Every vintage compact Mac owner should purchase his own personal copy of the Dead Mac Scrolls. I did.
Okay, I won't be stingy...
Page 65 says:
Symptoms: There is no startup bong. The display is filled with alternating white-and-black vertical bars.
Typical History: The problem occurred right after a disk drive/ROM upgrade or SCSI upgrade.
Solution: Verify that the ROM chips at board locations D6 and D8 are not reversed, backwards, or otherwise incorrect installed.
But the garbage pixels at the right side of the CRT indicates another, separate problem that stems from the Analog Board. It could be a bad ground connection (ground not connected well to the metal chassis), or it could be that the flyback transform had been replaced in the past but the BU406 transistor was not replaced (and needs to be replaced). Even so, the bad ground and bad BU406 tend to produce a CRT right-side "wiggle" (like a worm) rather than garbage pixels (as you photo indicates). Therefore, it could be some other problem, yet a problem that is still somewhere on the Analog Board. You can use your "Macintosh Repair and Upgrade Secrets" book to guide you through various Analog Board tests and repairs to eliminate that.
But first check the ROMs. Who knows. Maybe fixing that will also solve the right-side pixel garbage too.
Okay, I won't be stingy...
Page 65 says:
Symptoms: There is no startup bong. The display is filled with alternating white-and-black vertical bars.
Typical History: The problem occurred right after a disk drive/ROM upgrade or SCSI upgrade.
Solution: Verify that the ROM chips at board locations D6 and D8 are not reversed, backwards, or otherwise incorrect installed.
But the garbage pixels at the right side of the CRT indicates another, separate problem that stems from the Analog Board. It could be a bad ground connection (ground not connected well to the metal chassis), or it could be that the flyback transform had been replaced in the past but the BU406 transistor was not replaced (and needs to be replaced). Even so, the bad ground and bad BU406 tend to produce a CRT right-side "wiggle" (like a worm) rather than garbage pixels (as you photo indicates). Therefore, it could be some other problem, yet a problem that is still somewhere on the Analog Board. You can use your "Macintosh Repair and Upgrade Secrets" book to guide you through various Analog Board tests and repairs to eliminate that.
But first check the ROMs. Who knows. Maybe fixing that will also solve the right-side pixel garbage too.