Owner tried fixing and gave up! Can I get it working again? Pioneer SA-900 Integrated Amp Repair
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- čas přidán 30. 05. 2024
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This video almost ended around the 55 minute mark, but this was one of the rare instances where looking at the waveform on the scope exposed an issue that needed to be addressed. I'm very happy to have had the opportunity to work on this amp. I don't talk about it enough in the video, but the sound of this thing is quite good. If you have an opportunity to pick one up for a good price, I'd do it.
CZcams should require every video to include at least one kitty.
Pioneer service manuals typically list the type of capacitors. For instance, they are CEA, CEANL or CSSA, etc. The Pioneer Tuning Fork document that can be found online describes what these types are. CEA is electrolytic, CEANL is low leakage electrolytic, CSSA is electrolytic coupling capacitor (I use low leakage for these also). This helps to decide what to order. I only use a film capacitor if they are less than 1 uF. I basically buy UPW for CEA, UKL or films for CEANL, CSSA or CSYA depending on size. That handles most everything I need.
Great investigative work. Many failing parts in this old boy. Love the view from the deck of the mountains. Good to see the cats again!! Thanks for posting.
Thanks, Dave!
Hi Aidan. The non-symmetrical clipping wasn't due to the high ESR of that 1uF electrolytic capacitor, rather the leakage through the capacitor altering the bias on the base of the transistor. If you haven't disposed of that particular capacitor check it for leakage at the rated voltage. I'm 100% confident you'll find it's electrically leaky which BTW won't show up on your Peak ESR meter. Would I have replaced that capacitor? Yes, it's electrically leaky, but the ESR wasn't way off spec. Check out the ESR chart on page 9 of your ESR tester handbook for a table of typical ESR values. Considering the impedance of the circuit this capacitor is located in, there would be no audible difference between a 1uF capacitor with an ESR of 13 ohms vs 7 ohms.
Now having watched quite a few of your videos I fully realise you do this as a hobby and you don't factor in your time. However, in the real world of repair unless the customer is prepared to pay for parts and labour completely recapping equipment isn't an economic solution considering the monetary value of the amplifier (it wasn't an outstanding performer then and replacing electrolytics with "audio grade" parts won't improve either it's measured or perceived and subjective sonic performance). Save those expensive capacitors for equipment that would benefit from using them. With respect to the output coupling capacitors you replaced. It wouldn't have done any harm to have upped the capacitance. The -3dB roll off point of this amplifier is 25Hz so doubling the capacitance might extend the low frequency cut-off to about 13Hz using the same impedance speakers provided the low frequency response of the amplifier wasn't already limited earlier in the amplification stages. In conclusion it was pleasing to see you have started to resist the habit of shot-gunning parts willie-nillie. Learn by understanding what has caused the fault and more importantly why. It will serve you well as you progress with this hobby.
Valuable info, thanks from another hobbyist!
+1 on upping the coupling cap values. It's a fairly common upgrade. Modern speakers tend to dip way below 8 ohms raising the -3db into audible range. This particular amp circuit design and layout is almost identical to the early 1968 SX-1000TW I recently worked on. I was guessing bias circuit issues at first.
At 50 years old aren't those electrolytics like twice as old as there rated lifespan? If a customer is prepared to properly refurbish an item that old, it would only be a matter of time before one of the electrolytics fail and take other parts to the grave with it. At that point they would have to bring it in for a new repair and they probably wouldn't want to invest any more money into it and possibly blame you for not fixing it correctly. I would think that if the customer isn't prepared to completely refurbish it it's best just to tell them to buy something new and save that repair money. Of course for us hobbyists we supply the cheap labor and don't have to pay for brick & mortar stores, so the cost of the electrolytics is negligible.
Ya learn something new everyday. ;)
Sade and hodor look great. good to see the team altogether.
What a beautiful PLACE to work on electronics! I admire your discipline; I'd get distracted and just...stare...at those lovely mountain views. Nothing would get done if I had views of nature like those. That...PLUS...a cat would stop me from working on stereos. And THAT would be no good. Aloha.
I used to work in a shop that did Pioneer warranty repairs when these amps were new, there were many output transistor failures due to thermal runaway of the output stage bias pots when these amps were installed near heat sources!
