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Parasound HCA-3500 Upgrade & Question

Have to see what to do to eliminate dynamic bias. There is an update note from Parasound for reliability to eliminate it. Frankly I don’t see the need for it unless you leave the amp on most of the time with no music playing through it.
 
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Two resistors to remove to eliminate dynamic bias hopefully don’t have to pull the boards for two minutes of work. Arrggghhhh.
 
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Got the resistors removed. Managed to do it without removing output modules.
Set bias to 20mv both channels. Will do a re-test later and tweak.
 
The 2 main fuses in the back are 15amp slow blow.
The 4 fuses on the power supply board are 12amp 326 series. (Ceramic slow blow).
The 2 fuses on each output module are 1amp MDL (slow blow).

I can not verify if these are original or not.
 
Checked the BIAS again today but the readings were off.
TV1 = 100 ohm
TV2 = 2K ohm
The TV1's seem to be good but those TV2's are not acting correct. Just touch them with the screwdriver and they jump around. These two are in series so I will need to replace with one good trimmer and jump the other location. This could be a tad bit of work since you need to pull each module out and separate the main heatsink from the boards heatsink header in order to get in there for de-soldering (couldn't have been on the outside of the board!).
I've read that TV2 should be set for 220ohm's and then adjust TV1, maybe a 500ohm trimmer or the A21 that had a 1K trimmer, which is like the updated version of this amp, so just need to decide which ones to go with.
 
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Photo of the two trimmers?
I assume they are 1-turn?
Maybe replace with 4-turn. Some techs recommend against replacing 1-turn with 10-turn for somewhat vaguely supported reasons of either current handling and/or mechanical robustness. I've used 4-turn with good success where they are available.
 
GKTAUDIO said:
Photo of the two trimmers?
I assume they are 1-turn?
Maybe replace with 4-turn. Some techs recommend against replacing 1-turn with 10-turn for somewhat vaguely supported reasons of either current handling and/or mechanical robustness. I've used 4-turn with good success where they are available.
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3339H series. Have 2 or each 500 & 1K ohm coming. They look like they will be an easy fit. In there now are just some open frame single turn that even Parasound says to replace. Too bad I didn't read all this prior.
 
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Tightening heatsink to the riser, snapped a screw. Metric on top of it. Got some socket head bolts this time for the 8 bolts mounting the heatsink to the riser. Now it’s properly tightened up. Just need to install into amp.
 
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