Batboard

I have a VHF maratrac that seems to lose itself when the power is disconnected. I bought this radio with a known issue. When I turn it on for the first time none of the control respond and I have to TX or RX. I can program the radio and everything works great, turn it off and back on and things are fine with all controls responding. I disconnect power, turn back on, turn radio on and the memeory blank secenario arises. I have done some searching and cannot find any related problem. Any thoughts? I am stumped. I have the advanced control head and this is set correctly in the RSS.

If the logic board is using a Dallas non-volatile RAM device, it has a battery in it that has about a 10 year life. If the battery voltage isn't high enough, the memory will fail and the radio will forget a lot of things, like all its programming. Some info (such as tuning data) is maintained in EEPROM inside the CPU, but all the mode data is kept in the external device.

Open the bottom of the radio and remove the shield over the microprocessor area of the logic board. If you see a block next to the PROM about the size of a domino (1.5 inches by 0.6 inches by about 0.4 inches tall) with the name DALLAS on it, that's probably what's wrong. They're soldered in. They can be replaced by a similar device, which will fail in another 10 years, or by a real parallel EEPROM that will outlast the radio. This problem also happens with MaxTracs and Radius mobile radios as they all use the same logic board.

Someone else had the same problem with a MaxTrac and he may have posted something about it here.

Bob M.

I might be the one Bob referred to. I had a Maxtrac that would give me a checksum error on powerup (long boop). Removed the Dallas chip and replaced it with a 28C16 and it was good as new.

Thanks for info. That is exactly what is in there. A small black box with DALLAS written on it. It looks like the 28C16 chips are pretty available on ebay. I will post back if I am successful.

OK....Finally got the parts, but what is the secret to getting this logic board off?? I have practically unscrewed everything but it still won't come loose where the side screws hold it to the chassis section.

There are two T-8 flat-head screws holding the heat sink to the side of the chassis. These need to be removed, then the logic board will lift straight up. You may have to disconnect the connector on top of the RF board as the pins from the logic board go through the RF board. You may also have to remove the audio/squelch board to gain access to the side of the logic board, or use a right-angle Torx wrench (if you can find one).

Bob M.