Batboard

I have a new old stock maxtrac 300 mod. acd33mja7da5bk ser.428prq2076 the polarity was reversed when the radio was powered up and it smoked. It was sent in for service and they repaired a trace and found a board that was bad and said parts were no longer available and to throw the radio away if anyone can help I would appreciate it thanks Jeff

Usually, a big diode on the power amp module shorts out when reverse polarity is applied. Hopefully it protected the radio. A similar part should be available.

If the reverse voltage went past that, then you may be fighting a losing battle. There are some voltage regulators and of course the microprocessor which might not have survived.

With a service manual, it should be fixable, but there could also be some traces burned out in the boards. You might have to add wire jumpers on the top or bottom to get working again.

If repair time is free and you have the manual and skills, try to fix it. Otherwise just go buy another 16ch 25w VHF MaxTrac or Radius on eBay for around $100.

Bob M.

I would take a crack at fixing, but if the damage is too extensive i would probably recommend using it for parts.

Just depends on how it was hooked up and damaged. Did the power cord have a proper rating fuse? Did the fuse blow?

The diode across the power terminal inside is there so if the polarity is reversed current will flow and pop the fuse, hopefully before causing further damage. The fact that you mentioned a burnt trace makes me suspect the radio wasn't properly fused.

As kcbooboo said, the diode on the power amp module is intended to short and protect the radio by blowing the fuse if reverse polarity is applied. If this is the case, it usually only needs a new diode.

But, if the radio was not properly fused, the diode shorts and then burns open along with traces on the board and the regulators, microporcessor and other chips on the logic board get fried. Your description of "it smoked" instead of just immediately blowing the fuse does not sound good.

From what you describe, with the shop attempt at a trace repair and diagnosis of "a board that was bad", it sounds to me like the logic board is ruined which would be a very expensive repair.

It think the advice to get another radio on eBay is the way to go.