CPP 2 Temp Control

[pdt1pdt1]

I recently took my old processor out of the basement – it has been about 10 years since it was last used and I was excited to get my darkroom working again. When I filled it with water and tested it, everything seemed to work perfectly; LEDs lit up, the pump turned on, and the motor rotated and reversed direction perfectly. I checked the LED temperature display against a thermometer and it was spot on. I dialed in the set point at 30 C and waited to see if the heater still worked. 20 minutes later, the water had warmed from 20 C to 30 C. Great, I thought, but then the water temp just kept climbing – it had reached 35 C when I finally gave up and turned the power off. I have since taken the cover off of the electronics to see if there is any fuse blown or any signs of corrosion on the circuit boards, but everything looks clean and neat. I checked all of the wires and made sure all the connections were good. I reassembled and retested but found the same problem – the unit would heat but not hold the dialed in set point. After the water had heated up and I turned the dial down far enough, I could hear the heating element click off, and the temp would stop climbing, so the on-off circuit works. It just seems like the set point from the dials is not being read correctly. Is this a problem anyone has run across? If so, is it fixable? Thanks.

 

[jp80874]

Are you developing color or B&W? Do you need temperature control? I know it is nice to have everything working, but if not needed it may be very less expensive to do without. I have been developing B&W sheet film for five years and have never turned on the heat in my CPP-2. I fill the tempering tank with water just above the temp I want and it holds close enough for the five minute prewash, five minute Rollo Pyro developing time and five minute fix. It begins to cool off during the ten two minute wash changes but the water added is at temp. I developed 250 sheets of 7x17 and 100 sheets of 8x10 this past year.

John Powers

 

[fotch]

Have you tested to see if it reaches X temperature and then maintains it? Or will it reach boiling temperature? If it maintains a given point, you may be able to recalibrate your dial.

 

[eddie]

I don't know if this will help, but it seems to be heating faster than normal. Mine takes about 40-45 minutes (when full) to heat that much. The manual states that it takes about 1.25-1.5 hours to go from 20C to 38C. 20 minutes seems too quick.

 

[Paul Armstrong]

CPP2 Temp Unit Avail

I recently took my old processor out of the basement – it has been about 10 years since it was last used and I was excited to get my darkroom working again. When I filled it with water and tested it, everything seemed to work perfectly; LEDs lit up, the pump turned on, and the motor rotated and reversed direction perfectly. I checked the LED temperature display against a thermometer and it was spot on. I dialed in the set point at 30 C and waited to see if the heater still worked. 20 minutes later, the water had warmed from 20 C to 30 C. Great, I thought, but then the water temp just kept climbing – it had reached 35 C when I finally gave up and turned the power off. I have since taken the cover off of the electronics to see if there is any fuse blown or any signs of corrosion on the circuit boards, but everything looks clean and neat. I checked all of the wires and made sure all the connections were good. I reassembled and retested but found the same problem – the unit would heat but not hold the dialed in set point. After the water had heated up and I turned the dial down far enough, I could hear the heating element click off, and the temp would stop climbing, so the on-off circuit works. It just seems like the set point from the dials is not being read correctly. Is this a problem anyone has run across? If so, is it fixable? Thanks.

My drive unit failed a while back so my Cpp2 is toast. It's an older model 1984 that was never used as it was a backup for my King Concept Image Maker that has continued to work all these years. I fired it up to use the special sheet film tubes(Pro) and found the drive unit not able to turn the drum. A new drive won't fit, they changed the design. You are welcome to any parts you need. I was going to see how they fit in a trash can.

 

[Neal]

Dear pdt1pdt1,

If you are handy, an industrial temperature controller and relay can be purchased off ebay for less that $50.

Neal Wydra

 

[Nicholas Lindan]

After the water had heated up and I turned the dial down far enough, I could hear the heating element click off, and the temp would stop climbing, so the on-off circuit works.

An easy-to-fix possibility is that the potentiometer for the temperature set-point has gotten corroded/noisy. Try spritzing in some contact cleaner (also known as 'tuner cleaner' from the days TV's had click-dial tuners). It is available from Radio Shack. Get the plain & cheap stuff. Don't bother with any of the fancy 'audiophile' brands - they are nothing more than a snake oil ripoff in league with $100/foot speaker wire.

Another fix, even cheaper, is that if the unit holds temperature with the dial turned all the way down use the unit with the dial turned all the way down.

The most common failure is corrosion in the RTD/Thermocouple and/or it's associated wiring.

 

[Mike Wilde]

Nicholas is on target with his advice.

If it is a toast controller, and not the Resistor, Temperature Dependent or thermocouple, I have a few temp controllers to spare from when I rehabbed my Fujimoto CP31. Email me if they are needed. They will need a relay to control any heating load

Test a RTD by connecting a potentiometer in its place, and see how the control circuit reacts.

Test a thermocouple by disconnecting the wires at the board, and see if there is any lead in to spare cutting an 1.5" piece off, twisting it together and then re-connecting the stub. Then see how it reacts to body temp (in fingers) etc.

If either scenario causes the temp controller to act sensibly, then replace the temp sensor. They are not impossible to hand fabricate - look at automotive room temperature vulcanizing (RTV) silicones.

Good luck

 

[pdt1pdt1]

CPP 2 Temp Quick Fix idea

An easy-to-fix possibility is that the potentiometer for the temperature set-point has gotten corroded/noisy. Try spritzing in some contact cleaner (also known as 'tuner cleaner' from the days TV's had click-dial tuners). It is available from Radio Shack. Get the plain & cheap stuff. Don't bother with any of the fancy 'audiophile' brands - they are nothing more than a snake oil ripoff in league with $100/foot speaker wire.

Thanks for the contact cleaner idea - I'll pick some up after work and give it a try.