Hi All,
I have a Sansui G-7500 on the bench. One channel had shorted outputs and drivers. Now that I've replaced the dead stuff I'd like to set it up properly. The regulated power supply may need some attention as well. It was (poorly) serviced somewhere else before I got to it.
Does anyone have a schematic for this animal? I also need the bias current setting recommended by the manufacturer.
Thanks for any help - Chris
I have a Sansui G-7500 on the bench. One channel had shorted outputs and drivers. Now that I've replaced the dead stuff I'd like to set it up properly. The regulated power supply may need some attention as well. It was (poorly) serviced somewhere else before I got to it.
Does anyone have a schematic for this animal? I also need the bias current setting recommended by the manufacturer.
Thanks for any help - Chris
g 7500
Hi, did you ever find the schematic, i have a G7500, had the same problem, bad outputs in the right side, I pulled them, then the left side worked fine, i swapped the good outputs to the right side, the amp plays but is very distorted. By chance do you know what I am missing, I checked what I think are the drivers but cant find anything else bad. Thanks for your time
Hi, did you ever find the schematic, i have a G7500, had the same problem, bad outputs in the right side, I pulled them, then the left side worked fine, i swapped the good outputs to the right side, the amp plays but is very distorted. By chance do you know what I am missing, I checked what I think are the drivers but cant find anything else bad. Thanks for your time
Hi 1978chevyman,
I managed to repair it and made a close guess as to the bias current. Customer was extremely pleased after he got it hooked up. It hadn't sounded that good before it blew again.
Never swap good parts from one channel to the bad channel!
Don't do that! Did my message come through? I'm just tired of repeating this, it wasn't anything you said, except for "i swapped the good outputs to the right side". Made me see red.
All right. Obviously you are missing something very important. Let's start at the extreme basic stuff.
Did you clean the heat sink, transistors and apply new thermal compound and mica insulators? If you have not done this, stop and correct the situation. Make sure the outputs go back to their proper places on the correct channel. Let me know when this is done.
-Chris
I managed to repair it and made a close guess as to the bias current. Customer was extremely pleased after he got it hooked up. It hadn't sounded that good before it blew again.
Never, ever do that. The only thing you can swap between channels are your meter probes and your 'scope probes.
Never swap good parts from one channel to the bad channel!
Don't do that!
Did my message come through? I'm just tired of repeating this, it wasn't anything you said, except for "i swapped the good outputs to the right side". Made me see red.All right. Obviously you are missing something very important. Let's start at the extreme basic stuff.
Did you clean the heat sink, transistors and apply new thermal compound and mica insulators? If you have not done this, stop and correct the situation. Make sure the outputs go back to their proper places on the correct channel. Let me know when this is done.
-Chris
Re: g 7500
hi,
this could be a sign of one emitter resistor being open, (0.33 if i am right) distortion is due to the fact that the driver is delivering the ouput.
imho, these sansuis are great receivers...they use sanken output transistor parts,
i happened to own a g5000 once...
1978chevyman said:
hi,
this could be a sign of one emitter resistor being open, (0.33 if i am right) distortion is due to the fact that the driver is delivering the ouput.
imho, these sansuis are great receivers...they use sanken output transistor parts,
i happened to own a g5000 once...
yes, i installed them correctly, new HS compound, clean heatsink and all that. I admit , I am very much a rookie but I have seen many amps correctly repaired and I know some basics. I know it isnt good practice to swap from one side to the other but I planned on ordering a hole new set of outputs, I wanted to verify if there was any other issues and well, there is. I only played them for a few seconds, not even long enough to get warm, they are not shorted at this time. I can install them back into the left side board (the good side) but im not clear, do you want me to reinstall the bad pair as well? again, thanks for your help and patience with a rookie, Kevin
Hi all and thanks again for the help and info, yes, I have a Fluke MM, no scope yet. Seems Tony was right on the money with the emitter. Found one I believe to be bad, again, I don't have a schematic so I am using the good side for reference. Three of the emitters are showing .6 and one shows 12.7. Upon closer inspection, I noticed a small resistor in front of the emitter that looked a little burnt in the middle. It showed 222.5 on the good side and 8.2 on the problem side. This one is marked Red Red Brown Black.
