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39-85 code 121
#4

Hi TDump,

First off, welcome to the Phorum of Phrindly Philco Phans. (Notice a pattern here?)

Second, God bless you and continued prayers for your recovery from your brain injury!

Third, that IS a rather handsome set.

Fourth, here is a link to the service notes from the Phorum's library.
https://philcoradio.com/library/download...20Book.pdf
God bless the Nostalgia Air folks for the great free service that they provide, but some of those schematics are rather fuzzy.

I have 3 RCA Farm (Pharm?) sets, a 1937 5BT and a 1936 6BT both with 2V tubes and a 1940 14BT2. Interestingly, the 5 BT uses a 19 dual triode output while the 6BT uses 2 49 triodes in Class B Push Pull. These sets can be quite loud at 2watts. The 14BT2 is a 4 tube set with similar 1.4V tubes as your Philco. These sets have much lower power output than those big RCAs with the 2V tubes.

These are not terribly hard to deal with. the filaments will run off a 1.5V alkaline D Cell for a rather reasonable time. You can get the 90V from 10 9V batteries or from either a homebrew, vintage or ARBE III power supply.

To figure out what goes where, look at the power switch and trace the wires, or just ohm... Resistance between ground and one of those red wires should be very low with the tubes in place and infinite with the tubes out. Between chassis ground and that wire would be the 1.5V for the filaments. The other wire going to the switch should be the B+. trace the wiring. The B- does NOT go to the chassis but to an 800 Ohm resistor. One end of the resistor is the B Battery negative connection and resistors to supply grid bias to the output and possibly 1st amp tube. The other end of this resistor goes to chassis ground and is the B-. This can be figured out with the help of the schematic.

Replace the electrolytic cap that goes between B+ and chassis ground. It's a good idea to replace all of the paper caps, but they are less likely to go bad in these sets than the line powered sets that generate much more heat. However, best to replace them.

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis

Best Regards, 

MrFixr55


Messages In This Thread
39-85 code 121 - by tdump - 07-14-2024, 10:21 PM
RE: 39-85 code 121 - by morzh - 07-15-2024, 07:01 AM
RE: 39-85 code 121 - by tdump - 07-15-2024, 08:57 AM
RE: 39-85 code 121 - by MrFixr55 - 07-16-2024, 08:07 PM
RE: 39-85 code 121 - by tdump - 07-16-2024, 08:33 PM
RE: 39-85 code 121 - by morzh - 07-16-2024, 09:00 PM
RE: 39-85 code 121 - by Arran - 07-17-2024, 05:28 PM
RE: 39-85 code 121 - by MrFixr55 - 08-08-2024, 07:55 PM
RE: 39-85 code 121 - by tdump - 08-08-2024, 08:16 PM



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