AVO Universal Bridge B.150 - UK Vintage Radio Repair and Restoration Discussion Forum

Nanozeugma · 14th Aug 2020, 7:51 pm

Treated myself to one of these today for the princely sum of £30.

I suspect it's the first iteration of the design as it uses four discrete transistors
although the pcb reads ISSUE 2.

It was rather grubby, but I couldn't pass it up at that price as I've been after
one for some time.

The pcb seems original bearing several contemporary Hunts electrolytics.

It was designed to work from an internal PP9 battery. The original had
undoubtedly leaked badly in the past, fortunately downward into the case, which bears a significant rust patch (now neutralised with Fertan.)

I found an RS NiCD rechargeable PP9 fitted which read 3.3 volts.
In the past the battery leads had been extended to a pair of 4mm banana
sockets fitted into the side of the case to facilitate charging it, I presume.

Sadly, it seems that the original centre zero 50-0-50 microamp analogue panel meter became u/s as it has been replaced with an edge reading unit and adaptive mountings.

Having fitted a standard new PP9 and put it through it's paces it appears to work properly on R, C and L giving accurate results.

I suspect it will be difficult to find a drop in replacement for the original NULL meter movement, but I will ask if anyone knows a possible source.

It would also be useful if anyone could point me to a design for a suitable battery charger lash up (9v 100mA) so I can see whether the RS NiCD has any life left in it. New NiCD PP9 batteries can still be sourced from RS - at eye watering cost.

14th Aug 2020, 7:51 pm	#1
Nanozeugma Heptode Join Date: Nov 2017 Location: London, UK. Bury, Lancashire quite regularly :) Posts: 611	AVO Universal Bridge B.150 Treated myself to one of these today for the princely sum of £30. I suspect it's the first iteration of the design as it uses four discrete transistors although the pcb reads ISSUE 2. It was rather grubby, but I couldn't pass it up at that price as I've been after one for some time. The pcb seems original bearing several contemporary Hunts electrolytics. It was designed to work from an internal PP9 battery. The original had undoubtedly leaked badly in the past, fortunately downward into the case, which bears a significant rust patch (now neutralised with Fertan.) I found an RS NiCD rechargeable PP9 fitted which read 3.3 volts. In the past the battery leads had been extended to a pair of 4mm banana sockets fitted into the side of the case to facilitate charging it, I presume. Sadly, it seems that the original centre zero 50-0-50 microamp analogue panel meter became u/s as it has been replaced with an edge reading unit and adaptive mountings. Having fitted a standard new PP9 and put it through it's paces it appears to work properly on R, C and L giving accurate results. I suspect it will be difficult to find a drop in replacement for the original NULL meter movement, but I will ask if anyone knows a possible source. It would also be useful if anyone could point me to a design for a suitable battery charger lash up (9v 100mA) so I can see whether the RS NiCD has any life left in it. New NiCD PP9 batteries can still be sourced from RS - at eye watering cost. Attached Thumbnails __________________ Thermionic Emission, warms the cockles of your tubes.