A couple of days ago, I spent about an hour locked in battle with the Mains and H.T. fuse holders on a Marshall JCM800 head. The amp was working--I was simply checking the fuses to make sure the right values were installed, but when I tried to power the amp back up, there was no power. The fuses were good, but the fuse holder circuits were open.
These holders are snap-in types with a metal sleeve that fits over the fuse and a spring in the end-cap. I think the idea was that the spring presses the metal sleeve and spring against another contact inside the holder. The problem seems to be that if there's ANY binding between the plastic end-cap and the metal sleeve, no contact is made.
I finally got them to work by 1) seating the fuse completely in the holder (not the cap) 2) pressing the sleeve into position around the fuse and 3) fastening the end cap with spring inside. I can't imagine that this was how they were designed to work. And, of course, the springs have an annoying tendency to fall out of the end caps.
My conclusion was that these were an attempt at a clever new fuse holder design, but I've never had this much trouble with one in all the years I've been working on electronics.
These holders are snap-in types with a metal sleeve that fits over the fuse and a spring in the end-cap. I think the idea was that the spring presses the metal sleeve and spring against another contact inside the holder. The problem seems to be that if there's ANY binding between the plastic end-cap and the metal sleeve, no contact is made.
I finally got them to work by 1) seating the fuse completely in the holder (not the cap) 2) pressing the sleeve into position around the fuse and 3) fastening the end cap with spring inside. I can't imagine that this was how they were designed to work. And, of course, the springs have an annoying tendency to fall out of the end caps.
My conclusion was that these were an attempt at a clever new fuse holder design, but I've never had this much trouble with one in all the years I've been working on electronics.
Comment