Transmitter Cup - Capacitor??

[bingster]

Always remember this about asking "lots" of questions:  The question you ask and get an answer to, undoubtedly helps somebody who might have been hesitant to ask the very same question in the past.  We all learn from it.

[keysys]

A very old issue of the Bell System Practices, section 502-210-102 tells me that a G3 handset with a capacitor wired across the transmitter terminals was actually a G3Y handset, and that the G3Y handest was intended for use on a 2568HP telephone set.

I don't see a 2568HP listed in Paul Fassbender's web site.  The closest number I can find is a 2568HAA, which is described as a keyset with a hold button and five line buttons plus a relay for 2- or 4-wire operation.

I'm wondering if this equipment was designed for use in military applications or for the broadcast industry.

[Jim Stettler]

My guess is that it was a "field fix" for someone living to close to a transmitter.
JMO,
Jim

[jeremylivin]

I'm glad to have seen this thread!


The little "varistor" in my phone is loose and I think it might not be working.  Is there a way to replace this?

When using the phone it makes my voice sound a little scratchy.

[Phonesrfun]

Short answer is that whether the old style or new, replacements of just the varistor are impossible to find without robbing one from another receiver.  Old style is riveted on one side and needs to be pried off.  Newer style is soldered in place.  Unless you are real partial to the date code on the U1, I would just replace the whole U1.

By the way, scratchiness can have a whole plethora of sources.  Are you sure it is the varistor?  Not to say that it isn't, because it could very well be.  Have you tried simply swapping out the U1 receiver element?

-Bill Geurts

[LarryInMichigan]

Jeremy,

The first thing that I check when I hear static is to clean the contacts in the transmitter cup and the back of the transmitter capsule.  I also frequently bend the contacts in the cup outwards a bit so that they will make better contact.

Larry

[jeremylivin]

I assume it's the varistor because it would fall off if not held in place by the rest of the handset...

I had to gently hold it in place when reassembling.

It's probably not hooked up any more.

[bingster]

  Is it the big silver one marked "44A" or the little green one?  If it's the little green one, you could try soldering it back on.  If it's the 44A, you'll probably want to just replace the whole U1.

[Dennis Markham]

Jeremy, if you'd like a replacement U1, send me a PM.  I have extras.

[JorgeAmely]

Dennis:

While perusing the net, I found this BSP that shows pictures of how Bell used these capacitors in both the receiver and transmitter. Pages 4,6,7,8, 10 and 11 are of particular interest. Some illustrations show these caps connected to the network directly. There is a chart that shows the broadcast frequencies these parts were used for.

[Dennis Markham]

Thank you Jorge, I will give that a look.

[Phonesrfun]

Jorge:

I was pretty sure it was for RF suppression, but I must say, my hat is off to you for digging up the actual BSP.  That is pretty good!

-Bill

[JorgeAmely]

Bill:

I was looking for an electrical component in Google when this link to the BSP showed up.

So I was actually doing real company work when I found it.