CDM1550 doesn't power up!

[maxkelley_kc2spy]

Hi all, I purchased a DOA CDM1550 (knowingly) with the intentions of fixing it up... I assumed it would be something simple, like F0401 (the control head A+ fuse), or ignition sense! From what I can tell... it's not that simple
So, first off, I hooked it all up with an ignition sense lead and everything, powered it up, and immediately something wasn't right! The power supply was groaning, and the radio began to feel hot, so I turned everything off and opened it up. The component that had gotten hot was a transient suppression diode which is supposed to shunt the power supply to ground at 24V... it seems like it was shunting all the time? So, I decided to remove it, figuring that would be the problem!

I try again, and still no power up, and the ammeter shows about 19A or so (not necessarily accurate...), but there's not as much heating like before. I soon figured out that the previous owner had flipped the control head 180 degrees, so what I thought was pin 10 on the accessory connector was actually 9, I think, which is EMERGENCY (with wake-up). So, the behavior I was getting sort of made sense... the radio was turning on and immediately transmitting. (did not check RF power output)

So, I changed it over to pin 10 for ignition sense, aaaaand... still no go I notice that if I leave ignition sense disconnected, plug in the radio, and press the power button, the current draw goes from 0 to about .17amps or so (uC turning on?) and the LCD segments darken a *little* bit. No lights, no power up tone, nothing else, it seems. This same behavior happens when I leave the ignition sense plugged in, so *something* is turning on in there!

I've gone through the control head troubleshooting steps in the service manual, and I get stopped at the part where it asks you to check for a data signal on the BUS+ line while rotating the volume pot... First off, I don't have a scope to check this, so I used my DVM and hooked it up in DC voltage mode to see if voltage changed at all when turning the knob... which it didn't. This is probably not the best way to check it, but... I assumed that there was no data activity on BUS+, and so the troubleshooting guide told me to check the controller, using those troubleshooting steps.

All was well in controllerland until, once again, I got to the step where it says "BUS+ activity when volume knob is rotated?" Which... I already determined isn't happening. (I'm measuring BUS+ at pin5 of the telco jack on the front of the radio, btw)

So, I think I've been fairly thorough in explaining the situation... any ideas?

[maxkelley_kc2spy]

And, just an update, turns out that the 19 amp current draw was likely me shorting A+ to ground at the accessory connector... Oops This is what happens when you work on this stuff at 2am...

[KC2SDM]

Any luck yet? I was contemplating a similar purchase and I wondered if you found a resolution to your problem.

[maxkelley_kc2spy]

Not yet... I think, based on some research I've done, that the flash EEPROM is bad. I've been meaning to reassemble it and take it to a local radio shop to have them read it in the latest CPS which supposedly has a tool which can possibly fix the EEPROM problems.

I'll update this thread if I ever actually get around to it, and if it works or not.