I acquired an old Jobo CPP2 that I've finally gotten around to repairing. It's an OLD unit (AR 1141) that hasn't had any of the production improvements.
The 2 main problems that needed more than tightening screws to fix were the temperature sensor and the motor reverse. I had imagined all kinds of ways of fixing these before I got serious about troubleshooting, and found that just using a multimeter made diagnosing the problems simple, and the problems themselves were straightforward to fix.
Temperature
For the temperature controller, on power up it seemed OK if not perfectly accurate. After some time, either the temperature display would swing wildly, or it would display the same temperature while the water bath had heated up more than 10C. Taking a multimeter to the temperature control board between R57 and ground as shown in the schematic showed no change in voltage regardless of water bath temperature. I've tried attaching a picture of where I took readings from in case that helps someone in the future.
So the voltage readings clearly said the temperature sensor was bad. The sensor is a 2 wire PT1000 type sensor. I replaced the bad sensor with one purchased off of eBay from seller ganzheitliche-energiekonzepte-shop from this listing: https://www.ebay.com/itm/121532579169. Of course in the process of trying to replace it I made things worse and broke the old and brittle ribbon cable connecting the temperature board to the switch board - oh well, replaced that with some wire I had on hand and kept going. BTW, getting stranded wire through the PC board through holes was a lot easier if I tinned the wires a little first to add stiffness and keep them from fraying/catching. I replaced the sensor following the instructions in the service manual that others have posted, here's an example link: https://silvergrainclassics.com/en/wpfd_file/jobo-cpp-2-service-manual/
I didn't track down the genuine Jobo Isarplast adhesive called for in the service manual, a little reading makes me think E6000 (available at my local hardware store and Home Depot) is a suitable substitute:
The replacement sensor wasn't rigid like the original sensor and I think it was rattling around in the pump housing, so I wire tied it to something rigid (I used an acrylic rod) that I extended through the cap the sensor passes through into the housing and secured on the inside of the CPP2.
From there I followed the reasonably straightforward temperature calibration instructions in the service manual.
Reverse
No amount of fiddling with the chicken foot seemed to have any impact on the unit reversing. I unplugged the switch connector from the switch board (circled below) to troubleshoot it
The switch should always connect the center pin to one of the outside pins. My multimeter showed that wasn't working and that one switch position didn't close any contacts at the connector, and it seemed like one wire had broken at the switch itself in a way that wasn't visible. Resoldering the wire to the switch fixed the reverse problem.
Motor
Since this is such an early CPP2 I've thought about retrofitting some of the factory improvements.
The 2 main problems that needed more than tightening screws to fix were the temperature sensor and the motor reverse. I had imagined all kinds of ways of fixing these before I got serious about troubleshooting, and found that just using a multimeter made diagnosing the problems simple, and the problems themselves were straightforward to fix.
Temperature
For the temperature controller, on power up it seemed OK if not perfectly accurate. After some time, either the temperature display would swing wildly, or it would display the same temperature while the water bath had heated up more than 10C. Taking a multimeter to the temperature control board between R57 and ground as shown in the schematic showed no change in voltage regardless of water bath temperature. I've tried attaching a picture of where I took readings from in case that helps someone in the future.
So the voltage readings clearly said the temperature sensor was bad. The sensor is a 2 wire PT1000 type sensor. I replaced the bad sensor with one purchased off of eBay from seller ganzheitliche-energiekonzepte-shop from this listing: https://www.ebay.com/itm/121532579169. Of course in the process of trying to replace it I made things worse and broke the old and brittle ribbon cable connecting the temperature board to the switch board - oh well, replaced that with some wire I had on hand and kept going. BTW, getting stranded wire through the PC board through holes was a lot easier if I tinned the wires a little first to add stiffness and keep them from fraying/catching. I replaced the sensor following the instructions in the service manual that others have posted, here's an example link: https://silvergrainclassics.com/en/wpfd_file/jobo-cpp-2-service-manual/
I didn't track down the genuine Jobo Isarplast adhesive called for in the service manual, a little reading makes me think E6000 (available at my local hardware store and Home Depot) is a suitable substitute:
The replacement sensor wasn't rigid like the original sensor and I think it was rattling around in the pump housing, so I wire tied it to something rigid (I used an acrylic rod) that I extended through the cap the sensor passes through into the housing and secured on the inside of the CPP2.
From there I followed the reasonably straightforward temperature calibration instructions in the service manual.
Reverse
No amount of fiddling with the chicken foot seemed to have any impact on the unit reversing. I unplugged the switch connector from the switch board (circled below) to troubleshoot it
The switch should always connect the center pin to one of the outside pins. My multimeter showed that wasn't working and that one switch position didn't close any contacts at the connector, and it seemed like one wire had broken at the switch itself in a way that wasn't visible. Resoldering the wire to the switch fixed the reverse problem.
Motor
Since this is such an early CPP2 I've thought about retrofitting some of the factory improvements.
- The transformer seems like a custom transformer made by Marschner that outputs both 12V and 24V, despite being labeled as 10V and 20V. I couldn't find a suitable replacement, and if I could upgrade the motor I would probably use 2 external wall wart style transformers instead.
- The power board didn't change much between old and new versions, and only a handful of components (maybe 6?) were beefed up. If I could upgrade the motor I would upgrade those components.
- The motor in my unit is really integrated into the gear case (see below), and I don't see a way to retrofit another motor without risking destroying the current motor and/or gear case in the process. I'm using 2523 tanks for now and am content with the results so this isn't a major issue, and even a single expert drum would exceed what I paid for the CPP2. If I can find another gear case or motor and gear case in the future I might go that way towards a motor upgrade, though it seems equally as likely that I would find a later CPP2 at a decent price first.
