Philco 20A - Electronic Restoration Questions - Printable Version
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Philco 20A - Electronic Restoration Questions - MrGrnEgz - 08-09-2017
What do you typically do with that whole tar package in the big tin can?
Throw it away? Keep it? Keep it still in the can?
RE: Philco 20A - Old cap can caps - morzh - 08-09-2017
I toss them. No use.
RE: Philco 20A - Old cap can caps - Kenneth F. Besso Jr. - 08-09-2017
Gut the can,,,use can for NEW Capacitors,,,CHEERS
RE: Philco 20A - Old cap can caps - WallaceRoger - 08-09-2017
Into the garbage.
Capacitors for Philco Model 20 - MrGrnEgz - 08-09-2017
I'm very new to the different types of capacitors and where I live, I cannot go to a local store to pick some up, they've got to be ordered online.
Where are you guys finding these high voltage rated caps? The 2 uF film caps with over 400V rating that I'm finding are in the $7 - $10 ranger on Mouser. DigiKey doesn't even have them available...
RE: Capacitors for Philco Model 20 - Radioroslyn - 08-10-2017
http://www.tuberadios.com/capacitors/
Use two 1.mfd in parallel, there 75 c ea.
RE: Capacitors for Philco Model 20 - MrGrnEgz - 08-10-2017
Ah! I had completely forgotten about the parallel & series rules for capacitors. Thanks so much! And for the link too
RE: Capacitors for Philco Model 20 - Steve Davis - 08-10-2017
Since your radio is a 20A rather than a 20, the values of your original filter capacitors are a little different. The 20A was designed to work on 25 to 40 cycle AC so the filter capacitors were a little higher value. My recommendation would be to use a 1.0 uf for the first filter (terminals 1 and 2), a 4.7 uf for the second filter (terminals 1 and 4) and omit the capacitor that parallels the choke (terminals 2 and 6).
Steve
RE: Capacitors for Philco Model 20 - WallaceRoger - 08-10-2017
I bought some large assortments of 630v film capacitors and resistor assortments on ebay, they usually have free shipping, too. If you go that route, be sure you check where they're shipping from, a lot of them will be from Hong Kong and if so, you'll be waiting a couple weeks for them. There are several there that ship from within the US though.
The original resistors in the 20 are 1 watt, I only had 1/2 watt so I doubled up on resistance and ran them parallel to get back to 1 watt at correct resistance spec.
RE: Capacitors for Philco Model 20 - Nathan Slingerland - 08-10-2017
Sal's is good. While we're sharing links - a few more sources for parts (in general) you should know about:
http://www.radiodaze.com/
http://www.justradios.com
http://www.renovatedradios.com - reproduction parts (especially rubber parts)
For restuffing bakelite blocks I used the film caps from here:
http://www.capacitorworld.net/product/metallized-polypropylene-film-capacitors/
For replacement electrolytics I like to buy a good quality brand like Nichicon - usually from Mouser.
RE: Capacitors for Philco Model 20 - MrGrnEgz - 08-10-2017
Are the electrolytic caps the two business card sized units which go to ground? #13 & #14 on the diagrams?
RE: Capacitors for Philco Model 20 - Steve Davis - 08-10-2017
The Philco 20 has no electrolytic capacitors.
Steve
RE: Capacitors for Philco Model 20 - MrGrnEgz - 08-10-2017
(08-10-2017, 10:05 AM)Steve Davis Wrote: My recommendation would be to use a 1.0 uf for the first filter (terminals 1 and 2), a 4.7 uf for the second filter (terminals 1 and 4) and omit the capacitor that parallels the choke (terminals 2 and 6).
Got it. Would you mind explaining a little why deviate from the spec sheet recommendation on the 20A condenser values? I'd like to understand the change.
Does it smooth the DC out better?
RE: Capacitors for Philco Model 20 - Radioroslyn - 08-10-2017
The 20 was a US built set the 20A is Canadian. In CA the AC line power was 25cy not 60cy like we have here in the states. Being the the power is a different frequency it calls for a larger power transformer and a different sized filter cap to filter out the 25cy hum. That's the short answer.
RE: Capacitors for Philco Model 20 - Steve Davis - 08-10-2017
When this radio was made, large value capacitors were physically large and expensive. Radio manufactures tried to use the lowest value capacitors they could get by with. One of the tricks Philco used was to use a specific value capacitor in parallel with a choke to create a tuned circuit to filter the hum. The problem with that is, if the value of the capacitor is either too high or too low, it can actually increase the hum. Some may disagree, but I think it best to omit this capacitor and increase the value of the second filter to compensate. It is not a good idea to increase of the first filter because this will increase the B+ voltage.
Steve