Maxtrac 900 Receive Problems with HLN9313B Board and FVN4019

[60hzEE]

A 900 Maxtrac with a relatively new HLN9313B logic board was conventionalized and presto, no receive. I checked every discrete component involved and no failures. So, since I thought maybe I was dreaming, two more HLN9313B boards were tried, with the same results, no receive.

An older 9313A worked fine. What's the story here? Is there something unique and different about the 9313B boards that requires use of different firmware?

[xmo]

The HLN9313 logic boards do not belong in a 900 radio - they are for all the other bands.

The correct logic board for the 900 Maxtrac is FRN5529A which looks like a 9313 but is not interchangeable.

[Max-trac]

What front panel are you using? There is an extra hear-clear board on the volume/on-off board in the 900. I assume you are trying to get more that 16 chs.
Did you try the regular maxtrac eprom in the 9313b? (vs the 900 conventional)?
I was going to try this also, but havn't had the time.....

[60hzEE]

Thanks for straightening me out. The older board, which worked fine, was a FRN5529A. I did the other conventional prom in the 9313 and got screwy frequencies. But, kinda figured I would since the IFs are differenct, hence different divisors for the PLL.

The logic boards look the same, but another problem, at least with the ones I have, is that my base station mike, compact hand mics and DTMF mikes would not work with the FRN5529 logic boards. The reason, apparently, is that the 5 volts needed to power the mikes is not supplied from a 560 Ohm resistor (R651) as on the HLN9313 boards, but from a 56K resistor. I jumpered the 56K resistor with an 1/8W 560 Ohm resistor and now the mikes work fine.

I could key up the radio by jumpering PTT to ground, but all but the base station mike use transistors and without adequate voltage the result was no audio and no keying.

Guess the older radios used a different mike preamp and contact closure for PTT.