Pioneer SX 525 Repair & Restore With Difficult Alignment

Well, this was supposed to be a simple repair video, but as you will see, the alignment was quite difficult. All of you who like long videos should like this one. For those who don't, you may want to skip it!
Enjoy!!

[@mdzacharias]

The output coupling caps actually DO have constant DC on them. Approximately 1/2 the VCC of the main amp (single-ended push-pull). You can measure the "center voltage" at the positive side of the coupling cap. Probably around 25-30 volts on this model. There is no negative DC rail for the main amp.

[@CliveTrezona]

Love the dual camera setup. Thanks Tony

[@stores7735]

Great video, have this unit. Need to clean my pots. Thank you sir!

[@frankgeeraerts6243]

You are very skilled ,sharing your passion and experience.....but even more important , you are a very nice person.

[@26Jorgeb]

Thank you so much.I understand how complicated it is for you to keep everything simple for us viewers.Hope you keep doing these videos.God bless.

[@lungduan240]

Tony, i saw that Pioneer receiver when i was teenager in the 1970s. Looking to buy one to repair, thanks for your great work to share your knowledge.

[@kev-the-windsurfer.]

I really enjoy your videos, and comforting to know I'm not the only one having these issues with the book procedures for these older units, I started watching this after I did an alignment on a JVC5446, with equally as difficult procedures and similar weird faults like this one, uncanny in a way. These videos are very informative and I like the way you leave most of everything you do in there....in the ramblings is where the gold is, little tips and thoughts that we'd otherwise miss.....I like the way you found your own way through that alignment and its given me the some ideas when I have the same issues again. Thanks and keep them coming, especially the tuner alignments...... Oh the scope videos will be interesting too.

[@jwl9286]

I enjoyed this video! If I could access all the test equipment required to do these alignments then I could attempt doing what you did. I basically read the instructions and visualize what would happen. Your video, though I may not understand everything takes me way beyond anything I could imagine. I think it's wonderful! I enjoy actually seeing the scope respond to the adjustments and the voltage readings. Your commentary is very helpful too. Love following the circuit description on the schematic then seeing it respond. Again great job! Thanks!

[@antraciet]

Difficult, very difficult for me, but again, i learned a lot from your video. Thanks.

[@aklef]

I grew up with IKEA furniture and stuff all around me so I almost pissed myself at that IKEA bit XD I do appreciate the comment though, especially for people who don't know it . Great vid tony!

[@tonymontana897]

Looking forward to the oscilloscope videos Tony. I have a 465b and want to learn to use it properly in conjunction with my vintage stereo restorations. Great channel. Thanks

[@lsrx101]

Tony, I've been collecting and repairing old tube gear for for many years, but I always stopped short of FM, FM MPX and solid state gear in general. The theory and operation intimidated me. I've just recently started trying to learn what I've missed out with SS electronics, FM, etc. over the years. (at 55, my brain cells don't absorb and retain like they used to. I'll likely get a handle on 1990s vintage circuits when I'm about 115, lol.) I tripped across this video in route to other things, and a lot of what you explained while working with this receiver made FM "click" in my mind. I'm absolutely going to go back to the previous videos that you mentioned. Thanks for that. Subscribed, of course.

[@ronshaw80]

Great video. Even though it is a long one, it kept me interested.

[@saarike]

Great video! Difficult things. You are an expert of electronics. :)

[@johnnyhawkins43]

I just love the old Sansui stereo system from the seventies and the 80s!!!!!!!

[@barrysheridan9186]

Very informative video thanks for posting.

[@gearheadted9210]

great video,very similar to my Kenwood TK66 that needs lotsa love

[@Silent-Lucidity]

Watching this for the second time on my new Samsung Note9. The stereo effect of your camera mic is extremely pronounced. But it did pick up the mono vs stereo issue on your tuner really well!

[@apollorobb]

Lesson here kids is always replace the bulb first as A LOT of these indicator circuits are current dependent Some dont like LED's as the current draw isn't high enough to drive the Output transistor low and bias the CE junction off . So i ALWAYS use an Incandescent bulb first to verify function then try an LED and add a loading resistor if necessary.

[@timschutte8310]

, it's cool to see & hear a Brainiac at work. it's great

[@air54plane]

very nice. I learned a lot.

