I am restoring a philco 46-1201 code 128. I acquired it from eBay on the cheap and when I got it I realized that the previous owner had placed the tubes in the wrong sockets. Needless to say, it looked like someone put a campfire on the 50A5 socket. I have replaced all out of tolerance (and fried) resistors and every cap. Checked, re-checked and checked again, all the wiring (replacing the ones that got cooked). I then replaced the tubes with known good ones.
I am now getting sound out of it but at a very low volume.
Can anyone offer me a clue as to where this problem might be?
I'm starting to think the problem lies in the IF transformers.
Just say the word and I can give more info...
When you say, "it looked like someone put a campfire on the 50A5 socket," do you mean that the socket has some signs of scorching? That can cause problems right there because the burnt areas can act as resistances and screw up the circuit. Best to replace and cooked sockets. If you are receiving stations the IF transformers may be OK. Have you done an alignment on the set yet? Re-tuned the IF transformers so they are peaked? Done the rest of the alignment? When you replace condensers and resistors in a set it can change things and require a full alignment. If, after these thing are taken care of the performance is still unacceptable, then you may have deeper problems, but I would start with those.
Mikethedruid I will definitely start an alignment on my next day off. Yes the socket was scorched and I did indeed replace it. The alignment thing may be the answer. I've had some that were so far out I almost gave up not realizing it.
I'll post my results in a couple of days.
It is suggested that wherever possible, you should wire the new socket to use a 50C5 in place of the 50B5. This is because this arc-over is a well known issue with 50B5 because of the plate and AC heater pins being adjacent to one another making it easy for the B+ to arc over even with just a bit of dirt and or/moisture/humidity.
I did hear something about that but this model actually has a 50A5. Does this tube have the same issue?
I'm not sure what caused the issue other than the fact that the previous owner had the tubes in the wrong sockets.
Bings are not entirely clear when it comes to the chassis code so I can see where a mixup is possible (there is even a note about a mod to prevent damage in this event).
At any rate; I need to take a couple of days break from it. I'll get back to it this coming weekend (if not sooner).
50A5 is a lockal tube that is electrically the same as the 50L6 which has an octal base. The 50B5 and 50C5 are the same also but use a 7 pin miniature base.
If you want to make a change I'd go with the 50L6. The socket is easier to find.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
I thought it was strange as well Arran that they would choose the 50A5 but sure enough, there is mention of it being in the code128.
As far as replacing the socket Radioroslyn; would you say that it’s the best way to go? I just don’t want to waste much more time or resources of the change doesn’t solve the problem. Kwim?
(This post was last modified: 07-26-2021, 11:12 AM by robroot61.)
Hey folks; does anyone know how the volume portion of the 46-1201 on/off switch is designed? What I mean is this: Is the potentiometer that makes the volume increase/decrease a split design (1 for phono, 1 for radio) or is it 1 pot that is able to switch it's function one way or the other?
It may be a long shot but I'm beginning to think that the radio volume side of the switch is bad.
Just a thought.
It doesn't switch per say the center of the pot is connected to b-. But the wiper travels the length from phono to radio. The center point of the two resistances are connected to a separate terminal (1). Wiper is connected to terminal 2. This set uses an odd control.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 07-26-2021, 07:50 PM by Radioroslyn.)
Got it; thanks. At any rate, I tested the switch and all is well.
The only thing I haven’t changed out is the if transformers. I’m going to test them tomorrow.
OK folks the Bing is alive and kicking. Found a 2.2m ohm resistor inside the output if that was scorched. I replaced the entire part rather than trying to repair it and it not work. Now I have plenty of volume and reception is amazing!
I was waiting to restore the cabinet pending the outcome of the radio so now I can get things done.
Thanks for all the input from everyone!
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
