🚀 go-pugleaf

My Mac-128, upgraded with new roms, 2Mbyte, and a SCSI port (both from Levco)
exhibits a strange hardware problem.

Occurence:
	The Mac is functionally correct, but has vertical, thin, equally spaced,
	lines accross the screen, which originate on the top and descend from
	barely noticible to the full length of the screen. The length of the
	lines varie when the floppy, or harddisk is active. There are
	approximately 2 to 3 lines centimeter

History:
	First occurence is in the summer of 1986, and it only happens when the
	Mac is cold. Generally after 5 minutes the problems disappear.

	Over the year the problems become slightly worse, and in the summer
	of 1987 the occurences are much more serious (the lines are longer), 
	it takes longer before they dissapear, and sometimes don't disappear 
	at all.

	December 1987, the Mac becomes close to unworkable (the lines run from
	top to bottom and make the characters on the screen unreadable).

	December 1987, the Mac is moved from the US to Europe and now runs
	on 220V (via a transformer) and 50Hz. The Mac still functions
	but is unworkable, and is brought to a Mac repair shop.

	The Mac is repaired: the flyback, the picture
	tube, and deflect unit are replaced, and the power supply (the
	original (128k) one) is repaired.

	A couple of days later the problem reappears and now includes high
	pitched noises from within. The Mac is returned, the flyback is
	re-replaced and the Mac works perfectly again (2 days continuous
	in the repair center).

	A couple of weeks later (very light use, a few hours per week), the
	problem reappears. The Mac is returned to the repair center (last
	week) and I am waiting to pick it up.

Question:
	What is the real problem? apparently the problem disappears
	temporarily when the flyback is replaced, but the cause doesn't.
	
	Was it really necessary to replace the picture-tube and deflect unit?

When I get the Mac back from the repairman, I'd like to understand the real
cause to avoid getting screwed.

Any ideas or solutions appreciated.

Hans Mulder
mcvax!dutesta!hansm