Jobo CPP2 Motor Problem

The motor on my early CPP2 with lift seems to be dying and I am wondering if (a) this is truly a motor issue and (b) what my next steps should be.

I was preparing yesterday to develop film and noticed that the motor wasn't turning. I took it apart and cleaned the contacts on the rocker switch with paper towel, reconnected a wire to the motor that looks like a ground, cleaned the contacts around the fuses ,and inspected the rest of the unit. This is a second hand unit and only my second session with it but I could tell that there was a lot of white crud around the circuit contacts. I assembled the unit and all seemed well until this afternoon.

I've looked at the white cog that is between the main cog and the drum and it does have packing grease. It does not wobble when I touch it but does oscillate slightly when engaged to the main cog. I can spin it easily with my fingers.

The motor seems to have lost torque or power. I was using a 2521 drum with 560ml of developer when it started to loose power and eventually stop. Even with the rocker switch disengaged the drum would rotate a couple of revolutions and then stop. If I pushed lightly on the drum it would start to rotate again. It is more prone to stop at lower speeds like F than at higher speeds like 7. The motor will run and run so long as a drum is not attached.

Any help would be appreciated. Thank you!

I use Dave & Norma C. Smith for Jobo parts and service. The web page is http://www.darkroomdoctor.com/ . Norma is also a member of the Freestyle1 Advisory Board of Photographic Professionals [url]http://www.freestylephoto.biz/board.php [/URL]. There email address is joboman@aol.com.


1FreeStyle is an APUG sponsor.

Are the motor brushes OK?

I haven't removed the motor to look but if others think this sounds like a motor problem rather than a control board problem, I'll take it out and look at the brushes and gearing.

SMBooth said:

Are the motor brushes OK?

Click to expand...

I pulled the motor after verifying that the problem wasn't with the expansion ring that holds the main cog on.

The brushes have about 1/4" left on them ahead of the lead: I don't know if this is good or bad. The gearbox looked clean-ish to me: wine-colored grease the consistency of petroleum jelly, not too discolored with metal particles.

Here's a photo of the motor before I got greasy taking it apart. It's marked at manufactured in 1984 and is 24v.

Folks haven't been very helpful so far but I'll do my best to document this so that it may be helpful to others.

I had the motor looked at by a service that repairs small DC motors and the motor is in good shape: the brushes are long, the commutator was fine, it passed the "smell test", bearing were good, and the gear box was indeed clean. So the motor wasn't the problem.

I cleaned the contacts to remove oxidation, even on the board, using DeoxIt D5. I tested the voltage at the motor contacts and they read 21v-5v depending on the motor speed. I connected the motor and it ran stronger than ever! This time I could not stop it with my fingers.

The next problem is that the main cog: the motor shaft spins easily inside the expansion bushing that couples the cog to the shaft. This could probably be fixed with JB Weld but I am investigating different options.

I don't think "expansion bushing" is the right term. Maybe "collet" is the better one.

AgX said:

I don't think "expansion bushing" is the right term. Maybe "collet" is the better one.

Click to expand...

You're precisely correct. Thank you!

I installed a new collet and and cog. That did the trick.

What did you consider the the motor being faulty in first case? I mean before you inspected the brushes you must have seen that it was running (and not losing torque under ballast). Thus the fault must have been at the gear or further up.

AgX said:

What did you consider the the motor being faulty in first case? I mean before you inspected the brushes you must have seen that it was running (and not losing torque under ballast). Thus the fault must have been at the gear or further up.

Click to expand...

Initially the motor would stop under ballast. If I removed the cog, I cog easily stop the motor by pinching the motor shaft with my thumb and forefinger. On the advice of multiple people I decided to inspect the motor. While the motor was out I also inspected the circuits and observed that there was a lot of corrosion on some of them. I cleaned these with Deoxit, reassembled the motor and wired it back to the board. At this point I observed that the motor was considerably stronger, that I could not easily stop it with my finger and thumb. It was clear that corrosion was the primary problem.


With the motor working stronger than before I was able to observed that the main cog did not have a strong bite onto the motor shaft. It would spin freely after applying moderate friction. The cog had a hairline crack in it and the collet was loose. The loose collet was the hardest component to observe since it is hidden behind the cog. This secondary problem with the loose collet resolved the entire issue.

Now I see. The motor working strangely sure was puzzling. I never experienced such motor behaviour. They either worked properly or not at all.

Good that by cleaning the circuit and exchanging the collet you got it working again.

Baisao said:

I installed a new collet and and cog. That did the trick.

Click to expand...

I am glad that you quickly found success. Enjoy the Jobo system.

I had a similar problem wouldn't spin a 2500 series drum, but motor ran OK, mine was as simple as tightening the slotted screw that puts tension on the brass collet that holds the main (Black) drive gear to the straight motor shaft. It was weird only turned about a 1/4 turn but that was enough. (SOUNDS LIKE YOU ELIMINATED THIS ) Next problem I had was the motor speed control switch fell apart. Catlabs has a replacement switch, that will work, my unit was made in Nov. of 93.
Good Luck.
Mike

Duolab123 said:

I had a similar problem wouldn't spin a 2500 series drum, but motor ran OK, mine was as simple as tightening the slotted screw that puts tension on the brass collet that holds the main (Black) drive gear to the straight motor shaft. It was weird only turned about a 1/4 turn but that was enough. (SOUNDS LIKE YOU ELIMINATED THIS ) Next problem I had was the motor speed control switch fell apart. Catlabs has a replacement switch, that will work, my unit was made in Nov. of 93.
Good Luck.
Mike

Click to expand...

I didn't go to the end here sounds like you worked it through! Good Deal!

Duolab123 said:

I had a similar problem wouldn't spin a 2500 series drum, but motor ran OK, mine was as simple as tightening the slotted screw that puts tension on the brass collet that holds the main (Black) drive gear to the straight motor shaft. It was weird only turned about a 1/4 turn but that was enough. (SOUNDS LIKE YOU ELIMINATED THIS ) Next problem I had was the motor speed control switch fell apart. Catlabs has a replacement switch, that will work, my unit was made in Nov. of 93.
Good Luck.
Mike

Click to expand...

Welcome to APUG