Nice kick off with the you and the cats enjoying the mountains from the deck.
Enjoyed my morning coffee watching this vid. I learned a few things as always with your repairs. Thanks for posting and congratulations on the move.
Always enjoy your video. Taught me a lot as I am trying to learn how to fix old amps.
ESR is not the only failure mode of a capacitor, capacitors can also go leaking which means they get conductive internally. usually it will make the capacitance seem higher and the ESR lower. But that was probably what made your voltage drop because the cap was internally shorting...
It is interesting to watch you learn as you work. I’m sure that as you gain experience you will be able to get to the problem much quicker.
Great repair. You did went down to the wire to get the same range for both channels. Tough work and well done work! Enjoyed watching the video. catch you again soon!
I love rebuilding old things whether it's a amplifier or other things that are like antiques.
Yes, Load up on the old components, before they disappear into the void!
It's incredibly tidy inside. The tape head jacks are interesting. From the manual, those are inputs directly from a tape head without a pre-amp! Similar to a phono input. I assume it has a bias signal filter in the pre-amp as well. The manual also shows spade connector blocks can be inserted into the proprietary speaker terminals.
great job.. good teaching moments too. tracing a circuit back to the noise point is confusing. i have not had to do it yet but it's nice to see some hands-on here on the channel . Nice old amp too !
Great work. It's so obvious you are an engineer.
Nice fix it Aidan👍 Ahh, Montana...beautiful. When you started trouble shooting the unit, I wondered if you were going to remove the boards before attempting the work. Turned into more work than first thoughts, figured there would be some. Turned out great in the end though, determination and patience win the battle in the end. Great video and repair, well done. See ya soon.
Thank you , I did learn a lot. Not yet enough to repeat you thou. But perhaps once. 🙂 Greetings from the Netherlands.
I'm shocked that you didn't know in advanced that raised ESR will cause voltage drop. SHock! And because of that we always tend to buy only low esr capacitors.
Except this isn't a case of low signal voltage, it's incorrect transistor bias causing the transistor to clip off the bottom of the waveform. Hi leakage, which I'll bet that cap also had, was allowing DC through, throwing off the bias.
Usually the amplifiers that are capacitor coupled and with just a single rail power supply to put them on right parameters first is to measure between negative and the point on the positive side of the output capacitor and bring that voltage to half of the total voltage on the power supply and for biasing is to remove the fuse and put the multimeter on measuring the current and put the signal input to ground and set the idle current around 100mA for a class AB amp you can go also higher if there is enough big heatsink and keep you ear on the speaker and bring it up until you can hear a bit of hum and lower back just exactly when the hum disappears. And you will get the best performance from that amp
Excellent Work as normal. This video will be a great help to many. I normally take out all the 2sc871 transistors they are probably the most common faulty transistor in the pre amp stages. Can become very noisey.
Great video, good repair. Please be sure to replace the stv3 double diodes. These fail a lot, and cause the bias circuit to run away...
Good job on the SA900
Go with what's in there. That's the sound it had, it's the sound expected? It worked then, it will work now. So I think. Thank you for taking the time and effort to post this.
1:57 "...and yeah, I do plan to get a table here but, uh, I was actually going to buy a table for this in town but they don't have one that, uh, suits my needs A.K.A. is adjustable and taller..."
I hope you are able to find a table worthy of displaying such a fine piece of electronics. Having the original paper note on the tape head pulgs must be highly unusual.
However, if I may don my pedants hat, you sholud say "i.e." not "A.K.A."
Id est means "that is to say", which fits better than "also known as".
I don't think the ESR would have caused that problem. The issue is that it's leaking DC through it. Your test gear doesn't appear to measure leakage...
Great repair and nice information!!!
I replaced the audio capacitors in my car stereo with Nichicon 3300uf 25v high grade audio caps and the sound difference was mind blowing. Honestly the difference was astounding. Not only was the volume seemingly louder there was also no noticeable distortion at high levels where there would have been previously. They were quite expensive, i think about $35 USD for 6. But boy was it worth it.
Maybe the original ones had degraded?
Yeah whatever.
Lotta work. Great job!
I also Have an SA-9100,, very nice sounding amp.. A real keeper ! Very smooth sounding amp....
You've come up on my feed suggestions, probably because I also subscribe to XrayTonyB. I like hearing you work through the problems.
