Classic phone repair (was Re: 1966 Mag: Build NE-2....)

Tony Duell ard at
Sat Jul 21 15:43:51 CDT 2007

> Hi,
>   > 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).

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.

> 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 


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