are at the same rate as the load (8Ω and 8Ω), the power is divided equally, so in this case, at full power the relais contacts will suffer 70 Watts; anyone knows how much heat a 70 Watt bulb generates, but then that will be all concentrated in a tiny piece of metal contact.

[@PracticallyFixed]

Another great video. Thank you making this, it was very informative, entertaining and it was great to see that wonderful receiver working so well. Looking forward to the next part. I need to service my old Sansui 661 someday. (I miss my Cerwin-Vegas)

[@t1d100]

Wow, what amazing experiential knowledge, Tony... To know that the scratchiness was in the relay and not in the audio amp sections. Kudos!

[@fretlessfender]

Well done and well explained! I do like your choices, replace just in case... good job!

[@petefioravanti9371]

Thanks for the video, you published at the perfect time my 1250 started to have issues with the volume control. Followed the steps in the video and the smile on my face couldn’t be bigger. But my hearing is going to suffer.( Please look for a Marantz 300dc do work on)

[@johnnytoobad7785]

Adding a thermal fuse to soft start circuit is a great "enhancement". Most don't have them. For the soft-starts I've built, I use 4*50 ohm 10 watt ceramics and 24 volt Omron relays. This configuration won't get hot that quick and will also drop the voltage enough to distort the sound (or cause the amps to turn-off due to low voltage). So far the two I've built have yet to fail. One is 5+ years old and used almost daily.🤗

[@fretlessfender]

That "black paint" on the transistor legs, is actually oxidation. And that is the cause of the failure! A lot of Akai reel to reel recorders suffer from the same problem!

[@xraytonyb]

Some transistors suffer from oxidation on the leads, which also causes shot noise. In an attempt to prevent this, some of the manufacturers coated the leads with a black paint. You can tell the difference when you look at them closely. The painted ones have a consistent color all the way up the lead and all three leads look identical. The tarnished ones will have a different look on each lead. The tarnish will quite often rub off, at lease partially, with your finger, while the paint will require a fiber scratch brush or acetone to remove it. Also, the painted leads will have the paint stop at the same place on the lead, leaving the last 4 mm or so bare for solder. That said, it still didn't work and the transistors still developed shot noise. Thanks for the comment.

[@bobbyy8711]

WOW!!! I wish you could also give some tender loving care for a resting Sansui QRX-9001, given to me by a friend, thanks a lot Tony. Greetings..

[@scottrothe5947]

Wow, really nice job explaining what you are doing. I have an old Techniques receiver that needs cleaned. Not sure that I trust myself to do what you do. But extremely interesting. It is fun to watch a master do his work!! Awesome! You do honest, good work. That is becoming a lost art!

[@davidwolverton4858]

Technics had some nice receivers. Hopefully Tony will have one on the bench at some point.

[@rottmanthan]

the old stuff is the best, and one of my favorite items are old floor standing speakers.

[@AstrosElectronicsLab]

The size of your capacitor doesn't matter, it's where you stick it that counts!

[@EnriqueSar]

This video is equal to GOLD for many!

[@apollorobb]

Transformer/Cap setup looks really similar to the Sansui G-22000 Amplifier section im doing presently the caps in it are 15Kuf @ 100v dual transformers is the only difference. And i agree with you ive been doing resto and repair work on receivers and Juke Boxes for over 35 years and you are right if it works for you then keep on keepn on

[@MrPatdeeee]

When "Pioneer" first, came out with this awesome Radio/amplifier; I bought it. Then my son brought one of a lower cost. His one, was incredible. Sadly, mine had a problem. It broke my heart. The problem, happen to be in the RF (Radio Frequency) part of the radio. And being an electronic technician; I tried to fix it. But I couldn't, because the part was not to be had. And to hell with Pioneer. So for all these yrs; it just sits on the cabinet. It looks like brand new. For what it's worth. Oh Well.

[@DacMan777]

Great job.

[@somebodyx]

As an aside, regarding track pots channel balance, best way to test is see how sine waves meet up on the scope across turn range. Because tracks may measure different kΩ spot or total but the voltage division might be closer or further.

[@NovaluxStereophonic]

Some quick notes. 1. The back of the volume control usually just comes right off, I find the best way to get cleaner in the front section is by separating slightly near the legs. 2. The tone controls are not switches. They actually have very similar construction to the volume control. I clean them similarly to how you cleaned the balance control to make sure the carbon doesn’t get damaged.

[@NICK-uy3nl]

Putting a contact relay directly on the audio output path is a highly suspect design, a reed relay might have been a better choice for longer life

[@sguttag]

I looked up the relay you used (Omron MY4)...its contact rating seems a bit lite if it is handling the speaker outputs. Into an inductive load it's pretty sketchy. Omron is showing .8A into 220AC and 1.5A into 24VDC (neither of which exactly matches driving a speaker). Even with doubling the contacts, that is going to be less than what the amplifier can output at full rated power. One is very nearly at full contact rating if switching the output while playing a near rated power.

