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-   -   Bells ring when dialing out on 312F telephone (https://www.vintage-radio.net/forum/showthread.php?t=168888)

john777 10th Jul 2020 1:19 pm

Bells ring when dialing out on 312F telephone
 
Hello
I have a 312F call exchange telephone.
I have rewired it as per instructions at this link: https://www.britishtelephones.com/pstconv1.htm#312

Remove strap T10 - T11.
Remove strap T12 - T13.
Insert a 3.3K ohm resistor between T11 & T12.
Link all the following terminals together T1 - T2 - T3 - T9.
Red of line cord to T8.
White of line cord to T1.
Blue of line cord to T11.
Green of the line cord is spare and can be parked on T7.
Rectifier No. 205 (if needed) inserted between T6 & T5

For step 4 I put a strap between 1 and 2, wire between 2 and 3,
and wire between 3 and 9

It dials out and can be dialed into
However there is a problem where every time I dial out the bell rings. So as the dial returns it will ring according to the number dialed shorter for 1 and longer for 0 etc.
am sure this is a wiring problem but wracking my brains as to what can be causing it - Can anyone help
Many thanks for reading

Dave Moll 10th Jul 2020 1:59 pm

Re: Bells ring when dialing out on 312F telephone
 
I assume the reference to the bell ringing is that it tinkles in time with the dial pulses.

The problem may be placing the resistor between T11 and T12. Looking at diagram N412 shows that the bell's connection T13 should be disconnected when the handset is off-hook, but your resistor is retaining this connection. If you remove the link between T12 and T13 and move the resistor into its place, this should solve the problem.

john777 10th Jul 2020 7:43 pm

Re: Bells ring when dialing out on 312F telephone
 
Hello
That seems to have done the trick.
I moved the resitor from T11- 12 to T12-T13 and all now seems well
Many thanks for taking the time to reply on this

Dave Moll 10th Jul 2020 8:09 pm

Re: Bells ring when dialing out on 312F telephone
 
I'm glad you're sorted.

BigClick 12th Jul 2020 3:02 pm

Re: Bells ring when dialing out on 312F telephone
 
Can't remember what they were but we use to fit what I would call a mini neon bulb to mitigate bell tinkle. I really can't recall the name, I am getting older :-(

Station X 12th Jul 2020 3:20 pm

Re: Bells ring when dialing out on 312F telephone
 
Thermistor 1A-1?


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