[Milsurplus] Powering the TBW-4
Mark K3MSB
mark.k3msb at gmail.com
Fri Jun 14 08:59:54 EDT 2024
Thanks!
Mark K3MSB
On Thu, Jun 13, 2024 at 7:03 PM B. Smith <smithab11 at 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 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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