GM338 power on failed

[bh7juo]

I have a GM338 now it's failed to power on.When I press volume knob no any response form radio.
I checked votages according to service manual.Power supply was 13.8V.First checked controller head,after I pressed power key,J0801 PIN2 rised up to 4.4V and hold on itself,but not accurate 5V.
Next checked mainboard,U0611 and U0641 has 13.8V and 9.1V out also hold on.CPU reset pin was high level 5V. U0221 PIN28(SYN OUT)had 3.6864MHZ out and I have not checked if it feed into CPU yet.
Any have guide to this repair? Really appreciated.

[SteveC0625]

I have a GM338 now it's failed to power on.When I press volume knob no any response form radio.
I checked votages according to service manual.Power supply was 13.8V.First checked controller head,after I pressed power key,J0801 PIN2 rised up to 4.4V and hold on itself,but not accurate 5V.
Next checked mainboard,U0611 and U0641 has 13.8V and 9.1V out also hold on.CPU reset pin was high level 5V. U0221 PIN28(SYN OUT)had 3.6864MHZ out and I have not checked if it feed into CPU yet.
Any have guide to this repair? Really appreciated.

Let's rule out the easy stuff first. If the radio is programmed for Ignition Sense only, it will behave as you describe. Hook up the radio to a power supply and then apply +12vdc to Pin #10 on the accessory connector. If it comes on, a simple programming change to Ignition Sense and On/Off will solve the problem.

[bh7juo]

I have a GM338 now it's failed to power on.When I press volume knob no any response form radio.
I checked votages according to service manual.Power supply was 13.8V.First checked controller head,after I pressed power key,J0801 PIN2 rised up to 4.4V and hold on itself,but not accurate 5V.
Next checked mainboard,U0611 and U0641 has 13.8V and 9.1V out also hold on.CPU reset pin was high level 5V. U0221 PIN28(SYN OUT)had 3.6864MHZ out and I have not checked if it feed into CPU yet.
Any have guide to this repair? Really appreciated.

Let's rule out the easy stuff first. If the radio is programmed for Ignition Sense only, it will behave as you describe. Hook up the radio to a power supply and then apply +12vdc to Pin #10 on the accessory connector. If it comes on, a simple programming change to Ignition Sense and On/Off will solve the problem.

Thank you for your advise,I checked if connect 12V to PIN10 of connecter,still failed.And I tried to reprogram radio,CPS said connected failed.(I just took another radio to program it was OK).Now J0801 PIN2 hold high level after press power on,it takes mainboard CPU's IRQ pin still low.