Interestingly enough, You had mentioned the film vs. electrolytic caps video series Tony put out a while back. Checking my notifications and subscription page, I see that Tony put up "Film Vs Electrolytic Part 2 - Blind Audio Test" about 3 hours ago - June 7, 2024. I will be heading over to listen there after I'm done watching this/your vid.
Your work bench is so nice, clean and tidy! I like the protective rubber sheet on you bench, so that customers equipment can never get damaged. A lot of engineers do not do this, resulting in severe damage to peoples equipment! Great repair!
It's an ESD pad that eliminates static charges that destroy some electronic components.
@@JM800 Thank you very much for this information!
Been waiting for this
For the speakers jacks, get Cinch Jones Beau Molex P-303-CCT 38331-5603 , it’s has 3 pins but you easily remove one. Fits perfectly.
Works perfectly. Thanks👍
@@paulredfern3832 I’ve wired them directly to speakers but I also have a test set of speaker wires that has alligator clips on the ends. Just make the (pos) lead for one clip about 2” longer so you don’t short them out. Btw, the horizontal pin on the Jones plug is the pos.
3M foam tape or dollar store equivalent works well to enlarge the diameter of a cap too. Depending on the thickness needed, you just give it more or less wraps. May not look as pretty as the original but how often are you opening up your amps/receivers to admire the components inside it? You can save quite a bit of cash too as the smaller diameter caps are a bit cheaper too. Greater care to get the proper diameter sized capacitors would certainly be required if they are exposed like some higher end units like tube amps where the manufacturer made everything visible for aesthetics.
Great work! 👍 Thumbs up for you. 😊
In the end you realized first hand why elcos are no go in sensitive stages like preamps at least. Put film caps wherever you can.
You commented that you Own a KA-7100 ? I have two of that model, Kenwood ?
Did pioneer make an SA-7100 ? Just thoughts... I have been a Tech for 60 yrs.
Still enjoy fixing vintage audio stuff at age 74 ! Enjoy your videos also..
Pioneer SA-7100 yes
Our tech at Allied Radio store called the layout of early Pioneer transistor amps and receivers "Hirohito's Revenge."
Good Job!
Well done.
Good job!
Tony released a video today debunking his electrolytic vs. film. Conclusion same sound.
não basta somente todo o conhecimento, requer paciência e amor, Você é muito bom nisso um abraço do Brasil!
Hi,
I also saw the video of Tony regarding the coupling caps. I tend to agree on the part where he says things about occilating beeing a concern when using filmcaps as a coupling cap. Something to check. But electrolitics are far from linear, and do not age well. Also, the filmcaps where extremely big in the 70 's, and just wouldn't fit on the board....
It's true there are different electrolitics, and each type has it's place. As a coupling cap it's far from ideal, and i swap them out with small size filmcaps where i can. No occilation did occure, and soundwise things improved significantly...
Thanks!🎉
The idea of electrolytic caps is to remove noise. Digital cap's with low ESR stop the caps from over heating with high frequencies and helps to keep the voltage nice and stable based on the wire inductance run to it. So ya - better caps help reduce harmonics in the circuit. I suggest you run a signal generator and see how flat the audio sweep is between different caps. And don't use speakers use a none inductive resistor load and use a scope. As far as signal caps use current technology. Not film caps, they can have inductance in them. The new super ceramic caps are better at passing high frequencies. You should always use caps with higher voltage than what is in the circuit than what on the schematic. Everything lives longer that way. I have an SA-1000 broken ... but I would have changed the power supply caps also in your amp you fixed. After 30 years there ready to go bad. The new parts are just so much better in most cases.
