CDM1550 - I think I made a brick.....

[486dx4]

Hi -

I have a CDM1550 LS+ (UHF, 25W, S split) that I was changing control heads on. On the head I changed to the radio I put in the flex ribbon cable properly, applied 12 V power to the radio and the radio began to power up without pushing the switch which could mean that head was bad - not sure. while this powering up was happening the white flex from the head to the radio got disconnected from the radio (the head was not snapped/clipped onto the radio body of course). I connected the original control head and tried another control head from another 1550 and the radio will not power up anymore. I did verify the operation of the two "known to be good" heads on the other CDM1550 and also verified that the power supplies, etc are operational.

I have read on other posts with CDM mobiles about an F0401 fuse but it is not clear that this may be the problem since posters said some power does go to the head even if the fuse is blown and on other posts someone had seen the fuse as ok even though the radio did not power up. I also know the radio was not set for ignition sense since it did work without it before this problem occurred.

Any thoughts would be helpful - thanks.

[486dx4]

Just an update on this. Since I had nothing to lose I applied 12V to pin 10 (ignition sense) on the rear accessory connector and the radio powered up. The control head had its LCD display working but did not have backlighting though and none of the other LED's worked. The buttons to change channels, menus etc. all did work. When you connect a mic to the head the radio does not transmit (no red LED, power out, or increase in current draw saying something is happening). The radio receives fine.

Now this is looking more like some other posters had where that internal fuse F0401 may be the issue - hope this fixes the transmit problem as well. There was a post where someone had pics of the fuse location on the board that you were to replace with a jumper but they are not available anymore (that post/thread was over a year old).

[emsbuff3240]

Interesting, we had the exact same problem at the shop today, we put a jumper in, I forget from what to what, but it worked. I see if i can find out on mon.

[486dx4]

Ok - well any info would be great. I have ordered the detailed service manual anyway to see where these components are exactly. TX is working on the radio by the way.

The topic I was looking at was at this link which was about a CDM1250 but I'd guess the concept may be similar -

viewtopic.php?t=59671

They talk about a fuse on the PCB that if it blows you are to replace it with R0410 which one post said is a 0 ohm SMD resistor - which is a wire/jumper. The question I have is why replace the fuse with a jumper - what protection are you giving up with doing this? But if that is what the manual says to do and that is what the part is then I guess its an ok fix.

Thanks for the reply on this.....

[fire_master_21]

I also have the same problem. I too would like to know the fix you did.

[486dx4]

Just an update - I finally got the detailed service manual (it IS detailed - big binder - bigger than the Maxtrac manual I think...) and found F0401 on the board by J0401 (the black connector that the flex from the control head goes into. Sure enough the fuse was blown. If you short the pads where the SMT fuse was the radio powers up as it normally should, the backlight comes up and all LED's work.

F0401 is a 3 amp SMT fuse and the part number according to the manual is 6580542Z01.