The PHILCO Phorum
Philco 90 restoration - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Philco 90 restoration (/showthread.php?tid=22832)

Pages: 1 2 3 4 5 6 7 8

RE: Philco 90 restoration - morzh - 11-26-2021

There's nothing as satisfactory as a good whacking that yields some results. Doesn't even matter what or whom you are whacking. As long as it works.

RE: Philco 90 restoration - Arran - 11-28-2021

If the hammer had not worked I was going to suggest using a hydraulic jack under something solid to press it out, such as the main beam of the house, or a truck frame. The prior option would have involved using a wooden post on top, with a jack under it, a socket or stub of pipe under the jack, the speaker rear bracket, and a pair of blocks at the bottom, or one block with a hole drilled in the center.
Regards
Arran

RE: Philco 90 restoration - Bob Andersen - 11-28-2021

Thank you for all the creative solutions. A press seems like a handy thing to have and I'll keep my eye out for one.

I've been unwinding the field coil and found a couple breaks so far including this one in the center of the photo. It looks a little bit melted which makes me think it was overloaded or arced.

Still no continuity...
[Image: https://live.staticflickr.com/65535/51710325972_96f1ee2c31_c.jpg]

RE: Philco 90 restoration - Bob Andersen - 11-29-2021

I found the break with about 2.7K resistance left. I think that's about 80% or so. I plan to splice and wind some wire back on rather than take it all off and rewind from scratch.

Heck, I could probably leave it at is and add a resistor to make up the difference.

As for the chassis, I replaced some crumbling wiring, installed a new line cord and added a fuse hidden inside some red heat shrink tubing.
I just installed the two small filter caps under the chassis rather than restuff. I'll put the old caps back in but leave them disconnected.
[Image: https://live.staticflickr.com/65535/51712632698_2485d50f6b_c.jpg]

I told myself I wasn't going to detail the chassis, but I just couldn't help myself. Here's one corner after some rust remover and Boeshield T-9 rust inhibitor.

If I had to do it over again, I would have broken down the chassis, cleaned up all the parts and reassembled.
[Image: https://live.staticflickr.com/65535/51712632783_452634eed9_c.jpg]

RE: Philco 90 restoration - cknob - 11-29-2021

Beautiful! So you put in new mica caps for 14 and 19?

RE: Philco 90 restoration - radiorich - 11-29-2021

Hello Bob,
I can see you have been really busy
the radio looks great so far !!

Sincerely Richard
P.S. my next Philco is my 38-10t
or I may fix my little Philco tiny oscilloscope.

RE: Philco 90 restoration - cknob - 11-29-2021

Mica cap #14 is listed in the parts list as "110 mmf". What does that mean? #19 is listed as a more reasonable 0.00025 mfd.

RE: Philco 90 restoration - RodB - 11-29-2021

Hi Chris - Here's the scoop on capacitor values; mmf is the "old" designation of micro-micro farads. We used to call them micky-mikes. Today they are pico farads. So your mica cap is 110 pico farads (pf). Also known as .000110 mfd. BTW I've seen pf used in mid 50s German schematics, so pico is fairly old too.

RE: Philco 90 restoration - mikethedruid - 11-29-2021

The "Farad" is the basic unit used to refer to the quantity of charge a condenser, (modern term is "capacitor") is able to store. a MICRO farad is 1 / 1,000,000 of a farad. a MICRO MICRO farad (now commonly called a pico farad) is 1 / 1,000,000 of a micro farad. So, 110 mmf = 0.000110 mfd. You will find some of us old timers still call a condenser a condenser, and a micro micro farad a micro micro farad, and not the new fangled name. Worse yet, and to ADD to the confusion is the new addition by some fools of the term NANO farad which seems to mean 1 / 1000 of a micro farad, FORSOOTH ! In the saner documentation of the earlier period, however, you will only have to deal with mfd and mmf.

RE: Philco 90 restoration - RodB - 11-29-2021

Well said, Mike. I never understood why we didn't use milli-farads.

RE: Philco 90 restoration - Bob Andersen - 11-29-2021

I replaced those mica caps while troubleshooting a problem that turned out to be an open coil. The originals mica caps were fine I just didn't bother putting them back in.

RE: Philco 90 restoration - cknob - 11-29-2021

I've seen several restoration videos on old radios, maybe you made this comment as well (I can't remember) that these mica caps in vintage radios were installed as custom, "fine tuning" capacitors and probably should not be messed with although I don't see how that could be the case for a component in the general parts list with a specific value indicated.

RE: Philco 90 restoration - RodB - 11-29-2021

Although the theoretical value might be 110pf the actual value of any one mica would vary because manufacturing techniques weren't as precise as the theory. The same with other components such as resistors and coils. So maybe the specific circuit of a specific radio ended up requiring 114pf. The assembler would find one that worked the best. Maybe the next radio would need a 108pf. They were customized for the radio.

RE: Philco 90 restoration - morzh - 11-29-2021

>>The "Farad" is the basic unit used to refer to the quantity of charge a condenser, (modern term is "capacitor") is able to store.

Mike, would you like to re-phrase this?

RE: Philco 90 restoration - Steve Davis - 11-29-2021

I don't think values were selected as the radios were assembled instead, trimmers were used to compensate for the variation of component values.

Steve