FS or FT: Homebrew tetrode HF amp
Ku7i at WORLDNET.ATT.NET
Tue Mar 21 18:00:50 EST 2000
> This is a very well engineered homebrew 4cx1500B HF amp. Covers 160 to 10.
> The power supply runs 3500 volts and uses a Dahl plate xmfr (ARRL-001)
> at 2700 volts at 1.5 amps CCS. Oil filled cap for filtering. I believe it
> the Dahl 5kv unit at 53uF. Has a time delay, soft start relay. The supply
> an exact replica of the 3500 volt supply in the ARRL handbook from the mid
> 80s sans the variac.
> Wired for 240 only. if you run it on the 220 tap of the xmfr the plate
> voltage climbs to 4000 volts. Great for 3-500Zs but too much for the
> tetrode. keep it at 3500 and tune up with a tuning pulser and you will be
> The screen supply is seperate and is well regulated. User selectable taps
> for 150, 250, 0r 350 volts.
> RF deck uses large vacuum variables in the plate and tune side. Quality
> turns counters for tune and load settings. Fixed coil for the L with a
> ceramic bandswitch. Seperate meters for plate current and plate voltage.
> Multimeter for screen I and E and grid I and E.
> Amp will do 1500 out on all bands except the bandswitch arcs on 10 so I do
> not use this amp on 10. Could be self-oscillation problem on 10, not sure,
> you fix. 50 watts in gives full out on the other bands with only a
> width amount of grid current.
> In a 36 inch tall roll away cabinet. Shipping is possible minus the
> PS and rf deck will go in seperate units. The RF deck will fit in a 51J4
> size cabinet. The PS is a tad bit taller than that. This amp works great
> but for now I want to stick with triodes. If you want a serious legal
> amp look no further. I much prefer to demo prior to purchase.
> Schematics are piece meal. The builder has some reference data but not
> although as I said it is really built well.
> Price is $750 and includes a full output spare Eimac 4cx1000A. Whether or
> not you want the cabinet does not matter, price is the same.
> Will consider another HF amp in partial trade but it must cover 160. Will
> also consider a fully operational and nice looking blonde, er, I mean,
> Johnson Valiant I or II.
> San Diego
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