[Don Promillo]

My ME super has the bad habit of suddenly underexposing a few frames and then go on to shoot reliable times again.

As far as I have read, there seems to be some contact issue with the ISO dial. But so far, I have not found any instructions how to fix it.

Is there a way to fix it, other than buying another one?

Everything else is working nicely but a camera I can't trust 100% is the one I leave at home.

[RKKS08]

A collection of links for camera repair you can find here:
PENTAX ? MARKUS KEINATH PHOTO HOMEPAGE

The link to disassembling the ME Super leeds to a text version of the instructions written by Gordon Stalker:
How To: Disassemble the Pentax ME-Super Camera - Pick My Camera

Unfortunately, the (better) PDF with the pictured version seems not to be anymore on the net, see also my Post #10 of:
https://www.pentaxforums.com/forums/58-troubleshooting-beginner-help/290681-p...-f-repair.html

If you need it, PM me. I could send it as an eMail attachment. It's somewhere on my hard disks.

[TomB_tx]

Could be either metering wrong, or the shutter timing is unreliable. Most electronic shutters use an electro magnet to hold the closing curtain until the required delay is reached. I've heard of crud buildup making the magnet hold unreliable, which is fixed by a CLA.

[Xmas]

Most likely lube turned to wax on shutter 2nd blind latch.

Send for pro CLA
Attempt yourself
Fire camera 250 times at 1/125
Buy a serviced replacement

A second body is a reasonable option $ wise.

[Don Promillo]

This particular ME Super came as a "lens cap" with a lens I bought on eBay.

It's not really a "valuable" and I prefer the MX when shooting on a 135 film Pentax.
But it would be nice to attempt to save it instead of simply throwing it away. Sending it in for repair is a bit pricey though.

[RKKS08]

@TomB_tx
These 2 causes can be distinguished without opening the camera.

Wrong metering (as the unfamous ISO-wheel issue) will show by the shutter values in the viewfinder. Shutter failure itself (just as a faulty circuit which controls the magnet) will still show reasonable values.

I found another possible glitch:
It seems in the past incorrect shutter speeds were also sometimes caused by a crack in the ceramic plate holding the switches pushed by the exposure speed buttons. I am not sure whether this fault does effect also shutter speeds in Av.

I found with my ME Supers the proof for the ISO wheel issue were unresonable (big) jumps of exposure values when changing ISO or EV compensation values.

EDIT: With my first ME Super the ISO wheel fault showed a short time after using the camera at a coast with very fine sand (which was everywhere in the air).