Nice job of chasing the rabbit….! 😎
Your 1 uf 25v capacitor is probably leaking current. These epoxy style caps are becoming leaky. The orange ones with epoxy underside have the same problems.
it´s very good and a easy fix , these were built to last , just find a technician who can fixt it ,i have a lot of old pioneer´s even from the 60´s and they all that needed a fix ,it was easy and cheap, try new or restored speakers and doble the power because this seems to not have enough power to fire up some speakers but try it and be amazed like i was , that is a jewel ,hard to find and hard to find a matching quality amplifier or next to impossible ,i have a C3 with two M6 mono blocks and speakers ,giant ones(2401 twin, also Exclusive) also a 71, P3 turntable , all Exclusive series from Pioneer ,only from 10.000€ up will be close to this quality and the speakers were restored to original specifications but all work only some parts need to be substituted but one doesn´t notice only after being restored it even sounds nicer, i have a real big colection of pioneer 70´s components and that one i don´t have it but have the A-500 with tuner ,i think it´s TX-500 ,with a PL-12 turntable PC-/PN-30 cartridge and stylus ,it sounds amazing with some 70 watts mission 4 ohms speakers(mid 80´s) or SB-F3 from technics (79) i wouldn´t trade it for a 2.500€ system , i have a PD-7100 pioneer cd player and perfect and a CT-F750 cassette deck from 79. This you have to try to fix it but never sale it ,you would be sad for letting it go
Really enjoy your videos Aidan! I have a Pioneer vintage system including an RT909 reel to reel, an RT707 reel to reel, and a Pioneer SA7700 amp that I bought brand new back in the day. The amp still works and I purchased a restore kit with caps, transistors, relay, etc. I replace the 2 large filter caps and swapped the VU meters lights to LED. However I do not feel comfortable replacing the other smaller caps and transistors yet. Recently when powering up, the protection relay clicks, but then within a few minutes it clicks back off and the VU meter lights dim. A few seonds later it clicks back on and the lights get bright again. It will do this several times until it warms up and then it is fine. I have not checked the DC offset yet but will do that eventually. Question: Do you restore other peoples vintage gear? If so how much, and based on the relay issue, where do you think I should look first?
Thank you! Chris from Winter Garden Florida.
Start at the wall outlet...And work in!
Hey Aiden Big move from OH to Mt. Looks like things are going well. I asked a couple of videos back but no answer probably too busy moving. lol but... What's your Go To source for schematics? Great Videos & I'm Glad Your Back. Thank You in advance.
I use www.hifiengine.com but I hear they're not taking new users. I don't know where else to go unfortunately
Hello, love your work. Do you take out of state work/projects? I have a Bose 551 spatial stereo receiver I would love for you to service.
I think it may have been more of a leakage problem on that 1uF capacitor. I've seen that before on Pioneer's with the Sanyo caps.
👍👍👍
Smaller value 'lytic caps are more likely to shit the bed.
25:51 That will be the mid point setting for a quasi comp pair, corresponding to half the voltage between the ground and supply rail, measured at the input of the coupling capacitor and referenced to ground usually, for a positive value.
The correct way is to use an oscilloscope and adjust it for symmetrical clipping at full power, of course on the dummy load 😁
55:40 @@M-P-X I wouldnt bother tbh, the circuit is fundamentally asymmetrical Darlington/Sziklai and the difference between the quick and correct method too insignificant in practice to matter much.
I wish That I can send to you a Morantz 1075 . ( I have a sentimental value ) . but i guess it needs a lot work , so i just save it in the garage , but it looks nice .
Has anyone done a comparison between audio grade capped amp and the same amp with normal caps? What I always assumed is that capacitors do not really affect the sound as long as they work. A recap in my mind is prevention and not a sound improvement. I am sure distortion might decrease at higher wattage with new caps and properly recalibrated bias but I do not really 'get' how better (which I assume means more stable and more accurately selected) capacitors would cause an amplifier to sound 'better'. Just as you mention that engineers from the time accounted for using electrolytics instead of films I am sure that they engineers also accounted for bigger variations in the ESR and capcitance than even the cheapest caps you can find today. Sure they might not last nearly as long but I would expect the difference between ok quality caps now and the best of the best audio grade caps to be next to none. Doesn't mean I wouldn't want the best of the best stuff in the best of the best equipment but I wouldn't expect it to matter.
In decades of repairing, restoring and modifying high end audio, many so called "audio grade" capacitors are IME a bit of a con. This is especially true when you see or read about someone completely re-capping a device, not because it needs it but simply because they can and they did. Then when you look closely at what "audio grade" capacitors they have chosen then check out the specifications only to discover the capacitors have a lifetime of 1000 hours that isn't going to make the amplifier "good for another 40 years" LOL. Many CZcamsrs that do these "upgrades" never show measurements before and after to prove they have actually made the amplifier better, rather they simply claim it's better. Sure, electrolytic capacitors do eventually deteriorate and fail but simply shotgun replacing all of them isn't the solution. In vintage gear probably some other unobtainable part will eventually fail thus rendering the device useless but someone has over capitalised on a complete and often unnecessary re-cap simply because they can. :(
Thanks for filming this repair. What wattage is the bulb on your current limiter?
