D&A phantom 500 12 tube

Discussion in 'Amateur Radio Amplifiers' started by 17W1517, Jun 8, 2015.

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  1. AI3V

    AI3V Ham Member QRZ Page

    Actually Steve, on the clipperton V the meter switch was a multi position rotary switch. There were more available unused contacts.

    All I had to do to add metering was add shunts and remove the mechanical stop on the switch.

    The real reason Denny did not meter the amp is then it would have been immediately apparent just what a pile of crap the amp was.

    Bird watts Steve, turn all the knobs for maximum and it's good.

  2. WA9SVD

    WA9SVD Ham Member QRZ Page

    That was my second (almost instantly) thought. A 6M amp for a 4CX250 would be all I need, but the P/S might have to be a tripler to get to the 4CX level. I just have the 4 sweep tube version (ala SK estate sale at a good price) that I have no idea how else to use other than dedicated single band use. But the current with a tripler may not be sufficient for a 4CX250. A separate regulated screen supply shouldn't be too hard, at low current.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    4CX250B can run 350W output power with only 1600V on the plate, as the Gonset 903A and 913A proved, since that's all they used on the plate

    A "doubler" should do it.

    Actually, that's an interesting tube (especially if you have very little drive power available). The Clegg Zeus used one on 6/2 meter AM/CW and only had 900V on the plate. That was mostly because on AM it was plate modulated, so the peak anode voltage swing was big. It ran 120W carrier output power with 100% modulation = 480W PEP (4X150A modulated by a P-P pair of 811As).

    Very forgiving tube if you limit grid and screen current.
  4. WA9SVD

    WA9SVD Ham Member QRZ Page

    I'm not sure the 4 x sweep tube amp P/S of a Palomar would supply sufficient current from a doubler, but I'd be happy with 350-400 watts output (SSB) on 6 M. As it is, the defunct (no toobs) Dentron is useless as is. If it can be made into a dedicated 6 M amp, I'd be very happy! I could drive it easily with my TS-680, which has only 10 Watts max output on 6 Meters!
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The Dentron HF amps with sweep tubes (and Ameritron made some a long time ago, also -- as did others) are GG and cathode driven and won't do anything with 10W drive.

    Howsomever (love that word), sweep tubes even in parallel, if modified for grid-driven and grounded cathode, can work on six meters. The old Clegg Apollo used two big ones to run about 350W PEP output power. The Drake TR-6 used three of them to run about 200W PEP output power on six, and they were smaller, cheaper TV tubes.

    A 4x sweep tube amp with everything optimized for 50 MHz can probably do that...but it would have to be heavily modified for grounded-cathode, grid-driven. Would need regulated grid and screen bias supplies, different kind of tuned input.

    Since AB1 normally runs at close to no grid or screen current, these supplies don't need to be powerful...just regulated to maybe 10 mA or so. Zeners can do that.

    For me this wouldn't be that challenging a project. 4x sweep tubes might be easier to manage on six as two sets of paralleled tubes, then operate those in push-pull with link output. Link output works great for a single-band amp, since it's really easy to optimize "everything" for just one band and you don't have to deal with the parallel junque of four tubes.
  6. WA9SVD

    WA9SVD Ham Member QRZ Page

    Sweep tubes are near unobtanium. If I were to convert the Dentron to 6M, it would be with a 4CX250, grounded cathode, and grid driven. Should be good for about 400 watts output ,, and I can drive it with my TS-680 or TS-570, as long as I remember to turn down the power on the TS-570.
  7. W1BG

    W1BG XML Subscriber QRZ Page

    Getting back to the original poster (and topic) - - the old 12-tube (4 driving 8) D&A Phantom 500 I would not waste 5 minutes time trying to resurrect this relic because as others have posted, the tubes for it are extremely scarce. Likely you could get a lot of money for any of the tubes that are still good, but the rest of it is junk. I recall the 3 transformers being split secondaries, 350-0-350 @ about 275 ma. The transformers (both primaries and secondaries) were all wired in parallel and the rectifier was a full wave bridge with only capacitor filtering. These 12-tubers (4 driving 8) ran grounded-grid and, depending on vintage, ran either 6JE6's or 6LQ6's. The keying circuit was typically a 6AQ5 with a 5000 Ω relay in the plate circuit. The 12-tube models were early production units that date back to the late 1960s through the early 1970's, making this unit near 50 yrs old. At this age it would be a "given" that the electrolytics in the power supply are long-since dried out and equally worthless. With the possible exception of any tubes (with good emission) there is otherwise zero value here. For the historians, D&A Mfg. Co. was a partnership between Ed Dulaney & Glen Armantrout & the amplifiers were built in the back room of the local Overhead Door Co. facility in Scottsbluff, Nebraska. Ed Dulaney some old-timers may remember as being pictured in ads for Cleveland Institute of Electronics in "Popular Electronics" Magazine of this approx. same era.
  8. WA9SVD

    WA9SVD Ham Member QRZ Page

    That is why I want to "gut" the transmitter, and use it as the base of a 6 Meter only amp, with a 4CX250 final. There should be more than enough room for a low current screen supply, as well as a lower voltage bias supply.
  9. N2EY

    N2EY Premium Subscriber QRZ Page

    Yes and no.

    The tubes are worth a lot IF they're good. The transformers too, if their ratings are known. Some other parts, such as tube sockets and meters - maybe.

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