Hello. I'm looking for a manual, or just parts list and schematic, for the Graymark 533 transmitter kit. Can't seem to find anything on the Internet. Thanks!
I'm glad somebody brought something like this up, I had been thinking about Knight-Kit tube transmitters in this style, a couple of tubes and you could connect a microphone or phono to it.
It's almost the style of transmitter I'd been thinking of for a long time, but mine would have a dual triode and the two 50C5s. One triode would be a carrier oscillator, driving a 50C5 RF output tube, the other triode would be voltage amp, driving the modulated stage. It would be what the circuit is now, with an added carrier oscillator.
Having a separate oscillator can greatly improve the stability and sound quality of the signal, with less drift from moving the antenna around and getting close to it, by separating the functions of frequency generation and modulation.
There would be more expense from parts on the oscillator, but maybe it could be offered as a more premium kit for a few dollars more. The dual triode should have a controlled heater warmup to avoid a surge from the heavy filaments in the 50C5s taking time to heat. I see the commenter's point about the 27 ohm resistor being in series with the filaments though that would reduce the plate voltages too.
I keep seeing these dire warnings on direct line powered gear and AC/DC radios, and saying that one side of the AC line is connected to the chassis, and it's not true! Maybe they're trying for maximum shock value, thinking that people will just stick their tools and other body parts inside the chassis while the radio is on, because people today don't know about the circuit topology of these old radios.
I see the site warnings, and it looks to me that people are just repeating what they read and adding on, or they touched a tuning condenser in the family radio when they were three and got a tingle, which seemed worse because they were small.
Good looking page Carl, the facts with a good schematic and photos, nice.
The Graymark 515 Data CARL has on his fasinating site is actually a page from SMECC Museum www.smecc.org
Glad you find it of use... As a kid all of these wiress phono devices were a great love of my self personally and gald to see others still have them on their mind!
Our museum would like to find one of the GRAYMARK transmitters to go in our PART 15 brocast from the school and home collection. We posted the schematic hoping to encourge some interest in the GRAYMARK unit so glad to see it has!
Ed Sharpe archivist for SMECC www.smecc.org
Nate, here is our SMECC collection of info on the Knight Kit!
http://www.smecc.org/knight_kit_home_broadcasters_-_allied_electronics.htm
I had one of these in my youth! great fun and put out a pretty good signal!
Ed Sharpe archivist for SMECC www.smecc.org