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Philco 46-480 Electronic Restoration - Printable Version

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Philco 46-480 Electronic Restoration - jrblasde - 12-09-2024

Good evening, folks! It's been a couple of months since I completed the restoration of the cabinet on my 46-480. I've been working intermittently on creating a more readable schematic than the scan available on the Philco Radio Library. Not only are a few of the values too blurry to read, but I've noticed a handful of discrepancies.

1) In Section 3, the overall schematic on page 113 of the document shows resistor R300 to have a resistance of 4700 (in other words, 4.7kΩ), whereas the parts list on page 114 indicates that R300 has a resistivity of 47,000 (in other words, 47 kΩ). Furthermore, the given part number is 66-3473340, which is the part number for a 47 kΩ +/-10%, 1/2 watt carbon resistor.
           

2) In Section 4, the overall schematic on page 113 of the document does not show a grid resistor on pin 8 of the 7F8 tube, whereas the partial schematic on page 109 of the document does.
           

3) In Section 4, the overall schematic on page 113 of the document is missing an instance of the S401A switch, whereas it may be seen on the partial schematic shown on page 109.
           

Anyway, I have combed through all of the available paperwork and here's the resultant schematic (also see attached PDF). I now intend to comb through the chassis in its current state to verify that the schematic matches the as-built condition of the radio. Some of the capacitor values in the IF cans were not readable, so I'd like to confirm those by seeing what is physically installed. I also had to make my best guess on a few of the wires crossing over each other on the schematic--do they intersect or not? And, finally, I'd like to verify the pins on the wafer switch. Many of the pin numbers on the schematic were not readable.
   

I'll note that not everything is laid out exactly as you'll find it on the Philco schematic. I rearranged Section 2, for instance, to flow from left to right. I've also replaced older notations (for example MF and MMF) with modern-day equivalents (µF and pF, respectively). I've also moved the filaments of the tubes to the power supply section of the schematic (many other Philco schematics, for instance the 49-906, do it this way). You will also notice that tubes with multiple diodes and/or triodes within the same envelope (the 6H6GT/G and the 7F8) are shown as split. This is just how I've always drawn them.

I will follow up with a revised schematic after I parse my way through the chassis. I also plan to create a new revision depicting the replacement equipment. I'd like to add a 1A fuse to the power section for instance. I already have this depicted in revision 1 of my file. I also have the safety capacitors for the AC line depicted in revision 1.

RE: Philco 46-480 Electronic Restoration - radiorich - 12-09-2024

Hello Joseph,
Wow that is great news that schematics looks very well done !

Sincerely Richard

RE: Philco 46-480 Electronic Restoration - jrblasde - 12-10-2024

Thank you, Richard! The biggest effort is to create all of the symbols which don’t exist in much of the newer circuit software. It was a labor of love, but I’m happy to share what I find. I plan to get this schematic updated with all of my findings after going through the chassis. I’m always afraid to start disassembly until I am absolutely confident that I have the documentation to put it back together correctly.

RE: Philco 46-480 Electronic Restoration - morzh - 12-10-2024

I work mostly in DxDesigner (recently had to switch to Altium, which I don't like), and in it (as well as in OrCAD, which I have not used for a long while, but know fairly well) a symbol creation is a snap.
I did this about 1-1/2 years ago. In DxDesigner. The tube symbol took....5 minutes?

   

RE: Philco 46-480 Electronic Restoration - jrblasde - 12-10-2024

Thank you for sharing! I’ll have to investigate my options. I’ve long been an avid supporter of the Linux operating system and the free software paradigm supported by the GNU GPL. Consequently, I’ve taken to using KiCAD for schematic and PCB design. The software’s primary focus is on PCB development, and so the schematic is more of a means to an end. I do find that I have to fuss with the software sometimes to get a clean and well-styled schematic.

RE: Philco 46-480 Electronic Restoration - morzh - 12-10-2024

I used KiCad briefly; I never created parts in it; just had to quickly fix a problem in an old board done before me.
I know that PADS Logic, unlike DxDesigner, was a free tool, that CAD software, then Mentor and now Siemens supplied for free.
As I remember (I have not used it for quite a while) symbol creation was not complicated in it either.
Especially, considering that we do not have to create a parameter database that would always accompany a real part used in real schematics: P/N, internal P/N, price, PCB footprint name, manufacturer, etc etc.
Pretty much graphics with pins.