• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Accuphase E-202 Protection Circuit

E

edselguy

New Member
Hello Everyone!
I am new to this forum but everything I have read leads me to believe I am finally in the right place for gaining some knowledge on my old Accuphase amplifier.

So right off the bat, here's my basic setup. Accuphase amp driving 200w Pioneer HPM 100's. I have a Technics cassette player hooked up to Tape 2. I have left everything else disconnected.

Now for the problem. When I power on the amplifier, the protection circuit delay works as it should but a few seconds later it decides to click out again. It will continue to do this for roughly 5-10 minutes and once everything is "warmed" up, it will play just fine except that I have a higher pitch static noise on the left channel that is not affected by volume level or input. The noise is not present when in circuit protection mode.

I am not a tech but I am quite familiar and capable of following schematics and troubleshooting basic components. I am just looking for a helpful nudge in the right direction.

Thank You!!!
 
Register to hide this ad
I just fixed one a few months ago with the same issue. Lots of known bad transistors here, and the power supply gets too hot.

Remove both amp boards and see if the relay keeps behaving the same way. If it does -
Replace all transistors and capacitors ont he protection/power supply board. There are also 3-4 resistors that need to be larger in wattage rating and off the board. The issue will go away.

If the relay stays engaged if the amp boards are out, the issue is the transistors on one of them. The input pair and the predrivers are most likely to blame.
 
ivandezande said:
I just fixed one a few months ago with the same issue. Lots of known bad transistors here, and the power supply gets too hot.

Remove both amp boards and see if the relay keeps behaving the same way. If it does -
Replace all transistors and capacitors ont he protection/power supply board. There are also 3-4 resistors that need to be larger in wattage rating and off the board. The issue will go away.

If the relay stays engaged if the amp boards are out, the issue is the transistors on one of them. The input pair and the predrivers are most likely to blame.
Click to expand...
Thank you, I just pulled the amp boards and the protection circuit worked as it should. I swapped the boards side to side to see if my static issue changed and it did not move with the boards. I pulled all 3 boards out and found some resistor issues on one amp board and the power supply board. Do you have a recommended upgrade for these resistors? According to the service manual they are CFR style but I see someone at one point replaced the r11 resistor on one of the amp boards with what looks like a MOF style resistor. Any suggestions are appreciated!
 
Here is a picture of the 3 boards I pulled out. The top left board has the replaced r11 resistor.
 

Attachments

  • PXL_20250811_182934569.jpg
    PXL_20250811_182934569.jpg
    96 KB · Views: 15
edselguy said:
Thank you, I just pulled the amp boards and the protection circuit worked as it should. I swapped the boards side to side to see if my static issue changed and it did not move with the boards. I pulled all 3 boards out and found some resistor issues on one amp board and the power supply board. Do you have a recommended upgrade for these resistors? According to the service manual they are CFR style but I see someone at one point replaced the r11 resistor on one of the amp boards with what looks like a MOF style resistor. Any suggestions are appreciated!
Click to expand...
If it didn't move boards, I would say the issue is the preamp signal that's being sent to one of the boards. Try separating the amp and preamp on the back and observe the behavior.

I am partial to KOA Speer MOS series for anything over 1W.
 
ivandezande said:
If it didn't move boards, I would say the issue is the preamp signal that's being sent to one of the boards. Try separating the amp and preamp on the back and observe the behavior.

I am partial to KOA Speer MOS series for anything over 1W.
Click to expand...
I separated the amp and preamp on the back and the noise went away. So that tells me it's in the preamp. Any suggestions on where to go from there? At one point I had a shorted cable on the record side of tape 1. It severely distorted the speaker sound and when I unplugged it the distortion went away. It was on the left channel. I can only assume the cable caused this issue. The cable has since been disposed of so it cannot cause any more issues. All of my cables are now tested before they are plugged back in.
 
edselguy said:
I separated the amp and preamp on the back and the noise went away. So that tells me it's in the preamp. Any suggestions on where to go from there? At one point I had a shorted cable on the record side of tape 1. It severely distorted the speaker sound and when I unplugged it the distortion went away. It was on the left channel. I can only assume the cable caused this issue. The cable has since been disposed of so it cannot cause any more issues. All of my cables are now tested before they are plugged back in.
Click to expand...
Again, transistors going leaky/noisy. Replace them all. If one’s going, the rest will. No downside to replacing them.
I’m sure a few KSC1845/KSA992 will get you right.
 
You must log in or register to reply here.
Back
Top Bottom