[@davet3804]

I use diamond bits for dremel for opening traces ..not too expensive and work well

[@Tysman909]

Nice Amp. I use to have deoxit but it's to expensive I switched to corrosion x works same way and much larger can and cheaper

[@rossthompson1635]

I've restored a couple of this series at the opposite end of the range, SX450 and 550. The larger ones very rarely if ever seem to come up for sale in the UK, not sure if they ever made it over here. Out of interest, does anyone know why some of the resistors in the output stages are sleeved in fibreglass tubes? (many are in the SX550). They don't run that hot, and if they did it seems odd to put them in something that would limit their ability to radiate heat. Is it for safety purposes - i.e. if the outputs went short, is it to stop or limit flames from the resistors? (I know now you can get flameproof resistors, perhaps not back then?).

[@solomoncohen1861]

Hello. I follow you and watch your programs. I think you are one of the best technicians in US. I have SX1250 which needs some attention. It has a blown power supply fuse. Where are you located and if you know anyone in Los Angeles who can help me with it? Thank you

[@marks.2909]

I have the European twin of the Sx-1250 the Sx-5590 for anyone interested TeKton Lore speakers are a phenomenal match together, beautiful tone , big wide open staging with jaw dropping sub bass slam on orchestral , Rock and especially gaming , just spectacular,,..

[@wizzkidelectronics]

i still havent gotten to refurbishing my sx1280 i have all the parts just never enough time

[@dancorneliu7578]

Can you share the list with all the parts needed for restoration? Thx

[@ronwade2206]

Caps, leaky diodes, good luck finding them all.

[@6StringPassion.]

Any reason not to use a good ultrasonic cleaning machine?

[@TrevorsBench]

Hi Tony, great channel and long time subscriber. I have a question about capacitors. What's you opinion on Tantalum caps used in audio circuits? Do you.... 1) Leave them alone if they present no problems 2) replace them in kind? 3) Replace them with electrolytics or better yet, film? Do you know why these are used in audio gear? It seems during the 70s and 80s manufacturers were using them but later that practice stopped? They seem to be more stable than electrolytics because they use a dry pellet instead of a wet core which can dry out.

[@xraytonyb]

Tantalum caps can short out, especially when they have a lot of voltage across them. It usually happens when they are used as bypass capacitors or in power supplies. I have never really seen ones in the audio path short, however, so I usually leave them alone. If I need to replace them, I will use a low ESR type electrolytic of the same value. For smaller values in audio path applications, you can also use the wima or kemet film caps.

[@sguttag]

Tantalums are good but they REALLY can't take over-voltage conditions...not even for an instant. So, what will often take them out are momentary spikes. The safe way to use them is to ensure that the voltage rating is such that even spikes won't go over. This, often means, using voltage ratings double what is anticipated on the capacitor. So, if you have say a 15V rail...don't use a 25V but a 35V and the shorting/blowing their top problem should go away.

[@TrevorsBench]

@@xraytonyb We're all aware of shorted Tan caps in power supplies but I wanted to know how you handled them from a audio perspective and from what you said I think we're in agreement. I've never seen a shorted Tan cap in audio gear (yet). So, they seem to be holding up after 40+ years without concerns. Thanks for your reply Tony and can't wait for your next video. Cheers

[@TrevorsBench]

@@sguttag Good points and good to know these caps are sensitive to overvoltage

[@Craig_Spurlock]

Ever since I pulled a Tantalum for testing out of my Pioneer SX-450 that shot up to 35 ohm esr, I will at the very least pull ALL Tantalums for testing. This is how I found two dead tantalums that wrecked the performance of the tuner in my buddy's SX-980. If they test okay, I will put them back in.

[@etsojourner]

WHAT BRAND CAPS DO YOU PREFER AND FROM WHERE?

[@jaghifi]

I think you released a video on it but wasnt clear on the answer. But would it be ok or better or worse to use wima film caps in the audio path on the tone board?

[@xraytonyb]

I would try to stick to the original capacitor spec, especially if you like the way it sounded originally. Many folks have reported (and I have experienced this as well) that it will change the sound a bit, if you use film caps. I'm not saying it's better or worse, only that it was an audible difference. Some like it, some don't. That's the best answer I can give.

[@schorse1000]

Now my keyboard shorted from all the drooling...

[@Silent-Lucidity]

Hi sir, it looks like you have the same shaky hands that I have. It really makes it difficult for me to solder and desolder. Am inaccurate in my observation, and if so, how do you control it?

