Tecraft transmitter 2 meter AM transmitter

[W2PFY]

I recently acquired a Tecraft 2 meter AM transmitter. It did not come with the power supply. It requires 250 volts at 250 mills. Does anyone have a schematic for it and is there anyone out there that is using one? Are there any mods for it?

[Pete, WA2CWA]

This one:

http://www.qsl.net/la5ki/org/te/tr20.htm

[W2PFY]

That's the one Pete. Not too much information out there?

[WQ9E]

I have Tecraft 144 and 220 transmitter like the one pictured but they didn't come with information or a power supply.  They were in a box with Tapetone 144, 220, and 432 converters.  It was some stuff from an estate so any information was probably tossed prior to the sale.

[Rob K2CU]

I have one that I built a 300V power supply for from an old tv transformer. I drew a schematic of the unit and will dig it out, scan it and be able to post it or email you a copy. I pushed the 6360 to about 12 Watts output for AM on two, and also used it to drive a Varactor multiplier for 6 W on 432. For 432 use I tickled the crystal for NBFM. I paired it up with an Ameco CN-144 and a home brew for 432. I still have it all and will dust it off and measure the voltages, etc.

[W2PFY]

I have one that I built a 300V power supply for from an old tv transformer. I drew a schematic of the unit and will dig it out, scan it and be able to post it or email you a copy. I pushed the 6360 to about 12 Watts output for AM on two, and also used it to drive a Varactor multiplier for 6 W on 432. For 432 use I tickled the crystal for NBFM. I paired it up with an Ameco CN-144 and a home brew for 432. I still have it all and will dust it off and measure the voltages, etc.

That would be fantastic! Thanks to all that replied.

[W4AAB]

I have a homebrew power supply for my 220 Tecraft. I need to make a drawing for it. I also have a Tecraft 2m transmitter.BTW, wonder what would be a good frequency to use for 222 mHz AM? I am planning on using 144.45 for 2m AM(if I ever get time to operate).

[Rob K2CU]

    I found the schematic sketch I had drawn about 40 years ago. It is lacking the power connector and details of filament power. the unit was designed for either 6.3 V or 12.6 V filament power. My unit had also been modified prior to my obtaining it, in so far as a two channel 1/4 inch mic jack was installed for a PTT line that was run over to what must have been an unused pin on 8 pin the power jack. A miniature toggle switch was added to the front panel to do PTT as a "Transmit" switch. Another switch was also added to open the final cathode DC path to ground. It's purpose, operationally , is unknown. My only guess is that is was used for some sort of spotting function.
    Also, my unit is different than the tube lin up descirbed in the advertising literature linked in an earlier post. The RF section is: 6AU6 - OSC/Tripler, 5763 - doubler, 5763, doubler, 6360 - PA. The lierature calls for 6360 as final doubler in place of the second 5763, yet pix of unit shows the shorter 5763. The 6AU6 circuit is interesting as it uses the screen as the "plate" of the oscillator section and the actual plate as the tripler output.
    I am redrawing the schematic with Orcad and will try and get it done over the weekend. If anyone has the factory pin out of the power connector, please let me know so I can make the schematic right. I don't trust that my unit's pin out is correct. I will leave out the PTT modification and final cathode switch modification.

[W2PFY]

I'll open mine up later today to see if the the tube driving the final is in push pull, if it is, then the wrong tube is in my set as well. The literature clearly states that two 6360 tubes are used.

[W2PFY]

Just opened the bottom of the transmitter and it looks like a 5763 is what is required. I guess they made different versions? I also see there is a meter switch on the front but I have no idea what kind of meter is to be used?

I am also thinking this transmitter may have the original tubes in it. They are made by Calvertron of the UK. The 6360 has no markings and they are inexpensive on ePay.

[W2PFY]

Here's what I found on the 8 pin power plug looking at it from the bottom.

