21 Jul
2007
21 Jul
'07
1:43 p.m.
Hi,
Are you sure it's DTMF? Most GPO 'phones were pulse-dialing, even if they
had a keypad. GPO exchanges didn't eespond ot DTMF signals AFAIK.
There may have neen an N-diagram for it (there's an archive of these on
the web -- do a google search for 'N-diagram'). If you know the GPO
number for the 'phone (like the '706' that Jules mentioned the other
day), the N-diagram number is 100 more than the telephone type number --
so the schematic for a 706 is in N-dagram 806.
However, N-diagrams do not contain internal schematics of modules, like
the dialer or the ringer. There was, AFAIK, no field repair of PCBs.
The one next to me here is a rotary (1967 I
think, a GPO 706) - when
I get time it'll be replaced by my 1940's one (a 162)....
Just as an aside, you wouldn't happen to know where I could find a
schematic, or service manual, for a 1970's "Trimphone" (the DTMF model
rather than the rotary dial model). One of mine got "zapped" during a
thunderstorm and now crackles very quietly
instead of "chirping" when it rings.... :-(
I didn't think the ringer was that complicatated. Can't you trace out the
schematic?
-tony