To summarize: when it was acting up, bad voltages throughout right channel on Voltage Amp Assy. Overheating on Right Output Assy. Now things appear to be stable. But I'll have to power it up and leave it running to see if issue returns. I'm guessing it will.
I'd consider trying cold spray on transistors on voltage amp assy but that board is mounted upside down and difficult to get at components when it's up and running.
No I don't have a full bench of test equipment
I'd consider trying cold spray on transistors on voltage amp assy but that board is mounted upside down and difficult to get at components when it's up and running.
No I don't have a full bench of test equipment
So between acting up and not acting what have you done? Sounds like a flaky connection somewhere. Since you seem to think it's heat related it could be bad solder joint(s). Get a magnifying glass and inspect all of the boards, you are looking for dull porous solder joints possibly with rings around the component leads, circular cracks.
Craig
Craig
So I just powered on and idled for 15 minutes. DC offset at speakers fluctuated between 6.8 mV and 7.4 mV on left channel, -3.4mV and -4.3 mV on right channel.
I'll look over solder joints again. Only thing I have done is pull one lead of D39 and D40 to try any test them. And wiggle wires a bit on the Voltage Amp board as I removed screws to pull it away from heat sinks to get at components on the other side.
Next test will be running it with speakers and music at low volume for 15 minutes to see if issues return.
I'll look over solder joints again. Only thing I have done is pull one lead of D39 and D40 to try any test them. And wiggle wires a bit on the Voltage Amp board as I removed screws to pull it away from heat sinks to get at components on the other side.
Next test will be running it with speakers and music at low volume for 15 minutes to see if issues return.
Test done. Played music on Aux at 1/4 volume for 45 minutes. No issues. Next step is to play Phono as that is what I was doing the last time it went south.I go back to this thread I came across, that discussed possible oscillating with phono stage (read full thread, especially, 2nd page).
Pioneer Elite A-88X int amp service needed | Audiokarma Home Audio Stereo Discussion Forums
I'd like to set adjustment on the phone stage before testing it, but still need confirmation that when the service manual says Short the PHONO terminal as first step, that this means I should run an RCA cable between the left and right terminals.
Pioneer Elite A-88X int amp service needed | Audiokarma Home Audio Stereo Discussion Forums
I'd like to set adjustment on the phone stage before testing it, but still need confirmation that when the service manual says Short the PHONO terminal as first step, that this means I should run an RCA cable between the left and right terminals.
No!
It means you should short the signal with ground, individually, on each channel. Normally you would use RCA shorting plugs for this, but if you don't have any, simply cut off the ends of an RCA cable, and twist the shield together with the middle wire, make two of these and connect them as normal. Do not combine the two channels as you're suggesting.
It means you should short the signal with ground, individually, on each channel. Normally you would use RCA shorting plugs for this, but if you don't have any, simply cut off the ends of an RCA cable, and twist the shield together with the middle wire, make two of these and connect them as normal. Do not combine the two channels as you're suggesting.
That's good! In my experience, on these Pioneer amps with the PA0016 chip (there are lots of them), the bias is always spot on, and it's the Doug Self preferred number, too.
I guess it was part of Pioneer's "Non-switching amp" marketing thingy. They run quite hot, and the performance is sublime.OK, so there is something wrong with Phono stage. I went to set EQ Adjustments and was seeing 400mV on T1 (Left) and 1400mV on T3 (Right). Looks like Manual has a typo as T2 is the Ground. I tried dialing them both down to +- 100mV or less according to Service Manual and got in the ballpark, but both were fluctuating (oscillating?) and kept climbing back up.
I then noticed the left channel heatsink getting noticeably hot. Checked DC Offset at speakers and got 4mV on Right, but way up at 800mV on Left. Switching from Phono back to Aux did not help. Need to wait and let things cool down and check again with Aux selected to see if things return to normal.
I then noticed the left channel heatsink getting noticeably hot. Checked DC Offset at speakers and got 4mV on Right, but way up at 800mV on Left. Switching from Phono back to Aux did not help. Need to wait and let things cool down and check again with Aux selected to see if things return to normal.
Just checked DC Offset and the Left channel has dropped to 500mV and while still turned on, continued (within 1-2 minutes) to drop down to 250mV before climbing back to 500mV, so I turned it off.
Could IC1 be iffy, unable to auto-set bias? I have no way to test the PA0016 IC. (Pioneer Parts does have them for a whopping $28.25 ea.)
Could IC1 be iffy, unable to auto-set bias? I have no way to test the PA0016 IC. (Pioneer Parts does have them for a whopping $28.25 ea.)
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