Way back in time, I had a customer bring in an amp where they had tried 4 or 5 fuses to "fix" an amp. By the time they had finished there where blown transistors all the way back to the pre-amp / driver stages. That job was _fun_ Cheers,
Wow ! Nice going with the very detailed step by step diagnosis and repair of the stereo amp. Your attention to detail is impressive. You are definitely a pro at this high skill electronic repair. Thanks for sharing this quality demonstration for others to learn from and enjoy on RU-vid.
Your technical knowledge is inversely proportional to your sense of humor. Stick to what you're good at. ;-) Thanks for the tips. I wish you all the best.
I really appreciate this content. Unfortunately this is way beyond my understanding and ability. Trying to find someone like you that has the slightest interest in repairing the old stuff let alone making it cost effective leaves most of us with few alternatives. Much appreciated, entertaining too
James Meliti; feel free to review. This is a perfect example/explanation of "basic" electronics. Believe Me when I say "there are very complicated units out there".
In addition to a variac, my grandfather taught me to use a 200w light bulb wired in series with an outlet. A short in the unit on the bench wont blow fuses or "let the smoke out"... it just lights the bulb.
Hi teacher very very nice interesting, your age same my father I love it & I love your video too I got more technic in trouble shooting amps,but don't forget your wine really refresh your mind, thank you for the video too. More power & God bless.
Boy, you were lucky. I don't think I've ever gone thru an integrated amp of that era with blown outputs that didn't also take out the phase splitter or driver transistors.
Instead of variac, You can use a cool life-hack. Around '80 in Poland, transistors were extremly expencive and hard to get, so You can replace main fuse with light bulb socket, and 100w incandescent bulb, power on, and if bulb just flashed and then glowed a bit, there was no short, but if it was still bright glowing, there was a short. And transistors was saved without nearly unoptainable variac.
I must add that if the light bulb stays on even at low intensity there is still a problem on the board. I disconnected the left channel output power board because something was burning. When I did my second test without the defective board, the light stays off. Now I will continue and troubleshoot this defective board.
We've used this for vintage tube radios - when they were new, lol! Great tip. Some make a box with a bulb socket, power cord, and receptacle to plug in the device to be tested. NOTE this ONLY works with incandescent bulbs! Do not use LED bulbs!
@@markanderson8066 Shango066 uses this approach too, and yes, incandescent bulbs is mandatory because they act as high power resistors with soft current limiting due to filament temperature characteristics.
I used that technique, soldering a 75W incandescent light globe to two insulated wires, and putting it across a blown fuse. I called it an 'economical PTC thermistor'. (PTC - Positive Temperature Co-efficient (of resistance)).
Good video. One extra step that I usually do. But you need a 2 channel scope for this. Juxtapose the 2 channels over each other and check the bias. Sometimes it is needed to tweak a little bit to make sure they are the same.
That was great Terry, excellent points about the caps and the diodes if one is trying to fix something like this. An especially smashing job of getting rid of Dick as well !
I am totally impressed! Another tech who actually knows how to test components, and not use "universal" replacements. I use the 105C caps wherever I can in my repairs. They just seem to have a longer life. OEM semis all the way, if at all possible, especially on Sony products. Did you check the bias pot for opens or shorts before firing it up? I have found a number of times that bias pot is fried. I also check any bias diodes, transistors and resistors. Over the years I found that in the DC coupled amps, I replace the drivers as S.O.P. I normally clean off all the old heatsink compound as sometimes it gets pretty hard. The old clear compound often took a chisel to remove if the part had really overheated. Great video and explanation. You got a new subscriber. Thanks.
2SD371 finals are a TO3 package so the heatsink thermal compound doesn't go on the metal, there's a vintage mica or recent cloth washer between them. All the old thermal goop needs removed. The old filter cap is 70 volts and D-lab puts in an 80 volt. It could be D-Lab's know-how is 'monkey see, monkey do'. There are different types of snap-in caps and some take more current than others. Should we trust D-Lab with vintage audio? He's no expert, might be military radio trained. 🤠
@@generalcurtis3lemay180 All e-caps are rated by value & voltage, along with thermal tolerance.......nothing related to current. It's SOP to put in an equal value replacement with a little higher voltage rating. As a matter of practice, unless I'm using sil-pads, I clean all surfaces & re-apply fresh thermal compound to both sides of the mica insulator. But in a lesser powered unit with an ample heat sink like this, it could be excused.
