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Maratrac 9.6v regulator

Posted: Fri Jul 24, 2009 4:35 am
by maxkelley_kc2spy
I have a Maratrac (T74XTA7TA7BK) which was working fine for a while, but then one day stopped working. (wouldn't turn on) I diagnosed it to be the 9.6v regulator on the logic board of the radio, so I made a simple replacement regulator circuit with an LM317 variable regulator, and voila, she works again... sorta. I've come to realize that the radio is actually off-frequency on receive and transmit by a bit, and it doesn't seem to be triggering the final amplifier now. All of this worked fine previously before the 9.6v regulator failed. I've measured the output of my LM317 circuit and it seems to be around 9.41v.
I also was going to try replacing the bad transistor in the regulator circuit, and I believe it's the M9619 transistor bolted to the heatsink on the logic board, but I couldn't find anyplace that had them.

So, my question(s):
How much of a load on the 9.6v circuit is there (in amps); too much for the LM317 circuit?

Is the M9619 available someplace, or a compatible transistor?

Do you think the voltage level of the LM317 regulator is causing it to be off-frequency?

Any help would be much appreciated... Thanks :)

Re: Maratrac 9.6v regulator

Posted: Fri Jul 24, 2009 8:39 am
by Lake Effect
The transistor is still available on MOL. P/N 4800869619 $4.57 list.

L.E.

Also cross to ECG185

Re: Maratrac 9.6v regulator

Posted: Fri Jul 24, 2009 9:28 am
by chartofmaryland
Remember, the PA also uses 9.6 so there is quite a load for this circuit. Oh, you explained the PA part when you described it not working. . .

The replacement of the bad part would be the best course of action.

CoM

Re: Maratrac 9.6v regulator

Posted: Fri Jul 24, 2009 10:49 am
by maxkelley_kc2spy
Oh, ok, I just called Motorola with that part number, and yeah they have around 300 in stock I guess... Anyone had this problem in the past with the 9.6v regulator failing, or that particular transistor? I think its Q401 or something on the logic board, which is pretty similar to the Maxtrac logic boards from what I've heard..