[jrc0109]

Hi,
I have a Philco Model 51 Superheterodyne radio. It works with a load hum.  I read that I should not play it, so I haven't for quite some time. I'd like to repair it. Can anyone recommend replacement parts (capacitors  I believe) that I would need and also, where I can get them?
Thank you.
John

[RodB]

You can check here for a schematic:

https://philcoradio.com/library/index.ph...ams-vol-1/

Then, when you read it and the parts list you will see the capacitors listed. Some are stuffed in black bakelite blocks with terminals attached. There can be one or two capacitors or a cap and a resistor inside a block. Most capacitors in blocks are paper and should be replaced. Look elsewhere on the Phorum for methods to remove them from the blocks. My preferred method is to disconnect the capacitors, heat the block with a blower and push the guts out with a small drill bit. There is a service bulletin here that shows bakelite block wiring diagrams:

https://philcoradio.com/library/index.ph...lock-data/

There's also a block, #23, that has 5 capacitors inside and should be tagged so you can reconnect the new ones. Replace all paper and electrolytic capacitors, the mica capacitors (values in mmf) can be left alone. Note that one of the power supply filter capacitors' negative is not grounded. I get my capacitors from Mouser with $6 usps shipping.

Also measure resistors and replace any outside of 20 percent tolerance (I use 10 percent).

[jrc0109]

Thank you very much.
Not sure if I can do all this. Are there people that can do this, maybe in the Orlando, Fl area?

[morzh]

Look for an antique radio society. There is someone here who is in FL, but I do not know if he'd be interested.
Then again, if it plays, it is mostly OK.
If the hum started suddenly, it's one thing, if garduallyt - another.
If you got it off of someone and played it without having full recap, and the hum has been present all that time - it is not a fgood thing to do, but a full recap will likely cure it.

[GarySP]

Closest club I saw taking a quick look was the Jacksonville Antique Radio Society. https://jarsradioclub.weebly.com/
Changing out capacitors and out-of-tolerance resistors is fairly easy, and plenty of help is here to guide you along. The Bakelite blocks are easier than they look, and there are tutorials to help as well.
other sources for parts are JustRadios, https://www.justradios.com/
and Tony's Capacitor Corner, https://62bf1c-2.myshopify.com/collections/all
Take care and BE HEALTHY! Gary

[morzh]

Also, gutting and restuffing, while looks good and such, is not necessary: one could simply cut the backelites and electrolytic caps, use some backelite blocks' pins as solder posts, and replace all with tubular film/axial electrolytic caps. Functionally this is just the same.

[jrc0109]

Thanks again. I'll look at the sites suggested. Much appreciated

[Chas]

One can choose what ever method to work with the Bakelite block capacitors.  My opinion is to punch them out and place new inside. That keeps the chassis relatively neat.

I also suggest: Begin with the high voltage filtering electrolytic capacitors first. Again stuffing is tedious and may not "look" well when complete. Leaving the originals in place, disconnect them, install a terminal strip and connect the modern capacitors to that terminal strip...

Then attempt to operate the radio. It may still hum but should still work as it did. The hum can be improper installation of those filter capacitors, check carefully. Then proceed to change out all selected components, two at a time. Then, power test. If the radio fails, then there are just two last component installations that have not been done correctly.

The worst that can happen is to change out everything, then the radio fails. Then, stage by stage testing has to be done, very difficult for a "new" technician...

Caveats, do not alter the positioning of any of the wiring, if a wire is crumbling get replacement wire same size and length, follow same routing. Do not turn, rotate or other disturb mica capacitors, they seldom fail.

There are AC line bypass capacitors likely in a Bakelite block. These should be of the "safety" type, meaning if they fail they will go open and not short circuit.

GL

Chas

[RodB]

John, unless someone has added them in, you won't find AC line caps in your Philco 50. It's a good idea though to connect Y safety capacitors to each leg to ground of the primary of the power transformer. It reduces line interference which there seems to be a lot of nowadays. Add the switch side after the switch so they are not in the circuit until the switch is turned on.