HH-A-T5 will not lock in place

If after a restart you are still experiencing the failure, it would be a safe assumption that the mechanical lock has an issue and will need a replacement.

OK thanks. Is this a something a competent maintenance person can do? Will the CMM need to be calibrated or just all the probes?

Just the probes.
You want to get the head straight like you would on a star stylus (should be multiple posts about it, including from me... unless that was on other) within whatever range of clocking motion you have, particularly if you use LONG styli. This is a judgement call, you know what you do. I stick a 2mm stylus on a 1.5mm shank 70mm (2 3/4") into holes and don't want to shank. If I only had 20mm styli and the smallest was 4mm on a 1.5mm shank, I wouldn't care in the least how close to square the head was. As is, I'm compulsive about it.

Will the head lock into A90 B90? (you are showing - in front of your 90's so I'm taking that to mean you are at -90 on A and B).

If the head took a hit in one position and buggered the plates up, depending on what went wrong, you may be able to get around that (while you wait for a new head) by using the opposite position.

Just make sure you are moved clear before switching from an A-90 to an A+90.

Ok Thanks. Yes the head will lock in all of the other positions, this particular position isn't used much mostly just when the probe calibrates. The CMM operator skips that position in the calibration so that he can use the CMM. We will see about getting it fixed.

I'm not sure what they call it, but Hexagon has a similar practice to "Repair by Exchange", where, if they have one (a repair unit), they give you that unit while taking your unit as exchange.

Then they replace the one you gave them, and sell it to the next person, and so on.

It is much faster.

You can, I'm sure, have them tear your head apart and rebuild it. Might be cheaper. Will take weeks instead of days.

I think the one time I replaced a Hexagon head I had it in something like 4 days. It has been a few years.

Contact your local rep, they will help you and try to speed it up for you.

Replaced the probe head on our Discovery CMM with the same model that was on the CMM (HH-A-T5​) and now the control box gives me the error code "unlock error switch".
I put the old head back on and the error code went away. We shut everything off and rebooted but still have the error.
Any idea what the problem is?​