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".
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)).
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.
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 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.
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 TH-cam.
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! 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.
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
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 appreciate people like you sharing your knowledge. It is so rare to find anyone that can repair solid state electronics, I've resorted to working on my own. Thanks for your help in turning an industrial controls guy into a 1/4 funtioning solid state repairman. I've got a Sansui G8000 I want to hear before 2 years... I may kick the bucket before then .
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.
I broke down and bought myself a vacuum desoldering gun on sale a while back, it wasn't cheap but it saves a ton of time replacing parts on these old units.
Absolutely hooked on these how to identify problem solve and repair audio equipment, and going about it the correct way by being safe and showing what test gear is needed
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.
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.
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.
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.
this is awesome info. i wish i'd watched this before jumping straight into swapping my main transistor pair. i didn't realize it was fine to check for component shorts with the components still soldered onto the board. thanks again
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.
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.
I have a Realistic STA-85 I bought new in 1978! It's powered wall speakers on every computer Ive had since 1994 until about 3-4 years ago when it started periodically making noise like static maybe and I could see the bulbs inside kind of flicker at the same time. So I looked and didnt see anything obviously burned or wrong and bought a new amp/receiver. Still would like to fix the old STA-85 since it has mechanical switches and my computers and amp etc are all in the basement on a rack and I turn the power off to the amp, printer and monitor with a wall switch at night and when at work (computers, modem, router run 24-7) with the STA-85 this worked perfectly with the new one and its electronic controls, turning the power off means after I turn the power back on I have to go downstairs and turn the amp on and set the volume level every time. I figured on replacing the caps regardless of how they looked as they ARE from 1978 and see if that fixes the issue, havent done it yet, but it worked fine, powered up fine always, never blew a fuse, just that periodic noise over the speakers.
Back in the day bad i.e.; shorted power transistors figured heavily in blowing fuse issues. People would do all kinds of bad stuff to the outputs, including but not limited to, shorting out the speaker terminals. This actually an easy fix. Burned components made themselves known.
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.
Nice repair, very thorough. I know what you mean about using generic replacement transistors, sometimes they don't work properly, I've experienced that in the past. It is best to use exact replacements whenever possible.
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
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.
Dang! Really blew a lot of stuff on that one. Good thing it was sent to you to repair! Changing those caps was a very wise thing to do. Keep up the excellent work Professor!
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.
Thanks for all the repair/troubleshooting detail. That was really helpful. I learned a lot. I've got a Pioneer VSX-920 Audio Video amplifier from 2010 that has issues. A neighbor was going to throw it out. Hopefully, I can solve the DC 003 error code problem and get it going again. Regards, Tom
Probably already done it by now, but any electronics made in Asia between 2005-2007 (basically everything) is likely to have classic "cap cooties" issue. The Asian cap manufacturers got a bad recipe for electrolytic that lowered the life of the caps they made. Millions of them. Whenever you see a TV or monitor from that era that powers on for 5 seconds and shuts off, it's those caps. $10 fix in parts.
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.
Nice. Every time I try to check final transistor temperature, I remember (a split second to late) there is voltage there. On a 70 volt rail, that's 140 volts across.. OOPSIE Now I use a temperature gun (non contact) to check. Works well on tube envelopes also.
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.
The only thing you did not seem to do was test the amp at full power on your load resisters. It is also good to check with a triangle wave for linearity and a square wave at a lower power level. I also use a tone burst sine wave at 1/3 ans 2/3 duty cycle to check stability. The last three tests are not required but these wave forms will tell you a lot about the amp.
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.
Arguably the most hit or miss brand maybe that comes with the territory of a house brand. The stores for years tried to find a balance between the cheap hobbyist and the few doctors who walk in and were not interested in Macintosh price tags but were willing to pay more and everyone in between.
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 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".
tha't's got to be the neatest test bench I've ever seen. a real professional at work.
Lol I have burn holes everywere on my matt lol don't beer and solder
I have one of those silicon mats it's safe to drop solder on it, won't burn it.
Nice repair. May be better than ever with all of those new, modern capacitors.
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.
Thanks for this suggestion. The light turns on momentarily bright then dims to about 1/2 intensity.
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)).
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.
Thanks for the variac suggestion
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.
