My beloved Parasound HCA 2200 mk ii has just developed a rather distinctive failure symptom, I wonder if anyone can help identify the cause? The left channel is now only partially working, it seems to be dropping the lower level signals. I noticed with a track that normally starts with a ten second piano intro on the left only, almost nothing happens, then when the vocal comes in it sounds fine. If I switch the inputs the piano comes through perfectly on the right. The same occurs with both XLR and RCA inputs on the left. I also noticed on a phase checking track that the signal from that side has gone out of phase. I have had a good look at the boards (top only) and can't see any obvious problems. I have tried switching the input board power supplies so that the left regulated supply is powering the right channel, the problem stays on the left, so I have eliminated the input board power supplies. This is as far as I have got so far, I was thinking of switching the outputs from the input boards so they are driving the opposite output circuits but haven't got the courage together to do that yet. I did replace the main power supply capacitors recently (6 months ago) and readjusted the bias (could be related to the failure if I made some kind of error, but it has worked very nicely since then). If anyone could give me a steer it would be much appreciated!
Had a parasound 1000 HCA 2 that did the exact same thing. Of all things it was the input select mono/stereo switch.
I pulled it off the small board and low and behold no continuity. Taking it apart showed no obvious internal defects .
Putting it back together, still nothing.
Replaced it a C&K and the amp worked fine after that.
I questioned even going in that direction but a cheap part was all it was.
Your schematic shows similar.
Easy enough to pull and check to eliminate this area since you have the same issue.
Regards
David
I pulled it off the small board and low and behold no continuity. Taking it apart showed no obvious internal defects .
Putting it back together, still nothing.
Replaced it a C&K and the amp worked fine after that.
I questioned even going in that direction but a cheap part was all it was.
Your schematic shows similar.
Easy enough to pull and check to eliminate this area since you have the same issue.
Regards
David
Yes, if you have some spray contact cleaner, give the switch a shot and exercise it several times to wipe the contacts.
This usually works unless there's bad wear, which shouldn't be the case here.
Pulling the switch apart, I mean bending the stamping and breaking it open and looking at everything, spring, contacts, grease, etc. showed nothing out of the ordinary. Not even wear
Assembled everything back and one leg would not make contact.
Simply a cheap part made slightly out of tolerance or bad batch.
Spray did nothing for it
Simple replacement cured it and both channels worked like a charm.
Regards
David
Assembled everything back and one leg would not make contact.
Simply a cheap part made slightly out of tolerance or bad batch.
Spray did nothing for it
Simple replacement cured it and both channels worked like a charm.
Regards
David
David, thank you, I think you have put your finger right on it! Infact I have probably just inadvertently set the amp to mono-bridged. In this mode it only follows the right channel input - hence piano tracks on the left are missing, it connects the +ve output to the right speaker +ve, and the negative output to the left speaker +ve hence weird phase effects. There I was bracing myself for a major repair effort or just scrapping the amp, staring at the circuit boards when I probably just had to check the switches on the back! I will confirm this when I get home tonight, but it is a very good bit of advice, thanks for replying!
Tony
Tony
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