[Ron Ramirez]

+1 what Mike the Druid said. I've used clear plastic from "bubble pack" products for years with no problems.

[462ron]

To replace mica insulators, I’ve also used those mica insulators that are used to mount transistors like TO-3 or TO-220 to heat sinks!

Ron

[morzh]

Even though it will probably work in the majority of cases, I would prefer to replace like with like.

The capacitance of a flat cap (which is what it is in this case - a flat cap) is

C = (Permittivity * Area)/ Distance

The permittivity is the characteristics of dielectric materials and for Mica it is 3 - 6 while for Plexiglas (clear plastic) is 3.4.
http://hyperphysics.phy-astr.gsu.edu/hba.../diel.html


So your cap using mica could potentially have twice the capacitance of the same geometry cap using plastic.
This might still work as the cap is adjustable.
Mica will also not warp due to heat which may or may not be of significance depending on what the radio is like.


Of course plastic is easier to work with; drilling hole in mica, one has to be careful not to ruin the sheet.

[Ron Ramirez]

I've used plastic in several Philco 70 and 90 trimmers and never had a problem with a single one.

You don't have to agree with me. You have every right to be wrong if you want to be.
- Rev. Lowell Mason

[mikethedruid]

"The permittivity is the characteristics of dielectric materials and for Mica it is 3 - 6 while for Plexiglas (clear plastic) is 3.4." Notice that for mica the figure is indefinite, "3 - 6", so it could be less than plastic, or more, and, depending on humidity which can affect mica by getting between the layers, it can even vary on an individual sheet from day to day, whereas plastic is fixed and predictable. Except in applications where heat that would affect the plastic are involved, I see plastic as not only an acceptable replacement for mica, but actually a superior replacement. Of course, in 50 years or so, one is likely to have to replace the plastic pieces since they will age and degrade, where the mica would not, I will grant that, but I won't be around to worry about it, and it will be an east fix for some technician of a new generation.

[unclevinny86]

Thanks all for the feedback and info go far!  All good stuff!  I did get a sheet of mica fairly cheap on EBay, so going to see if I can make two new wafers from that. If not will go the plastic route if needed. I put original wafers back in for now and will cross that bridge when I get to the alignment which is still a ways out. Still waiting on my cap and wire order to arrive.

Enough with my questions, time for a progress report. I’ve checked most all resistors so far as well as coil continuity. Coils are all good so far and just a few resistors to replace. I’ve also tested all tubes and all are weak except for one which is a 7B6 which someone used at some point in place of the 7C6. Next steps are cleaning up some rust, clean the tube pins and replacing the electrolytics, wax caps, rubber wires and bad resistors. Not in any big hurry...just taking my time and enjoying the ride!

Another positive note, managed to get the super aerial loop apart without destroying the cardboard cylinder. Pretty neat little apparatus if you’ve never seen the inside of a nice one. Pictures attached for your enjoyment!

Cheers!

Vinny

[unclevinny86]

I spoke too soon. Tested field coil and output transformer tonight and appear to have an open output transformer. No reading between the plate pins of the 41 tubes, 76K ohms between center tap and black, no reading between center tap and white. Based on info found in other posts, ordered a Hammond P-T125C from AES tonight and will replace as I do the rewire and recap.

Vinny

[unclevinny86]

Hey All,

Removed the IF cans from the chassis last night and taped over tube sockets in preparation for some spot rust removal and cleaning. How have you all handled the tiny wires from the first IF can (see attached). Wire appears smaller than 22 ga, looks more like wire you’d wind a coil with but silver in color and covered in rubber insulation. I’m leaning toward just removing old insulation just to below the base of the coil and covering these with heat shrink. I’ll be replacing the red and black rubber wires with 20 ga stranded core.

Also for you seasoned restorers, what have you found to be the best method for desoldering without getting the tube pins too hot?  Add solder and use a solder wick and flux?  Use a solder sucker?  How hot do you typically keep your iron, and what is your preferred tip...pointed or small chisel?  Going to snip leads and join with new leads where I can for the new caps and resistors, but have a few places where I’m definitely going to have to work on the tube pins to replace wires.  Thanks in advance!

[morzh]

I mark the wires.
In this case clipping and adding new wiring, plus heatshinkables would do it.
Or just use heatshinkables over the old wire.

[unclevinny86]

Anyone ever seen this toggle switch/phono plug combo on a 40-180 chassis before? Not on the schematic, but if it was added later, whoever added it did a pretty fine job making it look like it came from factory this way. I saw something similar on another thread which makes me question if this was an option.  If so I would have thought the schematic would have noted such.

[Radioroslyn]

Nah Philco was busy selling the RP series of wireless phonos. You won't find any prewar sets with a factory phono input. https://www.google.com/search?q=Philco+r...6y1sIIGkkM

[unclevinny86]

Terry,

Thanks for the note!  I assumed this was an “after market” add.  As I do the rewire, I plan to remove this and  take it back to how it would have been originally.  With that being said, do you happen to know where the volume control connects to chassis ground?  Currently, the shield of the wire from the toggle switch is being used to connect the control to ground (see attached pictures); however, when I remove this wire, will need to connect to ground somewhere.  I assume there would have been a jumper wire from the volume control pin to one of the chassis ground terminals, just not sure which route this originally followed.  Not a big deal if no one knows, I’ll find a connection point that’s close...just was going to go back to original connection point if I can.  Thanks in advance...you all are great!

[Radioroslyn]

It may have a ground lug attached to the front to the pot where it bolts in. If it doesn't and you need one just clean off a spot on the metal cover of the pot and solder to it.

[unclevinny86]

Ok folks, making good progress on the recap and rewire but ran into a snag tonight. One of the pins for the 6J8G tube socket is broken. Is there a particular style of octal replacement socket you’ve found works best?  I know I need one for a 1 1/4 inch hole with 1 1/2 inch mounting centers, bottom mount but just looking for a little guidance on what has worked best for you all. Also when it comes to mounting, what’s your approach?  Use rivets or screws/nuts?  The bad part is I’ll have to drill a hole for the grid cap wire or route it through the eyelet of the 1232 tube socket either way. Minor setback, but shall persevere!

Thanks in advance all!

[Arran]

I would see if you can find a molded Bakelite socket, but ceramic would work too. I never liked the wafer sockets, if they are in good order I leave them alone, but if they break I usually go with molded ones. There are several vendors on fleabay in Ukraine, and Bulgaria that sell reasonably priced replacements, and I suspect the quality is better then the China made ones. North American made ones are usually overpriced, unless they are used. Maybe someone can supply you with a used one, ones made by Cinch are the correct size I think.
Regards
Arran