Same question.
@@andymouse incandescent clear bulbs are hard to find, stock up!
@@petermetro4686 :)
Enjoyed the repair process, I have a bad Kenwood KR-7600, what is your rate? Please PM
I've been watching your videos for some time, but had no idea you were based in Montana. Greetings from a fellow home tech/hobbyist in Billings!
I also have a 900:I know there are some caps at the border it still plays well but I would love to have it tuned up .How much to do this type of repair
I didn't see jumpers for preout main in
Quick question regarding refurbishing vintage stereos and maybe it's an unfair question to ask. Assuming that the refurbish kit I just bought consists of high-quality replacements for caps, diodes, and resistors, does refurbishing a 50-year old Marantz 2220B receiver ever result in a decline in sound quality? I bought this unit new in 1977 and it is in cherry condition. Everything works and after cleaning it and relamping,, sounds great just not as clear as I remember from the last time I used it about 23-4 years ago. I have the soldering/unsoldering skills and experience to do this right and will be very meticulous along the way to not make mistakes. I just worry about it sounding worse just from the new parts alone.
So after fixing the preamp, did you end up reducing the 1800k series resistor with the pot to a value which matches the other channel?
I put it back to the original resistor
Hey man. Ive been getting into repairing vintage receivers/stereos. Ive already done 8 or so. What are those cap testers you are using? They look like great tools
I believe it's a Peak Atlas ESR70
How did you learn amplifier repair?
The pre is running in class A and the dead cap pulled the rail down so the potential (22Vdc)was to low
Tweaker man on CZcams says to use Nichicon KA series for power supply as they are awesome and when it comes to audio signal caps Elna Cerophyn s or AudioNote Kaisi s are the way to go...also I understand that bipolar caps can be used in your pre amp board even if they are polar,
Hey buddy I'm new to this and would like to know what wattage bulb I should put in my dimbulb tester for working on late 70s receivers, tape decks and turntables? For reference the first one will be an Onkyo tx2500 mk 2. Thanks in advance!
The more powerful the device, the higher wattage bulb should be used. Typical 60w works fine for most stuff. Once you get into the really big stuff like a pioneer sx-1980 you need a higher watt bulb since it pulls so much current just at idle
@@AHFixIt thank you Sir! I'll start out with 60w and grab a 100w as well.
Is it for sale?
the tannoy 605 would be a nice set of speakers for it, i´ve seen them under 80€ ,they were expensive in late 80´s and early 90´s the MKII, a set of mission 761 would make it sound perfect 4 ohms ,it got loudness and two treble and bass for each independenjt channel ,it´s easy to make it sound perfect, but try to buy a old turntable before 79 and if the cartridge is a old one try to find a substitution needle ,why?because new ones even MM type sound even lower than mc old cartridges ,oit´s ridiculous
now that i thought better the 603 is the most compatible model from Tannoy Sixies, they were really expensive but now they are selling them working perfect for under 100€ but some are asked 350€ as it were very expensive in late 80´s or early 90´s the mkII´s
More likely that the capacitor had some dc leakage. I'm not sure your tester detects dc leakage.
Yeah. I think I'm going to get a device that measures leakage.
Adrian why would you just replace the capacitors in the main and pre amp without changing the one on the power supply board . Do you think they have got better with age ? 👎
Don’t really think it’s a good idea to “leap frog” on your troubleshooting. No ligcal flow
Meow meow
Don't fixate on ESR as the "holy grail" of caps . . . We didn't test that for decades, and nothing djed because of it. Far more critical measurements on coupling caps like this are capacitance and leakage, since the purpose of this device is to pass the signal, and block the DC bias between stages. ESR is an AC measurement, and leakage DC, and it was the excessive leakage of this cap allowing the bias of this amp to be pulled out of spec, and thus cause the amp to become asymmetric. ESR is a far more meaningful measurement on filter caps . . .
Good Job!