The AM Forum

Hi,

I am looking for documentation for an RCA UL- 4392 Oven controlled crystal oscillator. Looking for circuit diagram, voltage and current requirements and service info. I especially need pin out for the rectangular plug on the back of the unit, and any ideas where to find a mating socket for that plug.

Thank you very much,

Joe

Ebay has someone selling the male and female same connector:
https://www.ebay.com/itm/144937794607
Maybe you can find someone just selling the female connector.

From an ad for the BTA-250M Transmitter
"The BTA-250M Transmitter uses the UL- 4392 Crystal Oscillator with the TMV-129B Temperature Controlled Crystal Unit which maintains the frequency constant to within plus or minus five cycles."

Maybe documentation for the oscillator is covered in BTA-250M manual and it looks like other RCA transmitter models use the same oscillator. It probably can't be that difficult to trace out the circuity and power connections. Also, check out one of 1950's RCA tube manual for the 807 tube. Maybe the will show you a schematic for an 807 oscillator.

Mr. Google can be very helpful  :)

Thank you! I ordered 2 sets of the Jones plugs.

Joe

The BAMA manual library has manuals for the BTA-1MX, which uses the same oscillator. Those manuals include the oscillator schematic and pinout.  In my phone so adding a link is a pain, but Google BTA-1M rca and it?s on the first page of results?

Ed

Thank you again!

I have down loaded the manual for the transmitter. 

So far, I know for sure that the pinnout of the 8 conductor socket is as follows:

Pin 7 is chassis ground.
Pins 3 and 4 are the heater supply for the 807 tube (6.3 VAC)
Pins 5 ad 6 (I think) are for the crystal oven power (110 VAC).
Pin 8 (I think) is for the indicator light that indicates when the crystal oven is powered on.

That leaves pins 1 and 2. Pin 1 goes to the second grid on the 807, pin 2  (I think) is the plate Vcc that goes through the multi tapped coil to the plate.

I found no indication of the required voltages on pins 1and 2.in the documentation.

If I have missed something, please let me know. I really appreciate the assistance that has been freely given to me. I have just received two N.O.S. RCA 807 tubes, and two sets of the 8 conductor Jones connectors on the way.

Again, thank you for all of the assistance.


Joe

https://frank.pocnet.net/sheets/084/8/807.pdf

If you download the whole BTA-1MX manual, page 37 has socket voltages.  The oscillator plate and screen both get 270 volts through a 6300 ohm resistor along with an 18k resistor to ground.  Math and more schematic interpreting shows that B+ before the 6300 ohm is 550 volts.

Math: Cathode pin is 20 volts, cathode resistor makes that drop with 29mA through it.  That 29mA with the 6300 and 18k, work out to 550v.   Sanity check:  the rf driver plate is direct to B+, and the socket voltage for its plate is 550v, too.


Ed

Hi again,

So pins 1 and 2 should be at 550 Volts. I guess tomorrow I will check out the availability of Hammond 550 Volt x-formers. I have built power supplies in the mid 400 volt range, but never that high. Here is a silly question... will standard wire insulation work? I think that I have read that standard insulation is good to 600 volts. Please correct me if I am wrong.

Thanks again!

Now it is off to the refrence books for tube ps design.

Joe

NO!

The resistors between the host transmitter's B+ and pins 1/2 are in the transmitter not in the oscillator!  Only 270v on those pins!

Ed

That sounds much better. As you stated, the voltage on the grid and plate of the 807 oscillator is 270 volts. I really do not like to build things hotter than 350 volts or more.

Again, thank you.

Joe