[Steve Davis]

I'm really bad in that when working on a project, I sometimes forget to take pictures. I did take some. So here are the high points. I bought this Philco 20 almost a year ago. I did the electronic restoration right away, then set the project aside for several months. The cabinet was in poor condition. As with many of the Philco 20s, the speaker grille was broken and pieces were missing. When the radio came to me, it had a 45 tube and a 50 tube in place of the 71 tubes. The 45 was bad, but the 50 tested very strong. I was able to sell the 50 for the price of the radio, so I only have the cost of shipping in the radio!

Pretty rough cabinet

[Image: https://farm5.staticflickr.com/4751/3856...8ec1_k.jpg]Philco 20 Cabinet by Steve Davis, on Flickr

[Image: https://farm5.staticflickr.com/4695/3856...9ab0_k.jpg]Philco 20 by Steve Davis, on Flickr

[Image: https://farm5.staticflickr.com/4744/3856...a047_k.jpg]Philco 20 Cabinet by Steve Davis, on Flickr

This was a real windfall. A 50 tube in place of one of the 71s

[Image: https://farm5.staticflickr.com/4694/2549...5665_k.jpg]Philco 20 by Steve Davis, on Flickr

The chassis had a couple of modifications done in the past. The blue resistor does not belong.

[Image: https://farm5.staticflickr.com/4624/2549...bd5c_k.jpg]Philco 20 Chassis by Steve Davis, on Flickr


Someone had installed a headphone jack (I cut the wires off before taking the photo). There was no way this could have worked. When the plug is inserted, the jack opened one side of the output transformer to one of the 71 plates. The other 71 would continue to drive the speaker. Also, I just don't like the idea of a pair of headphones wrapped around my head with a couple of hundred volts going through them!

[Image: https://farm5.staticflickr.com/4667/2549...1e0d_z.jpg]Philco 20 Chassis by Steve Davis, on Flickr

More to come

[morzh]

Steve

Is this the one on eBay?

[Steve Davis]

I'm not allowed to say

Steve

[morzh]

Just in case it is, it looks really great.

[Steve Davis]

As usual, all resistors had drifted high, all were replaced with "dogbone" reproductions.

[Image: https://farm5.staticflickr.com/4770/3856...45e9_k.jpg]Philco 20 Chassis by Steve Davis, on Flickr

I restuffed the filter can using modern film capacitors, increasing the value of the second and third filters to 4.7uf and omitting the capacitor that is in parallel with the choke. All the capacitors were replaced in the bakelite blocks. Bakelite block number 8 contains a capacitor and a resistor. I normally reinstall the original resistors, but in this case the number 8 capacitor had shorted causing a high current to flow through resistor 8, burning it up.
[Image: https://farm5.staticflickr.com/4703/2549...64b6_k.jpg]Philco 20 by Steve Davis, on Flickr

I replaced the two missing output tubes and gave it the "smoke test". The radio came to life and played beautifully! The cabinet was going the need a lot of attention and I had some more pressing projects, so I set the chassis aside for a few months. A couple of months ago I started on the project again. I remembered Ron had posted a how to in the "Tech Section" of the Phorum, a modification to remove the B+ from the primary of the interstage transformer. Take a look here.   http://www.philcoradio.com/phorum/showth...?tid=14984    Open windings in the interstage transformer is a common failure in the Philco 20. I decided to do the mod to possibly prolong the life of the transformer. In the next photos you can see where I added an extra bakelite block with a .47uf cap and a 27K, 2W dogbone resistor.

 [Image: https://farm5.staticflickr.com/4671/3856...2b9d_k.jpg]Philco 20 Interstage Transformer Modification by Steve Davis, on Flickr

[Image: https://farm5.staticflickr.com/4753/3856...d7e2_k.jpg]Philco 20 Interstage Transformer Modification by Steve Davis, on Flickr

More to come

Steve

[Nathan Slingerland]

Looking great Steve!

Question: how do you paint your reproduction dogbones?
I've been using a paintbrush with gloss enamel paints but the finish isn't nearly as nice as yours.

[Steve Davis]

Nathan, I dip them in the paint can and give them a sling to remove the excess.

Steve

[Nathan Slingerland]

Ah - I see that now in your thread http://philcoradio.com/phorum/showthread.php?tid=5501

Anything special about the type / brand of paint you use?

[Steve Davis]

I use the least expensive paint that I can find. I mostly use implement paint from the farm store.

Steve

[Steve Davis]

The speaker that came with the radio was in good condition, however, I wanted to experiment with replacing the spider. I had another 20 speaker with a bad cone and an open field coil. I rewound the field and installed a new cone with a foam surround. I also installed a modern accordion style spider on the back side of the cone.
 
[Image: https://farm5.staticflickr.com/4660/4032...8294_k.jpg]Philco 20 Speaker by Steve Davis, on Flickr
[Image: https://farm5.staticflickr.com/4701/4032...3b23_k.jpg]Philco 20 Speaker by Steve Davis, on Flickr

[Image: https://farm5.staticflickr.com/4769/3856...f00e_k.jpg]Philco 20 Speaker by Steve Davis, on Flickr

The cabinet was in pretty sad shape. I replaced the front panel, the wraparound and the base moulding. You might say this is a reproduction cabinet using a few original parts, rather than a restoration.

I shouldn't even tell about this part. I had a real "dumb attack" while working on the cabinet. I placed the cabinet face down on the table saw and bumped the blade while it was coasting to a stop, taking a chunk out of the front panel!

[Image: https://farm5.staticflickr.com/4719/3970...e4d2_k.jpg]Philco 20 Dumb Attack! by Steve Davis, on Flickr

The damage was not as bad as it looks. The edge of the front panel had not been trimmed yet. When the edge was trimmed, the worst part of the damage was removed. I only had remove a small section of veneer and replace. you have to look very closely to see the veneer patch.

[Image: https://farm5.staticflickr.com/4699/3970...aac9_k.jpg]Philco 20 Dumb Attack by Steve Davis, on Flickr

The cabinet has been finished and the chassis and speaker have been installed. I could not find a match for the grille cloth, so I wound up using 70/90 cloth. Also the two small knobs are not correct and have since been replaced with excellent reproductions from Renovated Radios.

[Image: https://farm5.staticflickr.com/4712/2806...1284_k.jpg]Philco 20 Reproduction Cabinet by Steve Davis, on Flickr

[Steve Davis]

I did one more modification. A few days ago, there was a discussion on the Phorum about line filter capacitors. The Philco20 has no line filters and has to have a ground for maximum performance. When I disconnect the ground. strong stations get noticeably quitter and the weaker ones completely disappear. I decided to add a line filter. I used two .01 Y2 safety capacitors connect from both sides of the line to chassis ground. Now, listening to the radio, I tried connecting and disconnecting the ground, there was absolutely no change in volume.   

[Image: https://farm5.staticflickr.com/4749/2672...6189_k.jpg]109_0767 by Steve Davis, on Flickr

[morzh]

I take it, maybe when the 20 came out, there wasn't much noise on the AC lines.

[Steve Davis]

No doubt, there was less noise, but without the line caps, a ground connection to the chassis is needed.

Steve

[morzh]

Well, caps essentially provide a ground path, as both the Line and the Neutral are Grounds RF-wise.

[Arran]

I don't know if there was really less noise coming through the power lines so much as different kinds of noise, such as street cars, mercury vapor rectifiers, brush motors, and diathermy machines. The model 20s were built to a price, hence why they used 71As as power outputs whilst the industry standard was #45s, so I'm not surprised about there being no line caps, if someone wanted a better model they would get a model 96.
Regards
Arran