> > And for landline phoens, I've got
plenty of 700 series (1060's, 1970's)
> > that work fine and a 332 (1940's) in need of a bit of restoration. But
> > that I can do.
> Those will pretty much last forever.
other than some annoying carbon granule clumping.
You can always fit a Transmitter 21A (at least to UK 700 series
telephones). That's an electret microphone and amplifier IC (Plessey
ZN470 IIRC) that fits in place of the carbon microphone. It's possible to
put one in a 300 seires oto (there was an article in the lasted THG
journal on how to do it), but it involves some modifications, like
cutting a slot in the housing for hte Transmitter 21A.
But quite often a couple of sharp taps on the mouthpiece end of the
handset will cure it.
The balanced armature receiver inserts used in the 800 series handsets
9adn the tone ringer of the TRIMphone) do fail. Most of the time it's
just he soldered joint that conencts the armature to the pin on the
diaphragm that fails. The problem is that the hosuigns of said inserts
have spun-over flanges to hodl them together. You cna machine them off
to take them apaart, but you have to be careful wit hthe insert thereafter.
-tony
