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

The Philpott · 18th Feb 2018, 2:58 pm

Phil, I see the resistor you mention in the circuit diagram, my (pdf) instruction book is quite early, but the circuit diagram does specify that it relates to-

'Model 7 (with letter 'A' in serial number)'

I have opened the meter up and see that coming from contact 'e' there is only one wire, which goes straight to + on the rectifier. Consulting my notes this whole switch stack from 'a' to 'f' was changed for a later one, as the original switches were worn beyond adjustment.

My scruffy notes from this indicate that the (later) switch stack had the stubs of two wires coming from 'e', so this, i think, indicates that the 1939 meter lacks this rectifier biasing circuitry.

I wanted to take the meter out of it's box anyway as the Q bodge i detailed on pages 72/73 of the survey has suffered from a loosening nut, stopping the wiper from rotating.

Medium strength Loctite and possibly a star washer needed!

18th Feb 2018, 2:58 pm	#1582
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,107	Re: AVO Multimeter survey Phil, I see the resistor you mention in the circuit diagram, my (pdf) instruction book is quite early, but the circuit diagram does specify that it relates to- 'Model 7 (with letter 'A' in serial number)' I have opened the meter up and see that coming from contact 'e' there is only one wire, which goes straight to + on the rectifier. Consulting my notes this whole switch stack from 'a' to 'f' was changed for a later one, as the original switches were worn beyond adjustment. My scruffy notes from this indicate that the (later) switch stack had the stubs of two wires coming from 'e', so this, i think, indicates that the 1939 meter lacks this rectifier biasing circuitry. I wanted to take the meter out of it's box anyway as the Q bodge i detailed on pages 72/73 of the survey has suffered from a loosening nut, stopping the wiper from rotating. Medium strength Loctite and possibly a star washer needed!