At 9:00, an analog ohmmeter will check the transistor junctions, even *in circuit*, typically giving a reading of about 10 to 20 ohms between base and emitter, and base and collector. Short circuits are typically to be found between the emitter and collector. I didn't watch the whole video yet, but it bears mentioning, in case Terry doesn't, that if there is a polarized electrolytic capacitor used as a feedback capacitor for the differential amplifier input circuit, it should be changed to a bipolar capacitor. Sometimes those feedback caps get hit with a backward voltage surge as the power supplies are energized or depleted , leading to a damaged or, eventually, blown cap . An electrolytic bipolar cap is fine; or at the very least put a small film cap across it. I'm surprised this unit doesn't have a removable bottom panel, most units of its era did and do.
Transformers also age, and may exhibit AC leakage current to the case. If the unit does not have a ground (3-Prong plug) you could temporally attach one to the chassis (or any piece of case metal an operator may touch) if at ground potential and not a hot chassis. It is fortunate that D-Lab uses 115VAC at 60Hz power, in that you can make a simple AC leakage detector by using a GFCI as part of your isolated AC power supply. By supporting both a regular and GFCI receptacle, after repair and setting the AC voltage at high line, you can use the GFCI to see if the repaired device has AC leakage to the case above 5mA. If so, the GFCI will trip. To measure smaller leakage currents you will need to use a sensitive AC current leakage meter. All "appliances" should be checked for AC leakage before return to service. Traditionally this was targeted at AC motor powered devices with issues with motor insulation breakdown. However, as transformers age they will also exhibit insulation breakdown. You could HiPot test the transformer to understand a withstand voltage, or possible problems due to insulation breakdown. But, I think the leakage test is probably sufficient and quickest for most repairs. I would like to hear about if others test for AC leakage. Using a GFCI receptacle is a rather quick solution especially if apart of an AC variable isolated power supply. If replacing a transformer with a new unit you could HiPot test, although this test is usually done at the factory.
A quick way to diagnose any shorts in the system is get some tin foil the thick gauge is recommended wrap it around the fuse. Then install, plug in the unit and push the power button all you have to do is follow the smoke . No test equipment is needed .
I've got one of those in the shed. They're always blowing output caps. I think the original ones must have been under voltage. I need to get around to fixing it again. Great sounding amps for their time.
Eventually my dad replaced part of our late fifties hifi with one of these. The hard part was making a little frame to hold it vertically. That happened the day after he went to the smoke shop at the corner, and there wasn't a tube tester any more.
Excellent episode as usual, Terry. I am glad to see Dick suffer an alien abduction. My concern is, that he will piss off his extraterrestrial abductors to the point of returning him to earth, instead of vaporizing him. Lets hope he is dissected thoroughly and deemed unfit to mount on display. The Realistic caused me to wax nostalgic. I believe I'll pull down selections from my vinyl collection to listen with a renewed fervor. Enjoy what's left of the weekend. Cheers!
I've been watching various vintage electronic repair channels for 4+ years now and only now have I been recommended this video. I love you style and attitude. You aren't grumpy or preachy like some of the older repair guys and seem to be all about having fun. That's what it's all about in the end isn't it? If you aren't having fun then why are you into this hobby? I quit drinking over a year ago (not that I had a problem per se, but it really wasn't benefiting my life in an appreciable way), but seeing you enjoying a glass of wine really sold me. It really conveys the laid back nature of your channel and earned you a new subscriber. The alien skit pushed it over the top and I'm gonna head right to your patreon page and throw some money into your wine and cracker budget. Hopefully it's enough so you can afford to upgrade to a wine, cracker and cheese budget. If you prefer an aged hard cheese or a young runny variety you can't go wrong with a nice manchego or brie, respectively.
@@georgecrosscross8253 glad you replied after a year. lol. I think I was never recommended another of your videos even though I subbed and I completely forgot about it until now.
