W
William Sommerwerck
I'm new to this group. I'm a BS EE who's serviced electronic equipment most
of his life, so don't hesitate to get as technical as you like.
When I reviewed the NAD MR-20 for Stereophile 20+ years ago, I was so
impressed I bought one. It's given me yeoman service; I suspect it has 20K
hours on it. Until now, the only problem was some bad electrolytics on the
video driver board.
The current problem is intermittent loss of brightness accompanied by loss
of focus. Adjusting the Screen and Focus controls improved things, and
removing the back greatly reduced the frequency of the problem (presumably
because the set runs cooler).
This might be the CRT, but I suspect it's the HV rectifier. (Tapping the
neck of the CRT has no effect, but that's not a definitive test.)
The problem is that the HV rectifier appears to be potted within the flyback
transformer assembly. The transformer is no longer available (nor is the
CRT). Before I yank the transformer (it's not easily removed), I need to
know whether the HV rectifier is accessible. And, of course, I'd appreciate
_any_ thoughts on servicing this set.
Thanks in advance.
of his life, so don't hesitate to get as technical as you like.
When I reviewed the NAD MR-20 for Stereophile 20+ years ago, I was so
impressed I bought one. It's given me yeoman service; I suspect it has 20K
hours on it. Until now, the only problem was some bad electrolytics on the
video driver board.
The current problem is intermittent loss of brightness accompanied by loss
of focus. Adjusting the Screen and Focus controls improved things, and
removing the back greatly reduced the frequency of the problem (presumably
because the set runs cooler).
This might be the CRT, but I suspect it's the HV rectifier. (Tapping the
neck of the CRT has no effect, but that's not a definitive test.)
The problem is that the HV rectifier appears to be potted within the flyback
transformer assembly. The transformer is no longer available (nor is the
CRT). Before I yank the transformer (it's not easily removed), I need to
know whether the HV rectifier is accessible. And, of course, I'd appreciate
_any_ thoughts on servicing this set.
Thanks in advance.