I am moving this over from the chip amp thread as it really belongs here. I am repairing a Hafler TA-1100 amp for a friend. the mosfets were blown on one channel and the other distorted badly. after a bit of searching i see that this little amps are very problematic. so im hoping what i found might help others.
I replaced the mosfets and was able to power up each channel of the amp ok. but now both channels of the amp had the same distortion.
After a bit of troubleshooting i found C21 and C22 were bad! this was causing U2B to go open loop and distort. this was injecting distortion into the NFB loop of the amp. replacing C21 and C22 has cured the problem and now the amp works great.
At a guess, I suspect that 99% of the problems with these little amps could be traced back to these 10uf 16v little EL caps going bad. there are 7 of them per channel! I will order a handful and replace them all and test all that come out.
Now what i would like to know is what is U2B doing? I suspect some form of LF feedback??
and BTW....for a 50w pch amp this is one complicated bugger!
I have the schematic in PDF form but need to figure out how to post it here. its too large to post.
I replaced the mosfets and was able to power up each channel of the amp ok. but now both channels of the amp had the same distortion.
After a bit of troubleshooting i found C21 and C22 were bad! this was causing U2B to go open loop and distort. this was injecting distortion into the NFB loop of the amp. replacing C21 and C22 has cured the problem and now the amp works great.
At a guess, I suspect that 99% of the problems with these little amps could be traced back to these 10uf 16v little EL caps going bad. there are 7 of them per channel! I will order a handful and replace them all and test all that come out.
Now what i would like to know is what is U2B doing? I suspect some form of LF feedback??
and BTW....for a 50w pch amp this is one complicated bugger!
I have the schematic in PDF form but need to figure out how to post it here. its too large to post.
Warning this is a pretty big picture.
Also of note. the output of the amp is connected as NF in two places. the flag labeled OUT at R11 and the flag labeled out at R35/C11 junction.
Also of note. the output of the amp is connected as NF in two places. the flag labeled OUT at R11 and the flag labeled out at R35/C11 junction.
An externally hosted image should be here but it was not working when we last tested it.
turns out all 7 of the 10uf 16V surface mount caps on both boards were bad! I suggest anyone with these amps re-cap all the surface mount EL cans!
Hi Zero Cool can you send me a schematic for the Hafler TA1100
Thanks may address is mario6x2@hotmail.fr
Thanks may address is mario6x2@hotmail.fr
Hey Zero Cool, where did you get the capacitors? I have a ta1100 that sounds very "tinny" and suspect they may need new caps. Can you send me a link to the ones you purchased?
Thanks!
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