Compactron Tube Uses

Discussion in 'Amateur Radio' started by W5HRO, May 29, 2015.

  1. W5HRO

    W5HRO Administrator

    A recent post in one of the other topics started me thinking about Compactron tubes again and their possible uses. Many of these tubes are still available today and most are pretty cheap.


    Compactron tubes were compact 12-pin tubes first introduced by GE in 1961 and they contained more than one tube inside all heated by the same filament. The idea was to reduce the amount of power required to heat the tubes and the space needed on a circuit board. Basically GE was tying to apply an early concept of integrated circuits using tubes. It was done primarily because of advancements in solid state technology at the time and in a way was a last ditch effort by GE to try and save vacuum tube technology because of it.

    Anyway, there are probably still many uses for these tubes in our projects today and I'm trying to think of some. There were also a few Compactron tubes made that only contained one tube inside, but they were capable of very high power and up to 175Mc. A good example would be the 7984 which was a 46W beam-power pentode which had the 12EU compactron base. There still should be plenty of 12-pin sockets available on-line too.

    Below is a list of compactron tubes and their pin-outs

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  2. W5HRO

    W5HRO Administrator

    Some uses for compactron tubes that already come to mind are below.

    1. Complete VFO with buffer stage or Vacker circuit.

    2. Complete mic amplifier, driver amplifier and buffer stage.

    3. Complete push-pull amplifier stage with AVC diodes.

    4. Complete 2 stage RF amplifier chain.

    5. Complete 3 stage IF amplifier chain.

    6. Six-Meter RF amplifier or driver stage.

    Anyone have any more ideas and possibly using which tubes? I think some really neat and small size projects or add-ons for our stations could be built using these tubes. Compactrons were still used in many TV sets up until about 1980 so there should be plenty of them available.
  3. W5HRO

    W5HRO Administrator

    I dug through my collection and I have several NOS 7984 COMPACTRON tubes and new sockets to go with them.

    I'm thinking maybe later this summer to build a small transmitter that covers 20-meters on up to 6-meters including the WARC bands using all GE COMPACTRON tubes. From the speech amp to the RF amplifier it wouldn't take that many of them. I could maybe even use a built-in DDS VFO with it :surprised:

    Anyway, 4 X 7984 tubes would draw around 600mA though in the RF amp. Hammond does make a transformer, but that's a lot of current. At the same time though I'm thinking modified Heising or screen modulation to make things really easy. It would just take some low-voltage high-current iron to do it. Hey, it's the next best thing to solid-state and I hate solid-state.

  4. AF4K

    AF4K Member

    That looks like a cool project. The 7984 compactron is a worthy tube.

    A source of 13.5V AC for the heater should be very cheap and easy since there are surplus transformers everywhere for 26V CT that were designed for 110V AC primary.

    Put 750V DC on the plate and you have a tube that will perform like an 807 only have shorter leads, so yes - good for 6m AM I am sure. Maybe use 4 of them for an RF final. That should be good for 150 - 200 watts.

    The GE boys in Owensboro, KY said that these can be used up to 175 MHz, so heck you could put them on 2m AM as well!

    73 de AF4K Bry
  5. W5HRO

    W5HRO Administrator

    Actually, I think at 750V the tubes wouldn't last very long on AM. For Class C FM and CW the CCS ratings are only 600V. Then it says 315V at 175Mc.

    What I'm thinking is around 325V to 350V max for Class C AM up to 51Mc which would yield around 35W to 40W out per tube if each tube draws 150mA. So with 4 tubes it would be somewhere around 150W out.

    I installed one of them in my old Fleet Courier 30B with 10-meter xtals back in the 1970's and got almost 30W out. I don't remember what the plate voltage was, but I think it was lower around 250V to 275V.

