Carver MXR-150 Power Rail Voltage Troubleshooting

[raj5001]

Hi all!
I would appreciate any suggestions or assistance in troubleshooting the main power filter cap voltage supply rails. First I changed the 4 main power filter caps and tested the voltages to be +/- 40 and +/- 60 after the bridge rectifiers. Then I changed all of the caps on the main amp PC board. This brought the front panel of amp to life, but the power rails changed. I am getting +50/- 72 for the 60V rail and +30/-52 for the 40V rail. Since the cap is rated for 60V, I am now using a variac to keep the voltage below its rating for testing at powerup. I triple-checked all the cap orientation and values. Any considerations on how to troubleshoot? Thanks!

 

[krautmaster]

You should probably get 100V caps... Carver /Flame Linear are infamous for using caps rated at or below the rail voltage which never ends well.

 

[raj5001]

You should probably get 100V caps... Carver /Flame Linear are infamous for using caps rated at or below the rail voltage which never ends well.

After experiencing this amp, I whole heartedly agree. This is probably how it went down in the 90's
Carver Engineers: "This amp needs higher voltage rating caps so there is a margin of safety"
Carver design team: Yeah B****! MAGNETS!

 

[Dave1027]

Going by the voltages, looks like the ground shifted. Check grounding.

 

[raj5001]

Dave,

You saved my day. The main amp board is grounded to the chassis through the support bracket that I removed for the recapping. The screw highlighted in yellow properly grounded everything.

THANKS for your quick reply and sharing your intuition for my odd problem.