Happy comments, totally agreed!
@@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 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.
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 TH-cam.
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! 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.
I checked the dictionary for the word ''professional'' and I saw your picture.
Well done. I'm trying to learn basic electronics; theory is one thing... but there's nothing more instructive than watching an expert fix broke stuff.
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
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.
Time and patience is what shown here and very professional 👍
I appreciate people like you sharing your knowledge. It is so rare to find anyone that can repair solid state electronics, I've resorted to working on my own. Thanks for your help in turning an industrial controls guy into a 1/4 funtioning solid state repairman. I've got a Sansui G8000 I want to hear before 2 years... I may kick the bucket before then .
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.
I broke down and bought myself a vacuum desoldering gun on sale a while back, it wasn't cheap but it saves a ton of time replacing parts on these old units.
Beautiful bringing the devices into life again, this is an art.
I like Mr. D-lab's attitude and presentation style.
Absolutely hooked on these how to identify problem solve and repair audio equipment, and going about it the correct way by being safe and showing what test gear is needed
also check out Mr Carlsons lab
Wow this a clean looking and laid out unit , My Fisher TX500 receiver is full of wires soldered everywhere.
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.
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.
And used an out of manufacture STK module!
The 70's and 80's amps are super but man, the 70's and 80's guitar notes......just awesome!
PS:- Electronic repair instruction wasn't too bad either.
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.
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.
Pretty cool way to understand fundamentals
Very cool, D-lab. Moment I saw the burned resistor, I thought exactly all like you. Thanks for taking it home in the video.
03:25 "...and then the Circus Board..." Priceless!
Love your channel came here from
Amp Repair Guy channel
You are the best repair electronic engineer. I was the hobbiest electronic person.
You sir are very informative as well as entertaining!!!!!
this is awesome info. i wish i'd watched this before jumping straight into swapping my main transistor pair. i didn't realize it was fine to check for component shorts with the components still soldered onto the board. thanks again
Sounds good! Nice to see some solid state audio here, most electronics are tube oriented.
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.
I'm glad to see you tested all of the transistors. I've seen many shorted driver transistors take out the finals
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.
Well done! I bought a used Marantz 1030 in the seventies... loved it!
D lab Electronics your utube videos are awesome 📻😎😎😎😎👍👍👍👍👍👍👍👍👍👍👍📻😎😎👍👍
I have a Realistic STA-85 I bought new in 1978! It's powered wall speakers on every computer Ive had since 1994 until about 3-4 years ago when it started periodically making noise like static maybe and I could see the bulbs inside kind of flicker at the same time. So I looked and didnt see anything obviously burned or wrong and bought a new amp/receiver.
Still would like to fix the old STA-85 since it has mechanical switches and my computers and amp etc are all in the basement on a rack and I turn the power off to the amp, printer and monitor with a wall switch at night and when at work (computers, modem, router run 24-7) with the STA-85 this worked perfectly with the new one and its electronic controls, turning the power off means after I turn the power back on I have to go downstairs and turn the amp on and set the volume level every time.
I figured on replacing the caps regardless of how they looked as they ARE from 1978 and see if that fixes the issue, havent done it yet, but it worked fine, powered up fine always, never blew a fuse, just that periodic noise over the speakers.
Yeeeehhh man Realistic is live one more time!!!!!
Good repair Tery!
Back in the day bad i.e.; shorted power transistors figured heavily in blowing fuse issues. People would do all kinds of bad stuff to the outputs, including but not limited to, shorting out the speaker terminals. This actually an easy fix. Burned components made themselves known.
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.
Nice repair, very thorough. I know what you mean about using generic replacement transistors, sometimes they don't work properly, I've experienced that in the past. It is best to use exact replacements whenever possible.
Very good repair and instructions. Thanks for posting this Terry.
Thank you for such a comprehensive and clear explanation. And kudos for the mini movie troll abduction.
thanks for sharing your knowledge i appreciate a good teacher also like how you dealt with the troll.
Very helpful info, especially about checking the power supply diodes. I might have had to learn about that one the hard way. Nice sounding little amp.
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
Sounded like Emerson, Lake, and Palmer to me. I need one of those royalty-free CDs.
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.
