I suggest to check out my recent videos. They offered the tips for troubleshooting and identify the problem of the amplifier. I am glad to assist you if you need any helps. Please send your questions to my email which is listed in the home page on my RUclips channel. Thanks for your comments.
I recently purchased an untested AU-517, on A speakers I get nothing on B, I get beautiful music and after 5 or 10 minutes it gets bad. This video serves as inspiration to take a look inside with my multi meter and see what I can determine. I wish it wasn't so expensive to send to a qualified repair person, there are so few around that it is only getting more expensive to find someone. I'll cross my finger in hope of finding something I might be able to repair myself sometime.
To troubleshoot the problem, I suggest using another good working power amp connect to AU-517's pre-out to test it's preamplifier first ( don't forget sliding the switch to separated position when you perform this test). If you still experience the same problem from the new added power amplifier, then the problem is in the preamplifier section. If there is no problem, then the problem is in the AU-517's power amp section. Let me know the result, I may can help you to analyze the problem further. Your speaker selector may have bad contact issue, you can use DeoxIT to clean the selector. I think it will help solving B speaker's connection problem.
i am very impress with your repair. I am an electronic engineer myself, and needs lot of intuition to fix some failures. Also those old components are tricky. You are a great technician. Question: havent you think to make some money offering your services repairing sansui ?
Thank you for your compliments. The main purpose of my RUclips channel is to share the experiences and skills of vintage audio repair. I also provide the helps for the DIY fans to repair their vintage audio amplifiers or receivers but not for the profits or business. You can contact me by email If you have any problems on your Sansui. My email address is listed under "ABOUT" in the Home Page of "Vantage Audio Fan" RUclips channel.
My trusty AU5900 just stop producing sound. This has been in my family since 1976. I remember the day I went with Dad to buy it. I need a reputable service shop to fix it in the Carolinas.
Can you share more on how and where to measure DC offset and biasing. Is DC measured across the speaker output terminals, and biasing across which emitter resistor leads. Appreciate your answer. Thank you.
Does this apply to other amplifiers? I like to adjust biasing for my Simaudio Moon 340i. Out of warranty n replaced all the left channel output transistor. The amplifier runs slightly warm instead of much warmer. Can I apply the same measurement points on the 340i. Meaning measure the voltage across the emitter resistor from the center NPN and PNP transistor. Great to learn so much from your videos.
Generally, the manufacturers recommend to redo bias adjustment after the power transistors replaced. Yes, you can measure the voltage across the emitter resistors. I suggest adjusting the left channel the bias reading to match right channel if you don't have the service manual.
Thanks a lot for the very nice troubleshooting. Please help me, what is the replacement value for a 2SC1115 and 2SA746, these two are missing on my QRX9001, thank you for your answer, I'll be waiting sir..greetings from the Philippines.
There are few options you can use: (1) SANKA 2SC1586/2SA909 (Vcb 250V, Vce 200V, Veb 6V, Ic 15A, Pc 150W) or (2) Motorola MJ15022/15023 (Vcb 350V, Vce 200V, Veb 5V, Ic 16A, Pc 250W). Their prices are very competitive. But I preferred SANKA's transistors. I used them on my Yamaha M-2 power amp. You can check it out on my repair video. They work very well on my M-2.
@@VintageAudioFan Thank you so much, really appreciate it, that narrows down some of my future probs when I start fixing this monster, one thing more sir, can I incorporate these Motorola MJ's with the Sankens installed? Thanks again sir..
I noticed that the range of hFE of transistors between Sanka and Motorola is different. When you use them on the power amplifier is better to select closest value of hFE as possible. So I don't suggest to mix both transistors in same circuit. To find matched pair transistors (with same brand) is the right way to do.
Hi, thank you for this perfect video. I have question. I have AU-5900, without sound. Before 5 days, when i turn on amp, relay click and no sound. After inspection i found 4 fuse resistor /220ohm/ absolutly open (R31,R32, R41,R42) and i replace IC01/IC02 2SA798 with 2sa1015 pair. Two channels are 18mV, output terminals i have 2mV. +22V and -29V for EQ and tone board are normal. Can you tell me where i am wrong? Swith ''connected''/''separated'' is perfect.
It seems the problems may occur in the relay or the speaker selector switch. Sometime when there is bad contact in relay or switch, it may not have outputs even the replay kicks in. My suggestions are: (1) Use other working pre-amp's outputs to hook up the main-in of AU-5900 and test the power amp. Be sure turning the switch to the separated mode in back panel. If there are sound outputs, then the problem occurs in AU-5900's pre-amp. (2) Also try using another working power amp hook up to AU-5900's pre-out and check the pre-amp. If you hear the sound, then the problem is in the power amp. Base on your descriptions, the power amp should work if the output DC offset and bias can be adjust to the MFR's spec. Please let me know the test results. Thanks.
