I suggest a crude but quick and simple way to demonstrate the problem to them (and to yourself):
I'm assuming a couple things so please correct what's not right:
a) what do you drive this amp with?
Say... a CD player?
What outputs does it have ... a couple RCA jacks?
And your amp input, again a couple RCA jacks?
b) if so, grab a stereo RCA to RCA cable, split it into 2 mono RCA ones, discard one .
With the mono cable resulting, connect one player p\output ,say the right one, to one Sony channel, say the right one, play something you know and like and rise volume to what you use at home.
Then , touching no controls at all, neither at the player nor the amp, pull amp side RCA plug and plug it into the other channel.
Sound should be exactly the same.
Go back and forth 5-10 times, whatever , until difference (or lack of it) is evident even to a deaf man.
If obvious difference, go with amp and mono cable to service shop and demonstrate it to them until they acknowledge it.
Don't leave the amp and cable at the front desk with a promise "our Tech will check it later", have the Tech hear and acknowledge it before your very eyes ...... or else.
Then either repair it properly or handle $250 back with excuses or get a BBB/small claims court appointment, their choice.
Won't suggest physical violence though.
This way we are checking there is not a problem at your music player system; even if there is, you are testing with the exact same sound source, who cares (for this test) that it's "half what you should hear"?
Almost forgot: at home, switch speakers too, test with the right speaker on the left channel and viceversa; you might have , say, a dead tweeter on one speaker and that would account for what you hear, while amp itself is not at fault.
"Leave no stone unturned" .
I'm assuming a couple things so please correct what's not right:
a) what do you drive this amp with?
Say... a CD player?
What outputs does it have ... a couple RCA jacks?
And your amp input, again a couple RCA jacks?
b) if so, grab a stereo RCA to RCA cable, split it into 2 mono RCA ones, discard one .
With the mono cable resulting, connect one player p\output ,say the right one, to one Sony channel, say the right one, play something you know and like and rise volume to what you use at home.
Then , touching no controls at all, neither at the player nor the amp, pull amp side RCA plug and plug it into the other channel.
Sound should be exactly the same.
Go back and forth 5-10 times, whatever , until difference (or lack of it) is evident even to a deaf man.
If obvious difference, go with amp and mono cable to service shop and demonstrate it to them until they acknowledge it.
Don't leave the amp and cable at the front desk with a promise "our Tech will check it later", have the Tech hear and acknowledge it before your very eyes ...... or else.
Then either repair it properly or handle $250 back with excuses or get a BBB/small claims court appointment, their choice.
Won't suggest physical violence though.
This way we are checking there is not a problem at your music player system; even if there is, you are testing with the exact same sound source, who cares (for this test) that it's "half what you should hear"?
Almost forgot: at home, switch speakers too, test with the right speaker on the left channel and viceversa; you might have , say, a dead tweeter on one speaker and that would account for what you hear, while amp itself is not at fault.
"Leave no stone unturned" .
OK, let's think this through a bit before you go doing it.
What happens if you pull out the ONLY cable connecting the source and the amplifier? A cinch connection will first lose ground, at which point any mains 'wandering current' due to transformer capacitance will appear in the amplifier's input - with completely unpredictable amplitude. So as you are unplugging the source you will get a potentially huge mains hum signal, and the same as you are plugging it in. Just ideal to do more damage. Do it 5-10 times, it's likely you will have a dead woofer, and possibly amplifier.
Then uou send the bill to JMFahey above, whom I would advise to first try what he is telling you to do himself.
NO DO NOT DO what the above poster said, rather, keep the other cable and use it to connect the other (unused) channel on your source to a different (not used) input on the amp (except Phono) just to establish a ground connection. Then you can demonstrate as he says in his post.
What happens if you pull out the ONLY cable connecting the source and the amplifier? A cinch connection will first lose ground, at which point any mains 'wandering current' due to transformer capacitance will appear in the amplifier's input - with completely unpredictable amplitude. So as you are unplugging the source you will get a potentially huge mains hum signal, and the same as you are plugging it in. Just ideal to do more damage. Do it 5-10 times, it's likely you will have a dead woofer, and possibly amplifier.
Then uou send the bill to JMFahey above, whom I would advise to first try what he is telling you to do himself.
NO DO NOT DO what the above poster said, rather, keep the other cable and use it to connect the other (unused) channel on your source to a different (not used) input on the amp (except Phono) just to establish a ground connection. Then you can demonstrate as he says in his post.
Well, this is a good lesson for all of us.. I'm very sorry this has happened to you, because I have been repairing amps for awhile now, and I believe the 707 is among
the best integrated amps around.. It runs 70mv of bias across both resistors, the
808 runs 80. The TA-N90 sounds slightly better, running 180mv !
If they are not concerned, I would find another shop. - The amp is too nice, I would move on to a shop that cares. - You could even ask a few shops if they
have a lot of the output mosfets in stock, to get a better match..
For example, a TA-F808ES just sold on flea bay for 1075 dollars!
the best integrated amps around.. It runs 70mv of bias across both resistors, the
808 runs 80. The TA-N90 sounds slightly better, running 180mv !
