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

John_BS · 2nd Feb 2020, 5:24 pm

Andy: I can't quite get my head around the consequences of that relay kicking in, viewed from the perspective of the transformer secondaries, some of which are floating wrt ground. There's a possiblity that you have an insulation breakdown between a couple of those secondaries, and only when the supplies are "coupled" does the fault manifest itself. Bit of a PITA to actually eliminate this fault, but perhaps start by disconnecting wires from 20, 21 and use a megger from 20 to 5 etc?

John

2nd Feb 2020, 5:24 pm	#28
John_BS Octode Join Date: Dec 2008 Location: Wincanton, Somerset, UK. Posts: 1,784	Re: Tektronix 585A issues. Andy: I can't quite get my head around the consequences of that relay kicking in, viewed from the perspective of the transformer secondaries, some of which are floating wrt ground. There's a possiblity that you have an insulation breakdown between a couple of those secondaries, and only when the supplies are "coupled" does the fault manifest itself. Bit of a PITA to actually eliminate this fault, but perhaps start by disconnecting wires from 20, 21 and use a megger from 20 to 5 etc? John