@@VintageAudioFan I clean one more time all switches and nothing. When i connect my pre-amp Yamaha CX50 everything work perfect. What do you thing about my equavalent 2sa798 with pair 2SA1015..., is it good? Can you help me please, what can i see now?
@@vfdffdd2675 Based on your testing results, I think the problem should be in AU-5900's pre-amp section as you stated that you have hooked up a CX50 as preamp with AU5900's power amp. The substitution of A798 with a pair of A1015s shall be fine. I also suggest that using the AU5900's pre-out connecting to a working power amplifier to confirm the location of problem (in pre-amp). If the problem occurs in pre-amp section, there are three things which you should check first: (1) Power supply to preamp, (2) The voltage in collector and emitter of transistors (TR01/02, TR03/04 and TR05/06) in the tone control PCB (F-2604) (3) All coupling capacitors include C01/02, C09/10, C11/12 and C13/14. The reading of measurement should match (or close to) the value shown in the wiring schematics of AU5900. Please let me know if these steps help.
Hello friend, I have an AU-7900 to which I need to replace the TR05 and TR06 (2SC711) transistors on the F-2596 board. Which substitutes do you recommend?
Based on spec. of 2SC711, there are a couple options you can try: (1) 2SC1815 or (2) KSC1845, KSC2310 or KSC945- from website. See attached link: audiokarma.org/forums/index.php?threads/replacement-for-the-2sc711.408336/
I have one of these. How I dearly wish it worked. I find vintage (1970s era) Sansuis spend more time on the service bench than in the audio rack. Hardly anyone knows how to fix them.
... and I got a crippled AU20000 and an AU3900 sitting around feeling useless as paperweights. I am making do with a couple of "Natural Sound" Yamaha amps from the mid 1990s which haven't given me too much grief. I still consider these my "New" amps despite their age.
Have you thought about repairing or selling your Sansui amplifiers? They are still one of my favorite vintage gears and I hate to see them become a waste.
@@VintageAudioFan I would agree with that, I have had my Sansui AU-7700 since 1978, but since I am an electronics tech I know how to do my own work. Any direct coupled amplifiers can be problematic, such as the Marantz 22xx series. I would say anyone with a cheap DVM, like the $5 ones from Harbor Freight, can check the DC offset on the speaker terminals and foresee a minor problem before it becomes a big one. Anyone can take an infrared thermometer and check the output heatsinks to see if you need a qualified tech to adjust the bias before thermal runaway eats the outputs. Then you can take it to someone more qualified to fix it for you. Since I have had mine I have replaced the speaker relay and several capacitors that went open in that same protection circuit. I check the DC offset every 6 months or so, it is insurance. We here in the vintage audio community have an obligation to keep these amps alive and help those that need help to do do. Thank you for doing your part, if there is anyway I can help, I will do so. Cheers!
It is not that techs don't know how, it is the semiconductor devices inside are not made anymore, so many techs shy away from working on them. I am working on a G-8700DB receiver at this time and I have spent a lot of time tracking down quality replacement transistor substitutes. Lots of counterfeit parts on eBay, for example. I still have my Sansui AU-7700 I have owned since 1978 and I have kept it going all these years. Just like old cars, you may need a parts donor sometimes. Watching this channel I think you may find someone that can help get yours going. Is it totally dead?
@@zulumax1 Which one? The AU20000 is in perpetual protection mode, and the AU7900 makes popping and purring sounds, but still "audio" comes out. I also have an AU3900 where the last tech put in an incompatible transistor on the output circuit and it just sounds distorted. On the question of obsolete parts, would you contend this is simply progress as usual because similar products we can buy for the nominal amounts of money today are miles ahead of the audio equipment of the 1970s? Or is this yet another sign that we are in retrograde motion? BTW as you're probably aware, these amps started going bad in the 1990s. This all didn't just start happening recently. Thanks for the reply.
Buenas tardes señor. Amplificador Pioneer A20S, falla: colocado el balance en el centro sé escucha bajo canal derecho. Pero en ese momento está conectado en RCA señal de entrada en el canal izquierdo y no en la derecha. Solo está conectado el parlante estereo derecho. Por favor podría mostrar esquema completo de éste amplificador Pioneer A20S. Gracias de antemano.
