Motorola 65T21 restoration

[bandersen]

I just received this radio from fellow VK member RDusel. While I wait for the paint on my Philco 46-420 to cure, I decided to take a closer look.

I think it's from the early 40s, but might be post-war ?




Homemade cardboard back cover


It covers the AM and SW bands and has the same logo as late 40s Motorola TVs


The faux finish is in really good shape except for a few minor dings on top. I'll try to fix those with some artist paints. I think I'll refinish the rest of the cabinet someday.


Nice asbestos on the right.


After pulling the knobs, unplugging the antenna and removing two screws, the whole chassis slides out in one piece.


The only issue I found so far is the tuning mechanism is frozen.

[wa2ise]

Originally Posted by bandersen

Nice asbestos on the right.

Asbestos in radios, what to do about it

1. At present, asbestos is known to be hazardous only if inhaled. Although there is some ongoing study on ingestion, the results are so far not alarming. Certainly less alarming than the results on arsenic, lead or cadmium.

2. Asbestos will become airborne only if friable (easily broken into small pieces). It becomes friable primarily if disturbed. There are three significant forms of asbestos as it was commonly used in consumer articles: Chrysotile, Amosite, and Crocidolite. Of these, chrysotile (white asbestos) is the most likely fiber to be found in that mat in your radio.

3. Asbestos that remains in place or can be made to remain in place is NOT hazardous.

Safing (encapsulating): Most (not all) of the asbestos used in domestic radios is included in a soft mat, either woven (rare) or non-woven (common). Usually it is held together with either a cementicious or gypsum-based binder together with several other fibers. The trick is to replace the binder with a more permanent and less mechanically vulnerable material. The EPA and OSHA recognize many sorts of encapsulants, including the binders used in both Duco Cement and Amberoid Cement. (Personal comment: I recommend Amberoid for its distinct color and the fact that I find it somewhat easier to use and less expensive that Duco. But the processes are identical. Amberoid will also maintain the insulating properties of asbestos, I am not sure if Duco will do the same.)

Mix the material of choice (Duco or Amberoid) with equal parts by volume of Acetone and soak this diluted material into the asbestos mat. It will re-glue the mat in place and bind all the fibers together. Allow to dry and soak again. Do this work away from flame or any source of flame. Do this work outdoors if possible. Do not attempt to brush, clean or vacuum the mat prior to treatment. Glue ALL of it down.

The times when the insulating mat are most likely to be disturbed are when the chassis is removed or reinstalled in a radio. Given that the original binders were not all that effective in the first place, and that they were made with deliquescent materials (gypsum or portland cements) it is very likely that some of the fibers will have become loose over the years, and may be disturbed when the chassis is moved or removed. If mice have inhabited the radio, this is a certainty. So, some initial cautions MUST be taken. And given that some here will neither admit to the hazard nor take any precautions, and that others here may not have the financial resouces to "have it done", what I suggest here is not offered as a way to eliminate a significant risk, but a way to reduce it at least in part.

First: Work out of doors. If you choose not to believe in any risk, it is still unfair to introduce asbestos into a house (or household) where it may remain a hidden hazard forever. Work over a large leaf-and-lawn bag if possible.

Tools:
1. Good particle mask. Must be effective from .1 to 10 microns (a human hair is about 50 microns in diameter). Because asbestos fibers are small and light, they can be suspended in the air for long periods. This is NOT a paper painter's mask. But once obtained, may be retained for multiple uses.

2. Small spray bottle filled with a 15:1 water-to-dish-soap solution. You will need a couple of ounces for the process, and about a pint at the end to soak the debris.

3. Strong paper towels... those that will not dissolve in soapy water.

4. Small, soft-bristled disposable brush. About 1/2" wide or smaller with at least 1" bristles.

5. Single-edge razor blade (not always necessary).

Spray the soap solution around the base of the chassis before removal. Make sure that the entire perimeter where it touches the asbestos is saturated and damp. This will hold the fibers from becoming airborne as the chassis is removed.

Remove the chassis carefully. Use the razor blade if necessary to cut loose the mat from the chassis. The idea is to leave the mat in place and not on the chassis.

Look on the chassis. If there are any visible particles of the mat on or in it, they must be collected and removed. For this, you will use the towels, the brush and PLENTY of the soapy water. A wet asbestos fiber will not become airborne. Soap is the wetting agent. Take your time and be thorough. Clean ANYTHING, even spider-webs or other material from the chassis. Be sure that it is clean.

Gently spray the inside of the radio cabinet with the soapy water. This would be those areas around but not covered by the mat. Wipe this down with the paper towels and repeat. The idea here is to capture any bits of asbestos that may have come loose from the mat.

Allow the cabinet to dry thoroughly. Soak the now-dry mat with the safing material as above. While the cabinet is drying, collect all the other detritus (brush, towels, razor, whatever) into the garbage/leaf & lawn bag. Pour the remaining soap solution over it so that it becomes a soapy mess. Seal the bag and bag it a second time. If there are ANY leaks in the first bag, bag it a third time. Dispose of the bags with your township's hazardous materials regulations, or in a regular landfill, NOT an incinerator or where the trash may be incinerated. Remove, double-bag and dispose of the mask filter also. You will use a new one for each session.

A bit long-winded as always, but the proverbial ounce of prevention covers many pounds of care in this case.

