[GreenKeys] #2500 Telephone Sets

[Sheldon Daitch]

Well, I can think of three or four reasons.

Assuming it is working mechanically, it could be:

dirty switch contacts

one or more transistors are defective (I just can't remember
how many there are on the old DTMF pads - maybe it
was only one transistor - write only memory time, I think)

Open coil(s)

other defective component

(I can't easily find a schematic for the old style  DTMF pads
so I can't tell you what other parts there might be - all my
phone literature is at home!)

Last but not least, if the phone/pad combination is old enough,
remember the early phones were polarity sensitive, so if the
phone loop polarity is reversed, the pad won't work.  I'd try
changing the polarity of the phone line before working on
anything else.


Hope this helps,

73
Sheldon
WA4MZZ





wa2hwj at att.net wrote:

> Has anyone ever figured out why the old Touchtone dials go bad?
>
> Jack WA2HWJ
>
> -------------- Original message from Roy Morgan <roy.morgan at nist.gov>: --------------
>
> > At 11:41 AM 1/4/2006, Steve Hilsz wrote:
> > >... See www dot navysalvage dot com for more details on repairs to older
> > >telephones.
> >
> > Steve,
> >
> > Thanks for that link. I followed it and found details on princess phones,
> > some of which I have and want to get running again.
> >
> > ALSO: I found details on switchboard lamps - these are the long thin things
> > found in some telephone/teletype patch panels. I'm very happy to now know
> > the voltage of a few such lamps I have here.
> >
> > Roy
> >
> >
> > - Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
> > 7130 Panorama Drive, Derwood MD 20855
> > Home: 301-330-8828 Cell 301-928-7794
> > Work: Voice: 301-975-3254, Fax: 301-948-6213
> > roy.morgan at nist.gov --
> >
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