Batboard

Hi

I once knew where to add a supercap inside the Maxtrac to make it remember the last used channel for a longer time than it does normally, just for the case of a power failure. I even bought the caps then but haven't installed them since and now I can't find the info anymore. Can anyone help please?

73
Martin

Do you have the radio model number or better yet the logic board part number?

Also this is in the wrong forum section, should be in 'legacy radio discussion', maybe we can have an admin move it?

Perhaps I missed something. Is this not the "General Motorola Solutions & Legacy Radio Discussion"?

I wish I still had my 'thick' service manual for the Maxtrac Radio Series. IIRC there was an addendum from Motorola, which made reference to the 'supercap'. Sadly, I did not have the foresight to make a copy of it, back in the mid-1990's. If I find someone who has a copy of it, I'll be sure to let you know.

train_radio_guy wrote:Perhaps I missed something. Is this not the "General Motorola Solutions & Legacy Radio Discussion"?

Yes, you missed the topic being moved, it was originally in the 'base stations, repeaters, general infrastructure' section.

I believe the cap would go in the "RAM 5V" circuit that feeds pin 2 of the microprocessor, there's usually a 47uF cap in there, not sure of you just replace that with the super cap or if there's something else involved.
I might have that addendum, I'll have to look around for it.

My mistake. Sorry about that jackhackett.

I know this topic is a little old, but I was just looking at the GM300 manual and it shows a revision with a 4V battery and diode connected to that 47uF cap. You can see it at the repeater builder site, gm300 service manual part A.

Yup. On page 9 of the pdf - B401, 4 volt battery. The schematic diagram indicates it was optional. I'm trying to remember if I ever saw one installed. Perhaps, for one of the early ESDA Communication Vans, used by a nearby county. I think they eventually upgraded to a Spectra, for more channel capacity.

I recall doing this many. many years ago. just dug out an old manual and it shows the mod. It was just as jackhackett said, the 5VRAM line that feeds pin 2 of the of the SLIC logic array.

We added a lithium battery through a signal diode (probably a 1N914 or 1N4148). Battery negative to ground, Batty + to the diode Anode. Diode cathode (line) to the + side of the radios C408 (47 uf cap).

In this case, the logic board was a HLN9313, but should apply to other boards too.