Recent Surgery - JOBO CPP2

[Ed Sukach]

In operating my CPP-2 processor ... a disaster! The tank rotation motor only rotated one way ... when it came time for the tank rotation to reverse itself and rotate in the other direction .. nothing! The motor would only stop. Manually operating the cam follower, I could only get the motor to rotate in ONE direction.

So here I go - back to my old "Technician Days".

First "pull the plug" That I remembered. Electrical fireworks and sundry electric "wake-up calls" are really never forgotten. Next, remove the Processing unit from the "Water Bath" section. Then gingerly - a gingerly as possible, remove all six screws keeping the Upper Cover on the Main Frame - Oops! Remove all the knobs. Gently (as gently as possible - really not very) pry the cover off, releasing it from a whole lot of waterproofing compound - remove sundry bolts holding the Rotation Motor in place - as necessary.
I identify an ingenious "Contact Array" activated by a nylon cam. Remove the Cam (a struggle in itself) and try to clean the contacts in place. That done, re-assemble everything - and -- nothing. Still rotates in only one direction.

So - the next day, repeat the disassembly process, this time "dismounting" the Contact Array for better access and cleaning. Remounted it - tried activating manually, with the cover off. Still not fixed. In that process, noted a visible motion through the transparent case of one of the ... RELAYS!

I had forgotten the second Technician's Law, "Try whacking the relays!!" That done ( that IS what screwdriver handles are for - aren't they?) All is repaired!! The processor is now working as it should, reversing the tank merrily.

Twelve (12) hours to remember to whack the relays!

Ah well. I guess I can't complain. Far better than packing the thing up an sending it to ... I know not where, now.

 

[JHannon]

Well done Ed! Some of the clear case "ice cube" relays allow you to open them and clean the contacts. I used to clean them with a small burnishing tool (looks like a small flat file).

 

[glbeas]

In line with Johns observation the contact will lose the heavy metal plating them when they get long in the tooth, I think palladium is one metal used. As this happens you'll get arcing from the metal underneath which will occasionally spot weld things together. You will probably have to whack a relay again later, so if it's convenient you could see if it's a style you can replace without a lot of grief. Once obtained it can be set aside for the next episode and a permanent fix applied.