The PHILCO Phorum

I've been enjoying the holiday weekend by devoting some time to my Model 15X (June 1932).



I haven't run into anything too surprising but I thought I'd post some pics and notes from what I found since they might also be useful to anyone working on one in the future.

As usual before starting I tried to read over as many prior Model 15 restoration threads as possible - and had an especially good read of bandersen's 15DX thread - a great starting point to compare against.

I've seen that some 15X radios have a black fiber board back of later Philco. My 15X still has the wood / woven back that I've seen previously on the Model 112X (Jan 1932) that I worked on previously so I assume some time in 1932 was the changeover.


My 15X is one of the early production models with a hard-wired speaker harness. Awkward!
I ended up removing the speaker board and desoldered the harness initially. That was fine until the first power-up when I just ended up resoldering after protecting the speaker board with cardboard and balancing them on top of the chassis. I can see why Philco added a plug in later runs!


It seems like every K-12 speaker I've seen has rust on it. This one actually isn't too bad. I wonder if it has something to do with the cloth glued to it attracting moisture? The H-7 speaker below it is practically rust-free.

Here's the chassis as pulled. Dusty and some moderate amount of rust:





The bottom of the chassis looks quite a bit cleaner:

the chassis looks similar to the 112X that I just picked up (see Nov. finds).  Is it basically the same radio?

Oh, I see it has a shadow meter.  the 112X doesn't.

It feels very similar in many ways. The tube lineup is different. Right - it has a shadow meter. Also dual speakers. And a lighted speaker grille.

The recap went fine. I restuffed the electolytics - I happened to have another nickel over copper can like the remaining Philco cap.

Restuffing the blocks was made much easier thanks to Steve Davis' Philco Service Tools. Awesome!

The contents came out of the metal cans easily - including the filter block.





After replacing the filter caps and restuffing half of the blocks I decided to bring it up on the variac.
It had good volume but only received noise / static. That is until I moved my hand near the grid cap of the 1st detector when it suddenly started receiving clearly. Uh oh....

That made me pretty suspicious that a coil was bad. I went through them and found that sure enough part 15 (Part No. 3884-V) ('Detector Transformer') had an open primary. A common problem on this era of set.

Fortunately the Philco Repair Bench has info on exactly this issue:
http://www.philcorepairbench.com/rewindi...-rf-coils/

I pulled the coil and you can see from all of the green spots that it's exactly the problem described:

I carefully counted the number of turns in the primary. First I used a magnifying glass - too easy to lose track. Using the trick of running a pin over the surface was easier to keep track but in the end I found that blowing up a clear picture of the coil on the computer made it even easier.  



Anyway - I finally settled on a count of 60 turns of ~32ga wire. Looking at the bottom of the coil form and counting pins clockwise the primary starts on pin 3, is applied clockwise on the coil form and connects to pin 4.

I removed the remnants of the original primary and cleaned it up as described in the PhilcoRepairBench.com article.

I next cut out a plastic form the same size as the original celluloid form. 4"L x 1 3/16"H with notches in the same places. I used some tape to hold the form on the coil (just a temporary measure while rewinding it).





I then soldered #32 magnet wire to pin 3 and started winding clockwise. It wasn't too bad to wind thanks to the #32 magnet wire being quite strong and easy to work with and hold some tension.



After resoldering it in place the set came to life!



The new primary isn't physically spaced as much apart as the original cotton covered wire but it doesn't seem negatively affect performance.

Keep it up kid, you will have a fine radio, good luck. 

Paul

Thanks for the encouragement guys!

A few more updates:

Shadow Meter



Interesting that it's branded Westinghouse - perhaps it has been replaced? Or did Philco not manufacture the early shadow meters themselves?
Either way it still works.  

Tone Control

Rebuilt - soldered on a 2-pos terminal strip to anchor the caps and used heatshrink on the wires.





Chassis Derust

Cleaned up with naval jelly (it's a bit too cold in the garage now for Evaporust gel).

I also replaced the rubber tuner support with http://www.renovatedradios.com/product.php?product=321





Speaker Derust

Naval jelly applied with a small paintbrush.





Not sure if I'll put back the cloth since it's rusty and seems to be a moisture magnet.