QMS DRO went flakey

Is it the scale or the readout? (ie. if you swap scales will the problem follow the readout or the scale)?

Next thing to check is connectors and cables.

Then, if it's old enough (say > 10-15 years) the power supply.

Best regards, Spehro Pefhany

Have you checked for dirt or other obstruction of the scale's read head? The scales are remarkably tolerant of grunge, but there is a limit. I had a similar problem recently which turned out to be a ripped seal on the scale. The dangling end would occasionally flip up inside and, I assume, get between the light source and the scale.

I swapped scales this morning and it hasn't done it again so far. Leaving it on all the time helps too.

Like i said, happens just often enough to drive me nuts.

Karl

Indicates possible thermal expansion of a solder joint or component...oftentimes, you can poke around with toothpick or something to locate the culprit.

Beware of switching power supplies, they can produce a fairly nasty shock.

Maybe a bad contact then!

Hairline thermal stress solder fractures around component leads are fairly common. Back when I helped a friend at his repair business any Sony receivers that came in for repair automatically got a manual resolder at all points (heat and add a bit of fresh solder) as that was by far the most common failure. If you looked under a good magnifier you could see the circular fracture around the component leads.

Wave soldering is notorious for leaving cold joints, especially at any point where fairly large components are mounted, things like cable headers, rheostats and so forth etc.

Reason being, the molten solder is not in contact for a long enough period of time for the leads to heat up sufficiently.

It appears that QMS was bought.

Kevin Gallimore

Thanks, everybody for all the suggestions. I also found a fella that used to be their repair tech. He emailed an encoder calibration procedure, suggesting they may get off after a long spell.

Don Foreman just got invited out for dinner.

Karl