On Dec 16, 3:59*pm, "DaveM" wrote:
"Thiemo Nordenholz" wrote in message

- In about 4/5 of all power-on attempts, the display lights up random data
*shortly, then turns dark again.
*The service manual says that this is caused either by the "+5V logic
*supply in overvoltage protection mode"

Sounds like one or more of the power supplies in the unit are haywire. *Have you
checked the power supplies? *Electrolytic capacitors in the power supplies are
always prime suspects.

I second the 'bad capacitors' suggestion. Don't worry about which
ones,
they're all old-ish, just get replacements for the dozen largest
electrolytic capacitors and when the solder's cool, retest the unit.

None of the capacitor values will matter to the calibration, and
the values aren't critical.

Smaller aluminum electrolytic capacitors, distributed around
the logic circuitry, are also subject to age, and if you feel
inclined to do so, it won't hurt to replace them all.