[@diabolicalartificer]

I have the same thing, a glass or two of whiskey helps the shaking but impedes cogent thought after a certain amount.

[@kenmohler4081]

@@diabolicalartificerIt’s a balancing act, that’s for sure. You must practice over and over. You don’t get a lot of work done, but practice is an activity in itself.

[@jutukka]

In that era (and better class) Pioneers for example input selector etc. switches seem to be of quite good quality. In later (and cheaper) mid 80's models the Pioneer amps themselves have been very realiable and good but PCB mounted very small input selector push button switches of those seem to be a total nightmare. Contacts always start to fail to connect and it seems impossible to cure the symptoms using deoxit etc.

[@pioneernut7487]

Pioneer Elite c90a/m90a combo was More expensive than sx 1980. So you are wrong here. Sx 1980 cost in 1978 was 1295 USD which is around 6000 USD in today money. Pioneer Elite c90a m90a separates cost around 2700 USD, which is around 6900 USD in today money. And IMO prices for sx 1980 are ridiculous. I would never pay Such prices for oversized radio

[@jutukka]

@@pioneernut7487 When I mentioned switch quality problems of 80's cheaper Pioneer models, I was talking about MUCH cheaper model categories than those you mentioned.

[@user-cz6zp9em4l]

how would you know if its counterfeit from china??

[@danlivni2097]

This 1250 receiver was built

[@fretlessfender]

49:20 black transistor leads alert!

[@MrMersh-ts7jl]

Easy now. They do indeed have transistors with black paint. You're correct that not all do and it is indeed oxidation.

[@In-Full-Swing-Combo]

Hello! I watch all your videos. From your presentations, capacitor replacement appears to be very important. I find that Aliexpress has the best prices on for bulk capacitor purchases. What I need to know: what manufacturer brand name is best to order for re-cap repairs? Thanks so much for helping us all!

[@avassos7571]

How much is a service like this worth?

[@EnriqueSar]

$800 to $1200, now the way this guy is doing it, $1200 easily

[@Brian-mp6bg]

I bet the reside from the spray isn't good for the long term life of the board, either.

[@Digital-Dan]

No way the receiver could damage ears as effectively as a pit orchestra from inside a covered pit during the dance numbers of the Broadway Show Peter Pan. Ask me and my tinnitus how I know.

[@xraytonyb]

One of my daughters is a music major and plays in pit orchestras. I guess I'll be buying her some earplugs :)=)

[@mdzacharias]

That's not paint on the transistor legs, it's tarnish. It works it's way into the transistor; that is the failure mechanism. Contaminates the semiconductor elements, or as you say the bonding wires perhaps. It's been a known problem, "black leg syndrome". Sometimes it's so bad it will form a visible short between the legs.

[@xraytonyb]

No, the 2sc1313 actually has a paint coating on the leads. It is shiny and won't rub off. I will try to show one on the next video, if I remember. The "creeping doom" tarnish looks quite different. That said, the paint didn't seem to help the transistors from failing prematurely. ;)

[@mdzacharias]

@@xraytonyb Do a little research on the subject. I've been at this over 40 years.

[@wolkewietje01]

@@mdzacharias OK, I'm going to defend Tony here. He has been covering this quite a few times now and I have experienced it first hand as well. There are 2 types of black tranistor legs. One that is shiny and won't come off when you rub it. That means that they are painted to prevent corrosion in the first place. The second type is the actual black tarnish, and it looks like a matte finish and will come off when you rub the lead. So, that said, it's safe to say we all know that if the leads are black on these transistors, pull them out and replace them as a precaution. No need to publically belittle someone if you don't know the full story. He knows what he's doing.

[@mdzacharias]

@@wolkewietje01 Never seen painted legs. Pretty sure I would have by now. Tony is really good, but he can be stubborn when it comes to admitting when he's wrong. Like with De-Oxit D5, which does NOT damage carbon potentiometers. Back to the transistors, I've never seen an original 2SC458, with the orange body and gold plated legs, go bad in this way. Only the black plastic bodies and the legs with the silver content causing tarnish. Does it not make more sense that the tarnish works it's way in and contaminates the semiconductor material?

[@wolkewietje01]

@@mdzacharias they painted it to prevent oxidisation on some transistors, especially 2SC1312 and 1313. So Pioneer and the manufacturer of the transistors were aware this might happen. Everybody makes mistakes and have their own way of working what they know works for them. AudioKarma is also backing this theory even before Tony made these videos. He just put it out there for everyone too see and be aware of.

[@CulichorHimself]

Is there any specific reason why you don't use the contact cleaner on every switch before the deoxit? Thanks!