J'ai ce même amplificateur mais mes gros condensateurs étaient brûlés et je voudrais avoir d'autres, il me faut deux. Comment faire pour les avoir ? Salut.
To answer your question: Yes. When it is impossible to find the replacement parts for your unit. So it depends on which part needs to be replaced. Also if there is severe damage on PCB it may not be able to fix. Unless to find a usable same PCB which is selling on eBay or somewhere. You can send your request to my email (which is on my RUclips channel homepage). I can discuss with you and assist you repairing your amp. Thanks.
You are quite right. The indicator was in the off position when the amp first appeared in the first 30 seconds. We see the amp at 9:36 with the selector in the A position which is quite different.. I have one of these and it is the same.
@@VintageAudioFan Thank you for taking honest feedback kindly. I think of them as opportunities for improvement myself. Wish more people would speak their mind while being respectful to the content creator.
@@VintageAudioFan, i have a doubt about the sansui au707. It was bought second hand and was not used for sometime, it is send to my friend to use, he mentioned that when first time used for 1 hour there was no issues, after that even after volume is cut, there is a humming sound. He suspects it is some issue with relay, i am not much familiar with electronics, could you suggest what could be the reason
I inherited an AU-7900 from my dad. It needs repair, and I thought about just buying a new one. But your video convinced me to service it, thanks!
I suggest to check out my recent videos. They offered the tips for troubleshooting and identify the problem of the amplifier. I am glad to assist you if you need any helps. Please send your questions to my email which is listed in the home page on my RUclips channel. Thanks for your comments.
I recently purchased an untested AU-517, on A speakers I get nothing on B, I get beautiful music and after 5 or 10 minutes it gets bad. This video serves as inspiration to take a look inside with my multi meter and see what I can determine. I wish it wasn't so expensive to send to a qualified repair person, there are so few around that it is only getting more expensive to find someone. I'll cross my finger in hope of finding something I might be able to repair myself sometime.
To troubleshoot the problem, I suggest using another good working power amp connect to AU-517's pre-out to test it's preamplifier first ( don't forget sliding the switch to separated position when you perform this test). If you still experience the same problem from the new added power amplifier, then the problem is in the preamplifier section. If there is no problem, then the problem is in the AU-517's power amp section. Let me know the result, I may can help you to analyze the problem further. Your speaker selector may have bad contact issue, you can use DeoxIT to clean the selector. I think it will help solving B speaker's connection problem.
i am very impress with your repair. I am an electronic engineer myself, and needs lot of intuition to fix some failures. Also those old components are tricky.
You are a great technician. Question: havent you think to make some money offering your services repairing sansui ?
Thank you for your compliments. The main purpose of my RUclips channel is to share the experiences and skills of vintage audio repair. I also provide the helps for the DIY fans to repair their vintage audio amplifiers or receivers but not for the profits or business. You can contact me by email If you have any problems on your Sansui. My email address is listed under "ABOUT" in the Home Page of "Vantage Audio Fan" RUclips channel.
@@VintageAudioFan thanks. You are a great professional.
A very impressive repair, lot of talent, bravo !
Thank you for your comment.
C'est l'un des meilleurs amplificateurs fabriqués par la firme SANSUI. AU 7900
My trusty AU5900 just stop producing sound. This has been in my family since 1976. I remember the day I went with Dad to buy it. I need a reputable service shop to fix it in the Carolinas.
Mine make a loud noise when I turn it on, and no sound
Can you share more on how and where to measure DC offset and biasing. Is DC measured across the speaker output terminals, and biasing across which emitter resistor leads.
Appreciate your answer. Thank you.
Yes. As per MFR's service manual page 15.
Does this apply to other amplifiers?
I like to adjust biasing for my Simaudio Moon 340i. Out of warranty n replaced all the left channel output transistor.
The amplifier runs slightly warm instead of much warmer.
Can I apply the same measurement points on the 340i.
Meaning measure the voltage across the emitter resistor from the center NPN and PNP transistor.
Great to learn so much from your videos.
Generally, the manufacturers recommend to redo bias adjustment after the power transistors replaced. Yes, you can measure the voltage across the emitter resistors. I suggest adjusting the left channel the bias reading to match right channel if you don't have the service manual.
Thank you for replying.
Appreciated. 👍👍👍
Thanks a lot for the very nice troubleshooting. Please help me, what is the replacement value for a 2SC1115 and 2SA746, these two are missing on my QRX9001, thank you for your answer, I'll be waiting sir..greetings from the Philippines.
