Repair a Redifon GR 345D and GA 480 from the scrap yard

I got, from a friend, a broken Redifon GR 345D with the matching 100 Watt linear GA 480.
Nothing is working. No Receiving, no Transmitting, not output from the linear.
I think he have it from the scrap yard.
Its was very hard to get the schematics from the GR 345, so I take the schematics from the PRC-74. I OM in UK help me with the manual.
The GR 345 have only 100mW output for the Linear. The Linear is internal switchable from 100mW in to 15W in.


The Transceiver GR 345D:
At first I changed some transistors in the Gain Control board. Some connectors on the underside was burned too.

After that the 100 mW comes out the transceiver by transmitting. But the frequency is not right. Only the MC Knob works, the rest not. So I changed there some transistors too.

The changed transistors.
Inside the radio. Now the frequencies are OK, but still no Output and no ReceivingIMG_3260

I lose the connectors from the IF/Audio Module

Here I changed all transistors
On the second board from this module I changed 8 transistors.

After that I was happy and I hear a signal from the function generator 🙂
You can take for the BFX18 a BF199 and for the 2N697 a 2N1711 or a BFW67. It works 🙂
The 2N706 I got from eBay.

I changed near 30 parts in this radio and I worked near 40 hours on it.
Now I ordered a 1750 KHz LSB filter in the USA the replace the AM with LSB. The transceiver have only AM,CW and USB, what is not so nice for a frequency range from 2 up to 12 MHz.


The Linear GA 480:
The Linear is a lot of harder. I checked everything in this linear. It looks like OK. It must be the 100W module, was is broken.

This is the 100W Module

Normally its oil filled

This module full with parts

I resistor was burned. I had no 4.7 Ohm resistor, so I take some together.
The finals are RCA 60282 transistors. In the manual it is no schematics from this module, only from the rest of the linear. Over this transistors you find nothing in the internet. In the manual is wrote: “If this module is broken, replace it with redifon part number xxx.

I see some finals in eBay what maybe can fit. It was some KT904, what was not so expensive. I insert this and I change the parts what I see, what is broken.


Then I use the function generator as a driver and I start to test it. It came with 50mW in 5 Watts out for a little time. After that it burns after some seconds 🙁

So my finals for 20€ was broken again. The finals must be the wrong types.
I see that one little transformer is broken. But without any informations over the transformer and the finals, it is not possible to repair.

So I take all usable parts from this module and start to build a MOS FET Linear Module for 100 Watts. This will take a while…

But my transceiver works and I can test it so far. Here is the video.

20 thoughts on “Repair a Redifon GR 345D and GA 480 from the scrap yard

  1. DC2CW de Ex-oz1llu/Alpha-DL3LBI : Guten Morgen aus dem Norden der Republik lbr OM! Beim Anblick Deiner Basteleien wurden alte Wunschträume in mir wach, die ich auch im gegenwärtigen Ruhestand u.a. Aus zeitlichen Gründen nicht realisieren kann. Viell. Begegnen wir uns ON AIR @ QRP PhonIe 20 / 40 m?
    Weiterhin GL, Vy 73 von Hans

    • Hi Paul, thanks for the comment at my Blog.
      My LSB filter is not arrived from the states. He say he send it, but it’s loss 🙁
      So I try to find a other one, what ist very hard. In the moment it’s only USB and AM possible.
      Its not possible without big modifications to made it working under 2 MHz. The first its to try it with new crystals. The frequency you can calculate. The the seconds question is the filters are working for that frequency.

      • Hello
        Congratulations for the restoration of this radio.
        Locate the SSB filter of the IF module and remove it completely. Then solder input and output wires together so you can bypass it. With this easy modification the receiver works as DSB, and you have both LSB and USB reception.Tested on a PRC-74A which is the same design and works perfectly, hope this helps.
        Another experiment is to use a DDS signal generator instead of crystals.

  2. Hello and congratulations for the restoration of this radio.

    You can try the following for LSB:
    Disconnect the input and output wires from the SSB filter on the IF module and then connect them together so you can bypass it. This results that the receiver works as DSB and you can hear both LSB & SSB. Tested successfully with a PRC74.
    You may also use a DDS Signal generator for replacing crystals.
    Keep up the good work

      • Hi Donald, I’d like to make a proper mail as an answer. Can you mail me, I guess you see my mail adress, but I cant find yours.

        As a teaser, there are two things that has to be altered during LSB compared to USB…

        • Hi Lars, if you still have the GR345 LSB modification data, I would like to see it. I have the GR479 version and have now got it working for a 1973 vintage Desert Rescue Team Signals Land Rover recreation. Even my 100W linear now works!
          I was a member of that team and I am now a Ham. 60m is very restricting and noisy and I would like to use LSB on 40m. 73deRayM0XDL

  3. Today I had some thoughts on the possibilty for a 1.8-2 MHz mod…

    The xtal saving synth has to get an extended range, the easiest way would be to add two more stages to the 100 kHz osc, somehow giving it 12 steps, two below zero; with xtals at 26630 kHz (-100k) and 26530 kHz ( -200k).
    Then the filters around transistors VT605 and VT606 may need some tweaking, to bypass the wider range of frequencies. And also, the final mixer VT608 and it’s bandpass output filter L610-L613 and the capacitors associated may need to be tweaked to bypass the extended range 3.73 – 13.750 MHz , compared to the original 3.75-13750 MHz.
    When the synth is ok, the nest issue is the preselection filters. It is probably possible to retune the preselection filter for the band 2-2.999 MHz to accept 1.8-2 MHz, maybe sacrificing the top end

      • The easy part of this is, that xtals on 26630 and 26530 kHz are avaliable at RC-shops, used as reciever XTALs on 27075/27085 kHz.
        Donald, did you recieve my mail on the LSB mod?
        BR Lars /SM4RZW

          • GR8 🙂

            I remembered, that I also tried to shift the 1.75 MHz XTAL down to 1.747 MHz by capacitive loading, but it stopped oscillating long before.

          • Hi Lars,
            yes I tried the same. The oscillating stops by me too. Maybe we can build a new one?
            In the moment I have a modified filter (second USB one) installed. I tried to push down the filter window with capacitors.
            It works, but it’s not so nice to show it here. You still can hear something in the other sideband.

  4. Hi Ray, just checked in here to see if Donald published anything new, then I saw your message. I found the notes I sent to Donald, and I most gladly send you a copy.
    Please send me an Email and I’ll reply withthe file included.

  5. Btw, browsing the subject I found indications that there’s a published document of the LSB-mod on the PRC-74, the radio set that´s is the origin of the GR-345.

    The author of that document is James Karlow and it can be downloaded as pdf here:

    Interesting, to me it seems as if he’s taken the same route as I did 🙂

  6. Hello !
    Many years ago, l modified my PRC-74 A according Jim Karlow KA8TUR LSB conversion. It works fine on 80 and 40 m band. I made some orher modifications, and particulary added a digital frequency meter. Best 73. Cyrille F4HUE

  7. Hello, I noticed you have technical documentation for both the Radio and Amplifier, could you direct me to the source of these documents?

    I have both units, but my radio is an FUG-15 with UG77 type connectors, you dont happen to know if the H-33 type handset will work with the FUG-15 radio?

    Best Regards,

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