Model 96 Restoration - Printable Version

Model 96 Restoration - Printable Version

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Model 96 Restoration - rfeenstra - 11-28-2017

I've begun the process of restoration on a 96 that I picked up. Not a great radio, but it will be a good experience. This is the first time I've run across the cap blocks that include the wire wound resistor. I've been able to extract the resistor intact and reinstall it in the block with the new cap. Is this wise? They all measure within a few ohms of spec and install quite easily. Has anyone had any issues with doing this?

Many of the cloth covered wires are very brittle and I will replace individual wires. The wires in the harness that runs around the perimeter of the chassis are also very hard. I hate to disturb that. If it's not flexed, is it safe to leave it?

I am taking pics if anyone is interested.

RE: Model 96 Restoration - klondike98 - 11-28-2017

I just did the same thing you did in the 91 I'm working on. Reinstalling the resistor should be just fine. Follow the link and you'll see what the guts of one looks like.

RE: Model 96 Restoration - rfeenstra - 11-28-2017

Awesome! Thanks. I was able to unwind the resistor wire from the terminal so I didn't need to get more wire out. Didn't realize it would have been so simple. This is a great forum (phorum)!

RE: Model 96 Restoration - morzh - 11-28-2017

I restored 111 which is the same generation as 96, same type chassis except it is a superhet.
I did not disturb the wire harness, and yes it is very hard. It is safe to leave it be: the ibsulation is there abd unlike in rubber wires it isn't going anywhere, just don't disturb it so it doesn't crack.

RE: Model 96 Restoration - rfeenstra - 11-29-2017

That's kind of what I figured. Don't flex it too much and the insulation will be there. It shouldn't be a problem. I have the main cap can disconnected an out without moving the wires a lot. It shouldn't much of a problem to re-connect..

Most of the dog bone resistors are a bit over spec value. One is open. I think I will hide a resistor under the dog bone in parallel to bring the resistors within range. They are small enough that they should not be readily seen hiding behind the original. With a cursory glance from above, it will all look original. I really don't want to go the painted plastic tube with a new resistor inside route. Do these old resistors vary much in resistance with temperature? I would think it is a slow degradation of value over a great deal of time. My observation is that they usually increase in resistance. Thus a calculated parallel resistor would bring things into design specs.

RE: Model 96 Restoration - Arran - 11-29-2017

There is a trick that I heard of that some guys use whilst restoring early post war RCA TV sets, such as the 630TS, to deal with the stiff wires. Basically you can heat the wire up with a heat gun, on low setting, and it will soften the insulation enough that you can bend it without breaking the insulation. I don't know whether this would work in an early Philco with the pan chassis but it's worth a try if you absolutely have to move something. It's been a few years since I had the chassis out from my model 96 lowboy, but I know what you mean about the wiring, it's laced into a harness like a piece of old military or telephone company equipment. Apparently cable lacing is not that hard to do but I've never had occasion to try it.
Regards
Arran

RE: Model 96 Restoration - rfeenstra - 11-29-2017

I did notice that the wire softened up a bit when heated for un-soldering. I think I can get by without having to move the harness much. This harness is in a cloth sleeve, not the string tied, laced harness. I've actually done that when I upgraded the avionics in my plane. Everything had to be bundled and laced so that vibration would not affect the wiring.

RE: Model 96 Restoration - rfeenstra - 11-29-2017

Got into the volume control. That's an impressive little piece of electro-mechanical apparatus! The schematic says it should be 500K. I measure 3.3 meg. The variation in resistance from one side to wiper seems to be a nice, gradual change from 0 ohms to 3.3 meg. The part number is 4093.

If it should be 500K, is there a way to refurbish the carbon resistor? Or, will the control still work but volume adjustment would occur in just partial rotation? It appears that the volume control is providing the bias for the grid on the driver tube from one end and signal from the bypass capacitor on the other. Perhaps sufficient bias is maintained even with much higher resistance in the circuit??? I suppose time will tell!

RE: Model 96 Restoration - rfeenstra - 11-30-2017

To paint or not to paint. That is the question. I've seen several restoration videos of people painting the chassis. Here is a pic of the 96 chassis. This is the only place there is rust. Should I paint the entire chassis to protect this area after it is cleaned? The painted chassis I've seen in the videos look pretty good when done. The RF cans look pretty good and will be much better if I can get them clean. I would hesitate to paint them. Thoughts?

RE: Model 96 Restoration - morzh - 11-30-2017

In my opinion, if you want it to look a certain way, yes, paint it, but after de-rusting, if kept inside a house with normal humidity, it will not likely rust anymore as the rust typically develops as a result of the radio having been kept in a humid conditions, like humid basements, barns, poorly climat-controlled storage etc.

RE: Model 96 Restoration - Ron Ramirez - 11-30-2017

What Mike said.

Don't paint the coil shields (you called them "RF cans"). They are aluminum. You will be amazed at what some Mother's Mag & Aluminum Polish and elbow grease will do for those coil shields. Icon_thumbup

RE: Model 96 Restoration - rfeenstra - 11-30-2017

I'll try it! I still may paint the chassis to give it a nice look. The old cadmium (???) plating is so dull, although the naval jelly is cleaning it up a bit. Painting would give it a more consistent look.

RE: Model 96 Restoration - rfeenstra - 12-03-2017

Here's where I am so far. Chassis has been powered up w/o the 80 (field coil not yet checked out). Power transformer voltages checked and tubes light. Chassis painted, all caps replaced and resistors "modified". I hope the old dog bone resistors are reasonably stable after this amount of time as they are still in circuit. Parallel resistors have been added to bring them within specs. the only question I have is the antenna coil resistor. it is spec'd at 5k but measures 4K. How does this affect the antenna circuit performance?

RE: Model 96 Restoration - rfeenstra - 12-03-2017

Oh ya. Here is what I listen to while working on the 96.

This is the exact condition i remember this radio in as a kid. the "R IV" you see on the front stands for Ranger IV. this was a space program in 1962 designed to crash a spacecraft onto the moon. Brother Rog, who had the radio at his workbench in the basement and who's initials are on the chassis, was a follower of all rocket launches. He now has has Alzheimer's but got a big kick out of seeing his old radio in working condition again. the radio is working great even though almost all of the tubes measure way below the rejection level on a HeathKit TT-1 Mutual Conductance tube tester. I wonder what it would do with stronger tubes!

RE: Model 96 Restoration - rfeenstra - 12-03-2017

Rats! Open winding on the output transformer. One side of CT measures 3.7K, other side 12K. Deja-vu all over again (model 14). Guess I better get at rewinding the 14 transformer so I can try the universal here.

Field measures ok (3.3K) so I may fire up the radio slowly to verify voltages and basic operation.