If they are not concerned, I would find another shop. - The amp is too nice, I would move on to a shop that cares. - You could even ask a few shops if they
have a lot of the output mosfets in stock, to get a better match..
For example, a TA-F808ES just sold on flea bay for 1075 dollars!
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what it sounds like is they did replace parts however
The bias has to be set and obviously one side is warm and the other side is not that means the output transistors are biased to0 cold and not dissipating heat as they should. Maybe the bias pot is dirty or has a bad spot in it which I have seen on many solid state amps that are up in years.Now,I have also seen generic replacements not work correctly but it sure sounds like the bias current wasn't for the new transistors that were installed,or maybe they moved the bias pot and forget to set it back to spec after cleaning it..I will look at a schematic on this unit.
The bias has to be set and obviously one side is warm and the other side is not that means the output transistors are biased to0 cold and not dissipating heat as they should. Maybe the bias pot is dirty or has a bad spot in it which I have seen on many solid state amps that are up in years.Now,I have also seen generic replacements not work correctly but it sure sounds like the bias current wasn't for the new transistors that were installed,or maybe they moved the bias pot and forget to set it back to spec after cleaning it..I will look at a schematic on this unit.
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You make it sound like eating Haagen DAZ ice cream
I agree tho. I will gladly talk to that shop if he wants to take it back there and I'll ask them why they didn't feel it was necessary to the check bias in the output stage.
when you talk about indulging and I'm all out so that settles that.
I agree tho. I will gladly talk to that shop if he wants to take it back there and I'll ask them why they didn't feel it was necessary to the check bias in the output stage.
I found the service manual but it's yoo big to upload here but
The bias in each channel needs to set to 30mv. ..Here is the thing.He told you he replaced transistors and three resistors but you need to find out if he replaced the MOSFET outputs and if he did,it is imperative that he used the .22 ohm resistors in the drain whether it's the driver or the outputs.I have seen times where shops put anything .47ohms or less in there and you can't do that because the protection circuit monitors that and in your case if there is ANY DC voltage on the base of Q402,it' going to turn on and limit power.
Lets assume he did he put the right values in.He would still have to set the bias for the parameters of the new transistors just like when we change output tubes. RT402 and RT452 are the bias adjustments for each channel and it's measured at TP1 and TP2 respectively.
I would be more than happy to talk to this man and I will email him the service manual or anyone that wants a copy free of course..I don't think there is a major problem with your unit.I just think he did what I have seen being done a number of times on McIntosh where people put the wrong value emitter resistors in when changing outputs and that causes the power guard to limit power until the problem is corrected.
I teach mon/tue/and wed until noon and then I'm home the rest of the week..If you email me,I will give you my cell number you can call during lunch break or anytime after 5 in the evening .I will me more than happy to help you out and talk to the tech and find out what he did replace..I don't think it's a major issue but if you don't have the bias properly set,it's going to sound awful especially when it's under biased. I can call the tech and explain this because he may just be a parts changer like many of them are.
My email is merccougar89@gmail.com
The bias in each channel needs to set to 30mv. ..Here is the thing.He told you he replaced transistors and three resistors but you need to find out if he replaced the MOSFET outputs and if he did,it is imperative that he used the .22 ohm resistors in the drain whether it's the driver or the outputs.I have seen times where shops put anything .47ohms or less in there and you can't do that because the protection circuit monitors that and in your case if there is ANY DC voltage on the base of Q402,it' going to turn on and limit power.
Lets assume he did he put the right values in.He would still have to set the bias for the parameters of the new transistors just like when we change output tubes. RT402 and RT452 are the bias adjustments for each channel and it's measured at TP1 and TP2 respectively.
I would be more than happy to talk to this man and I will email him the service manual or anyone that wants a copy free of course..I don't think there is a major problem with your unit.I just think he did what I have seen being done a number of times on McIntosh where people put the wrong value emitter resistors in when changing outputs and that causes the power guard to limit power until the problem is corrected.
I teach mon/tue/and wed until noon and then I'm home the rest of the week..If you email me,I will give you my cell number you can call during lunch break or anytime after 5 in the evening .I will me more than happy to help you out and talk to the tech and find out what he did replace..I don't think it's a major issue but if you don't have the bias properly set,it's going to sound awful especially when it's under biased. I can call the tech and explain this because he may just be a parts changer like many of them are.
My email is merccougar89@gmail.com
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You guys should really heed JMFahey's advise: make you sure you know exactly what the issue is, and whether it really is in the amp.
Fall on your face at that shop again and you can't go there anymore ever!
You can't really ask them to do their homework when you don't.
Jan
Why thanks Pete.
Maybe they'll let me chauffeur the Pope in his Maserati or was that one of the other Popes? Argh argh!
Maybe they'll let me chauffeur the Pope in his Maserati or was that one of the other Popes? Argh argh!
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I just realized something.I'm responding to an OP that was made a month ago.
It's a different forum than I am used to but maybe this gentleman resolved the issue already?
It's a different forum than I am used to but maybe this gentleman resolved the issue already?
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