[@lego40404]

Thank you SO much for this. I have a Pioneer SX-1280 that I've inherited and in working condition, but want to clean up and replace two missing knobs. I was also given a Onkyo TX-4500(not MK II) years back, came out of a garage depot. Aside from dust, dirt and smoke it was a gem once cleaned up. So after a few years of playing, it started doing some funny things. One being lots of static and out of tuning calibration. I blew out the dust, did a board visual check and was a little better for a while. But the next time I went into it I made the mistake of spraying contact cleaner in the tuning capacitor while spraying up the pots not realizing that was a BIG No No, Oh Boy was it wacked out after that. Now, I'm into electronics, I have some knowledge and the basics. I've built tube amps for myself, on my second Hifi SE stereo tube amp build now and I've built effect pedals. I have a good oscilloscope, DDM, analog meter BUT I need a function/signal generator to do this calibration and I,m lost on what to get for that. I can follow schematics thankfully but definitely a noob to doing this. Sorry for the ramble but I'm glad I found this. Even If I cant fix this tuner( shoot I'll replace the tuner with a donor) its a great practice piece. If you can give me a pointer on a generator to look into that would be great. Thank you

[@goodun6081]

lego4040, to clean a tuning condensor: carefully blow out the dust with compressed air, being careful not to bend the fins in any way, and you can use a fine paintbrush or toothbrush if you are very careful with it, to remove grungy dust from in between the fins. Again being very careful not to bend them! You should apply a drop of tuner cleaner to all the electrical junction points at the sections of the tuning condenser, at those little brass looking or coppery colored metal clips that contact the groove in the shaft. A very small controlled droplet. Use a syringe, or a jewelers screwdriver dunked into the cleaner to gather up a droplet. If the tuning capacitor is already gunked up from having been sprayed with cleaner then you will have to clean it with a degreasing solvent that leaves no residue, and start all over. And you don't want that solving residue to wash onto any of the RF or IF circuit boards either.

[@goodun6081]

The SX-1280 is a BEAST, far more complex then this unit; it will certainly need dozens of small caps and black-leaded transistors replaced; and if you do something wrong or screw up the biasing, or a pivotal part fails, it will blow up in a heartbeat. Recommend you learn on a smaller, simpler unit!

[@jasonhawkins4528]

great videos, i new to your channel, well good, gosh that is confusing, and the equipment you need wow

[@kennethiman2691]

Great job!

[@larryshaver3568]

i'm having a similar problem with a weak channel in the stereo fm mode so this video may give me insight

[@kellykane312]

Those output capacitors are there because the power supply is a single ended and the output junction of the transistors is about half of the supply voltage. The caps are coupling caps that block DC and pass the signal. Bigger amps use a positive and negative power supply and have a true DC offset not just a bias control.

[@larryshaver3568]

the resistors on the stereo fm board were the first things i checked on my Astro sonic receiver

[@ricardolopez4055]

Hi from Montreal,Canada. I’worked for 10 years as an electronics technician,mostly in audio gear.I really enjoy a lot your fabulous videos and your amazing skills and knowledge. I think you are the best here in KZbin! Congrats and thank you very much for your beautiful work !!

[@BijuKumar-kj7qr]

Thank you !

[@piwex69]

Output capacitors: they are used to decouple speakers from the DC on the output, you are right, but mainly because the half of the rail voltage will always be there. It is normal for receivers with one line asymmetric power supply.

[@stanislavsemanko55]

Exactly, right i wanted to say it...

[@markanderson350]

Those came out when I was in high school. In those days we were spec driven. The more you paid, the better the specs, the more stations a tuner would get or more power, less distortion etc. For the common person, a low end was fine, like this one. Probably $200 new. That's like over a grand today. Good job.

[@larryshaver3568]

i use a brush like that on records to get deep down dirt out of the grooves

[@InsideOfMyOwnMind]

When you do these kinds of repairs in a production environment as opposed to youtube land many of the general checks that "require" a procedure become second nature to fly through. I can tune through a few stations and tell you basically how healthy the tuner is just by the sound of tuning through a signal. Granted this doesn't replace the full run through but it can give you direction in a hurry when you troubleshoot a mpx problem for example. The manual has to address the tech who has never used an FM tuner before. If I have two meters, center and signal the two should agree regarding center tuning. Max = center. If it sounds right as mono and the meters are acting reasonable I will check certain things in the mpx before I mess with the tuner.

[@doughenry2249]

Tony can you tell me where you buy your capacitors, led lamps etc. from.! I really enjoy your video’s, but a lot is over my head, but learning a lot, thank you😎

[@scarakus]

I think I dissected one of these way back... When I was a kid...

[@jpawlacz]

Do you have a list of all the components you replaced on the Amp board. I need to replace one of the resistors that burned up. I was hoping you had a list to save me some work. Thanks

[@midmodaudio6576]

Thank you for another informative video. You replaced the electrolytic s of the tuner board with film capacitors. When is it okay or not okay to replace electrolytic's with other types of caps ?