I love watching your videos, I have absolutely no clue what you’re talking about because I am not that technical but for some reason I just like to learn. Not like I will ever use this information but it’s just fun to watch. I like watching you get in there and soldering putting components into boards. The grunt work you know what I mean
16:16...and if the heatsinks are NOT "cool as a cucumber"- does that mean that YOU'RE in a PICKLE-(?) (get it? get it? get it? snucker-snucker-snucker- snucker-snucker-snucker!!!)
WOW! What a fantastic channel. Incredible, detailed, work. Talk about going the extra mile. I have six, 70s-80s-era solid state amps and they each need a little bit of help. Thank you so much.
Good catch on the diodes. Also, very good point on checking further into the driver circuit. I’ve repaired a couple of amps that had collateral damage like that.
I have so much fun watching your repairs. Comments are fantastic, it's like reading the pages of a magazine. I learn a lot with the vintage HiFi. And they are beautiful also. No plastic. Amazing.
2:22 The 2SD371 NPN transistors have their collector connected to ground? That seems odd to me. Is it push-pull with NPN's only and the collecctor of the bottom NPN is grounded?
I like yer style dude! I am wondering why you didn't check the BIAS current? You even mentioned it "could" have drifted, which it usually does with age. If it had drifted high, it could (possibly) account for the final getting toasted. Even if the driver trannies are good, aging and oxidized pots can do that, especially the "exposed" ones used back in those days. Although those particular ones are quite "stout" (especially for this amp), I have seen them go "open" and cause a runaway BIAS situation. BTW, I like the old RS stuff. It was built well depending on who actually made it for RS.
Thanks man, I do not always cover every aspect of a repair. I target certain subjects to help others troubleshoot. There is no bias setting info published for this model amplifier (I searched). I simply did a comparison to the other channel, which would also be scrutinized on this site, therefore I did not include it. Hope this helps
@@d-labelectronics Probably better for another day anyways. It's a cap-coupled output so you would need to use the scope to adjust for clipping while having dummy loads hooked up, and would be a bit more involved. Teaching people to look for the root cause is definitely a good point to make! A DBT makes for a great visual cue too. Oh and don't worry about the "scrutinizers".. Just keep on truckin'!
That cap with 4 legs is 3 stage cap , most of the time when you see those you cant change them like that , for usually those are 3 caps in one case , i would also check that for frequency sweep , there is a chance its made with just NPN transistors , if so its worthless , back in the day , NPN transistor was more expensive then the other type , so ppl made AMP with just one kind of transistor and that required topology that doesnt sound good . I would check for that . Does sound like its the case . With 50hz ripple on it
They just don't make em like they used to. I had an old Akai Amp that was .are in 1975. That mfr jammed from the time my dad passed in on to me for 12 more years.
Nice one Terry. I actually thought you were playing The Who’s - Behind Blue Eyes in the test. I love these 70’s and 80’s amps. Appreciate all your tips
Hi Terry, really appreciate your videos on the Realistic sa-1000 amplifier, I am rebuilding one here at home, can you help with the transistor numbers located at Tr608 & Tr609 and resistor value at R533 & R526 on the power supply and driver circuit board… thanks!
Don't knock the old Realistic amps. This one is rated 20 WPC, and this was when they were rated using the old honest rating system. Now you'll get the cheapo Chinese amps on Ebay claiming 500 WPC, and they are really 8 or 10 WPC using the old method.
I have a wonderful amp that I would love to have repaired it's not just a great sounding amp it's also beautiful. I wonder if you would be interested to repair it here. Or have a suggestion for who in the Southern California Area could fix it? It's the Onkyo M5090 amp. And of course, I'm willing to pay for the repair.
Hey brother, I would like to build a couple of 'geetar' amps; one SS and one tube. Therefore, could you guide me to some readily available transistors and ICs that I can use for the SS amp? Thank you, William
I took my NAD 7400 receiver for repair, but the guy is having a hard time finding transitors/capacitors repalcement. Can you suggest a place where to buy those components?
