Hi Williams Audio,
The schematics are like a book all broken up on different pages. A pain.
What do you need to do? <asks the ex-Counterpoint warranty tech?> I can't release them as Michael sells them. I will warn you that the output fets need to be matched insanely closely or it'll blow up.
-Chris
The schematics are like a book all broken up on different pages. A pain.
What do you need to do? <asks the ex-Counterpoint warranty tech?> I can't release them as Michael sells them. I will warn you that the output fets need to be matched insanely closely or it'll blow up.
-Chris
Hi Williams Audio,
1. What is wrong with your unit? I am trying to help you.
2. The SA-220 is very close to the SA-100 in general concept. All the ss stuff on the output board is an analog computer designed to sense the actual junction temperature of the outputs. It is jumpered to it's least effective position (basically off) and has no effect on the circuit operation. They merrily blow up. Much smoke and ash when they go. Flames out the top cover are common - and much smoke.
If one output is gone (unlikely, many are expected to be dead), you still must do one of two things.
Get the M.E. upgrade, choose your metal level
.
Or, get a set of outputs (a repair kit really) from M.E., if you plan to buy your own and match them, then budget two days and 40 of each number. I am not kidding here. They are that tight. You will need a jig that mounts 4 at a time and a temperature probe. Plus test gear and good DC supplies. I've done this.
-Chris
1. What is wrong with your unit? I am trying to help you.
2. The SA-220 is very close to the SA-100 in general concept. All the ss stuff on the output board is an analog computer designed to sense the actual junction temperature of the outputs. It is jumpered to it's least effective position (basically off) and has no effect on the circuit operation. They merrily blow up. Much smoke and ash when they go. Flames out the top cover are common - and much smoke.
If one output is gone (unlikely, many are expected to be dead), you still must do one of two things.
Get the M.E. upgrade, choose your metal level
.Or, get a set of outputs (a repair kit really) from M.E., if you plan to buy your own and match them, then budget two days and 40 of each number. I am not kidding here. They are that tight. You will need a jig that mounts 4 at a time and a temperature probe. Plus test gear and good DC supplies. I've done this.
-Chris
hi anatech,
the problem is that one channel's fets is getting very, very hot and the other is cool, when i adjust the bias currents it holds on for a short time and then it happens once again, some times the opposite ch is getting hot, that's why i need the schematics for
sa-220if it is possible.
when is getting very hot are a lot of distortions as well.
i will try to use the sa-100 drawings, so........
best regards
williams
the problem is that one channel's fets is getting very, very hot and the other is cool, when i adjust the bias currents it holds on for a short time and then it happens once again, some times the opposite ch is getting hot, that's why i need the schematics for
sa-220if it is possible.
when is getting very hot are a lot of distortions as well.
i will try to use the sa-100 drawings, so........
best regards
williams
Hi Williams,
This amp uses a standard Vbe multiplier with an added emitter degeneration resistor. The thermal time constant is very long and the tracking is not ideal.
Remove one supply fuse and install a 1 ohm resistor. You will measure the voltage drop across this resistor. At 1/3 nominal AC input voltage, you should measure less than a 10 mV drop. Anything greater than this indicates a defective mosfet.
The bias current should be set for a reading of 0.48 to 0.52 VDC across the 1 ohm resistor. The bias will climb with temperature. You should allow at least 1/2 hour for the bias to settle down before readjusting. The entire procedure will easily require 1/2 day or more.
I hope this allows you to complete the job.
-Chris
This amp uses a standard Vbe multiplier with an added emitter degeneration resistor. The thermal time constant is very long and the tracking is not ideal.
Remove one supply fuse and install a 1 ohm resistor. You will measure the voltage drop across this resistor. At 1/3 nominal AC input voltage, you should measure less than a 10 mV drop. Anything greater than this indicates a defective mosfet.
The bias current should be set for a reading of 0.48 to 0.52 VDC across the 1 ohm resistor. The bias will climb with temperature. You should allow at least 1/2 hour for the bias to settle down before readjusting. The entire procedure will easily require 1/2 day or more.
I hope this allows you to complete the job.
-Chris
Hi Williams,
Due to the high power dissipation from each output, I would strongly recommend you stay with the originals. Never mind the horror story involved with matching them close enough. You really want to avoid having to do this.
BTW, never tighten the screws just short of damaging the sockets as stated in the manual. Follow all mounting recommendations from IR or MOT. Overtightening the parts will increase the thermal resistance of the interface and may crack the die inside the part.
Basically, don't play with the outputs unless there is no other choice.
-Chris
Due to the high power dissipation from each output, I would strongly recommend you stay with the originals. Never mind the horror story involved with matching them close enough. You really want to avoid having to do this.
BTW, never tighten the screws just short of damaging the sockets as stated in the manual. Follow all mounting recommendations from IR or MOT. Overtightening the parts will increase the thermal resistance of the interface and may crack the die inside the part.
Basically, don't play with the outputs unless there is no other choice.
