Common items you passed up that turned rare when you wanted

It's not failing EHT (HV) on its own. That will cause a dim picture, but it'll also cause a large picture (low EHT means the beam is 'less stiff' and is deflected more easily). One (embarassing [1]) cause is notthing more than a dirty screen. Clean it [1] Well, it's embaarassing if you're staring at a 'scope and meter, got the schematics open, etc, and have spent a couple of hours looking for an electronic problem. Other, more serious causes include : Low emission CRT. A CRT of that age might take being 'blasted' if you can find somebody with the right device, or feel like making one (there were plenty of designs in the magazines between about 15 nd 30 years ago) Low first anode (g2) voltage. In monitors that produce this from the EHT by a resistive divifer network it's not at all uncommon for this to fail and lower the first anode voltage. It's often, alas, part of the flyback transformer, and those are even harder to find than CRTs. Incorrect voltage on the cathode or grid of the CRT. Normally the easiest fault to put right (in that it'll be a common small component in most monitors), but the hardest to trace. Power supply problems. A low supply rail to the monitor might cause a dim picture with no other problems. Does anyone have a working monitor of the saem type and suitable test equipment. If so, bribe them (:-)) to measure the supply rails, CRT electrode voltatges, etc. It'll give you something to compare against. I actually do this when I get a new monitor, and write the values on the schematic. Then when it fails I know where to look. If it is a quatrature output mouse, and is TTL levels, then I would think an ST, Amiga, or Acorn Arc mouse could be used with a connector change. -tony