Kenwood TR-9130 problem with PA
 

Hello,
I have here a Kenwood TR-9130 for repair. Rx is ok, TX no output.
I checked the PA and voltages, replaced the electrolytes and ordered a new M57727 module. I replaced it and found no improvement.
I sent it back, because I determined it was also broken. The dealer sent me a new one, with the same result.

The driver voltage to the module (at pin 1) is 2,5V peak-peak at 145Mhz, output (on pin 5) is about 20mV.
I also tested with open output pin 5 on the module: also some mV output.

The DC voltages on the module in TX mode are :
Pin2 12,2V (11,8V in service manual)
Pin3 9,2V (9,0V in service manual)
Pin4 13,5V (13,7V in service manual)

Can somebody give me a hint or further informations?

Thanks for answers! Fred, OE5BAL

Re: Kenwood TR-9130 problem with PA
 

Problem in the TX/RX changeover circuit?

What sort of current is the unit consuming on transmit?

Can you try attaching a coax tail direct from the PA section to a power meter?

Re: Kenwood TR-9130 problem with PA
 

Is there any easy way you can measure the current the module is taking?

I gather that the Mitsubishi PA modules available on the open market are quite often fakes!

Re: Kenwood TR-9130 problem with PA
 

-- The unit takes in Rx 0,5A and in TX 0,58A.

-- I measured the output on the module with the 150Mhz scope, and it shows 2,5Vpp.
I also tested all capacitors and diodes and so on. There is no fault.

-- The unit takes in Rx 0,5A and in TX 0,58A

Re: Kenwood TR-9130 problem with PA
 

Sorry, the input is 2,5Vpp, output (pin5) from the module 20mV !!!

Re: Kenwood TR-9130 problem with PA
 

2.5V of RF input is around 130mW, so I would think there is enough drive to the PA for around 25W output.

The TX current is way too low.

Is the module grounded properly? - all of the DC conditions seem to be about right, according to the datasheet.

Have you tried connecting directly to the module RF output to see if anything is happening there, I don't think these modules have foldback protection, but I could be wrong.
Sorry, just seen that you have. By the sounds of it, you have another duff module.

Re: Kenwood TR-9130 problem with PA
 

-- Hi, the module is very good grounded, this was one of my first checks.

-- I have measured on pin 5 (output) without the other components, there are only some mV RF signal. I think I have the second dead module...

Re: Kenwood TR-9130 problem with PA
 

Fred

If you still have the old broken one, see if you can remove the plastic cover then check continuity from each connecting pin through the circuit to the device mounted on the ceramic. My fault was no DC to one of the devices. Bridge it and you should be back in business. However it is not easy to solder to a track on the ceramic because it conducts away the heat from the soldering iron quite a bit but it can be done. 73

Re: Kenwood TR-9130 problem with PA
 

Well done for sourcing a module. My Standard 2m multimode uses the same one and I couldn't find a replacement so I had to repair mine.

Re: Kenwood TR-9130 problem with PA
 

I've repaired several Mitsubishi transmitter modules.

The radios have no protection. You can just keep transmitting until the heat kills the module.

The ceramic substrate cracks, breaking several conductors. Sometimes a module works when cold and stops working once it has raised in temperature.

I used fine tinned copper wire and solder across the breaks. One needed a new diode, so I used a wire-leaded one which I thermally linked to the substrate with silicone grease.

You need a small but powerful soldering iron like a Metcal with various bits. A stereo microscope makes it easier.

These radios long ago used up the stocks of real spare modules. It's unlikely that you found a real one that had been overlooked.

David