Pin 1&2 tied together Filament
Pin 3 NC
Pin 4 NC
Pin 5 B+
Pin 6 NC
Pin 7 Filament
Pin 8 Filament & ground.

One additional note: 7 must be tied to 8 for all the filaments to light.

[Rob K2CU]

Thanks for power connector pin out. I will incorporate that info into the schematic I am drawing with Orcad Capture. It looks like it will require two pages, one with the bulk of the circuitry and the second with the connector and filament circuit arraignment. I found it strange that some lines going from the modulator section to the RF deck had feed through bypass capacitors and others did not. when done I will post to this thread as PDF files. I have a bit of clean up to do, tube pin numbers for example.

[Rob K2CU]

Well, I finally got this finished. I think it is all there. Oops, missing value of R10, screen of 6360. I think it is 15K.  Also, my unit's R14 is cooked a bit but measures 50 Ohms. Any feedback is appreciated.

[W2PFY]

That's great Rob! Just saw the 2nd page. Not awake yet
Thanks a bunch for doing this. This is the only schematic that I know of in existence. I noticed you have 12.6 volts on pin 1 & 2. The advertisement called for 6.3 volts with no mention of 12.6. As I said in an earlier post, in order to light all filaments I need to tie pin 7 & 8 together when running on 6.3 VAC. Maybe I need to re-visit this area again and fire up the filaments once again?

I'll be building a PS for mine after the holidays. I don't think there is any two meter AM activity around here.

I'm up to three transmitters and one receiver just for two meter AM. I may have to force feed someone a transmitter, just so I have someone to talk with

  

[Rob K2CU]

I can't speak to any others than the one I have. And, with that, there were a few mods (that I left out of the schematic), though, to add things, like a PTT line to go to the power supply connector...probably for an antenna relay. Regardless of the true pin out, the tube sockets in mine were clearly originally wired for either 12.6 V or 6.3 V. To use 12.6 V, you only connect filament power to pin 1 or 2 only. I checked and the current is balanced. IF you want to use 6.3 V, you apply it to pin 7 and ground pin 1 or 2.

Unless you open your unit up to verify/compare wiring, just apply 6.V to pin 7 and see how many tubes light up. If your unit is the same, you should find the 6AU6, one 5763, one 6AQ5, and half of the 6360 lighting up. IF so, ground pin 1 or 2 and see if the rest light up as well. The posted ad may list 6.3V but it also shows a rig with one 5763 and two 6360's. And yes, the rig will work with just 6.3V, so the ad is not incorrect either way.

[W2PFY]

Thanks Rob, I'll check it out next week when I return from my road trip to my camp where my radio station is located. I'll be on 3.885 & 7.290 and maybe 20 meters.

Thanks again for your help.

One more question. What kind of meter is used to set this transmitter up?

[KC2TAU]

If I remember correctly you're close to Albany, correct? I just picked up a Hallicrafters SR-42 2m AM transceiver and I've been looking for folks on AM to use it with.

[W2PFY]

If I remember correctly you're close to Albany, correct? I just picked up a Hallicrafters SR-42 2m AM transceiver and I've been looking for folks on AM to use it with.

kewl, let me know when you are thinking about getting it on the air. I know of one other guy who we can get on the air. Maybe it's possible to get a hold of one of the local radio clubs and let them know what we are doing.Maybe they have others who may enjoy AM?

[KC2TAU]

The Hallicrafters is all set to go. Which clubs did you have in mind? I can send out e-mails if necessary. I'm a member on the Yahoo Group for the Troy Amateur Radio Association and I know quite a few people at the RPI Amateur Radio Club, W2SZ.

[W2PFY]

The Hallicrafters is all set to go. Which clubs did you have in mind? I can send out e-mails if necessary. I'm a member on the Yahoo Group for the Troy Amateur Radio Association and I know quite a few people at the RPI Amateur Radio Club, W2SZ.

Cool, let me get my antenna up next week. I do have an old Sonar ready to go. Last year I called CQ on it for about 4 months and no one ever answered me.