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Lisa horizontal video smearing

Forums > Vintage Apple > Lisa & Macintosh XL

Elemenoh
Active Tinkerer
Bay Area
--------
Joined: Oct 18, 2021
Posts: 428
Likes: 415
Apr 15, 2025 - #1
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:
Attachments:
IMG_3333.jpeg [View]
IMG_3575.jpeg [View]

Liked by _nec6678

Stephen
BetterBit
San Francisco
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Joined: Sep 5, 2021
Posts: 215
Likes: 264
Apr 15, 2025 - #2
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
Active Tinkerer
Bay Area
--------
Joined: Oct 18, 2021
Posts: 428
Likes: 415
Apr 15, 2025 - #3
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.

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