Nico, bedankt! I found and installed another with reasonably good specs when loaded carefully. I also discovered that the power transformer secondary has an unused center tap, so with the full-wave bridge, that would make a useful 300V source.

Love those Philips radios, and Grundigs and Lowe Optas... heel goed!

My next task is to determine why adding negative feedback causes the screens to go into super-conduction regardless of polarity. Supersonics?

Troubleshooting homebrew equipment designed and built 50 years ago can be quite a challenge!

Filament Transformer from a BC-1T Broadcast Transmitter


Shipping Weight: ~ 30 Lbs.
Dimensions: L = 9.75,” W = 7.25,” H = 6”
Pri: 230V, Secondary’s: 10.1 V@10A, 10.1 V@10A, 10.1V@20A

For more information please see the PDF file:


Phil - AC0OB

Actually, I may have an even better option. The power transformer HV secondary has an unused CT (full wave bridge) so there’s a nice 300V source.

So @ 300vdc how much rf does it make? My little HW will make abt 10W at the 300v level (switch in low). In high (450v) on AM puts out abt 30W and few more on CW. Very similar tx w/6L6's x 807. Have had the bug to put it back on the but not much motivation. Maybe we'll catch you on 40 sometime.

Terry N3GTE

Some ideas
Many Philips radios from the years 50 / 60 have small AF output transformers that have a negative feedback winding for approx 500 Ohms There you have 500 - 7 kOhms. I used these, worked very nice
Microphone transformers, sometimes in the base of CB table mic's
I may have one for you, but my stuff is still in my sea container until my house is ready. So that is the least probable at short notice

This is a LV choke from the LV (650V) Power Supply.


Please see PDF file for details.


Phil - AC0OB

This modulation reactor was removed from a working 1kW Gates BC-1T Broadcast transmitter.


Please see the PDF file for more information.

Phil - AC0OB

I got a clean Elmac AF-67 off eBay some time ago and had to make a power supply for it.  I finally got around to finishing it and here it is.  I'm using two 12 volt transformers back-to-back to work as an isolation transformer, and then double the 120 volts for the low voltage.  B+ is 300 volts with a filter choke.  That same toroidal transformer has a couple 6.3 volt windings. 

I'm going light on the voltage, but I'm just trying to have it make a little RF.  It's more of a show piece rig than an actual daily operational rig.

Jon

This was connected to 833A’s in Push-Pull Class B service modulating a pair of paralleled 833A’s with 2500 Volts on the plates.

Frequency Response: 40-15000 cps (40-15k Hz).

Please see the PDF file for more information.


Phil - AC0OB

Looking for an O-5C/FR FSK Exciter - Similar to the TMC XFK, it generates an FSK RTTY signal using a 200 KHz oscillator and mixes the FSK 200 kHz signal with an internal crystal or external oscillator to produce an HF signal. There was also an O-5B/FR variant. If you have one to sell and going to Dayton (Xenia) next month, I'll be there. Tnx for reading.