Lisa horizontal video smearing

[Elemenoh]

This Lisa had horizontal video smearing that didn't improve after recap of the video board or power supply.

The culprit ended up being Q2, a D40N2 transistor in the contrast circuit. Fortunately I had a parts Lisa I was able to get another from which resolved the problem.

Unfortunately, D40N2 is no longer made and its pinout is E-B-C which modern parts don't use. I'm still hunting for an ideal permanent replacement. Please LMK if you know of one.

Before swapping Q2:

After swapping Q2:

 

[Stephen]

Have you ever used alltransistors.com? You may be able to find alternatives which are either still made (unlikely) or has NOS. Perhaps a modern transistor could be used with an adapter board.

 

[Elemenoh]

Not that specific site but I’ve been researching substitutes. My plan is to get a more modern part with a B-C-E pinout and just jumper and insulate the emitter.