[jrblasde]

Good evening, folks! As my cabinet restoration has been winding down, I've begun to work on the electric restoration. I think this one will be more a story of resurrection than of restoration. Just like every other radio I find out here in Oklahoma or Kansas, I believe this one has been leasing out to mice in the past!  We'll start out by looking at some photos. 

From the front and top, it's not too bad! Dirty, yes, but it'll clean up. It is missing one of the 6V6GT tubes, but that's because I robbed it when my 46-480 needed a new one!  The dial will also need to be restrung.

   

   

Unlike any of the other Philcos I've worked on, this one has a protective plate covering roughly half of the bottom, on the power supply and audio section.

   

I removed this cover, and that's when I first suspected mice. The inside face of that metal cover was coated in that special rust that only mice can produce. I also notice chewed wire insulation and capacitors.

   

   

   

   

Here's an overall picture of the underside of the chassis, with the metal plate removed to expose the entire interior:

   

I can use naval jelly to clean up the rust on that removable panel, but I don't know if I'd be able to use it on the interior of the chassis without needing to remove everything. Does anyone else have experience with that? My fear is the rinsing and neutralizing with baking soda; I don't want to soak good components. You can see rusty areas in a few of the other photos, but this corner has a good amount of it, too.

   

Now I'll move on to talk about recreating the schematic. Y'all probably are used to my process by now, but I always strive to create a fresh, digital copy of the radio's schematic in KiCAD. I always begin by copying from the available Philco schematics, and then I trace through every component and wire in the chassis to make sure there's no errors with the Philco schematic (or any errors I've introduced in copying, both cases happen!). I know some folks here have expressed interest in me producing smaller schematics that are more readable, and I've been thinking about ways to do it. I realized that I can use KiCAD to my advantage, because it allows the draftsman to utilize hierarchical design. That is to say, I can create a "main" drawing composed of blocks representing the various sections of the circuit (power supply, audio output, IF, and RF). This "main" drawing also depicts the buses and signals which interconnect the sections. Then I can create subpages for each of those sections, with flyoffs representing those buses and signals. Each subpage is concise, and contains only the section of the schematic pertaining to that respective portion of the circuit. I've been able to reduce my usual E-size drawing down to five 11" x 17" drawings. Attached is what I have so far, showing the "main" page, the complete power supply page, and part of the audio output page. I'm also attempting to capture all the nominal voltages and test points called out in the original Philco documentation (you can see it in the power supply section, but it's not yet complete in the audio output section.

[klondike98]

That's pretty ugly on the upper side of the chassis! The underside looks like most of the ones I've worked on. Hope it cleans up OK. Recreating the schematic sure help's you get to know the radio.


Sitting back to watch things unfold.

[jrblasde]

Agreed, recreating the schematic gives me the opportunity to flush out any questions (and ambiguities or errors found in the original documentation) before I start working on the radio. I’ve gotten the audio section completely recreated now, and should be done with the IF section tonight. Hopefully by the end of the week I can complete the entire schematic.

[Arran]

Joseph;
I would give that bottom cover a soak in a mix of vinegar and water, that crusty rust will be gone in a few days. One method I figured out was rather then immersing the object in a container full of the vinegar/water mix you can also wet some wads of rag or paper towels and place them on the crust which works well on top of a chassis where you don't want to dismantle everything. Hopefully using the chassis as a washroom was the worst of what they did and that they didn't naw on any coils.
Regards
Arran

[jrblasde]

Thanks for the tip, Arran! I will definitely be using that trick for the rust on the chassis itself.

[jrblasde]

I was able to get the schematic buttoned up according to schedule. It is attached. Now comes the part where I print if out and do a second pass to compare it against the original Philco schematic, to make sure I didn't introduce any errors. Then the third pass, where I compare the listed values against the parts list from the original service manual. I've already found one such discrepancy-- it piqued my interest when I saw that C325 was listed as a 0.008 pF capacitor on the schematic. I figured that can't be, so I checked the parts list to find that it lists a capacitance of 0.008 µF.

   

   

[Joe Rossi]

Joe, A beautiful and easy to interperet schematic. Well done! Joe

[MrFixr55]

Dittos!! Nice Job.  About 40,000 schematics on NA await your talent.  Get movin'!

[jrblasde]

Bwahaha 

Honestly, I feel that I would enjoy being part of a team who digitize these schematics. With each successive radio I restore (and, in turn, each new schematic I create), I really hope to save someone down the road from squinting and trying to interpret some of the old scans. It also gives me the chance to purge out some of the inaccuracies.

[Joe Rossi]

Joseph,  Have you ever noticed that mice seem to find the Philco wax/paper caps especially tasty?  Thanks for the schematics.  They are great!  joe

[jrblasde]

Amen to that! Philco's old paper and wax caps must be the Johnnie Walker blue label of capacitors! 

[Jayce]

Also, have you ever noticed how kids and pets love to rip up Philco grill cloths and speaker cones? Seen several like that in my area. Either kids or dogs.

[jrblasde]

I’ve got a pesky little Dachshund who once hiked up on my 46-480. I looked at him in shock! I told him I’d take that leg right off if he did it again, and I think he understood! He hasn’t repeated the offense!

[Arran]

It might be that they like the taste of the wax coating on many old capacitors, I think it may have been bees wax. As for torn grill cloths, many of the Philco ones tend to have straight patterns woven into them, and between that and the tension of the cloth makes them vulnerable, being 80+ years old and exposed to heat, light, dirt, and moisture likely doesn't help the fibers. I think that many of them were actually made out of rayon, which is produced from cellulose. The chevron cloth really likes to tear, I think more sets have at least one hole in that stuff then ones that don't.
Regards
Arran

[jrblasde]

I’ve been working on treating the rust on this chassis. I took Arran’s advice and used a rag dampened with vinegar, and pressed it onto the rust. I did that for about 24 hours, but re-wet the rag with vinegar about halfway through. It loosened up a bit of the rust, but I’ve got more work to go. This here is the result after using a brush, some grade 0000 steel wool, some 320 grit sand paper, and even a wire wheel on my drill to attack that large rust spot on top of the RF sub chassis. It looks better, but there’s still some rough material that is ever so slowly chipping off. Here’s a before and after. I covered the nearby tube socket with electrical tape to keep it dry, in case you’re wondering what that’s about.

   

   

I may change tactics. I was afraid to jump to naval jelly if I didn’t first plan to empty the chassis, because I thought you had to rinse the naval jelly off with running water and neutralize with baking soda. But I’ve been reading online and it sounds like you can use smaller amounts of it without so much hassle. Apparently I can wipe it up with a wet rag to clean off the leftover naval jelly. Does that sound right?

Edit: I forgot to mention that the hinges for the speaker panel that pulls out for the turntable cleaned up much better. I was able to soak them in vinegar, and it was more successful.