Philco 40-95 Farm Set - Printable Version
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Philco 40-95 Farm Set - 7chip7 - 01-05-2024
I am starting the restore project on a 40-95 battery set. While getting the schematics and docs ready and researching the history of this radio, noticed that the power tube in my radio is a 1Q5 instead of a 1A5 . The schematic calles for a 1A5 and I can't find a document anywhere that shows a 1Q5 being used in this set. I know the the 2 tubes are basically the same but I am just wondering if any of you folks have run across the same.
Regards
Chip
RE: Philco 40-95 Farm Set - Radioroslyn - 01-05-2024
Stick with the 1Q5 the 1A5's plate load abt 3x as high. There is also a 3Q5 which has a tap in the filament for 1.5v operation. May have to move a wire to make it work but they are a common tube. More than likely the opt when out and the shop couldn't find one that had a 25K pri. So change the tube to an 8K tube and opt problem solved.
RE: Philco 40-95 Farm Set - klondike98 - 01-05-2024
A 1Q5 and 1C5 are listed as possible substitute tubes for the 1A5 (its listed as a 1A5GT) on the NJ7P tube database
https://nj7p.org/Tubes/SQL/Tube_query.php?Type=1A5GT
RE: Philco 40-95 Farm Set - 7chip7 - 01-05-2024
Thanks, I will go with the 1Q5
Chip
RE: Philco 40-95 Farm Set Case - 7chip7 - 01-05-2024
I got the 40-95 as a gift from my stepdaughter a few years back. The case is in such good condition I decided I would do a rebuild. The radio was tossed out to a recycle place where my stepdaughter worked in South Carolina, so she grabbed it and sent it to me. The only bad thing about the Case, is someone put a large plate on top, and it is really on tight, but I got to get it off. See attached photos. The radio chassis was in very bad shape, someone tried to put a radio shack speaker with a big magnet on the chassis, the primary on the audio transformer is toast.
Chip
RE: Philco 40-95 Farm Set - 7chip7 - 01-06-2024
Started work on the chassis, II striped the parts off the chassis and the gave the chassis a bath using dish soap in soak for 24 hrs, I replaced 3 sockets and cleaned one, 1st photo is before cleaning. see attached photos.
Chip
RE: Philco 40-95 Farm Set - Arran - 01-07-2024
As far as I can remember the main differences between these power output tubes is that some are beam power and some are power pentodes, but 1T5, 1C5, 1A5, and 1Q5 will all work in place of one another, and on an AC powered battery eliminator it does not matter. As for the output transformer I would pull one from a junker battery set using similar tubes, it doesn't have to be a Philco.
Regards
Arran
RE: Philco 40-95 Farm Set - David - 01-07-2024
Nice clean up! David
RE: Philco 40-95 Farm Set - MrFixr55 - 01-07-2024
Very nice job on that chassis, Chip!
What output tube to use depends on what output transformer that you can get your hands on. The following chart may be useful (Data from RCA Receiving Tube Manual Version RC24):
Tube Base Diag Grid Bias Output Impedance Type
1A5 6X -4.5V 25,000 Ohm Power Pentode
1C5 6X -7.5V 8,000 Ohm Power Pentode
1G5 6X -6.0V 8,500 Ohm Power Pentode
1Q5 6AF -6.6V 8,000 Ohm Beam Power Pentode
3Q5 7AP -6.6V 8,000 Ohm Beam Power Pentode
Of all the tubes listed, the 3Q5 is likely the most common, as it was used in battery / line power portables. 1Q5 and 3Q5 are the best choice if an output transformer with 8K Ohm primary is available to you. The tubes and output transformers are quite common and deliver the most power output of all of the choices. However, the bias resistor may have to be adjusted based on the tube current and required grid bias. Try a 390 Ohm resistor if using an AC power supply to obtain the 90VDC B power. Most RCA sets using the 1Q5 or 3Q5 use this resistor. A higher value will reduce current, acting as a "battery saver" but will lower output and may increase distortion.
The 1A5 is a good choice if it is available and a good output transformer with 25KOhm impedance is available. No modification is required, but the power output is much less than the 1Q5 or 3Q5 (100mW vs 400mW). Sets that use the 1LA4 output will have a 25KOhm transformer and would be a good donor set, as the 1LA4 and 1A5 have similar specs but different pinouts.
Pin connections for the 6X Pentode and 6AF Beam Power socket diagrams are essentially the same. Pin 7 is chassis ground and A battery Negative (A-). Pin 2 is A+ To convert to the 7AP diagram used by the 3Q5, pins 2 and 7 are connected to each other and A+ and Pin 8 is connected to A- and chassis ground.
Pin Diagrams below:
1A5, 1C5, 1G5:
1Q5 (Note similarity to 1A5 pinouts):
3Q5:
This set, like almost all 1.5V / 90V farm or battery only portabes use a "PM" (permanent magnet) speaker. AlNiCo (Aluminun / Nickel / Cobalt alloyed to Iron) Magnets were just becoming available in 1940. Earlier PM speakers had an extremely large magnet structure.
