The PHILCO Phorum
39-85 code 121 - Printable Version

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39-85 code 121 - tdump - 07-14-2024

My first post and of course i have questions. I have reworked a few radios over the years, used to love it, got to working everyday and such, lost track, but now i have time, and I have my 12x24 shop cleaned up and my stuff setup so I can work on radio's again. And schematics seem to be a problem, well i bought a flash drive on ebay, a couple cd's on ebay, and still can't find a schematic in all that for this particular Philco I felt sorry for at a local hamfest yesterday for 15 bucks.He was asking 25 . it is a 39-85 code 121, No B after the 85,  I didn't need it, i have a boo coo of radios but since it is battery,that is what i prefer, i am ,please forgive me, a bigger fan of RCA farm radios but have numerous Philcos and enjoy them to. This 1 drew my attention because of the low price. BUT I didn't realize the push button tuning was unhooked, no "obvious" battery connections, speaker unhooked, in other words, A mess.
So if you could find it in your hearts to help me figure this 1 out I would appreciate it.
Part of why I was retired years ago is because of a brain injury so if you can, bear with my grammar and seemingly simple questions.

RE: 39-85 code 121 - morzh - 07-15-2024

http://www.nostalgiaair.org/Resources/312/M0013312.htm

RE: 39-85 code 121 - tdump - 07-15-2024

Thank you for the help. i can't figure out why that is not in any of my groupings of diagrams. But I have it now.
thanks.

RE: 39-85 code 121 - MrFixr55 - 07-16-2024

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/service%20info/yearbooks/1939/split/Part31-Philco%201939%20RMS%20Year%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.

RE: 39-85 code 121 - tdump - 07-16-2024

thank you for the help and welcome.
RCA 14BT2! YES< that was the first radio I ever restored back in high school,Actually got my picture took and a half page about me and that radio in the high school annual! Sits in the living room now. I was told by the old man i bought it from it was 1936, but as life and time have passed i do believe it is a year or 2 newer.I was about 15-6 when I bought it for 30 dollars.
sorry to get off brand with my post but wow, another 14BT2 ,couldn't help it

RE: 39-85 code 121 - morzh - 07-16-2024

I am yet to see a problem with your grammar or simple sentences.
To me you are (at list linguistically) doing just fine.

RE: 39-85 code 121 - Arran - 07-17-2024

Nothing wrong with RCA sets, or G.E ones for that matter, in Canada they are pretty much the same thing in different cabinets. I have a soft spot for old tube battery sets, and portables, unless they have been stored improperly, or abused, they are usually in better condition then their AC counterparts electrically, low hours, lower voltages, and low heat tend to help. It looks like someone cremated a resistor, I'm guessing that was in the B- circuit.
Regards
Arran

RE: 39-85 code 121 - MrFixr55 - 08-08-2024

Sorry I haven't been responding but my neighbor that I was caring for ended up in the hospital with complications from COVID and metastatic cancer that rapidly spread to her liver. She passed last week at home under hospice care very peacefully with friends, including me, at her side, 2 hours after the priest gave her last rights. God's work must truly be our own.

The 14BT2 couldn't be from 1936, as the tubes for the set were not released until 1938. These tubes were developed by Sylvania and these should be the longer skinnier version. BTW, looks like an adaptor in the 1A7 socket, I guess for a 1R5. Does the grid cap go to the side of the adaptor? 1A7s should be found easily on ePay. I believe that the 14BT2 was vintage 1940. Had an "RCA" Jack for a phono input. Bottom Line is if you fixed a 14BT2, you can fix the Philco, because other than the pushbuttons and the weaker 1A5 as opposed to the stronger 1Q5 output tube used by the RCA, the circuits are rather similar. If you paid $30 for yours way back when, they haven't increased in value. I bought mine for $35 on ePay back in 2013.

Re the Philco, it is rare to see resistors burned unless something shorts. In this case, looking at the pic, one end goes to chassis. If the other end goes to a junction with the grid resistor for the output and a wire that should be B-, then this is definitely the "bias" resistor and all B Current goes through it. If the wire is not at that junction, just add it. that is 1 less wire that you need to figure out. A- is chassis ground. Those 2 red wires going to the switch are A+ and B+. Your mission, figure out which is which. Trace the wires to the switch and see where the wire "on the other side" of the DPST switch goes. B+ goes to a junction between the output transformer B+ Lead, Pin 4 of the 1A5 and one of the leads of C16. A+ goes to Pin 2 of all the tubes. I may be repeating from my previous post, sorry. (Look up in redundant in the dictionary, it says see "redundant")

Don't worry that the wires to the push buttons are cut, the rotary switch selects manual tuning broadcast, pushbutton broadcast or police / shortwave.

Pull the tubes and ohm each between Pins 2 and 7. these are the filament pins and there should be a rather low resistance.
Check part # 16, a 2 section electrolytic. better yet, just cut it out and replace it. It is likely shorted. This can be common for 'lytics. While rare for paper tubular condensers to short in battery sets as opposed to the House current sets where these get hot, it is not impossible. The culprit here would be C32, a 0.0005 uF Cap. However, this is from the 1A5 Output tube plate to ground, and the transformer primary impedance is 25K Ohm for that tube (I believe). DC resistance could be lower. Best to just clip out and replace the caps. Ohm the Output xformer to make sure it is not toast.

RE: 39-85 code 121 - tdump - 08-08-2024

Thanks for the help, I bought my 14BT2 from it's original owner and he was about 80 or so at the time, so he may have had his years mixed up.1940,that's fine by me!
I spent many a night alone listening to it as a young fellow in high school and college.

As for the philco, I set it aside for the moment, having issues with some non topic projects and plus I am really noticing issues with my eyes when i try to read schematics. get headaches even though I am using 2 different reading glasses 1 for the computer screen and 1 for the circuit .annoying to say the least.
I will mostly be doing radio work during the winter months as it is a good thing to do when you can't garden and such. thanks for your time folks.