CDM1550, Power Issue - Please Help...

[maansman]

Hi Everyone -

Well, I have a CDM1550, with the remote head. Had to reprogram the radio for some more freq., so after I assembled the radio back to the remote head config, I am having power issues.

When I shut the car down (or disconnect the 10pin) the radio will not go back on..nada...like it's dead. After I disconnect the head (or base) and put it back, I get power. It's just went I shutdown, it won't go back on unless I disconnect the head or base. I even put the radio back to a single configuration (to verify it was not the remote head cables) and the same thing. The fuse did blow on the 10pin cable, but I think that happened because it came out of the connector, and grounded.

The radio has been fine for months....it has power both on the 12V & 10pin.....all this after I disconnected the re-assembled the unit....

What gives?

Thanks,
- Mark

[RadShop]

Check connections to head, likely the flex cable isn't seated firmly, or has a few traces that got lifted up / bent off

[maansman]

Thanks. I did some more investigation today.

The unit works fine in the "On/Off" mode only (ignition disabled). All the bells & whistles work. But, when I put it back to the ignition sense (pin 10), it won't go back on unless I disconnect the head. It even does the same thing as a single unit (have to kill the power), so I ruled out the remote config.

I think I know how the ignition fuse went, I think I connected it to another pin, other than 10, and it blew. I am feeling that I might have screwed something internally by doing that......

I can live with the On/Off, though not ideal, but do you know if maybe there are fuses inside the unit? Any other ideas? There must be another fail safe I would think.,

Thanks a bunch to all,
- Mark

[Karfield]

Sorry for the delay. The only actual fuse in the CDM series is for the control head. And even it doesn't really turn off power to the head just some other odd things that I can't remember. The fuse starts out as a hard wired line that can blow and then is replaced by a small surface mount fuse. If you can remember what pin you hooked the ign sense up to maybe we can give you a better idea of what happened.

[chartofmaryland]

If your issue is wanting pin 10 to work again it can be a simple fix. Depending on the board.

Inside the radio on the board is a zener package and resistor they are the protection for the pin.

You can dig around inside and find the problem or you can jumper pin 7 and 9 on the 16 plug and cycle B+ on and off.

The jumper fix was my way around pin 10 blowing on school buses that would reverse polarity or spike voltage from the master solnoids.

Jason

[wa6ylb]

If your issue is wanting pin 10 to work again it can be a simple fix. Depending on the board.

Inside the radio on the board is a zener package and resistor they are the protection for the pin.

You can dig around inside and find the problem or you can jumper pin 7 and 9 on the 16 plug and cycle B+ on and off.

The jumper fix was my way around pin 10 blowing on school buses that would reverse polarity or spike voltage from the master solnoids.

Jason

Jason is on the right track. There is an 470K (value may be different - I have the replacements in a bottle at work) ohm chip resistor that turns into a blown fuse if something happens (voltage spike) on the ignition sense lead.
If you remove the board from the chassis, and look right next to the connector that hosts the 20 pin external connector, you'll see a very tiny chip resistor. If you have experience with this kind of thing, its pretty easy to change.
However, if your eyesight isn't what it needs to be, and or you've never changed something so small as this chip
resistor, I suggest you find a repair facility or someone who does this kind of work for a living. We use stereo microscopes
at work to do this kind of work.
B.