HCA-1000A Repair / Refresh

skrol

I had picked up a Parasound HCA-1000A from a fellow Polkie a few months ago understanding that it had a hum. When I received it and tried it out, there was no hum and it played well. I did notice that the power supply caps were bulged and figured on replacing them. It sounded good enough on the bench that I got brave enough to take it up stairs and try it in my 2ch system. Something happened when moving it. It now has a bad hum and has DC on one channel output putting it in protect. I managed to find a schematic that is very similar to this amp. It is labeled HCA-1000A but some of the component values are different. Based on my experience refurbishing my HCA-800ii, in which 1/3 of the electrolytic caps were out of spec, I decided to replace all the electrolytics. I had posted to DIYAUDIO.com and Mr. Curl himself responded, recommending no need to touch the other caps. I ordered up a bunch of caps from Mouser.com, which arrived today. I do plan to do some upgrades, namely the PS caps. Mr. curl mentioned that this was one area of compromise with the amp due to space limitations and what was available at the time. They were 10,000uF 63V. I found some 12,000uF 80V that will fit. The rail voltage is measuring ~60V.
Stan

skrol

I got the caps swapped out, fixed a couple damaged traces on the PCB, got it back together and turned it on. I initially set the bias for 10mV. Later I found that the bias had dropped out on one channel. This was due to a broken solder joint on one of the emitter resistors and probably the source of the intermittent behavior. I pulled it apart again and went over the entire board. It seems that all the emitter resistor solder joints could easily be broken with a little wiggling if the resistor. All the connections were re-soldered and the amp was reassembled.

After a few hours run time, I adjusted the bias first to 17mV, checking the heatsink temperatures. Eventually, I set the bias to 20mV with the heatsinks running ~42deg C with the cover off. Mr. John Curl himself responded to my post on DIYAudio.com saying the optimal bias for this amp would be between 17mV and 20mV vs the factory setting of 10mV. The main thing is keep the heatsink temps below 50deg C. It is now running on my bench reproducing beautiful sine waves as I build confidence to place it in operation.

VSAT88

Wish my HCA 1206 was put together like that. Hard to work on that one...thanks for the info. My 12066 has a hum as well and I can use this info. Thank you.

skrol

Good Day! that 1206 looks like a beast to work on. I bet it is similar to the 1000a but just more of it. Might try emailing Parasound to see if they have a service manual or tips on disassembling and repairing the amp.

The first time I had it apart, I did it the hard way and disassembled just about everything to remove the bottom cover. I basically took every screws out of the thing. The next time I figured out that I could just remove the screws holding the main PCB down, remove a small PCB at the front, and disconnect the connectors. I had to be real careful of the heatsinks as once the PCB is removed, they were only held on my the transistor leads.

voltz

Nice job Stan! hopefully it will last many more years for ya.

skrol

Good advise.

skrol

I put the HCA-1000A in service in my 2-ch system and it sounds fantastic. The sound stage with the LSi15 is very dimensional and spacious. The bass is better controlled (tighter).

voltz

You know those new Cap's are gonna need some serious burn in time, so its time to do some late night listening session and do a whole lot of listening

skrol

I look forward to it. I did do some burn-in on the bench with but unloaded. With no caps in the signal path, I wonder how much difference there will be.

VSAT88

skrol wrote: »

I look forward to it. I did do some burn-in on the bench with but unloaded. With no caps in the signal path, I wonder how much difference there will be.

Well, how did she turn out ? Finally took down the HCA 1206 here and yes, it is a beast to work on..

skrol

I did a full re-cap with Nippon Chemicon for the PS that I upgraded to 12,000uF 80V and Panasonic for the smaller caps. I also biased higher per John Curl's guidance that he gave me on DIYAudio.com.

The noise floor is lower and I think it packs a little more slam than it used to. It is better able to control bass of my LSi15.
Stan

VSAT88

skrol wrote: »

I did a full re-cap with Nippon Chemicon for the PS that I upgraded to 12,000uF 80V and Panasonic for the smaller caps. I also biased higher per John Curl's guidance that he gave me on DIYAudio.com.

The noise floor is lower and I think it packs a little more slam than it used to. It is better able to control bass of my LSi15.
Stan

Thanks Stan, i was working on the BOM from Mouser when i noticed your reply. I will really be glad when this one is over..

skrol

Mouser has an excellent selection. There were size constraints for the PS caps in the HCA-1000A, which is why Mr. Curl was limited to 10,000uF 63V. The rails operate at 60V so this was pretty tight. I guess capacitor materials and manufacturing has advanced a bit and I found the 12,000uF 80V at Mouser that would fit.

Here is my thread from DIY Audio with some biasing advice and instructions. http://www.diyaudio.com/forums/solid-state/274906-parasound-hca-1000a-refresh.html