[@frankarmstrong5329]

Hi Tony I love watching you do this stuff. It’s probably made me over confident. I have just completed a recap of my Technics SA 600. Power supply, Amps, Tuner and EQ boards. It’s mostly sounds awesome but the FM Tuner acts very strangely. I have not performed any tuner alignment (I have and appointment with a local tech). I am not sure if my symptoms will be resolved by alignment and wanted to see what you.thought. From around 104 MHZ works fairly well, It will pick up a signal and FM Stereo / signal strength and tuning meters seem to work well. Below 104 MHZ the signal meter sweeps up pretty high and the tuner meter sweeps to left and stays. I get no signal regardless of what the strength meter reads. Any idea. I have rechecked all caps to insure they are correct against the manual and against the parts I removed.

[@Justplast]

In the power supply did you install the same value caps and the same voltage caps?

[@CrashZombie]

If I may.., suggest... chopsticks make great pointers & can be helpful in troubleshooting tubed amps. I don't think plastic ones will work though, but wood is good. (No phun intended. lol)

[@larryshaver3568]

Pioneer made equipment for allied the sx525 looks very similar to an allied that was made around 1970

[@larryshaver3568]

I had an Allied receiver that had Elna capacitors

[@Slartibartfas042]

@xraytonyb: Have not seen the whole video up to now but at 52:00 kind of malfunction (?) of Pilot tone detection indicator without FM signal: I did not see any muting circuit that kicks in when there's no FM signal there - is there any? If not, then the circuit is working perfectly correct, as for the "white noise" that is produced when there's no RF signal in FM mode there actually *is* some 19 kHz component within! So, no Audio muting *before* the MPX detector, no chance to detect if there is valid MPX pilot tone or just white noise coming from the discriminator. Or am I missing something?

[@nicknackthenoo]

Hi Bud, I need a volume control for this amp. Have you any recommendations on where I can aquire one. regards.

[@sordello51]

Oh oh oh... I know this one! BE junction on regulator board opens up when hot... ;)

[@zestynachos1]

Make sure to tune to WDVE, where they’ve been playing the same 15 song loop for the last 25yrs! Lol

[@bikdav]

I’m glad those old tuners are gone. They made have pulled in stations good. But, when things went wrong .......

[@Alo762]

At 11:28 you say that those capacitors between main amp and speakers dont have DC on them. I presume you mean DC voltage. They actually have constant 25 volts over them because main amp output rests at 25 volts. And theoretically they could color the sound but as you can see in schematics, main amp feedback comes after those caps, and through smaller caps because the feedback point's bias isn't at ground but somwhere near 25 volts as well. You could recap those, too, with high quality low ESR electrolytes. Same capacitance value would be optimal but as technology has advanced, you could probably find higher voltage ones with same physical dimensions now.

[@xraytonyb]

You are correct. What I meant by my comment is that the output capacitors isolate the DC from the speakers. If one of the output transistors were to short, it would not damage the speaker, as the DC would not pass through the capacitor. Output capacitors can always color the sound, but if you use good low-ESR caps, this could be minimized. The ones used in this amp tested very good, and as you could see from the tests at the end, they performed very well, even up to 20kHz. At 20Hz, there was some distortion at full power,. I agree that some newer caps at a little higher capacitance might help reduce it, but I think it was pretty good as it was. I also think the power supply was railing out at 20Hz, causing some of the problems as well. Thanks for watching! Great comment!

[@PecanPie1102]

Just to questions one, in new radios(20years) that digital PLL (digital display) do they/can need to be adjusted .two, if you swap out the transistors can you increase the gain and would it be safe?. Another great video to take us away from the madness of the news. 👍

[@xraytonyb]

Some of the newer radios still need alignments. It just depends on the design. Some digital radios have a frequency counter for the display and still use an analog design in the background. They can have PLL for the multiplex section, but still have a standard IF and oscillator section. Other units use PLL with computer logic, and even have varicap diodes in place of the variable capacitors. For the transistors, I assume you are talking about the HFe gain of a device. Current gain in a transistor isn't that important, in many cases. I have, however, found that you need to be pretty precise when replacing small pre-amp transistors, as well as transistors in radio oscillator sections. In those cases, you need to find a close match to what you are replacing.

[@celsostarec6735]

:-) Still have one of those!

[@SoddingaboutSi]

Always found FM alignment a pain. Simple peaking of portables is OK, but getting the s curve seems open to interpretation.

