On Thu, Jun 13, 2024 at 7:03 PM B. Smith <smithab11@comcast.net> wrote:

Here is a link to my GO-9 project for some possible ideas. I also did a
external HV supply.
http://k4che.com/GO-9%20Transmitter/Index/GO-9%20Index.htm
k4che

On 6/13/2024 5:49 PM, Mark K3MSB wrote:
> Hi Ray
>
> My RMU had two of the three 800 Hz transformers missing. Since I will
> be running my TBW off of 120 VAC I decided to get rid of all remaining
> 800 Hz related parts and wiring. This resulted in the bottom deck
> being completely devoid of parts and the middle deck almost free of
> parts. The middle deck still has R-219 which is still needed but can
> easily be relocated. I've attached two photos.
>
> I plan to mount all new transformers (except the 2 KV supply) onto the
> bottom two decks of the RMU. This will be the 500V supply as well
> as the 2.5V, 10V, and 12.5V Filament transformers.
>
> At present, I plan to have all primaries go through the Filament
> Rheostat control.
>
> The two 837's require 12.6V for the filament but they are fed by an
> 18.6 VCT secondary off of the non-existant T-202. I think this
> increased voltage was needed due to the voltage drop in L-302 and
> L-303 in the Oscillator filament circuit. I think this then
> required dropping resistor R-213 in the filament circuit of the
> Intermediate Amplifier. I plan on bypassing (shorting) L-302, L-303,
> and R-213 so that I can use a standard 12.6V transformer for the two
> 837's.
>
> The 2 KV supply will be external to the RMU and will be fed in via a
> new plug on the bottom of the RMU, then to S-208C. The new 500V
> supply will feed S-208B.
>
> What I still haven't figured out yet is what voltage the 803
> suppressor needs on Phone. This voltage is developed from the
> non-existant T-203 HV secondary CT via the bias adjustment pot R-205.
> There is nothing in the manual about adjusting R-205 (or maybe I'm not
> seeing it....). Looking at the 803 data sheet, for 2 KV plate
> voltage in Suppressor Modulated Class C phone operation, I'd need
> about -110V on the suppressor. Still not sure of this area yet,
> but I should have room for a bias supply in the RMU. The bias
> supply would feed into the ungrounded end of R-205 then to the 803 via
> S-209A in Phone operation.
>
> The front panel AC ON/OFF and DC ON/OFF switches will be used as
> intended. Both required a good bath in DeOxit for them to work
> (Well, they are 85 years old.....)
>
> I plan to repurpose some of the 4 front panel AC Compensation SPST
> switches.
>
> One will be for a “TX/RX” switch for lack of a better term. In TX,
> relay K-301 in the HF transmitter will close as it's supposed to do.
> Except..... I plan to ground the Oscillator with a new modern relay
> instead of K-301B. That new relay will be controlled by the key or
> mic switch from the RMU.
>
> When receiving, the 2KV and 500V power supplies will still be
> providing voltages to the 803, but the oscillator will not be enabled.
> I was discussing this with Howie and we feel this is OK as long as
> plate dissipation is not exceeded, and that concern may require me to
> run less than 2KV on the plates.
>
> I ran a TBW-5 for a few years with 1200V on the plate and that gave me
> more than 100W output on CW which is adequate for my needs.
> Running phone with the TBW will be a new experience for me.
>
> Any and all comments welcomed.
>
> 73 Mark K3MSB
>
> On Thu, Jun 13, 2024 at 10:23 AM Ray Fantini via Milsurplus
> <milsurplus@mailman.qth.net> wrote:
>
> Don’t know, maybe smarter people can tell me how but think the
> wire that’s used is something like the stuff they use on heater
> elements so it can not be soldered, if somehow you were able to
> get a couple turns un-wound maybe you can just tie them together
> but looks to me as far as the power pot is concerned, its game over!
>
> How are you doing the entire T-202 mess? The original circuit for
> 800 cycles had that pot (R-201) and all those weird power
> compensation capacitors switches and all that stuff. I did
> separate filament transformers for all the tubes except for the
> weird 2.5 volts for the 843 and a separate huge 10 amp transformer
> for the ten volts for the 803, used the power stat or whatever you
> call those huge wire wound pots just on the AC primary of the ten
> volt 803 supply, the good thing if you got to replace it you don’t
> have to get an exact match, just something that fits in the same
> hole.
>
> Ray F/KA3EKH
>
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