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Philco 48-482 Electronic Restoration - Printable Version

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Philco 48-482 Electronic Restoration - jrblasde - 01-04-2026

It’s been about three months of on-and-off-again work, but at last I have a schematic put together for the 48-482. I have combed through two complete chassis and compared them against the scanned Philco schematic available from the Philco Libraries. There are five sections to the schematic:
  1. Power Supply
  2. Audio Frequency 
  3. FM Demodulation 
  4. Intermediate Frequency 
  5. Radio Frequency 

Per my usual process, I drew the underside of the chassis and showed all terminal blocks, tubes, and other major equipment. I then made five copies and drew out all of the wiring for each of the five sections. I also made a drawing of the switch board for the ten push buttons:


   

Additionally, I checked each resistor and capacitor to verify the values listed in the Philco documentation. Whereas the documentation indicated that capacitors C302, C406, C412, and C418 should be 0.01 uF, I discovered that they were all 0.006 uF in both the chassis I have. The information for C503 was incomplete but I confirmed it to be a 0.01 uF, 600 VDC paper capacitor. Additionally, C511 is a 25 pF Mica capacitor, not 22 pF. So far as resistors are concerned, R406 is listed as being a 3.3 kohm resistor, but I found it to be a 2.2 kohm resistor in both chassis. The listed part number (66-222340) for R505 was one character short. It is a 2.2 kohm resistor as the documentation indicates, but I had to deduce the wattage. The schematic indicates that there are 4.5 V across R505, and thus a 1/2 W resistor will suffice. 

One more note about my schematic. The Philco schematic shows all of the push buttons switches, but it inconsistently shows the push buttons as being selected or not selected throughout the schematic. I decided to depict the throws of each SPDT switch consistently as though the OFF button were depressed. All push buttons are interlocked, meaning that no push-button preset nor the AM, SW, nor FM band push buttons can be depressed if the OFF button is pushed. However, I preserved the style of the Philco schematic by indicating which modes correspond to both throws of each SPDT switch.

I have attached the schematic to this thread. It’s a massive and complex schematic, so it’s on an E-sized sheet. But the readability is much better than the original scanned schematic!

RE: Philco 48-482 Electronic Restoration - jrblasde - 01-25-2026

Here's a good question. I'd like to empty this chassis, clean it with Navy Jelly, and rebuild it. Majority of the components are out of tolerance, so I'm not losing anything by replacing the caps, resistors, etc. However, the tube sockets are in fine condition. As difficult as it is to find replacements (these are all 1-1/8" sockets with 1-5/16" center-to-center mounting; 2 octal sockets and 7 loctal sockets), I am wondering if they may be reused if I desolder the old equipment from them. Does the heat from desoldering damage the sockets? I know they are exposed to heat while soldering components onto them, but I worry that they'll be exposed to much more prolonged heat while desoldering.

If I can reuse them, what do you all think? Can I leave them mounted in the chassis while using the naval jelly, or should I remove them and re-install after cleaning the chassis?

RE: Philco 48-482 Electronic Restoration - morzh - 01-25-2026

We desolder sockets all the time. If you are careful, they will be OK.
Of course, it also depends on their existing condition.

If you decide to rebuild (what? From scratch?) and take out every single part and teh sockets in order to clean the chassis, then upon a socket full separation it will be easy to clean it. I would then recommend cutting parts off vs desoldering, and then cleaning the sockets' pins.

RE: Philco 48-482 Electronic Restoration - jrblasde - 02-11-2026

Work has been busy lately, but I think we're about caught up! Anyway, progress has been intermittent on the electrical restoration lately, but I'm about set up to get it in motion. 

I've been working on a design for a new multisection cap for C102. I had so much fun designing PCB replacements for the top-of-chassis mounted multisection caps for my 46-480 that I figured I would do it again here for the 48-482. There's three multisection caps this time around, but only one is mounted on top of the chassis. It's a twist-lock style, like one of the two I had designed for the 46-480 last year.

   

Essentially, I followed the same process with the lessons learned on those two prior designs. However, this new PCB came with a challenge of it's own--for this new C102 capacitor (Philco part number 30-2570-1), there are three capacitors stuffed inside the can: a 10uF, a 15uF, and a 30uF capacitor. They all share a common negative. I found some high-hour Nichicon electrolytics for my new design (had to substitute a 33uF for the original 30uF), but the 33uF capacitors have a sizeable footprint. In fact, it's a bit bigger than a third of the real estate of the 1.5" diameter disc of a PCB. I couldn't find any way to place all three through-hole mount caps on top of the PCB with through-hole solder lugs on the underside and the same four quick-connect lugs I used previously for the twist-lock tabs. 