Hello, question for yeh? Anyway' I have a older model sony home av stereo receiver model da5600es its around say 12-13 years old maybe. I unfortunately did a memory reset or memory clearing due to the receiver previously having been already presetted in the past! All I wanted to do was a factory reset, that's it! Now it's stuck on MEMORY CLEARING! can you maybe help with this problem or have some ideas regarding this major mess-up? Thanks
Hello! Sorry if my english is not good! Thank you from the bottom of my heart! I had an AKAI AM-U310 - this amplifier means a lot to me. Before it died out it was connected to PC, I was listening music at a relatively high volume and my PC is setted to enter in standby after no commands is performed and HDD and monitor stopped. In that moment I've heard a big boom sound and no sound in speakers after I've exit in standby. I stopped the amplifier and turned on and the click start sound no longer appeared and no sound in speakers. Also sometimes I had sound only on right channel together with a crackling sound from speakers on left channel. All being said you think that STK / STK's is broken? If yes, can you tell me please where can I find the original STK's? I don't want to broke this very good quality product with bad STK's, I want to make this amplifier to work as good as it can be. I'm sort of audiophile person. Kind regards!
Hello! Sorry if my english is not good! Thank you from the bottom of my heart! I had AKAI AM-U310 stereo integrated amplifier since 1982 till few days ago. This amplifier means a lot for me. Before it died out it was connected to PC, I was listening music at a relatively high volume and my PC is setted to enter in standby after no commands is performed and HDD and monitor stopped. In that moment I've heard a big boom sound and no sound in speakers after I've exit in standby. I stopped the amplifier and turned on and the click start sound no longer appeared and no sound in speakers. Also sometimes I had sound only on right channel together with a crackling sound from speakers on left channel. All being said you think that STK / STK's is broken? I want to make this amplifier to work as good as it can be. I'm sort of audiophile person. Kind regards!
Can you teach me how to fix a Pioneer SX-950. It has a feedback problem, it works, but there is a feedback problem, dried up capacitors.. It makes a sound when cranked up. If not, it will end up as 'EE Avfall' here in Norway
I have an optical SM 1515 B amplifier I bought with my high school graduation money so it's special to me if it ever needs a power capacitor which is a dual capacitor 50 volt 6800 microfarad if it goes bad can it be replaced and also if the power transformer goes bad can it be replaced and what about the output I see if they go bad can they be replaced they are sharp part number RH -ix1066afzz are they still available if not can it still be fixed
There are options today for "better" components which will easily surpass older designed semiconductors and Electrolytic Capacitors. Now can you get them the same package, lead space and diameter through-hole configuration, well that could be a challenge.
I have a Logitech z5500 speaker system and it started making this it’s a extremely loud buzzing sound that was so loud on all speakers and sub shook the floor that is was totally unusable. I replaced the 3 largest caps on it. It helped a lot. But it’s still lightly buzzing all the time. But at least I can use it again. I heard that as amps they age. That they will start buzzing. It’s bout 10 years old. What else can I replace to make the buzzing stop? It’s a 5.1 audio system
Quick question: wouldn't it be a good idea to have checked your DC offset on those speaker connections prior to plugging in your speakers or was there something you tested beforehand that let you know that it wasn't necessary? Cheers! 👽✌️
Yes, checking DC offset is crucial for direct-coupled amps, but this amp is the older type that has a single-ended power supply, therefore a large blocking capacitor is required between the output transistor and the speaker terminals. While it is possible for this blocking capacitor to leak DC, it would be rare. Also, he replaced all the caps in the output section, so, no chance of that.
It's my opinion that the simpler analog amps/receivers many times sound better than some modern digital ones. If it's reasonable to fix, why the heck not.
DeadKoby, absolutely; simple circuits with a low parts count usually sound the best, as long as they didnt skimp on the power supply (big tranny, lots of filtering), heatsinking, and designing for stability (bias-feedback transistors or diodes mounted to the heatsink; parts not being run at 95% of their ratings all the time, and so on). Good layout and wiring practices, and clean simple grounding, also helped a lot. Once you start designing a product to be a Swiss army knife and do a million things, it invariably does most of them poorly.
Of course they do. Sound is an analog medium, not a digital one. Our ears are also analog. Anything digital will only be an approximation at best and doesn't contain the full sonic information as the original analog waveform.
I have an older surround sound 5.1 . Worked just rt . Thot I needed a new system . Put the older 1 up for 2 years daughter wanted her own system put older 1 in her room and dead 0 . Cant see a thing wrong or burnt , what might go out just sittin in my closet ? Thx for any help .
