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 on: September 20, 2022, 11:37:41 PM 
Started by lu8dam - Last post by Opcom
Welcome! It's always good to find another ham using a phase rotator. More people should use them on AM.

 on: September 20, 2022, 11:26:12 PM 
Started by w8khk - Last post by Opcom
For what it is, the 6DQ6 is probably capable of maxing out the power supply. Look at the peak current to be had for the 6146-like heater current, which is somewhat a measure of reserve emission, not that the average rating should be exceeded. Tons of current with low screen and plate voltages.

Unless you want to put a larger transformer in there or go outboard with the power supply, would I be wrong to say that the 6DQ6 is enough? 

Maybe a slight tweak to anode load resistance to take advantage of what the 6DQ6 offers over the 6146 could be in order but that's probably nit picking!

 on: September 20, 2022, 10:45:20 PM 
Started by KD1SH - Last post by Opcom
Some pictures:
  Not a single switch, panel meter, or connection is labeled. Maybe there were labels at one time and they've since fallen off, but I see no evidence of glue residue or paint discoloration.

--I really like the looks of that amplifier! The plate heat dissipation caps don't bother me a bit.

 on: September 20, 2022, 10:22:43 PM 
Started by Opcom - Last post by Opcom
Who can these be? It's my impression that this is the standard non-custom tube.

 on: September 20, 2022, 10:20:22 PM 
Started by Opcom - Last post by Opcom
The image on the target plate

 on: September 20, 2022, 10:19:22 PM 
Started by Opcom - Last post by Opcom
Here's a nice one, picked up at an auction. This is the National Union 2203, an Monatron tube.

It provided a test pattern for the alignment of TV cameras, monitors, TV sets,  and the like. This type of tube was popular with TV amateurs and hobbyists because it was much lower in cost than the RCA version, and required only a simple oscilloscope-like electronics circuit compared to the CRT inside the high-end, complex RCA TK-1.

This 2203 tube seems to have some visual issues, but as of yet I don't know what it will look like when making a TV picture. I don't know who the two people are. In those days one could order just about any monascope or monotron tube with one's choice of imagery and the factory would apply it and make the tube(s). The tube is identical to the National Union 2003 CRT except for the image plate and 'plate cap' instead of a phosphor coating.

About the RCA Monoscope Camera TK-1 and its 2F21 tube:
We have all seen the famous monochrome RCA test pattern with the Indian Chief artwork. It was generated by a special CRT type 2F21 inside the TK-1 Monoscope Camera (test pattern generator). The image was intended to allow resolution and linearity checks on TV receivers, and indeed served as the gold standard for test patterns at many TV stations before the days when similar video test patterns were made possible by technological advancements.

The Indian Chief artwork contained carefully formulated gray shades and details intended to include subjective yet technical information within the pattern of lines, wedges, and circles. The entire pattern was placed on a metal plate and a terminal pin extending through the CRT face provided the output signal for the TK-1's video amplifiers. Sync and blanking was added and shipped to an SO-239 at the standard 1V peak to peak into 75 Ohms. I am currently doing an electronic restoration of a TK-1 for a friend. At this point, a surplus HV power transformer has been found and ordered and we believe that his RCA Monoscope tube is good.

A low voltage power supply (280V@300mA/-3V@1A, ) must also be found or constructed, but first heat will be done with laboratory power supplies, so that the tube can be checked before undertaking that considerable task. In case anyone has an RCA model 580-C (MI-21523-B1) power supply, that is the proper unit for the TK-1. Close regulation of all voltages including mains power is essential.

I can add only one image per post for some reason.

 on: September 20, 2022, 09:07:50 PM 
Started by N3GTE - Last post by N3GTE
I have a DX-100 that came from N3IBXsk yrs ago. Have had a couple on the air over the yrs but this needs to be serviced before it hits the airwaves.
The big question is how do you get to get to the parts the are connected to the 12AX7 & 12BY7? Can that shelf be removed for easy access? Or loosen the screws up shove it back a bit?

Tnx for your sage advise

Terry N3GTE

 on: September 20, 2022, 05:44:08 PM 
Started by lu8dam - Last post by lu8dam
Hello, Shane.
Excellent work you have done.
I left it with 8 poles. When I mount it in a cabinet I will add switches and a bypass.
I transmit on 7150 kHz to crystal.
Maybe you can listen through some remote receiver on the web.
Best regards.


 on: September 20, 2022, 05:26:31 PM 
Started by lu8dam - Last post by KD6VXI
Hello from the USVI!

I used the w3am phase rotator.  I put swit he's for 4 poles 6 poles or 8 poles.  Followed that with a compressor configured more as a limiter.  Then I fed that into a positive peak stretcher that allowed me to dial my pos peaks wherever I wanted them.

That fed my PWM and a 100 watt carrier 125 pct mod rf deck.

It was a great setup.

Hopefully March 2023 I will have my gear down here and we can QSO...  What frequencies do you operate AM?


 on: September 20, 2022, 04:21:31 PM 
Started by KD1SH - Last post by KD1SH
Power supply seems to work fine: 3800vdc out with 240vac in. And with the tap-selector in the "low" position: 2100vdc out, which will be handy if I ever want to use it with lower voltage tubes like 4CX-250's and the like, or 813's and such.

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