There are few options you can use: (1) SANKA 2SC1586/2SA909 (Vcb 250V, Vce 200V, Veb 6V, Ic 15A, Pc 150W) or (2) Motorola MJ15022/15023 (Vcb 350V, Vce 200V, Veb 5V, Ic 16A, Pc 250W). Their prices are very competitive. But I preferred SANKA's transistors. I used them on my Yamaha M-2 power amp. You can check it out on my repair video. They work very well on my M-2.
@@VintageAudioFan Thank you so much, really appreciate it, that narrows down some of my future probs when I start fixing this monster, one thing more sir, can I incorporate these Motorola MJ's with the Sankens installed? Thanks again sir..
I noticed that the range of hFE of transistors between Sanka and Motorola is different. When you use them on the power amplifier is better to select closest value of hFE as possible. So I don't suggest to mix both transistors in same circuit. To find matched pair transistors (with same brand) is the right way to do.
@@VintageAudioFan there total of 8 trans at the back, 4 per heatsink, I'll look for the hfe specs you mentioned, thanks a lot..
the background music is the best
From 25 seconds during testing the speaker switch is OFF!
I actually saw the same thing!
Hi, thank you for this perfect video. I have question. I have AU-5900, without sound.
Before 5 days, when i turn on amp, relay click and no sound. After inspection i found 4 fuse resistor /220ohm/ absolutly open (R31,R32, R41,R42) and i replace IC01/IC02 2SA798 with 2sa1015 pair. Two channels are 18mV, output terminals i have 2mV.
+22V and -29V for EQ and tone board are normal. Can you tell me where i am wrong? Swith ''connected''/''separated'' is perfect.
It seems the problems may occur in the relay or the speaker selector switch. Sometime when there is bad contact in relay or switch, it may not have outputs even the replay kicks in. My suggestions are: (1) Use other working pre-amp's outputs to hook up the main-in of AU-5900 and test the power amp. Be sure turning the switch to the separated mode in back panel. If there are sound outputs, then the problem occurs in AU-5900's pre-amp. (2) Also try using another working power amp hook up to AU-5900's pre-out and check the pre-amp. If you hear the sound, then the problem is in the power amp. Base on your descriptions, the power amp should work if the output DC offset and bias can be adjust to the MFR's spec. Please let me know the test results. Thanks.
@@VintageAudioFan Thank you very much for answer. Today I will try all and write here my result. God bless you.
@@VintageAudioFan I clean one more time all switches and nothing. When i connect my pre-amp Yamaha CX50 everything work perfect. What do you thing about my equavalent 2sa798 with pair 2SA1015..., is it good? Can you help me please, what can i see now?
@@vfdffdd2675 Based on your testing results, I think the problem should be in AU-5900's pre-amp section as you stated that you have hooked up a CX50 as preamp with AU5900's power amp. The substitution of A798 with a pair of A1015s shall be fine. I also suggest that using the AU5900's pre-out connecting to a working power amplifier to confirm the location of problem (in pre-amp). If the problem occurs in pre-amp section, there are three things which you should check first: (1) Power supply to preamp, (2) The voltage in collector and emitter of transistors (TR01/02, TR03/04 and TR05/06) in the tone control PCB (F-2604) (3) All coupling capacitors include C01/02, C09/10, C11/12 and C13/14. The reading of measurement should match (or close to) the value shown in the wiring schematics of AU5900. Please let me know if these steps help.
@@VintageAudioFan thank you after replace 2sc1313 (all 6) with 2sc1845 work now. May be all au series are defective... Thank you
Hello friend, I have an AU-7900 to which I need to replace the TR05 and TR06 (2SC711) transistors on the F-2596 board. Which substitutes do you recommend?
Based on spec. of 2SC711, there are a couple options you can try: (1) 2SC1815 or (2) KSC1845, KSC2310 or KSC945- from website. See attached link:
audiokarma.org/forums/index.php?threads/replacement-for-the-2sc711.408336/
@@VintageAudioFan Thank you. 👍
Nice repair. Bravo.
I have one of these. How I dearly wish it worked. I find vintage (1970s era) Sansuis spend more time on the service bench than in the audio rack. Hardly anyone knows how to fix them.
... and I got a crippled AU20000 and an AU3900 sitting around feeling useless as paperweights. I am making do with a couple of "Natural Sound" Yamaha amps from the mid 1990s which haven't given me too much grief. I still consider these my "New" amps despite their age.
Have you thought about repairing or selling your Sansui amplifiers? They are still one of my favorite vintage gears and I hate to see them become a waste.
