Junior Roberts 2nd - UK Vintage Radio Repair and Restoration Discussion Forum

Boater Sam · 9th Jul 2018, 7:29 pm

Acquired another Roberts Junior, this one has all the rexine covering unlike the last one.
Its in fair condition, all the valves have filaments, the handle is good. No battery rot inside.
But its stone dead. Output transformer O/C primary.
This is the 3rd battery valve set in a month with the primary gone.
I have on average more battery sets failed this way than mains sets.
How does a puny xx91 or xx96 battery output valve pass enough current to burn out a copper winding?
This one is well coated in wax, it shows no signs of heating so it must be the green spot disease. Acid or alkaline fumes off the battery does not seem likely.
It will be another marathon with 48 swg wire and the winder.

Sam.

9th Jul 2018, 7:29 pm	#1
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Junior Roberts 2nd Acquired another Roberts Junior, this one has all the rexine covering unlike the last one. Its in fair condition, all the valves have filaments, the handle is good. No battery rot inside. But its stone dead. Output transformer O/C primary. This is the 3rd battery valve set in a month with the primary gone. I have on average more battery sets failed this way than mains sets. How does a puny xx91 or xx96 battery output valve pass enough current to burn out a copper winding? This one is well coated in wax, it shows no signs of heating so it must be the green spot disease. Acid or alkaline fumes off the battery does not seem likely. It will be another marathon with 48 swg wire and the winder. Sam.