[Amps] 17 x pix of the 10 kw 6M amp...using the new Pentalab 3CX-6000A7 tube

[John Lyles]

Hi Jim

Good to see the 6m beast complete. I know it was fun.

I have found one source of commercial ribbon wound and tubing RF 
inductors to be 1-5 kW medium wave broadcast transmitters. 
Johnson/Multronics, Gates, Kintronics Labs, etc. Some stations in USA 
are ditching their vacuum tube rigs and switching over to silicon-based 
or going dark completely due to insufficient profit margin. They cannot 
find techs to keep the HV and tube rigs alive in some regions,  If you 
approach the station owner offering to haul away their rig, or buying 
parts from it before they haul it to the scrap yard, you will find some 
choice parts. I have acquired quite a small collection of 15-25 Amp 
inductors for big tuners and transmitter projects, and occasionally sell 
them back to some broadcasters in need for significant savings. Also 
some large meat-slicer air variables, the ones with wide spacing. Many 
broadcast rigs used fixed mica caps and made the inductors variable. 
There are far less with vacuum variables in them. Since 1.7 MHz is below 
our amateur allocations, the inductors tend to be too large, but can be 
modified, tapped or cut down, with soldering skills.

73

John

K5PRO

> Date: Fri, 25 Aug 2023 06:19:11 -0700
> From: "jim.thom jim.thom at telus.net" <jim.thom at telus.net>
> To: amps at contesting.com
> Subject: [Amps] 17 x pix of the 10 kw 6M amp...using the new Pentalab
> 	3CX-6000A7 tube
>
> 17 x pix of the 10 kw 6M amp...using the new Pentalab 3CX-6000A7 tube. If
> you want to see pix of both top + bottom of the RF deck, + pix of the HV
> supply, here is the link.
> https://amprepairguy.com/10kw-6-meter-custom-pa-3cx6000a7...
> <https://amprepairguy.com/10kw-6-meter-custom-pa-3cx6000a7.html?fbclid=IwAR1rqa0I-Op9lEPcKJt2UzdmTBJxTGZa9G72wrgr6HSQcQXsD3sL2_LnWMo>
> The next amp is the 80-15m band switched unit, using the same 3CX-6000A7
> tube. I have finalized the design for the RF deck. Components of course are
> a lot bigger. 1/2" silver plated tubing used for the 20-17-15m coil (and
> also the L coil before the main PI-net). The 80-40-30 coil will be hand
> wound, using 3/8" tubing.
> 500 pf ceramic vacuum tune cap, and a 3000 pf vacuum load cap. Same setup
> for the TR relays. RJ1A for the cutoff bias, and a 2nd RJ1A for the input.
> 2 x paralleled RJ2B's for the output. 7-16 DIN connector for the output. 4
> x 200pf HT-57 plate blockers used. I have also finalized the design for the
> 160-80-40-20-17-15m version. It uses a 4000 pf vac load cap, and one extra
> coil.... for 160m (silver plated 1/4" tubing used). 8-9 x 200pf HT-57 plate
> blockers used.
> The HV supply will use a lot more B+ (7500 vdc)...and will use 2 x
> identical plate xfmrs in parallel. Both designs employ a bandswitched PI
> tuned input. (C1 + C2 are padded on 160m) Stay tuned.
>
> Jim VE7RF