Again, please excuse my Rookieness but it has been 15 years since High School and I cant remember how to tell values on Resistors anymore.
Ok, now for the drivers, again, no schematic and very little expeirience but I believe they are the transistors mounted to small heatsinks right in front of the emitters, 2 per side,one is blue and one is black. They are both NEC's and each have 2 numbers, one says D381 & 2M88C. The next one 8536 & 2M81C. I havent been able to find any info on these except for other postings inquiring about where to find them. I could be wrong and these may not even be the drivers.
Oh and yes, check the first two bad outputs with a DMM, they are dead shorted, I was able to find actual Sanken replacements for the outputs on ebay, they are on the way.
Again, thanks for any help, Kevin
Again, please excuse my Rookieness but it has been 15 years since High School and I cant remember how to tell values on Resistors anymore.
Ok, now for the drivers, again, no schematic and very little expeirience but I believe they are the transistors mounted to small heatsinks right in front of the emitters, 2 per side,one is blue and one is black. They are both NEC's and each have 2 numbers, one says D381 & 2M88C. The next one 8536 & 2M81C. I havent been able to find any info on these except for other postings inquiring about where to find them. I could be wrong and these may not even be the drivers.
Oh and yes, check the first two bad outputs with a DMM, they are dead shorted, I was able to find actual Sanken replacements for the outputs on ebay, they are on the way.
Again, thanks for any help, Kevin
to add to the previous post, I had an error, the NEC transistor is actually a B536. Did a little more research and found the PN's to be 2SD381 and 2SB536, they are the drivers and are turning out to be hard to locate. Also, I figured out my resistor is a 22ohm 1% and I think it is a 1/2 watt. If anyone has the drivers I need available for sale, let me know Thanks again, Kevin
Thanks again, Kevin
Hi 1978chevyman,
I'd rather see you do it right and learn the proper ways to proceed.
You have to understand that you can blast transistors to kingdom come before the power switch contacts come to rest from bouncing. Well, maybe a little longer, but the point is that transistors can fail before your brain figures out what the smoke / noise / flash is all about. Before your finger leaves the power lever / button.
I'll say this one more time ........
Never swap good parts from one channel to the bad channel!
I'm not kidding, there is a reason for this and you don't seem to understand. I've trained many technicians (and fired many) over the years. Most guys who work in the field assume they know how to repair an amplifier. I can tell you with certainty that over 90% haven't got the first idea and don't understand what they are doing.
Also, cleaning the heat sink and new compound was very good. Many techs don't even do that. So you are ahead of the game. Remember to work clean, solves problems down the line.
-Chris
It is so hard to unlearn very bad habits. Most service techs I see working do very silly things. Step one, think about what you are about to do and ask yourself if it makes sense. If you don't understand what can happen, do not do what you were about to do.
I'd rather see you do it right and learn the proper ways to proceed.
Right!
You have to understand that you can blast transistors to kingdom come before the power switch contacts come to rest from bouncing. Well, maybe a little longer, but the point is that transistors can fail before your brain figures out what the smoke / noise / flash is all about. Before your finger leaves the power lever / button.
I'll say this one more time ........
Never swap good parts from one channel to the bad channel!
I'm not kidding, there is a reason for this and you don't seem to understand. I've trained many technicians (and fired many) over the years. Most guys who work in the field assume they know how to repair an amplifier. I can tell you with certainty that over 90% haven't got the first idea and don't understand what they are doing.
No, there is no point unless you want to stick them in there so you can remember what goes where.
That may have been a mistake. Your chances of getting a fake are extremely high. I can't remember what the numbers on the outputs are, can you refresh my memory please?
Also, cleaning the heat sink and new compound was very good. Many techs don't even do that. So you are ahead of the game. Remember to work clean, solves problems down the line.