Comment added 01/08/24- The 1Q5 and 3Q5 are Beam-Power tubes. However, this cannot be told by the base diagrams. I don't know why RCA drew the diagrams this way. It is possible that the base diagrams are drawn by the company that invented these tubes. They were invented in 1938 by Sylvania. I believe that most Philco, Silvertone and Zenith tubes in the mid 30s were made by sylvania, based on the number stamping and location being the round Sylvania style vs the octagonal RCA style. The taller skinnier "G" version of this tube without the wafer and metal type base are definitely Sylvania design. The shorter "GT" version with the metal / wafer base are more of an RCA design. The difference may be important for the 1H5 Detector / 1st Audio and 1N5 IF tubes as these may be shielded. My BF Goodrich Mantola 419 battery portable requires the "G" style, as the GT would not fit through the shield base.
Hope all of this helps
RE: Philco 40-95 Farm Set - 7chip7 - 01-08-2024
Thank you for the tube and transformer info, I made a note of it. I am now in the process of getting some info on the coils in the front end (ANT and OSC) as well as the two if cans.
Antenna part #32-3183
Osc # 32-3184
1st If #32-3198
2nd IF #32-3296.
I need to replace the corroded wires, I am having a bit of a time finding info on these (connection points and color code etc.). Any help with this will be greatly appreciated.
Regards
Chip
RE: Philco 40-95 Farm Set - morzh - 01-08-2024
Chip
Just the soap soak got it to this shape?
Wow, great.
So, other than that rust spot at the top left, it was just grime?
RE: Philco 40-95 Farm Set - 7chip7 - 01-08-2024
I soaked it in a pan of hot water and liquid dish soap for 24 hrs, and then used a small dollar store brass wire brush and went over it while in the water, rinsed it of with fresh water. I put a small wire wheel in a dremel and removed small rust spots, letit dry in the sun and that was it.
Chip
RE: Philco 40-95 Farm Set - MrFixr55 - 01-08-2024
The RCA receiving Tube Manual (RC14) would be your best source for pin diagrams. These diagrams are usually "worm's eye" view (underside of chassis) as opposed to "bird's eye view" from above chassis. The base diagrams for the 1A7 Convertor, 1N5 IF and 1H5 Detector / 1st AF are reproduced below. The diagrams for the various output tubes are in my previous post. Try to score a 1Q5 instead of the 3Q5, as the base diagram for the 1Q5 is the same as all of the other output tubes available except the 3Q5.
The following are helpful tips.
- Print a copy (or several copies) of the schematic diagram from either the Philco Library on this site or the Nostalgia Air site. Write the pin numbers from the attached tube base diagrams onto the schematic. This should be fairly easy for all tubes except the convertor.
- 22 gauge wire would be sufficient for all connections, although 20 gauge would be better for the filaments and battery connections.
- Pin 7 of each tube is the filament (cathode) connection to the chassis (A- and B-) Pin 2 is the A+ connection to the filament. Pin 3 is usually the plate (or main plate in multi-function tubes like diode / triode). Pin 4 is usually the screen grid. For the Output tube, Pin 5 is the control (or signal input) grid. For the other tubes, the grid cap is for the control (or convertor signal input) grid. For the 1N5 IF and 1A5, etc. Output tubes, the suppressor grid (or beam plates) are tied to the filament at pin 7.
- I am not sure what colors were used by Philco in this time frame, but most post war radios used red or orange for B+, blue for the plate connection to a transformer, green or yellow for a grid, black for wires going to the chassis, white for AVC and for negative bias. This may not be true for pre-war Philcos. Maybe any expert who has a pre-war Philco using these tubes can take pictures. The colors are not important unless you are building a museum quality restoration (and based on the condition of the case, you may choose to do so.
- The IF transformers should be around 15-20 Ohm for primary and secondary. On my RCA 14BT2, same vintage as the Philco that you are working on, Plate for these transformers is blue, B+ is red, Grid or detector diode plate is green and AVC or audio out is black.
- Build backwards! Build and test the Audio Output and the Detector / 1st Audio. Then build the IF. Finally, build the convertor stage. If you have a signal generator, you can test the stages as they are built.
- This set will require an antenna and ground wire. Alternately, you can replace the antenna coil with a loopstick, but you will have to peak the trimmer on the RF section of the tuning condenser.
- Good luck!
Diagrams below:
1A7 Convertor:
1N5 IF Amp
1H5 Det / 1St AF Amp
1A5, 1C5, etc Output (1Q5 same)
RE: Philco 40-95 Farm Set - 7chip7 - 01-08-2024
Thank you again so much for your help, its been awhile since I played around with RF coils, at age 74 the light gets a little dimmer. I just got back from the radio hobby after a 12 year absence. I spent many years enjoying the hobby, getting the old ham receivers from the 30s-50s was a favorite of mine, as well as home brewing the regenerative receivers. I got back to it about a year and a half ago after going to a ham fest, I ended up coming home with four old ham boat anchor receivers in not bad shape and got them all working, so here I am at it again and I love it.
I am going to go with the 1Q5 amp tube, and I do have to replace the audio transformer as the primary is toast.
Thanks again
Chip
RE: Philco 40-95 Farm Set - MrFixr55 - 01-08-2024
Found an On Line copy of the RCA Receiving tube Manual, Version RC-14 (ca 1940). Note that the base diagram is the same as the one I previously posted but the tube is drawn as a Beam Power tube. The specs are a little different from those in the RC-24 version. Like the disclaimer states, "Specifications subject to change without notice".