    Attached Files:

    • 7984.pdf
      File size:
      693.1 KB
  6. WD5JKO

    WD5JKO Member

    As some may know, I took an interest to the Central Electronics 20A starting back in 2003. One of the projects was to see what I could do with QRO'ing a 20A within the original case and power supply. Fortunately the original power transformer was hefty, and was open to a full wave bridge power supply. This is a long story which I will keep short. I picked the 7591 tube since I had several, and believe it or not these are good RF a point. After many hours, and three rigs in succession, I could do 20 watts RF output AM, or 80W PEP on SSB. This was on 160m and 80M. Going to 40M and above had additional challenges.

    Along the way I corresponded with many, but it was Larry NE1S that took a suggestion from me. I told him my story, and suggested he try the 7984 tube instead on a QRO 20A project. It was about 5 years later he called me up on the telephone, and told me he had the 20A working with a pair of 7984's. To be honest, I had completely forgot this prior conversation, and then boom, he had this 20a on the air, and was really wanting to tell me about it. He had the rig working 160m to 10m, and on the lower bands was getting over 100w PEP RF out. The output was good up through 15m too. He told me that the major stumbling block was the RF driver stage. He had to completely redo that, and neutralize the driver stage. The 7984's did not need neutralization, running class Ab1 linear mode on HF radio.

    A short time later I went on a business trip to Portland Maine. On a Saturday I went to visit Larry in Gray, Maine. Also there was the Timtron WA1HLR, and XYL Marci. I got to see that 20A. Larry had really done a good job with it.

    On my bucket list is to try some 7984's....

  7. W5HRO

    W5HRO Administrator

    The thing with the 7984 is that it was primarily designed for mobile FM business band radios used with short transmissions back in the 1960's. For use on AM the plate voltage would need to be lower for CCS service. On SSB you could run the plate voltage up higher in class AB1 or AB2 for ICAS service. That or maybe class BC AM with a slightly higher plate voltage.

    I was looking through Hammond's transformer list again and they have two transformers. One is 700VCT at 863mA and the other is an 800VCT at 535mA.

    The 350V one at 535mA may be a little lite unless you only run 2 or 3 tubes in the RFPA. On the other hand the 400V one at 863mA might be able to run 4 tubes in the RFPA and in the modulator when fully loaded down, maybe to 375V. I think for normal class C with 100% or greater modulation the plate voltage would need to be kept under 400V for CCS service. Since the ABS voltage for the tube is 750V then no more than 375V max with 100% modulation. In my case more than 100% so that's why I said 325V to 350V max.

    Attached Files:

  8. WD5JKO

    WD5JKO Member

    Back in the early 70's when I was a Johnny Novice, I tried to reproduce a simple transmitter that was in one of the ARRL handbooks. This was a one tube Compactron transmitter using a 6AD10. Being poor, I salvaged a 6AW8 from a TV set, and made a 7 watt input CW rig, and with a crystal I was on 3740.....CQ CQ DE WN8PEP....From New Baltimore, Mich.

    A few years later, I had my first phone, and Advanced class Ham ticket. As a Freshman in college, I volunteered at the local AM carrier current broadcast station. There was 17 Dorms where they broadcast on 560 Khz where the RF was injected into the building three phase power grid from the boiler room. Most of the transmitters were made by LPB, and for tubes inside there was a pair of 6AD10's. The RF power was about 5 watts where one tube was for RF, and the other for audio.

    Today I keep seeing that ABC Vacuum tubes sells the 6AD10 for a buck apiece!

    Doing some internet searches of the 6AD10, there are many in the audio business / hobby that are using the 6AD10 as a low power SE output tube.

  9. W5HRO

    W5HRO Administrator

    Attached below is a list of some other compaction tubes. I need to go through one day a compile a complete list, but this list has a lot.

    Attached Files:

  10. W5RKL

    W5RKL Member

    Heathkit used Compactron tubes in the SB-300, SB-301, SB-310, SB-400, and SB-401 receivers and transmitters. I buy my Compactron tubes from

    Mike W5RKL