UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

Test Desk · 3rd Jun 2018, 8:21 pm

Hi all.
Years ago, I would have said the possible cause is a late choice final selector, in your local Strowger exchange, not sending enough 75V AC down the line intermittently, due to a fault.
Anyway,back in the real world, boombox you mentioned two old 700 type phones in your set-up? I was wondering if they have been properly modified to work in parallel ? They should have high impedance bell coils (4000 ohms) instead of the usual 2000. You should check as it may be your phones have simply had a modern plug and cord fitted and your REN may be borderline.

Regards, Dave G0BZI

3rd Jun 2018, 8:21 pm	#36
Test Desk Tetrode Join Date: Nov 2017 Location: Bromsgrove, Worcestershire, UK. Posts: 63	Re: Calling the old BT technicians... Hi all. Years ago, I would have said the possible cause is a late choice final selector, in your local Strowger exchange, not sending enough 75V AC down the line intermittently, due to a fault. Anyway,back in the real world, boombox you mentioned two old 700 type phones in your set-up? I was wondering if they have been properly modified to work in parallel ? They should have high impedance bell coils (4000 ohms) instead of the usual 2000. You should check as it may be your phones have simply had a modern plug and cord fitted and your REN may be borderline. Regards, Dave G0BZI