@@VintageAudioFan I would agree with that, I have had my Sansui AU-7700 since 1978, but since I am an electronics tech I know how to do my own work. Any direct coupled amplifiers can be problematic, such as the Marantz 22xx series. I would say anyone with a cheap DVM, like the $5 ones from Harbor Freight, can check the DC offset on the speaker terminals and foresee a minor problem before it becomes a big one. Anyone can take an infrared thermometer and check the output heatsinks to see if you need a qualified tech to adjust the bias before thermal runaway eats the outputs. Then you can take it to someone more qualified to fix it for you. Since I have had mine I have replaced the speaker relay and several capacitors that went open in that same protection circuit. I check the DC offset every 6 months or so, it is insurance. We here in the vintage audio community have an obligation to keep these amps alive and help those that need help to do do. Thank you for doing your part, if there is anyway I can help, I will do so. Cheers!
It is not that techs don't know how, it is the semiconductor devices inside are not made anymore, so many techs shy away from working on them. I am working on a G-8700DB receiver at this time and I have spent a lot of time tracking down quality replacement transistor substitutes. Lots of counterfeit parts on eBay, for example.
I still have my Sansui AU-7700 I have owned since 1978 and I have kept it going all these years. Just like old cars, you may need a parts donor sometimes. Watching this channel I think you may find someone that can help get yours going. Is it totally dead?
@@zulumax1 Which one? The AU20000 is in perpetual protection mode, and the AU7900 makes popping and purring sounds, but still "audio" comes out. I also have an AU3900 where the last tech put in an incompatible transistor on the output circuit and it just sounds distorted. On the question of obsolete parts, would you contend this is simply progress as usual because similar products we can buy for the nominal amounts of money today are miles ahead of the audio equipment of the 1970s? Or is this yet another sign that we are in retrograde motion? BTW as you're probably aware, these amps started going bad in the 1990s. This all didn't just start happening recently. Thanks for the reply.
Some narration would be appreciated!
Buenas tardes señor. Amplificador Pioneer A20S, falla: colocado el balance en el centro sé escucha bajo canal derecho. Pero en ese momento está conectado en RCA señal de entrada en el canal izquierdo y no en la derecha. Solo está conectado el parlante estereo derecho. Por favor podría mostrar esquema completo de éste amplificador Pioneer A20S. Gracias de antemano.
Sorry, there is no service manual or circuit diagram I can find in the website.
@@VintageAudioFan gracias dé todo modo
A narration would be better than music.
Thanks for the suggestions.
Grazie
Brilliant piano work on this take of Misty. Who plays it??
Music is from Three Blind Mice CD by Tsuyoshi Yamamoto Trio.
J'ai ce même amplificateur mais mes gros condensateurs étaient brûlés et je voudrais avoir d'autres, il me faut deux. Comment faire pour les avoir ? Salut.
For sale ?
How much ?
have a sansui amp,have been told it is unrepairable ,is that possible
To answer your question: Yes. When it is impossible to find the replacement parts for your unit. So it depends on which part needs to be replaced. Also if there is severe damage on PCB it may not be able to fix. Unless to find a usable same PCB which is selling on eBay or somewhere. You can send your request to my email (which is on my RUclips channel homepage). I can discuss with you and assist you repairing your amp. Thanks.
Is it me, I saw the speaker selector in the off position, (maybe that's why it had no sound?
Hard to tell from the viewing angle. In fact, it was set in A speaker position. The speaker relay won't kick in if the output voltage was high as 9V.
You are quite right. The indicator was in the off position when the amp first appeared in the first 30 seconds. We see the amp at 9:36 with the selector in the A position which is quite different.. I have one of these and it is the same.
I have a question about sansui au707, would you be able to help , is there any messenger contact can share with me?
My email address is listed in my RUclips channel home page under "About". Please send your inquiries to my email so I can help you the best I can.
Content was good, but I found it hard to follow reading text, and watching pictures at the same time.
Thank you for your comments. I will try improving my video with your suggestions.
@@VintageAudioFan Thank you for taking honest feedback kindly. I think of them as opportunities for improvement myself. Wish more people would speak their mind while being respectful to the content creator.
Could you repost this video and "talk." Tell what you did, how long, anything.
Please email me the issue you have and I'll do my best to help you.
@@VintageAudioFan, i have a doubt about the sansui au707. It was bought second hand and was not used for sometime, it is send to my friend to use, he mentioned that when first time used for 1 hour there was no issues, after that even after volume is cut, there is a humming sound. He suspects it is some issue with relay, i am not much familiar with electronics, could you suggest what could be the reason
@@VintageAudioFanmay i have your email id?
Sooo....musical!
Misty...Erroll at piano ;)