GPO 312 Phone - UK Vintage Radio Repair and Restoration Discussion Forum

jrh_james · 28th Apr 2015, 9:30 pm

Hi,

I purchased a cheap GPO 312 phone from a car boot as I thought it would make an interesting thing to restore. I was rather disappointed by the internal condition of the phone which is rather corroded.

I used a multimeter to check the resistance across the various components and it doesn't look good. The capacitor, the solenoids and the inductor all have infinite resistance across their terminals. I did scrape the oxide off the terminals before testing.

I removed the wrapping from the inductor to inspect it - couldn't see anything obviously wrong.

On the plus side the dial seems to work reasonably well although it doesn't return fully when the high digits are dialed.

I take it there is no source of original spare parts for these phones? Can I replace some of the duff components with modern parts or is that sacrilege? Given the condition is this beyond repair do you think?

James.

Nickthedentist · 28th Apr 2015, 9:50 pm

Hello James and welcome.

Nothing is beyond repair here!

It's sad that it's been damaged like this. Maybe it sat in a puddle on a garage or shed floor for a long time. At least the receiver, case and dial seem OK.

The bell motor can be replaced by the sort used in the later 700-series phones very easily, but the ASTIC (coil) is another matter.

Your best bet would be to scour eBay etc. for a chassis taken from a scrap phone, or a phone which has a smashed case. They do crop up.

Nick.

recordamus · 28th Apr 2015, 10:01 pm

You can try a firm called Telephone Lines, Higher Tippacott Farm, Brendon, Devon EX35 6PU - Telephone 01598 741443. Malcolm has most bits-and-pieces or he can certainly tell you where you can get what you need
Kind regards
Pete

jrh_james · 28th Apr 2015, 10:30 pm

Thanks for the advice.

I made a little progress with the induction coil. It seems that the ends of the windings are not soldered to the tabs but wrapped around them, and the tabs were so heavily corroded that they were no-longer forming a circuit. So I cleaned off some of the oxide and soldered the wires to the tabs and I got all but the 75ohm winding between 3 and 4 working. Unfortunately the wire for the 4 tab seems to connect internally so I can't get to it to repair it, so it is still duff

28th Apr 2015, 9:30 pm	#1
jrh_james Diode Join Date: Apr 2015 Location: Stevenage, Hertfordshire, UK. Posts: 5	GPO 312 Phone Hi, I purchased a cheap GPO 312 phone from a car boot as I thought it would make an interesting thing to restore. I was rather disappointed by the internal condition of the phone which is rather corroded. I used a multimeter to check the resistance across the various components and it doesn't look good. The capacitor, the solenoids and the inductor all have infinite resistance across their terminals. I did scrape the oxide off the terminals before testing. I removed the wrapping from the inductor to inspect it - couldn't see anything obviously wrong. On the plus side the dial seems to work reasonably well although it doesn't return fully when the high digits are dialed. I take it there is no source of original spare parts for these phones? Can I replace some of the duff components with modern parts or is that sacrilege? Given the condition is this beyond repair do you think? James. Attached Thumbnails

28th Apr 2015, 9:50 pm	#2
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,861	Re: GPO 312 Phone Hello James and welcome. Nothing is beyond repair here! It's sad that it's been damaged like this. Maybe it sat in a puddle on a garage or shed floor for a long time. At least the receiver, case and dial seem OK. The bell motor can be replaced by the sort used in the later 700-series phones very easily, but the ASTIC (coil) is another matter. Your best bet would be to scour eBay etc. for a chassis taken from a scrap phone, or a phone which has a smashed case. They do crop up. Nick.

28th Apr 2015, 10:01 pm	#3
recordamus Triode Join Date: Apr 2007 Location: Nottinghamshire, UK. Posts: 23	Re: GPO 312 Phone You can try a firm called Telephone Lines, Higher Tippacott Farm, Brendon, Devon EX35 6PU - Telephone 01598 741443. Malcolm has most bits-and-pieces or he can certainly tell you where you can get what you need Kind regards Pete

28th Apr 2015, 10:30 pm	#4
jrh_james Diode Join Date: Apr 2015 Location: Stevenage, Hertfordshire, UK. Posts: 5	Re: GPO 312 Phone Thanks for the advice. I made a little progress with the induction coil. It seems that the ends of the windings are not soldered to the tabs but wrapped around them, and the tabs were so heavily corroded that they were no-longer forming a circuit. So I cleaned off some of the oxide and soldered the wires to the tabs and I got all but the 75ohm winding between 3 and 4 working. Unfortunately the wire for the 4 tab seems to connect internally so I can't get to it to repair it, so it is still duff