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Old 16th Aug 2019, 12:30 pm   #1
baumfred
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Default 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
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Old 16th Aug 2019, 1:59 pm   #2
Sean Williams
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Default 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?
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Old 16th Aug 2019, 3:04 pm   #3
G6Tanuki
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Default 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!
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Old 16th Aug 2019, 4:52 pm   #4
baumfred
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Default Re: Kenwood TR-9130 problem with PA

Quote:
Originally Posted by Sean Williams View Post
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?
-- 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.

Quote:
Originally Posted by G6Tanuki View Post
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!
-- The unit takes in Rx 0,5A and in TX 0,58A
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Old 16th Aug 2019, 8:51 pm   #5
baumfred
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Default Re: Kenwood TR-9130 problem with PA

Quote:
Originally Posted by baumfred View Post
Quote:
Originally Posted by Sean Williams View Post
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?
-- 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.
Sorry, the input is 2,5Vpp, output (pin5) from the module 20mV !!!
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Old 17th Aug 2019, 7:24 am   #6
Sean Williams
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Default 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.
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Old 18th Aug 2019, 2:44 pm   #7
baumfred
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Default 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...
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Old 25th Sep 2019, 10:05 pm   #8
Richard Witney
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Default 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
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Old 25th Sep 2019, 10:14 pm   #9
Richard Witney
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Default 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.
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Old 26th Sep 2019, 5:43 am   #10
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Default 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
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