UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Simple reformer for HT capacitors in valve-rectified equipment

GrimJosef · 20th May 2019, 9:48 am

The real change for me was being able to use the unit's own mains transformer, so I could get the reforming voltage I needed without having to sort out a separate supply.

In a cold Quad II (no valves powered) in situ reforming would put the full HT voltage across the Hunts interstage coupling capacitors. These were only rated for 350V when new and they're notorious for going leaky after 50-60 years, even though they only see 100-150V in service. It's not worth risking destroying them with the reformer, and their leakage current might well confuse the situation when I'm trying to check the HT electrolytics. Since I'm almost certainly going to replace them anyway I just detach one end of them before I start.

Cheers,

GJ

20th May 2019, 9:48 am	#3
GrimJosef Dekatron Join Date: Sep 2007 Location: Oxfordshire, UK. Posts: 4,311	Re: Simple reformer for HT capacitors in valve-rectified equipment The real change for me was being able to use the unit's own mains transformer, so I could get the reforming voltage I needed without having to sort out a separate supply. In a cold Quad II (no valves powered) in situ reforming would put the full HT voltage across the Hunts interstage coupling capacitors. These were only rated for 350V when new and they're notorious for going leaky after 50-60 years, even though they only see 100-150V in service. It's not worth risking destroying them with the reformer, and their leakage current might well confuse the situation when I'm trying to check the HT electrolytics. Since I'm almost certainly going to replace them anyway I just detach one end of them before I start. Cheers, GJ __________________ http://www.ampregen.com