My new project, bought a barn fresh 304 for $10

[Greg G.]

I pulled the trigger on a 304 I found on the Seattle Goodwill website (not far from me).  They wanted $9.99, but I bid $10.00.

It's in sad shape, I knew that from their pictures.  If anybody else bid on it, I would have let it go. If I don't fix it, I'll keep it as parts.  Fortunately, I have a black 302 shell that is like new.  That was the main thing why I bought it.  When I inspected the handset, I couldn't twist the mouth piece off with just my hands, I had to use the RoboTwist, worked well. 

I can't get the mouth piece transmitter out, it's stuck.  I thought of heating up the transmitter cap with a hair dryer.  I have another 302 that has the same problem.  The ear piece is shot, inside and out.  There's no element in it, I'll have to dig through my parts to find one.

Another question is, how do you get the rust off the bottom w/o erasing the stamp on the bottom? 

With all that said, it's going to be fun (I'm retired now).  You're inputs would be valuable.  Thanks

[countryman]

If you could disassemble the innards, the rust on the base plate might be improved by a bath in citric acid. That would remove the visible rust but keep the patina. Flaky paint might come lose, still. To save the stamp I'd leave this part out of the bath.

[allnumbedup]

For base rust, you could also use "EvapoRust" by remoivng the suede feet and ringer then setting the base bottom down in a shallow pan filled with a small pour of the liquid. Neatly apply petroleum jelly over the vermillion stamps first. You will likely be left with grey metal wherever you have rust to the level of wherever the liqui soaks. If rust is under any of the paint it will flake off too.  I usually leabe mine like that or you could repaint. You can get the Evaporust at auto stores and pour it into a jar to reuse.

[TelePlay]

Covering the stamp with pure lanolin or Vaseline would protect it from an acid bath.

I restored many rusted kerosene lanterns by putting them into a mixture of Grandma's Molasses and water. Posted most of them on the forum, here's one that gets deep into the comparison of different molasses:

https://www.classicrotaryphones.com/forum/index.php?topic=23842.0

Take the components and feet off of the base, cover the lettering with Vaseline and put it in the molasses bath warmer than 70°F for several days to a week with intermittent cleaning with a Brillo (not SOS) pad.

The rust will be gone but the surface won't be perfect, it will be rust free with character, "patina" and missing paint.

The sugar in molasses chelates the iron out of the rust leaving a brown, muddy dirt easily removed with gentle scrubbing. The internet is full of sites showing rust being removed from parts and tools.

It'sa rust removal method used by antique dealers and any other's with rusted stuff.

There are other rust removers out there but they are not as safe to use as molasses.

Here's David's before and after photos.

[Greg G.]

Thanks for all the rust repair info.  Has anybody had the same problem of getting the mouth piece (or ear piece) transmitter out?  I have another 302 that has the same problem.  I haven't tried a hair dryer yet.  I don't know if the material it sits in (Bakelite?) expands well enough.

Next question.  You can see all the crud on the electronics.  How are they cleaned, what is used? 

[countryman]

I suppose the transmitter is stuck on a disintegrated rubber seal. Gently heating the handset over an extended period of time really should help releasing it.
Isopropyl alcohol is often recommended for cleaning electronics.

[TelePlay]

Are the handset caps plastic or Bakelite? The hot pin test can quickly determine that.

If Bakelite, the risk of damaging the cap is very low. I'd put it in a sealed plastic bag and put it into the freezer for several hours. The metal will shrink more than the Bakelite hopefully breaking the seal between the element and the cap.

Heating the Bakelite cap first would be better than freezing it first (see the edit below).

Given what the other parts look like, that same crud may have grown between the cap and the element "gluing" the two together. WE never put rubber seals in their F1 handsets, that I know of. Alcohol put in the cap around the edge of the element, from the back with its holes down may help dissolve that bond.

Heating may not work in that the metal will expand more than the Bakelite, make it larger pushing against the cap.

EDIT:  looking at the coefficient of thermal expansion for common steel and Bakelite, Bakelite expands/contracts at about 20-45 x 10-6 inch per °C. Common steel expands/contracts at about 11.7-13 x 10-6 inch per °C. The actual change per linear inch is small but significantly different, in the range of about 0.0000065 inches per inch of length for every 1°C change. But with the expansion difference between the two materials being 2 to 3 times, heating and cooling will put lateral pressure, lateral movement, in the bond and hopefully enough to break it apart, but it may take more than one heating/cooling cycle. This would be a trial and error application with close observation to see what happens.

[TelePlay]

Above reply has been edited.

[Greg G.]

Are the handset caps plastic or Bakelite? The hot pin test can quickly determine that.

If Bakelite, the risk of damaging the cap is very low. I'd put it in a sealed plastic bag and put it into the freezer for several hours. The metal will shrink more than the Bakelite hopefully breaking the seal between the element and the cap.

Heating the Bakelite cap first would be better than freezing it first (see the edit below).

Given what the other parts look like, that same crud may have grown between the cap and the element "gluing" the two together. WE never put rubber seals in their F1 handsets, that I know of. Alcohol put in the cap around the edge of the element, from the back with its holes down may help dissolve that bond.

Heating may not work in that the metal will expand more than the Bakelite, make it larger pushing against the cap.

EDIT:  looking at the coefficient of thermal expansion for common steel and Bakelite, Bakelite expands/contracts at about 20-45 x 10-6 inch per °C. Common steel expands/contracts at about 11.7-13 x 10-6 inch per °C. The actual change per linear inch is small but significantly different, in the range of about 0.0000065 inches per inch of length for every 1°C change. But with the expansion difference between the two materials being 2 to 3 times, heating and cooling will put lateral pressure, lateral movement, in the bond and hopefully enough to break it apart, but it may take more than one heating/cooling cycle. This would be a trial and error application with close observation to see what happens.

The hair dryer worked very well.  I put the mouth cap w/element down on a hard surface with the holes up.  I turned the hair dryer on high and held it close to the cap.  It took less than a minute, around 30-40 seconds and the element just fell out.  The cap wasn't harmed.