EFJ 5100 sudden loss of TX?

methusaleh · Apr 22, 2015

Radio is a VHF model, has worked flawlessly since I obtained it from a fellow ham a year or so ago.

All of a sudden it does not appear to transmit. The LED turns red as if it's transmitting, but no RF seems to be coming out. I even put a frequency counter right up to the antenna and it does not register a signal.

The last time I used the radio was the first time I tried out a (new to me) speaker mic with it. Not sure if I screwed something up with that. All of the pins on that speaker mic match the ones on my other identical speaker mic, and the newly-acquired speaker mic works fine on my other radio.

Any ideas without opening up the radio ?

ecps92 · Apr 23, 2015

Interesting

I have one that stopped as well, never tied it to the Accessories, but I did try a "M" Surv Kit on mine and that was when I noticed it had stopped transmitting on all bands.

Other than bringing it to a shop, wonder what can be done...

methusaleh said:
Radio is a VHF model, has worked flawlessly since I obtained it from a fellow ham a year or so ago.

All of a sudden it does not appear to transmit. The LED turns red as if it's transmitting, but no RF seems to be coming out. I even put a frequency counter right up to the antenna and it does not register a signal.

The last time I used the radio was the first time I tried out a (new to me) speaker mic with it. Not sure if I screwed something up with that. All of the pins on that speaker mic match the ones on my other identical speaker mic, and the newly-acquired speaker mic works fine on my other radio.

Any ideas without opening up the radio ?

jim202 · Apr 23, 2015

If you take the speaker mic off the radio and use the side PTT button, does it still not transmit?

Do you have a way of listening to the output frequency or go to a simplex channel, can you hear the transmitter and voice on the second radio?

If so, there is a chance the antenna is not making a connection to the circuit board. People have a bad habit of using the antenna as a way of picking up the radio. This causes undue strain to the circuit board and can cause damage to the electrical connections.

Not saying this is the problem, but it's a bad habit to be in.

jaspence · Apr 23, 2015

EF Johnson 5100

I have several of these on different bands. When I had this problem a couple of years ago, the fix I was given was to open the radio and carefully remove the ribbon cables. Clean the ends with a soft eraser or even just a soft cloth. I was able to return a couple of radios to service and even made one good radio from 2 parts radios I bought for $10 each.

ecps92 · Apr 23, 2015

a. Yes - no TX with or without the external accessories
b. Yes - both Freq Counter, Close-Call and Scanners and other Radios on the TX Freq
c. Yes a bad habit, but your talking to two folks who know better (both the OP and myself)

jim202 said:
If you take the speaker mic off the radio and use the side PTT button, does it still not transmit?

Do you have a way of listening to the output frequency or go to a simplex channel, can you hear the transmitter and voice on the second radio?

If so, there is a chance the antenna is not making a connection to the circuit board. People have a bad habit of using the antenna as a way of picking up the radio. This causes undue strain to the circuit board and can cause damage to the electrical connections.

Not saying this is the problem, but it's a bad habit to be in.

mancow · Apr 23, 2015

Some older units had a problem in the RF section that caused them to fail. I had one that had that happen and I had to send it in for repair.

methusaleh · Apr 23, 2015

ecps92 said:
a. Yes - no TX with or without the external accessories
b. Yes - both Freq Counter, Close-Call and Scanners and other Radios on the TX Freq
c. Yes a bad habit, but your talking to two folks who know better (both the OP and myself)

Ditto here. No TX with or without the speaker mic. Nothing heard on a scanner with Close Call, or a freq counter. Not even a harmonic somewhere above VHF.

Radio may have been bumped around slightly on a shelf when not in use, but was not dragged around by the antenna.

I will have to try the suggestion of cleaning the ribbon cable contacts-- thank you!

jaspence · Apr 23, 2015

ecps92, what did you mean by "all bands". Other than the 700/800 public service radios, I thought all 5100s were single band.

ecps92 · Apr 23, 2015

I look at the VHF as broken into 3 bands for this radio
138-150 - tried my Amateur w/o luck
150-160 - tried my Part 90 w/o luck
160-174 - tried my NTIA w/o luck

Was hoping it was something peculiar to the band, just like the UHF where you can't FPP Part 90, but can 380-450

jaspence said:
ecps92, what did you mean by "all bands". Other than the 700/800 public service radios, I thought all 5100s were single band.

methusaleh · May 6, 2015

Thanks to all who have read and responded.

I have no updates, nothing has changed with the radio. Tried different antennae just for the heck of it.

Is there a service manual online, or disassembly instructions? I could not find any. I am ready to open 'er up at this point.

methusaleh · May 10, 2015

Update: Someone pointed me where to find how to put the radio into a sort of service/test tune mode. I followed the directions precisely and could not get it to work. I tried all buttons on the radio while the power was cycling on, but it never went into that mode.

Any ideas?

EFJ 5100 sudden loss of TX?

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