-Chris
I have a good friend that repairs car audio amps for a living, a shop called Short Circuit in Millpitas CA. , several a day every day, he is a member here and has a very good rep for repairing, he has repaired over 100 car amps for me and I have yet to have a problem with any of them, that is where i learned a few things like checking transistors for short and cleaning the crap out of everything before, during and after any service performed.
So, since I am into just about everything to do with audio, I collect home equipment as well, my friend is not into repairing home amps, he just doesnt have the room or the extra time so, I am tyring to learn some stuff on my own. In High school took at least 2 electronic classes a year but that was 15 years ago now and very little stuck with me.
As for the outputs, there is an A1106N and a C2581n per side. On ebay I found new old stock Sanken A1106 and C2581. There is actually pics of the posted and they look identical to the ones I have with the exception of the "N" at the end of the P/N. My partner said there would be no issue with the PN's but said I need to make sure everything else is in good working order before installing them, that is why I swapped the old ones.
So, I have checked most of the components to the best of my ability, like Tony mentioned, I found a couple bad resistors and i have a feeling the drivers should be replaced. One of the emitter Resitors is is open and a small resistor between the driver and the emitter is bad as well. I am also having trouble finding the drivers, 2X 2SD381 and 2X 2SB536.
So, let me know where you think i should go from here, the receiver is in mint condition and I would hate to screw it up but on the same note, it isnt worth sending out for repair, im pretty sure I could buy a working one for less, if I can repair it myself, i would be thrilled!!!!
Thanks for your time, Kevin
So, since I am into just about everything to do with audio, I collect home equipment as well, my friend is not into repairing home amps, he just doesnt have the room or the extra time so, I am tyring to learn some stuff on my own. In High school took at least 2 electronic classes a year but that was 15 years ago now and very little stuck with me.
As for the outputs, there is an A1106N and a C2581n per side. On ebay I found new old stock Sanken A1106 and C2581. There is actually pics of the posted and they look identical to the ones I have with the exception of the "N" at the end of the P/N. My partner said there would be no issue with the PN's but said I need to make sure everything else is in good working order before installing them, that is why I swapped the old ones.
So, I have checked most of the components to the best of my ability, like Tony mentioned, I found a couple bad resistors and i have a feeling the drivers should be replaced. One of the emitter Resitors is is open and a small resistor between the driver and the emitter is bad as well. I am also having trouble finding the drivers, 2X 2SD381 and 2X 2SB536.
So, let me know where you think i should go from here, the receiver is in mint condition and I would hate to screw it up but on the same note, it isnt worth sending out for repair, im pretty sure I could buy a working one for less, if I can repair it myself, i would be thrilled!!!!
Thanks for your time, Kevin
kevin,
it would be wise to follow anatech's advice, he knows what he is doing and been there...
myself used to own a repair shop in late 80's to mid 90's before going overseas as an OFW, overseas pinoy worker.
i have repaired lots and lots of japanese amps and some usa made ones, like soundcraftsmen, GAS, etc.
key to a succesfull repair i would say would be troubleshooting, that takes 90% of the work, the other 10% would be actual replacement of defective parts....
if you do not know why you are about to do what you are about to do, then better not do it...
i do not see any reason why MJE15033/15032 can not be used as replacement, they are likewise to220 and available in the us of a.....
it would be wise to follow anatech's advice, he knows what he is doing and been there...
myself used to own a repair shop in late 80's to mid 90's before going overseas as an OFW, overseas pinoy worker.
i have repaired lots and lots of japanese amps and some usa made ones, like soundcraftsmen, GAS, etc.
key to a succesfull repair i would say would be troubleshooting, that takes 90% of the work, the other 10% would be actual replacement of defective parts....
if you do not know why you are about to do what you are about to do, then better not do it...
i do not see any reason why MJE15033/15032 can not be used as replacement, they are likewise to220 and available in the us of a.....
