Maxtrac Problem, Non Operational, lost digit display

jmr061 · Post by **jmr061** » Tue May 15, 2007 4:28 pm

Okay I have a VHF Maxtrac Model D33MJA7DA5AK that I have been running for aprs in a vehicle for a while. Well the other day I noticed I the vehicle was no longer sending out packets. I looked under the seat today and the backlighting behind the control head buttons was on but the segment display was dead. There is no speaker beep on power up anymore either.

I swapped control heads that isn't the issue. So there is a problem in the radio somewhere. I am swapping it with another for the time behing but does anyone ran into a similar problem before?

Thanks

Jason

n7maq · Post by **n7maq** » Tue May 15, 2007 5:00 pm

The first thing I would check (in the radio) is the fuse on the logic board (most of time it is a green pico fuse) unless you have ignition sense, then that fuse would be out anyway. I assume you have confirmed B+ to the back of the radio.

Jim

jackhackett · Post by **jackhackett** » Tue May 15, 2007 5:48 pm

I can't see the ign. fuse causing those symptoms... if that goes there'd be no backlight.

Sounds more like the micro isn't running. If it's one of the older units with a NOVRAM instead of a EEPROM I would suspect that. I've also seen a few where the crystal for the micro went bad, you can check for a signal from it. Then there's always voltage regulators, and there are some zener diodes across some of the control head signal leads that will get zapped occasionally and cause weird problems.

n7maq · Post by **n7maq** » Tue May 15, 2007 7:45 pm

Well I need to learn to read better "and the backlighting behind the control head buttons was on" I did not catch that at all

JH is correct in what to look for. I have seen a bad EEPROM act close, but 1 bar was lit in the ch dispaly.

Jim

jackhackett · Post by **jackhackett** » Wed May 16, 2007 5:11 am

Happens to the best of us

Batwings21 · Post by **Batwings21** » Thu May 17, 2007 9:30 am

I have seen these symptoms before, and it sounds like a b+ lead problem. If the unit uses the ign lead, and it has power, but the b+ is dead you will have the same symptoms. Make sure you check that voltage by partially pulling the connector out, but so the radio is still connected and probe it that way, I have also had them where there was voltage present with the cable disconnected, but the radio would make it drop. Good luck, hope some of that helps.