I ran through SEVERAL iterations of the design, but here's what I settled on. Fair warning, but it is absolutely over-engineered. I'm okay with that, though. Something is very fun about designing a rugged part to install within the exact slot of the original capacitor.

I decided to design two PCBs, a lower and an upper. Because of the total footprint of the caps, I also needed to change from a circular PCB outline to a square (same tab locations, so it will still click right into the chassis; there are also no interferences on the chassis for fitting a square PCB in this space). The lower board would be used for the solder lugs for each of three capacitors' positive connections and for the four quick connect lugs used for the twist-lock tabs. These four tabs are connected to the common negative of the capacitors. The upper PCB, in turn, will have all three capacitors mounted on its top side. To connect the two layers of PCB, I needed a solution with a minimal footprint. I came up with a 2x2 header and receptacle (photos below; notice that the receptacle photo shows a sample with more connections than the 2x2, but it is merely a representative photo from Mouser).

   

   

This combination of header and receptacle provides secure electrical connection between the two PCBs, but what about secure structural connection? To solve that, I designed through holes for spacers:

   

And here is the resultant product. We'll start with lower and upper schematics (in that order):

   

   

And now the lower and upper PCB outlines (in that order):

   

   

And, now for top and bottom views of the lower PCB:

   

   

And, finally, top and bottom views of the upper PCB:

   

   

I learned a few new tricks that I've implemented on this one. One trick was the conversion of images into silkscreen graphics. You'll notice that the "PHILCO"on the top PCB is stylized per the PHILCO logo. I also added my signature so that someone eighty years from now will know who wasted their time designing this part.  Icon_lol

Now for the important calculations.
    - Trace width: I went with 0.5mm. This is an 80W radio.The caps operate at 250VDC; assuming (conservatively) that all current will pass through any one capacitor, that gives us a current of 0.32A. This equated to a trace width of just shy of 0.2mm. I had the space for it, so I went with 0.5mm. Never hurts to upsize traces on these power supply components. I also added tear drops. 

    - Minimum creepage and clearance: I designed for 450VDC (the original cap is rated for 450VDC). For the rest of the parameters in the calculation tool, I made the same conservative assumptions I detailed in my cap design summary for the 46-480. All traces and components meet these requirements.

   

Here's a mockup of the full assembly:

   

RE: Philco 48-482 Electronic Restoration - morzh - 02-12-2026

The full current does not travel through a cap. Unless charging upon power-on (slow, tube rectifier) the current mostly comes from the rectifier and the cap conducts the ripple component current. Which could be, in it's peak value during charge, higher than the load current, but is pretty short, and the RMS of it is smaller than the load. So it is not 320mA.
This said, it is a good idea to beef up traces.
I would make them even wider, plus I would increase the pads' sizes: the caps a fairly large and larger pads provide more stability for tall parts.

I assume the 2x2 strip header in the middle is 100 mil type?
So your distance will be 100 mil then to the nearest Plus, and the creepage is that minus one pad size (let's say 80 mils made by 40 mil hole and 40 mil ann. ring) so you have just 20 mils left. If your pad is 60 mils, then you have 40 mils left.
The recommended creepage on FR-4 for 250V is 100 mils (2.5mm) for pollution type 2 (normal indoor), and desired for UL standard is 128 mils (3.2 mm).

For 450V it is 5mm. Nowhere close.

of course if my assumption for 100 mils header is correct.

BTW, who makes your PCB? And what did you pay for it?

RE: Philco 48-482 Electronic Restoration - jrblasde - 02-12-2026

I have always used OSH Park for producing my PCBs. They charge something on the order of $2-$3 per square inch, and they give you three copies of the board for that price.

And, yes, 100 mils is the correct spacing. I made sure to pick connector rated in excess of 450 V (in this case, they are rated for 1kV).

RE: Philco 48-482 Electronic Restoration - morzh - 02-12-2026

By the connector, do you mean the strip header?

Some, like this one, will be "rated" for some high voltage.
https://www.mouser.com/datasheet/3/71/1/M22_201.pdf
This says "Voltage proof".
Voltage proof rating is not quite the same as the connector working voltage rating. It is the insulator proof, that is will not experience a breakdown, flashover etc if subjected to oa short surge of high voltage.
But the WV rating of these often is not even given, as these headers (again, I assume we are talking about the same type of part) are never intended to connect high voltage power line.
WV rating is what you need. It is sustained over long time voltage. Not surge.

This said, even if it were rated to this voltage, you have the FR- surface with indoor type usage. This in itself will bring down whatever specs you have on your connector, unless special measures are taken, like cutting slots or potting.

What is the connector you are using and how exactly the rating is formulated? I have seen it like this: (rating quoted by Mouser)
https://www.mouser.com/ProductDetail/Amphenol-FCI/77313-124-04LF?qs=xJiur%252Bgubk0AYTro2P7kXA%3D%3D
and it is not to be found in the datasheet , but, again, is likely to be the dielectric proof, not WV rating.