Above section on asbestos written by:
Peter Wieck

[RDusel]

Bob,
I found 5 or 6 other 65T21 (they must have been a popular radio) examples and they were all 1946.
Strange about the tuning mechanism, I had the radio playing for an hour or two before I sent it and it tuned fine. Must have been abused by Fed Ex. At least it is intact, including that valuable back cover....
Good luck and enjoy!
RD

[bandersen]

Originally Posted by wa2ise

Asbestos in radios, what to do about it...

Now that's informative! I think some version of that should be made into a sticky in the tech forum. Previously, I've only seen advice like 'just leave it alone' or 'get rid of it or you're gonna die!'.

Originally Posted by RDusel

Bob,
I found 5 or 6 other 65T21 (they must have been a popular radio) examples and they were all 1946.
Strange about the tuning mechanism, I had the radio playing for an hour or two before I sent it and it tuned fine. Must have been abused by Fed Ex. At least it is intact, including that valuable back cover....
Good luck and enjoy!
RD

Interesting. I'm just wrapping up a Philco radio from 1946. Very different designs. This one reminds me of late 30s transformer set while the Philco is closer to a 50s AA5.

Yes, the tuning shaft was bent somehow and it's binding in the bushing.


A little gentle persuasion took care of that


Just kidding. I carefully applied pressure with my thumb to the shaft and was able to straighten it out.

Which brings me to the next oddball problem. I pulled all the tubes to test them and the key on this 6SG7 broke off. I examined the socket and was surprised to see a metal collar that's grounded underneath. I though only loktal sockets had them ? I glued the key back onto the tube base and it tests fine.

On to recapping.

[Reece]

That's a nice radio. If you do decide to remove the asbestos, soak it thoroughly and keep soaking it (spray) while removing.

You can replace it with a piece of ductboard. Go to an HVAC contractor, ask them for a scrap of it. They have dumpsters full of it daily. It's a compressed fiberglass material 1" thick with a foil face. Cut a piece the size you want and then with a long knife slice it so it's only 1/4" thick. Glue to the cabinet with the foil facing the tubes. If you want I can mail you a piece.

[wa2ise]

Originally Posted by bandersen

That's a shield intended to shield the plate circuit from the grid circuit. To avoid undesired capacitance coupling that could cause feedback and make the IF stage go into oscillation. Miniature tubes' sockets have a center post to do the same thing.

[bandersen]

Ah, that makes sense. I've seen miniature tubes with a center post and wondered what they were for.

I'm recapping the set right now and will be powering it up shortly. Fingers crossed.

Originally Posted by Reece

That's a nice radio. If you do decide to remove the asbestos, soak it thoroughly and keep soaking it (spray) while removing.

You can replace it with a piece of ductboard...

Thanks. I'll let you know if I need any.

[bandersen]

I replaced the 3-section electrolytic and all the paper caps. Also, two way out of tolerance resistors.



Next, I popped the tubes back in and did a slow power up while monitoring the B+ voltage. The loop antenna is integral to the cabinet so I just clipped in a short test lead. After fiddling with the controls, I heard some familiar local stations


Next up, I'll clean the scratchy controls with DeOxit, slide it back in the cabinet and use the proper antenna. I'm also going to replace the 6K6 output tube which tested borderline good.

[Reece]

Good deal. But it seems odd to me to still see dogbones in a postwar set (NostalgiaAir says pre 1948.) Guess they were using up old stock to crank out radios like hotcakes during that time of high demand.

[bandersen]

I thought the same thing. It's a 270 ohm power resistor used in the bias network. Maybe they didn't have any carbon comp 1W resistors ?

Using the built-in loop antenna, the AM reception is fantastic - easily the best of my small radio collection.

The SW is a little flaky though. Sometimes I get nothing and have to wiggle the tuning shaft. I get lots crackles as I tune as well. Probably a bad contact somewhere, Not much to hear with the built-in 6' antenna so I hooked up a 50' length of wire. Much better. Bunch of stations between 5.5 and 6.2 MHz. Not much else though. Only the CHU time service at 7.85 MHz from Canada.

[Reece]

During the day you'll hear the 25 meter band. At night the 31 meter and 49 meter. Sunspot activity is supposed to improve and bring these bands back more. I heard Romania etc. during the afternoon yesterday on 25 meters on a set with a tuned RF stage.

[wa2ise]

But I wouldn't just parallel the new filter caps with the old one. As the old one could still short out. I'd use a terminal strip to make the new cap connections. Or you could remove and gut the old can, and hide the new caps in the now empty cap can.

[bandersen]

Originally Posted by wa2ise

But I wouldn't just parallel the new filter caps with the old one. As the old one could still short out. I'd use a terminal strip to make the new cap connections. Or you could remove and gut the old can, and hide the new caps in the now empty cap can.

Actually, I didn't, but it's just not easy to see. I removed the wires from the old cap lugs and soldered them onto the new caps. The new caps are just supported by those solder connections right now. Not the safest approach for sure. I'll mount them more securely now that I know the radio is working.

[bandersen]

Originally Posted by Reece

During the day you'll hear the 25 meter band. At night the 31 meter and 49 meter. Sunspot activity is supposed to improve and bring these bands back more. I heard Romania etc. during the afternoon yesterday on 25 meters on a set with a tuned RF stage.

Interesting - I though they were all better at night. I'll try out the 25 m band during the day tomorrow.

[dieseljeep]

Hey Bob. I have the same radio. Haven't pluged it in lately. I thought the knobs were very modern looking for a radio that age. Good design. Separate oscillator and mixer. Dave.