GPO telegraph sig & galvanometer - UK Vintage Radio Repair and Restoration Discussion Forum

Gi4CZW Cliff · 21st Sep 2021, 10:01 pm

I have a galvanometer in very poor condition, which I would like to clean up. Internet gives it different names, " Differential Galvanometer ", " Cathedral signal indicator ", "Type 22a". This one has center zero with 60 to either side. Any experience on how to dismantle and how it was used, of interest.

Gridiron · 22nd Sep 2021, 12:47 pm

Normally there is a thumbscrew on the back near the top. Remove it and the hood with the glass in it can be carefully tilted forwards, this is located by 2 pins on the base section.

Gi4CZW Cliff · 23rd Sep 2021, 2:01 pm

Hello Gridiron, thank you for reply and yes I had done that. So that is how I knew to ask for help. As the needle/pointer is stuck, the small screws really tight and the pivot, near pocket-watch delicate, I hesitate to proceed. In the past GPO telephones had engineering instruction for dismantling/calibrating such things, even with exploded views.
How the ( telegraph ? ) line was connected ( from underneath ? ) and it's intended use also of interest. many thanks . Cliff.

21st Sep 2021, 10:01 pm	#1
Gi4CZW Cliff Pentode Join Date: May 2011 Location: Enniskillen, Fermanagh, UK. Posts: 188	GPO telegraph sig & galvanometer I have a galvanometer in very poor condition, which I would like to clean up. Internet gives it different names, " Differential Galvanometer ", " Cathedral signal indicator ", "Type 22a". This one has center zero with 60 to either side. Any experience on how to dismantle and how it was used, of interest. Attached Thumbnails

22nd Sep 2021, 12:47 pm	#2
Gridiron Heptode Join Date: Apr 2010 Location: West Midlands, UK. Posts: 662	Re: GPO telegraph sig & galvanometer Normally there is a thumbscrew on the back near the top. Remove it and the hood with the glass in it can be carefully tilted forwards, this is located by 2 pins on the base section.

23rd Sep 2021, 2:01 pm	#3
Gi4CZW Cliff Pentode Join Date: May 2011 Location: Enniskillen, Fermanagh, UK. Posts: 188	Re: GPO telegraph sig & galvanometer Hello Gridiron, thank you for reply and yes I had done that. So that is how I knew to ask for help. As the needle/pointer is stuck, the small screws really tight and the pivot, near pocket-watch delicate, I hesitate to proceed. In the past GPO telephones had engineering instruction for dismantling/calibrating such things, even with exploded views. How the ( telegraph ? ) line was connected ( from underneath ? ) and it's intended use also of interest. many thanks . Cliff.