Dang! Really blew a lot of stuff on that one. Good thing it was sent to you to repair! Changing those caps was a very wise thing to do. Keep up the excellent work Professor!
Terry looks like a clone of my late grandfather . Wow!
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.
Great video Terry. You put a lot of work into these!
My new fav channel! Glad I found it.
I'm trying to fix up my Sansui Au-717.. this helped a lot!
Excellent video Terry
Extremely good job. Congrats Sir.👏👏👏👌👌👌
I should have been doing this my entire life! Now I'm at the end and not enough time to get back in it! Good job!
Thanks for all the repair/troubleshooting detail. That was really helpful. I learned a lot.
I've got a Pioneer VSX-920 Audio Video amplifier from 2010 that has issues. A neighbor was going to throw it out. Hopefully, I can solve the DC 003 error code problem and get it going again.
Regards, Tom
Probably already done it by now, but any electronics made in Asia between 2005-2007 (basically everything) is likely to have classic "cap cooties" issue. The Asian cap manufacturers got a bad recipe for electrolytic that lowered the life of the caps they made. Millions of them. Whenever you see a TV or monitor from that era that powers on for 5 seconds and shuts off, it's those caps. $10 fix in parts.
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.
D lab Electronics your CD player is so awesome
this is SOOO great! thanks much for posting, great info.
Great job. Like that you accept the challenges!!
They are really good sounding amplifiers.
Great video, thank you!
You are great Terry. Thank you very much for this informative video!
Nice. Every time I try to check final transistor temperature, I remember (a split second to late) there is voltage there. On a 70 volt rail, that's 140 volts across.. OOPSIE Now I use a temperature gun (non contact) to check. Works well on tube envelopes also.
Brilliant! I enjoyed that - tools for the job!
I work on the cyclotrons that make the radioactive stuff in those needles. There's cool science with those machines.
An enjoyable watch. Thanks for posting.
I have to say much thanks for your repair videos, one of the best if not the best.
Very nice Sr Terry, thanks i like your job, i'm study audio amplifier.
Great video.
Very informative.
Looking forward to more.
Thank you for doing this!
Very educational fun. Thanks!
WOW a old Beckman DDM!!!! Haven't seen one of those in years!!
Yep, I love the vintage Beckman's with the rotary select switch
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.
subbed because of the of the glass of wine
Great work! - amps/tuners/decks etc ... can be a nightmare to fix, one issues leads on to another etc.
White wine and lightly toasted (over a class A amplifier) almonds are the key to solve all hifi issues
The only thing you did not seem to do was test the amp at full power on your load resisters. It is also good to check with a triangle wave for linearity and a square wave at a lower power level. I also use a tone burst sine wave at 1/3 ans 2/3 duty cycle to check stability. The last three tests are not required but these wave forms will tell you a lot about the amp.
Very efficient repair!
I loved this video-very informative, funny as well. Great job!
Very good troubleshooting step by step!
Is that you Mr. White?! 😁Walter White😎
Great video, thank you!🙋
i have 4 2n3055 from rca us made unbelievable performance when i put them in technics su 7600
Very much informative... learnt a lot.. thanks..
This was a great and very detailed video.
Its an Entertaining clip and you set a puppet show.
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.
Another cool repair video from
D-Lab Electronics
Exceptional job You have inspired me to work on my channel, thanks. 🐼
Some of the Radio Shack vintage audio gear is severely underrated.
Arguably the most hit or miss brand maybe that comes with the territory of a house brand. The stores for years tried to find a balance between the cheap hobbyist and the few doctors who walk in and were not interested in Macintosh price tags but were willing to pay more and everyone in between.
@@dpt4402 ,,,,,,,,,,,,,,,,great analogy,,,,,,,,,,,,,,,,,,,,,,,,$$$$$$$$$$$$ Macintosh tube amps.......wish I had two........ebay,,,,$$$$$$$
Thanks, I enjoyed watching you at work.
I was doing Amp repair back in the day
we were quite busy at times
surprised that quite alot of people looking at these repair vids these days
Good fix great sound
clean and perfect work
nice job, keeping that Realistic out of our land fill.
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 !
Initialy i wanted to learn whats wrong with my older amp, which is way newer then this one. Stayed for the great content! Subbed!