Avo Model D (10S) - UK Vintage Radio Repair and Restoration Discussion Forum

Nymrod121 · 28th Nov 2018, 12:19 am

I've been investigating one of these (see pics) and first off, a big thank you to PMMunro and others for their informative and useful posts here:

https://www.vintage-radio.net/forum/...ad.php?t=19856

There appear to be issues with voltage ranges so I'll be having another look tomorrow, armed with the information mentioned in the link.

Many thanks.

Guy

The Philpott · 28th Nov 2018, 1:36 pm

You don't specify Guy, but in the event you are intermittently getting double or half the reading you were expecting don't exclude a dry joint in the connexions to the K button. Hard to pin down and impossible to access with the movement installed.

It would be unusual for ALL of the 75v,150v slab windings and 300v,750v glass tube windings to be serviceable now, but there is a later 300/750v shunt (if you can find one) composed of welwyn resistors which will bolt and solder straight in to an earlier meter. (famous last words..)

The early shunts mentioned are even prone to fading in and out of connectivity, and a DMM test can give misleading readings in this case.

(One of) the most common faults with a Model D is worn switch spike contacts. Almost all of them have had a hard time and a few are too worn out of tolerance for the leaves to be bent in compensation. To clarify i don't think i have encountered a Model D that did NOT require attention to the switch leaves & contacts!

Dave

28th Nov 2018, 12:19 am	#1
Nymrod121 Nonode Join Date: Apr 2012 Location: Worcestershire, UK. Posts: 2,052	Avo Model D (10S) I've been investigating one of these (see pics) and first off, a big thank you to PMMunro and others for their informative and useful posts here: https://www.vintage-radio.net/forum/...ad.php?t=19856 There appear to be issues with voltage ranges so I'll be having another look tomorrow, armed with the information mentioned in the link. Many thanks. Guy Attached Thumbnails

28th Nov 2018, 1:36 pm	#2
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,107	Re: Avo Model D (10S) You don't specify Guy, but in the event you are intermittently getting double or half the reading you were expecting don't exclude a dry joint in the connexions to the K button. Hard to pin down and impossible to access with the movement installed. It would be unusual for ALL of the 75v,150v slab windings and 300v,750v glass tube windings to be serviceable now, but there is a later 300/750v shunt (if you can find one) composed of welwyn resistors which will bolt and solder straight in to an earlier meter. (famous last words..) The early shunts mentioned are even prone to fading in and out of connectivity, and a DMM test can give misleading readings in this case. (One of) the most common faults with a Model D is worn switch spike contacts. Almost all of them have had a hard time and a few are too worn out of tolerance for the leaves to be bent in compensation. To clarify i don't think i have encountered a Model D that did NOT require attention to the switch leaves & contacts! Dave