[@rleeAZ]

Can you comment on replacing the electrolytics in the tuner section with film capacitors? When is it ok to do that? When is it not? Why did they use electrolytics in the original design/construction instead of a non-electrolytic alternative? Great video, I like that you go into a good deal of detail. Thanks!

[@xraytonyb]

You can always use film caps in place of electrolytics, when practical. When they built the vintage gear, they didn't have film caps in small packages, and the ones they did have were more expensive. Today, I have even seen the really high end tube amps use giant film caps as the main power supply filters (really expensive option!). Even low-ESR electrolytics have some ESR. Film caps have very low (almost immeasurable) ESR. They often sound noticeably better than the electrolytics (especially at higher frequencies) and they last a super long time. I'm only talking about caps in the audio path. Caps that are used in oscillators or RF circuits should be replaced with the same type (i.e. replace mmica caps with new mica caps. Replace NP0 ceramic caps with new NP0 ceramic caps). Hope this helps. Thanks for watching!!

[@rleeAZ]

Thanks for the explanation Tony... will keep that in mind going forward.

[@Kennynva]

Dont that JFET amplify the signal at the front end??? at 56:28 in the video??

[@vitorlupribel]

Hello, would you like to know if you could do a favor to send the sx-525 electric reciever through the post office

[@wenkev02]

Would you be interested in repairing a Centex by pioneer model number KH-5151? One channel out and back light not working.

[@ronwade2206]

Which filter cap is bad? All of them

[@Washburn-rr5eh]

Hi Tony I have the same HP generator 8656B.? Do you have any videos on using that signal generator? For example, what setting to use on the DBM. I'm just trying to understand my equipment a little better. If you have any videos or point me in the right direction on setting up the HP signal generator.

[@xraytonyb]

Many of the tuner-related videos have a lot of references to the use of signal generators. I try to use different equipment on different videos to show different methods of alignment.

[@colinhepburn2818]

Hi Tony Enjoyed the SX 525 video the power amp board is the same as my SA 6200 but psu caps is larger 4700uf 63v and the output caps are 3300uf 35v. Tony you say not to change out the output caps if good whats your views on adding bypass caps to the output caps the idea is to lower the impedance? Looking forward the scope video as need some help on this the scope I have is an old analogue hammeg HM 203-6 . I also have the feeltek single gen you showed on one of your vids maybe you could use it in part your scope vid Thank again Colin

[@xraytonyb]

Thanks for watching! Bypassing the output caps with a smaller low ESR cap can help with the High Frequency response. If the main caps are really good with Low ESR, they usually will do pretty well as they are.

[@colinhepburn2818]

Thank you for your reply Tony

[@kennynvake4hve584]

A thermal camera would help a lot...since 'most' failures are because of heat..I think it would be nice to see where the heat is....or was..if it still is operating. After a part is burnt up..I dont think it will help you as much..I could be wrong.

[@larryshaver3568]

what year was that receiver made,do you know?

[@MaximRecoil]

The kind of brushes that women use to put on makeup work good too; they have very soft bristles.

[@RobertKohut]

Nice!

[@larryshaver3568]

i found that while working my magnavox that there are so many different transistors that cross to an ecg 102

[@UGScience]

Tony - I just watched your video on the Pioneer SX-535 restoration. I am interested in having someone go through and checking out my Pioneer SX-626. The unit has been partially re-capped. Do you accept commissioned outside work? Thanks.

[@xraytonyb]

I'm not taking any new projects at this time. You might want to check out my video "Frequently asked questions - xraytonyb" Where I explain it a bit more. Thanks for the comment!

[@hagbard72]

So how much did it cost the owner to have it fixed? BTW, its 17wpc.

[@tomscotland]

Can I ask some advice? I have a 535 and a 434, and on the 535 there’s a problem with (I think) voltage getting to the speakers. It would make a dreadful noise and you could see the speaker cones being sucked in if that makes sense. Any ideas?

[@xraytonyb]

Sounds like an output capacitor is shorted/leaky.

[@tomscotland]

@@xraytonyb thank you, it’s not easy to find a specialist local to me.

[@larryshaver3568]

I SAVE all those capacitor brackets when i throw the old capacitor out myself

[@larryshaver3568]

When did transistors with TO_220 cases first come out?

[@mmaranta785]

I know they had them in the 1970’s, don’t know about the 1960’s

[@DoRC]

Where did you get that sliding arm mount?

