The PHILCO Phorum

I was talking with a good friend of mine about the model 21 and he gave me this:


Philco Model 20 as found by TBS-50B, on Flickr

more pics:
http://www.flickr.com/photos/53710524@N06/

Not sure what to do with it where to restore or use for parts. Driver transformer is OK along with some of the coils and speaker which could be used in the 21.
Terry

I believe that the two chassis are very similar, the only exception might be the late model 21s that used 45s for output vice the 71s. I only know the model 21 from a friend that restored one, so my knowledge is not first hand. I know Dick also makes cabinet parts for the model 20 radios as well. Not sure if Steve Davis does these models or not, but it is worth checking.
You have two radios that would look swell next to each other after you finish them!

Well I think front panel I could salvage but the veneer on the sides/top is really pretty bad. This is a good thing as I could use pieces of it to repair the front on the 20 and a section of the side on the 21. Years ago I had a 1931 Silvertone cathedral that the grill work was broken and I was able to get it all back together with a lot of patience. It's like building a ship in a bottle.
The chassis are the same expect for the power transformer, filter caps, bias resistor,and the output tubes.
Alot of work ahead. Got to find a good source for veneer!
Terry

Hmmm... I do have the base moulding and wrap (top/sides) from a model 20 deluxe, also have a decent speaker with couple of repairs and the jack present but cut off. I believe the wrap is in good shape, but would have to check. Also have the cabinet face but someone had taken most of the grillework out. The deluxe pillars/maple archs are in good shape. Interested?

Hmmmm Sounds interesting!If you could shoot me a few pics of what you got I think we can make a deal. Please send pics to

tbs50a@aol.com

Tnx greatly. Would like to keep costs down if I can. If I can repair what I have I would prefer to do that than buy new part for the 20. The cabinet parts and tube shield for the 21 is up to about $200 already. Now I know why good looking cathedrals are bring $400+
Tnx again
Terry

Well have started replacing caps and rewinding the rf coils (one down two to go). This one is in a bit better condition than the model 21. Mostly just the secondaries are open on the coil and the driver transformer is good too.
Terry

After further investigation I found that the Model 21 just had open primaries the secondaries are ok. For those taking notes the primaries of the 2nd and third coils are 49T of 36g magnet wire. The coils in the model 20 are all done. Onward to the filter block on the 20.
Terry

Last night I was able to remove the filter bank. Baked it in the oven at 275 deg for 30min. Removed innards and will take it and the chassis to work to day for cleaning. I'm working in the shop so will be able to do some work on it to clean up some of the tar that leaked out of the bank onto the chassis. Hopefully in the next day or so will have it up and running. Am busy tonight so probably won't get a chance to rebuild the filters unless I finish up work early.
Terry

Had a few minutes to play radio. Rebuild the filter bank and did a little cleaning. Wired it all up and she's making music on the bench. I ran out of a couple of the larger bypass caps the .25 @600v so I haven't replaced those yet. I think one of them is leaky 'cause the BC resister gets pretty hot. It also has an odd speaker problem. The output transformer and the voice coil show a low resistance but the speaker doesn't work. Hooked a replacement speaker to the output transformer and it work fine. Voice coil must be shorted. Darn thing plays pretty loud with the 71A's in the output. Bet the model 21 with the 45's is going to be really loud!
Off to find some caps
Terry

Found that both of the large bypasses were bad. One was leaky and pulling down the voltage on the 24A detector tube. BC resistor is running a bit cooler with 90v on the ac line. The speaker had a bad connection at the voice coil so it's work too. Paper is stiff it doesn't produce the volume the replacement did. And one of the 71A's died rip.
Terry

Sounds like your 20 is coming along well...

Well I was over at my radio buddies house and along with a Atwater Kent Keil table (model 55 chassis) he gave me a 171 tube. Fixed the smoldering BC resistor problem. Converted the power supply a choke input. Dropped the voltage down a bit but plays fine. Funny thing is it as less 60cy hum than without the input capacitor.
The only thing that's got me stumped on this set is the plate voltage on the 24A detector tube. Diagram sez 30v. I've got like 130v. All the series resistors check ok and replaced the cathode resistor (was open). Did put in a 5meg resistor in the plate circuit to lower the voltage. Plays better with about 60 to 80v. Don't know if it matters much just bugs me that doesn't match up with the diagram.
Still need to recone the speaker and give the chassis a good cleaning.
Terry

The reason you are getting a higher reading is you are using a VTVM or digital meter. In the old days, voltmeters presented a load (about 2,000 ohms per per volt) on whatever was being measured, so that's why the specs were written that way.

Could be, I'll pull out the old Triplett 630. I get so use to using what ever is handy on the bench. The digital meters are great for ohm measurements. But like you say sometimes they be confusing or can be confused by hv with any sort of rf signal. Not in this case but have done some tv work where a vom is the only way to get accurate readings.
Tnx
Terry

Hats off to you sir! The digital meter(Beckman)sez 90v Triplett sez 50v which is a lot closer to what I'm looking for. The Triplett is 20k per volt. Somewhere around here I've a really old vom have been able to put my hands on it.
Tnx
Terry