Pioneer VSX-1021 MCACC flashing, can't find problem

[burntonnerings]

Have a Pioneer VSX-1021 that goes to MCACC flashing as soon as it is plugged in.

If I enter release mode, it powers on, the screen display is correct, but then it shuts down and goes back to MCACC after a few seconds. I can shut it down to standby (w/o flashing MCACC if I hit the power button as soon as release mode finishes the boot sequence).

Entering reset mode and executing a reset doesn't change this.

I am unable to enter service mode to see the error counts - Enter + Power button doesn't do anything, whether from normal standby or from MCACC flashing.

No DC voltage present on any speaker outputs.

Checked for shorts on all of the output transistors attached to the heat sink - they're all fine.

No physical evidence of bad caps or burns or anything on the amp board.

Read some of the other VSX threads but still not clear what to check next.

Any thoughts?

[CapLeaker]

Try powering the receiver up and press and hold the tune down and multi-zone on off buttons down at the same time. See what she does.

With amps, you always look for you power rails and the PA stages. Do you hear a relay click when you turn this turkey on? If not, that explains when you don’t measure anything on the speaker outputs.

[burntonnerings]

Try powering the receiver up and press and hold the tune down and multi-zone on off buttons down at the same time. See what she does.

With amps, you always look for you power rails and the PA stages. Do you hear a relay click when you turn this turkey on? If not, that explains when you don’t measure anything on the speaker outputs.

Thanks - that procedure is the "release mode" I referred to in my post - powers up, behaves normally for about 3 seconds, shuts down to MCACC flashing

Relay clicks, but I'm assuming that is to disconnect the outputs from any DC present on the output stage.

Will find a service manual and test the rails.

[CapLeaker]

If memory serve me right, I thing this amp has grounding points on the bottom of the main PCB. So if you take that PCB out and don’t jumper the proper ground points, it will go into protection mode as well.

[burntonnerings]

If memory serve me right, I thing this amp has grounding points on the bottom of the main PCB. So if you take that PCB out and don’t jumper the proper ground points, it will go into protection mode as well.

yes - but its going into protection mode even before I disassembled it.

found a service manual, so going to check out what the supply voltages should be for the amp board

[CapLeaker]

Did it say any error codes beside the flashing mcacc?

[burntonnerings]

Did it say any error codes beside the flashing mcacc?

Nope - and I am unable to enter the service menu to see the error count for each code.

[CapLeaker]

Hmm… that’s something new, usually they greet you with an error message of something. Is there a history that goes with it? Usually the MCACC has something to do with the output section. When you checked the finals, did you check the driver and pre driver? Try taking a measurement direct at the output, before the protection relay and turn it on. You may have to use the min /max setting on your DMM.