[Milsurplus] Powering the TBW-4

[B. Smith]

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 at 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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