MT500 Tx Problem

[Vercomm]

Thats right, I have an old school customer who needs a MT500 fixed. The radio is older than me!! My solution is replace it but he just can let go of it. I think the problem is fairly easy, but could use some insight from more expirienced techs (i didn't just want to blurt out older techs).

Ther radio receives great, but zero tx. When you key the PTT, you don't hear the internal relay click. I am assuming that's what's wrong with it. Needs a new PTT relay. The other 3 models the customer left with me all work perfect. When you press the PTT you hear the relay click and life is good.

I have no manual for this radio, but i think the relay is NLE8361A, can anyone confirm?

Thanks Guys!!

Jamie

[abbylind]

Check the PTT switch. If its a BBU model attach a remote speaker mike and see if it TXs. If it does, its the PTT switch. The PTT lever can be removed by removing both fron and back covers the PTT bar has a push pin that goes through the frame. Once you remove that the PTT button is under that. If the remote mike doesnt TX then its probably the RX TX relay. The MT and MX series use the same relay. Sometimes you can jumper the relay and make the radio TX, unfortunately I cant remember which pins.
Hope this helps.

Fowler
KC5AEE

[Tom in D.C.]

On the MT500s it's also not unusual for the wire from the PTT switch to get disconnected at the switch. If that's the case just solder it carefully back into place. With the receiver board removed it's a radio that's pretty easy to work on.

[Vercomm]

Beginner question, but how do I remove the front cover. I have the back off and I am able to get the front cover to lift from the bottom of the radio, but not sure whats holding in place around the RF portion of the radio.

also how do I get the receiver board out. I can lift it from the bottom, but the top is stuck. I don't want to pry to hard.

[Tom in D.C.]

1. Look at the locations where the back's screws are screwed in. You'll see a slot in these devices which is made for a screwdriver blade. When you unscrew them the front of the radio will come off.
2. Take off the front of radio and disconnect the multipin connector which runs to the front from the main radio chassis.
3. Find the small screws that hold the receiver board (receiver board has the hole in it) and unscrew them; they're captive units and most of the time don't come out all the way.
4. NOW you can safely pry out the receiver board. When you do you are pulling the board out of two multipin sockets, so be careful and go slowly.
5. A UHF MT500 has a cable which stays attached to the receiver board from the main chassis. The VHF board comes completely free when you remove it.

[Vercomm]

Awesome instructions Tom!! It was a broken wire from the PTT to the board. I resoldered and its working 100% again.

Thanks for all the tips and insight!!