Seems like the caps are a big issue as equipment gets old. I've had a Sony receiver now for 30 years, I'm sure the caps will leak eventually, but so far the receiver works well.
The other neat little trick if you don't have a variac is to replace mains fuse with 60W or higher, regular light bulb. If your amp has no shorts, light bulb should flash and then dim after power is applied. If it keeps bright constantly, you have a short in the circuit. Light bulb will protect the circuit and take the energy away from the short so you will not be burning components if the short remains. Mind you it has to be an old type regular, plain light bulb. No led, energy saving fluorescent or other rubbish.
That would work fine if the fuse is off the main voltage, the same idea can be used if the fuse is on the lower voltage(s) most cases a 12 volt bulb would we work just fine. You could even use a tail light. That is a brake/turn and parking light bulb. That gives a choice of two current limits.
That's what I generally do when I'm hooking up something of unknown condition. Saved me many a time before the smoke got out and couldn't repair it LOL.
I have an Arcam integrated that has a bad channel. The right channel is fine until the volume is turned up. How do you check components that only fail under load?
Could this procedure also be used for other amps? I have a Pioneer SA-510 that has no sound on the right channel (on both A and B) I searched but I didn't find a visual shorted component so far.
Your load with the speaker looks like.a great bit of kit. Can you show it in more detail please? Is it something you built? If so that would make a very useful video . Thanks for your videos they are very educational.
Hi Terry, love your videos. Thanks for uploading. Anyway i am just started this whole electronic stuff as a hobbyist. There’s a lot to learn and your videos sure helps me a lot with my learning journey. Anyway, I noticed, when you check the speaker tranny. On emitter and collector, when it’s good. It will show up ‘OL’. But At about 12 min. When you check the other tranny.. collector to emitter showing a value instead of OL. Do you mind tell me why? Love to hear your feedback. Thanks!
He was using the "Diode Check" function on the meter. The meter puts a current limited voltage to the test leads connected to the device under test. The reading is in Volts and represents the forward voltage drop across the junction. Base to Emitter, Base to collector, then emitter to collector. Then reverse the leads. His meter may count to 1.99 or something like that and the applied voltage may be above that so three meter shows "OL" over or out of limit without an automatic range change. I hope my explanation helped. Good luck with your hobby. Keep at it!
How do you know that the pair of power transistors are paired? Is there any marking on the case that tells something about the manufacturing series or something?
He didn't say, but my guess is he bought them from a reseller who specializes in used semiconductors. Ideally they were tested with a transistor curve tracer. Maybe Terry Will clarify.
Wow I have an old JVC boombox (RV-NB20B). This was my outside source of music for more than 10 years. I loved it and bragged about how tough it was and how good it sounded. It quit working about 7 years ago. When I turn it on, the red power light comes on for a second and then there is a static pop from the speakers, and it shuts down. I have kept it with me always hoping I would come across a proper electrician who could fix it. I wish your were close by. I bet you could fix it. I'm old enough to remember when most towns had a shop where you could bring your electronics to be repaired. Now-a-days folks just throw the unit out and get another one.
Nice job on getting the amp working. However, I was startled when you kept your right hand on the (metal) volume knob while reaching into the powered-up unit. Yeah, it turned out okay, but first, it's possible for that heatsink you're touching to have voltage on it, and second, this is an older unit with a 2-prog cord. So the chassis is not grounded, and if it has a hum-stopper zap cap that's gotten leaky, you could even get a lethal shock. My rule: when touching a powered-up unit that has its cover off, I keep my non-dominant hand in my back pocket. This makes me stop and think before I decide whether it's safe to touch the unit with both hands. Also, it seemed like you did a LOT of work on the amp without checking to see if the transformer was actually shorted. Easy to do, just lift one of the leads going to the board, power it up, and measure what's coming out. Maybe you did that off-camera? Yes, a shorted output transistor will pop the fuse, but finding one doesn't mean the transformer's not roasted.
Cool to see a solid state repair. It makes sense that the caps work just like a tube amp, but I'd never seen one described like that. Thanks for bringing us along on this one.