[@xraytonyb]

I actually salvaged it from a wall mount that holds a keyboard, mouse and monitor. We use them sometimes in hospitals to mount the keyboard and monitor to the wall in a digital x-ray room. That way, we don't have to take up floor space with a desk. This one came out of an old system we removed from service.

[@DoRC]

xraytonyb ah ha. I knew it looked familiar. I used to do IT at a hospital and have dealt with those

[@sordello51]

Oh yes capacitors leak cause a lot of noise in the controls. Change them all!

[@grahamtownsend3751]

I'm trying to recap an old amp (1970)it has a number of electrolytic aluminium cans with no indication of polarity, I am assuming the pins grounded to the can are negative, but I would like to be sure, thanks in advance.

[@xraytonyb]

Be careful with those caps. They may be non-polarized electrolytics. I see them a lot in some of the vintage gear out there. They didn't have small-packaged film capacitors back then, so they used low-ESR non-polar electrolytics. You have to replace them with the same non-polarized electrolytics, or if the capacitance isn't too high (under 5 uF), a better option would be to use small-package film caps that are readily available now. They are more expensive, but they last a really long time and have super low ESR (almost unmeasurable with a cheap ESR meter) and usually sound better. If you install a standard electrolytic, it could damage the amp, the cap or cause distortion.

[@grahamtownsend3751]

Thank you very much for the response, it is a large cap 4000uf at 70volts.

[@xraytonyb]

Most of those caps have the ground lead connected to the can. They usually will mark the polarity on the bottom, next to the pins. Be aware that some amps with negative power supplies might use an isolated or insulated can, because the positive lead of the cap is tied to ground for the negative supply. Some McIntosh amps have these, as well as some of the tube gear out there.

[@josegallardos4265]

I have one exactly like this one, bought it a few days ago alone with a technics turntable for 25 dls at a yard sale. it came also with small Hitachi speakers withe the special type connection, I wanted to listen music at a higher volume and connected 8 ohms speakers and noticed that it doesn't have that high volume. at the highest volume speakers sound distorted, I connected same speakers to my other fisher amplifier and they sound way better without any distortion and higher volume. is that normal with this pionner amplifier to do that? or is there any problems wit it? thanks.

[@AlainL57]

Jason, old post but if still not fix, could be one output transistor that is open so you hear only half of the sinusoidal curve.

[@hotsound3593]

More do you medil this capacitor to know if it is giving the capacitance of 6,800 mf? Because there are a lot of fake capacitors, except for the siemes line

[@tonymontana897]

Is a 727 much the same as the 525 ?

[@ClaytonDTucker]

I'm watching this to learn for my 828. No one on here has close as detailed on the sx-x2x series.

[@j.zingler6735]

Captain obvious explains... Who instigates you to fiddle around with electronics? What kind of solder points are those? You Sir are a monster when it comes to soldering.

[@justincase3880]

The cap was gonna fail “shortly” (pun intended) ...

[@charliewathen5259]

Thanks for the detailed info. On my SX-525, I have a "thumping" when adjusting the bass. It's not the control pot as I have cleaned it, but I think it's described in this video: kzbin.info/www/bejne/pYHSeJiHgrCDr7M I could not tell from that video link which board location this cap would be on?

[@vintagesouthern54]

Do you have a website? Do you accept new work? I have 2 six-828's and a Harmon Kardon 930.

[@xraytonyb]

Yoou can E-Mail me at [e-mail]. I am taking on new work as time allows. Thanks for watching!

[@dannyjaar]

there are all old

[@deangale4496]

Basting brush , lol.

[@bobofky]

Would you consider my SX1280 ? My name is Bob, I’m from Kentucky. Was unsuccessful making contact with you a couple 3 years ago. Thanks

[@johnnyhawkins43]

Hey Bob from Kentucky my name is Johnny HAWKINS KENTUCKY!!! And I had one like that but I got rid of it and now listen to it little brother!!!!

[@williamsquires3070]

You realize the brushes can build up static charge, right? Don't get those near any FETs (or, worse, MOSFETs)!

[@RaulHernandez-lg5nw]

It's a ratio detector! Not a discriminator detector! That are used in FM tuner circuits.

[@dannyjaar]

recap all electrolytics

[@user-ub6mi1zq9z]

Много болтовни.

[@davidcasper312]

using a digital scope to teach analog? do it right tony.

[@pibbles-a-plenty1105]

I can say you are an able radio mechanic but you really need to understand circuitry to explain things accurately. Spend more time learning theory and math analysis of circuits. Get the books you need, study, and you will become a good instructor in time. Good luck!

[@dimitriapproved]

Enjoy the video and leave your keyboard alone. And learn to word better. Good luck.