Hi Tony, yes I agree, I am ready and willing to do whatever Anatech says I should do, I would love to get the receiver up and running and most of all learn something in the process. I think I have the bad parts narrowed down, just need to know if there is anything else I should be checking before installing new components. thanks, Kevin
Hi Kevin,
The current Japanese drivers would work well, 2SAxxxx and 2SCxxxx. For outputs, I would have gone with a pair of MJW types from On Semi. They are current and represent an improved device. Best of all, not fakes.
Look around for a schematic close to a G-7500. Given that the set is yours, it's well worth paying for a manual. I wouldn't kid you on that. I am familiar with these if it's on my bench and I can touch it, so I can sometimes get away without one. I don't expect you to succeed without a manual. I'll see if I have anything close.
-Chris
The current Japanese drivers would work well, 2SAxxxx and 2SCxxxx. For outputs, I would have gone with a pair of MJW types from On Semi. They are current and represent an improved device. Best of all, not fakes.
Not even close! Newer sets are scrap for sound quality on average. Those older sets that are well designed (yours is) will outperform the new ones easily. They even sound better than some new separates. They are most certainly worth paying to get repaired if they are in cosmetically good shape. It is worth learning as you do it yourself.
Look around for a schematic close to a G-7500. Given that the set is yours, it's well worth paying for a manual. I wouldn't kid you on that. I am familiar with these if it's on my bench and I can touch it, so I can sometimes get away without one. I don't expect you to succeed without a manual. I'll see if I have anything close.
-Chris
Hi Tony,
Thank you for your kind words.
So 1978chevyman, you are getting good advice from more than one person. Just use your common sense and ask if you don't know something.
-Chris
Thank you for your kind words.
They are too slow, and a little different from the originals. Newer Japanese parts are closer to the originals. Trust me on this.
This set uses a VBE multiplier (bias transistor). Check and clean the bias pot. Good advice.
So 1978chevyman, you are getting good advice from more than one person. Just use your common sense and ask if you don't know something.
-Chris
kevin,
this should come close: http://www.eserviceinfo.com/download.php?fileid=23222
it comes in two parts, you need winrar to decompress the file, good luck!
this should come close: http://www.eserviceinfo.com/download.php?fileid=23222
it comes in two parts, you need winrar to decompress the file, good luck!
Hi Chris, what I meant by replacing it was, I can find another working G-7500 on ebay and wouldnt expect to pay more than about $125. I fully agree about the older equipment, this receiver is one of many i currently own. While I do have some newer stuff I consider good for watching TV/movies, I dont listen to my music through my surround amp. My current audio system consists of 4X Sansui AU-717's, 2 running a pairs of Klipsch Heresys and 2 pairs of Bose 901s with the other 2 717's.
I also own a Sansui 990DB, over seas version of a 9090db and a Sansui 1000A tube Receiver. Various Pioneers as well, in fact I just sold a mint SX1250 on Ebay a few weeks ago. I run an E-waste recycling center here in my town and this stuff comes in every day, in fact someone dropped off a Sansui TR 707A today, apparently Sansui's very first solid state receiver, I brought it home but havent had a chance to mess with it yet but it looks almost new.
And yes, I also agree, I need to find the schematic and or manual, I have been looking, most all I find are other people looking for it to, that how I found this posting. I will keep looking, Im pretty sure I can get an overpriced one on ebay. thanks again Chris for the advice, Kevin
I also own a Sansui 990DB, over seas version of a 9090db and a Sansui 1000A tube Receiver. Various Pioneers as well, in fact I just sold a mint SX1250 on Ebay a few weeks ago. I run an E-waste recycling center here in my town and this stuff comes in every day, in fact someone dropped off a Sansui TR 707A today, apparently Sansui's very first solid state receiver, I brought it home but havent had a chance to mess with it yet but it looks almost new.
And yes, I also agree, I need to find the schematic and or manual, I have been looking, most all I find are other people looking for it to, that how I found this posting. I will keep looking, Im pretty sure I can get an overpriced one on ebay. thanks again Chris for the advice, Kevin
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