RE: Philco 48-482 Electronic Restoration - RodB - 02-12-2026

Joseph, are you of German descent? Will it ever get off the ground?

RE: Philco 48-482 Electronic Restoration - jrblasde - 02-12-2026

Mike, you are correct. I dug into the available paperwork and confirmed that the headers have a dielectric withstand voltage of 1.5kV and the header receptacles have a DWV of 1kV. The working voltages are not specified. 

You have raised a great concern! That’s why it is fun to work on these custom designed parts. I only have formal experience in low voltage PCBs, and so these give me some exposure to additional considerations with high voltages. I will reach out to Amphenol to see if they have defined working voltages. If not, I’ll research other headers.

My design currently uses these headers and receptacles:

https://www.mouser.com/ProductDetail/Amphenol-FCI/67996-104HLF?qs=zh4O8xspOuzEuQFUEWDpLQ%3D%3D

https://www.mouser.com/ProductDetail/Amphenol-FCI/76342-302LF?qs=5xI8GKdkXllUp0iR6yBizw%3D%3D

Rod, I’m of English and Irish descent. Several generations have been in the states, though. In fact, the Blasdel family have great documentation on the family tree. Ralph Blaisdell (1593-1649) was the first to immigrate to the states as a wool textile merchant. The name Blasdel comes from St. Blaise, the patron saint of wool combers.  Icon_lol

Anyway, I suppose you’ve lost me on the comment about it getting off the ground.

RE: Philco 48-482 Electronic Restoration - morzh - 02-12-2026

Germans, in fact, have no problems getting things off the ground.
Either V2 or the moon rocket (same guy). Both are highly successful (depending on the point of view).

Anywho.

Joseph,

You do not need to ask about the connector rating: it is pretty much comes down to your FR-4 surface space between the solder pads of where this connector is soldered, which is the weakest point and the voltage rating of your board is no longer dictated by the connector (whatever it is), but by the surface type and its contamination. This is why the creepage for 450VDC is desired to be at least 5mm. Or, if you want 250V, then 2.5mm. Which your pads' size eats into.

That is not to say, it will necessarily experience electrical breakdown. But it is not protected from it.
Now, what you could possibly do is use some potting. Clean it well with IPA, and then apply some corona dope or any suitable electrically used epoxy to both sides. This will increase the effective creepage.
Your pins are still close to each other in the air but not as close anymore, plus the air breakdown is way better than the FR-4 surface.

RE: Philco 48-482 Electronic Restoration - jrblasde - 02-12-2026

Thank you for the additional information! Meanwhile I also had an online discussion with some folks at Amphenol. They confirmed a working voltage of 250V. They did, however, send me some information about another series of equipment rated for 600V working voltage. That’s all the time I had over lunch, but I will look into these options this evening.

RE: Philco 48-482 Electronic Restoration - morzh - 02-12-2026

Yep. You and I pretty much found the same Amphenol series connector with the same ratings.
And the Mouser will list 1.5kV. Whereas the WV is 250V (as you have just found out).

So basically to not to degrade the connector rating by much, use some potting/coating. Corona dope etc. On both sides where the pins go to the boards' pads. Both the socket and the header.

RE: Philco 48-482 Electronic Restoration - jrblasde - 02-13-2026

Good news! While I hit a dead end with the new components Amphenol recommended (not because they weren’t rated sufficiently, but rather because the new lineup of equipment didn’t feature a male/female pair of board-to-board headers and receptacles), I did find a suitable solution from Samtec. They have an IPS1 line of headers and and IPT1 lineup of receptacles. The rated voltages listed in Mouser were not communicated explicitly, so I reached out to Samtec last night. I got connected with their engineers this morning, and they provided some data sheets listing out the working voltages, dielectric withstand voltages, and breakdown voltages. Looks like the components I need are all rated with working voltages in excess of 600V, so I’ve got a viable solution!

RE: Philco 48-482 Electronic Restoration - morzh - 02-13-2026

Good! make sure your board does not de-rate that too much (boards almost always do, but that could be controlled).


What connector is it?

RE: Philco 48-482 Electronic Restoration - jrblasde - 02-13-2026

I’m looking into the Samtec IPS1-102-01-L-D female socket connector and the IPT1-102-01-LD male pin connector. Their engineering team provided me with the attached data sheet when I reached out.

The pin spacing is still 100 mils; considering that the diameter of the through hole solder pads encroaches on the minimum creepage distance, I will still need to include some slots in the PCB between solder pads. But at least these new components have an appropriate working voltage rating. I feel better about using these than I did the original Amphenol components.