-Chris
Hi Elso,
Maybe not. Wrong adjustment can do this since there can be a big lag between adjust and effect.
Try first before messing with this amp. If something goes wrong it will really cost $$$$$$$$$$$$$$$$$$. It will also prove to be a pain in the rear end to fix.
-Chris
Edit: Parser didn't like that either.
Maybe not. Wrong adjustment can do this since there can be a big lag between adjust and effect.
Try first before messing with this amp. If something goes wrong it will really cost $$$$$$$$$$$$$$$$$$. It will also prove to be a pain in the rear end to fix.
-Chris
Edit: Parser didn't like that either.
"oh, and i'v come to the conclutions that cables have no decernable impact on sound, that subjectivism is the death of facts, and that psudo science is to be feared like the black plauge."
- Demogorgon
--I've come to the conclusion that the proper understanding of the function of the human hearing mechanism makes it abundantly clear why people hear differnces is cables, power cables, amplifiers, and reproduced sond overall....
--that subjectivism is the point at which the human mind advances to the next level of understanding, which is one that mechanistic and materialstic views completely deny, thus banishing the adherents to objectivism and scientific methodology to the bin of confused animalism--basically a comfortable wallowing in the 'will to ignorance'.....
--And that pseudo-science is at the edge of understanding..ie it fades in and out of and is on the edge of the darkenss of the unknown, where all advances in human endeavor come from. That it exists AS a point that is not understood. Very important to embrace that which is unknown and try it on for size, drive it down the road a bit, test it out. If false, in either the short or long term, discard..but also remember, so it can be looked at again, anew, when more information comes along. Only a fool discards the unknown and the 'pseudo'. That would be wallowing in the safety and comfort of mother's arms. There is NO discovery there. None whatsoever. But do NOT have the stupidity or the affront to call out those who choose to explore and risk, for they are at the forefront of human endeavor. It is they who try to bring you brave new worlds. Remember, the unknown is the challenge, and the textbook is the joke.
The majority of humanity fails to understand these basic and simple truths, thus...the majority forces/enforces a life of 'wallowing in the mud' as the sociological and cultural 'norm'. An awful truth of the herd instinct. Sad indeed, but true.
The conclusion could be that the original commentor does not have the capacity for invention--and is frightened by new things. An exceedingly dangerous and shortsighted combination.
- Demogorgon
--I've come to the conclusion that the proper understanding of the function of the human hearing mechanism makes it abundantly clear why people hear differnces is cables, power cables, amplifiers, and reproduced sond overall....
--that subjectivism is the point at which the human mind advances to the next level of understanding, which is one that mechanistic and materialstic views completely deny, thus banishing the adherents to objectivism and scientific methodology to the bin of confused animalism--basically a comfortable wallowing in the 'will to ignorance'.....
--And that pseudo-science is at the edge of understanding..ie it fades in and out of and is on the edge of the darkenss of the unknown, where all advances in human endeavor come from. That it exists AS a point that is not understood. Very important to embrace that which is unknown and try it on for size, drive it down the road a bit, test it out. If false, in either the short or long term, discard..but also remember, so it can be looked at again, anew, when more information comes along. Only a fool discards the unknown and the 'pseudo'. That would be wallowing in the safety and comfort of mother's arms. There is NO discovery there. None whatsoever. But do NOT have the stupidity or the affront to call out those who choose to explore and risk, for they are at the forefront of human endeavor. It is they who try to bring you brave new worlds. Remember, the unknown is the challenge, and the textbook is the joke.
The majority of humanity fails to understand these basic and simple truths, thus...the majority forces/enforces a life of 'wallowing in the mud' as the sociological and cultural 'norm'. An awful truth of the herd instinct. Sad indeed, but true.
The conclusion could be that the original commentor does not have the capacity for invention--and is frightened by new things. An exceedingly dangerous and shortsighted combination.
SA-100 with NP-100 board
Hello,
I know this thread is old but I haven't found anything else...
My SA-100 I just picked up has 2 driver transistors removed, a blown rectifier bridge and numerous other faults. Supposedly the right channel works, but I'm not going to power this up to find out...
One thing I noticed was the YELLOW/BLACK (8V) and YELLOW (0V) wires attached to the board are crossed. Can anyone with a basic NP100 confirm if this was a misprint on the board, or if someone inadvertently crossed them after attempting repair? I can't see the traces (apparently they're on the bottom of the board)
Thank you!
Hello,
I know this thread is old but I haven't found anything else...
My SA-100 I just picked up has 2 driver transistors removed, a blown rectifier bridge and numerous other faults. Supposedly the right channel works, but I'm not going to power this up to find out...
One thing I noticed was the YELLOW/BLACK (8V) and YELLOW (0V) wires attached to the board are crossed. Can anyone with a basic NP100 confirm if this was a misprint on the board, or if someone inadvertently crossed them after attempting repair? I can't see the traces (apparently they're on the bottom of the board)
Thank you!
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