Hafler TA1100 problem

[vfluxrob]

I have a Hafler TA1100 amp and it has a really strange problem.

Channel A works, but only high frequencies come through - almost like a high-pass filter has been applied. I verified this with swapping all cabling and speakers. Otherwise, the amp works fine, and channel B's audio is fine.

So my questions are these:

Does anyone know offhand what might cause this and at what components I might look to fix it?

Where can I get a schematic for the TA1100? Hafler's site only has an operations manual.



Thanks

Rob P in Michigan

[bwalraven]

Rob,

I've got one with a similar issue.

I can tell you that each channel is basically a separate amp. If you're interested in selling yours I might be interested in buying...

If you're interested in getting schematics, I emailed Halfler and they emailed me a copy of the schematics. I'd be happy to email them to you. You can just PM me here.

Thanks,
BJ

[vfluxrob]

Thanks! Sure, send the schematics to boatinrob@gmail.com

I appreciate your help.

Depending on how things go, I may indeed sell the amp. I've peeked inside and nothing looks amiss, so we'll see where the schematics get me.

BTW I'm in Novi, so not far to travel if I sell it to ya.

Thanks again

Rob

[Zero Cool]

I need a set of schematics for one of these as well. tetech2@doitnow.com if anyone has a set.

[dekayz200]

Could I get a set too?

Dekayz200@Yahoo.com

Thanks!

[Zero Cool]

well i have schematics now. but no info on how to set bias. Mine had both channels blown. mosfets toasted. i replaced the mosfets and now i can power each channel up. but it has some odd problems. from 0 to 1vp-p the waveform is clean. after that it distorts badly with some rapidly increasing spikes on the trailing side of the sinewave. I spent hours today checking every resistor, diode and transistor. I even checked ALL the caps for shorts. I didn't find anything wrong, but now I am suspecting a bad VIA on the PCB someplace. Adjusting bias made no difference. but adjusting CMRR control did but it only changed the level as which the spikes appeared. I'm missing something simple as both channels do the same thing. need a fresh look in the morning.

[bwalraven]

Well, I changed my email address just after posting above, so I never saw any of your responses. Anyhow, I am just finally getting to look at the amp, and found this thread again when I was looking up some info.

I've updated my email with the forums, so I should see your responses now!

I sent schematics to vfluxrob and dkayz200 via email.

According to the local shop where I had it benched, there are 20 bad caps on one channel. He wanted $180 to fix it. I (obviously) said no thanks.

If anyone is looking for one of these with one bad channel, PM me. I'd be interested in selling. Or, if someone has one with one bad channel, I might be willing to take it off your hands.

Thanks,
BJ

[gootee]

Originally Posted by Zero Cool

well i have schematics now. but no info on how to set bias. Mine had both channels blown. mosfets toasted. i replaced the mosfets and now i can power each channel up. but it has some odd problems. from 0 to 1vp-p the waveform is clean. after that it distorts badly with some rapidly increasing spikes on the trailing side of the sinewave. I spent hours today checking every resistor, diode and transistor. I even checked ALL the caps for shorts. I didn't find anything wrong, but now I am suspecting a bad VIA on the PCB someplace. Adjusting bias made no difference. but adjusting CMRR control did but it only changed the level as which the spikes appeared. I'm missing something simple as both channels do the same thing. need a fresh look in the morning.

Both channels do the same thing? Have you checked the power supply voltages?

How old is it? Maybe one or more of the electrolytics in the power supply needs to be replaced. And electrolytics don't usually fail as a short (except for tantalums). Their ESR (equivalent series resistance) usually rises, which typically can't be detected with simple test equipment. If you don't have an ESR meter, but do have a scope and a pulse or square wave generator (or can throw one together with a 555 timer chip), you can try this: http://www.fullnet.com/~tomg/esrscope.htm . It often works even in-circuit.

Cheers,

Tom