Jobo CPP-2 malfunction

Discussion in 'Darkroom Equipment' started by arigram, Jul 14, 2008.

  1. arigram

    arigram Member

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    I think the tempering part of my Jobo CPP-2 is busted.
    I've noticed that lately it doesn't seem to warm up the water.
    Anything I can do to fix it?
     
  2. snallan

    snallan Member

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    Has the thermal overload circuit breaker cut out? If you look at the outside end of the control head, at the bottom and just about central on the head, there is a little recessed white button. Try pushing it with a blunt object, and see if the heating circuit works again.

    If that does not work, it may be that the temperature circuit fuse has blown. Jobo have an online manual containing a description on replacing the fuses.
     
  3. Frank Szabo

    Frank Szabo Member

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    While it's not exactly a "fix", I had intended to make a tempering bath using a small circulatory pump and an aquarium heater.

    A suggestion if all else fails.
     
  4. arigram

    arigram Member

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    Thank you Steve, I will take it apart one of these days and see what I can do.
     
  5. arigram

    arigram Member

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    So, I got down to opening the Jobo.
    Man, its not that easy, but its doable.
    Here are some photos for those who would like to see the insides of a CPP-2.
    The fuses don't look blown. I am not that experienced, but should they look "blown", black and everything? For what's worth, the thin wire inside each of them looks intact.
    I think I have more serious problems:
    I've found one of the chips, the one under the top right knob to have been dirtied by chemical spill and what appears like rust, so did a couple of... (well, I don't know what they are called!) balloon like little thingies close to it.
    Is the chip gone to meet its maker? Can I clean it?
    Maybe the problem is elsewhere.
    The manual says that if the temperature fuse is blown, the LEDs wouldn't work at all, but they do in my case.

    Damn, I hope I don't have to send it to Jobo in Germany... do they still service the rotary processors?
     

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  6. glbeas

    glbeas Member

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    Yeah ,that corroded spot looks like a killer! You might try to get a computer tech to look at it and see if the chip can be cleaned and resoldered but odds are the circuit may have shorted when it got covered in chemicals. Good luck!
     
  7. arigram

    arigram Member

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    So do you think its fixable if its cleaned or does it have to be sent to Germany to have the chip replaced and whatever else it needs? The LEDs work, the thermometer works, the pump and the rotor works, only the heating element doesn't.
     
  8. glbeas

    glbeas Member

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    The chip may have been part of the control circuit for the heater, no way to tell without a schematic. That much corrosion can cause cross circuits and open circuits if it eats the copper away from the chip leads. A competent and creative repair tech would need a good look to know. Usually they will tell you to replace the board, which may not be a bad option to do yourself if you can get Jobo to send you one. Have you tried contacting Jobo to see about parts availability?
     
  9. hka

    hka Member

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    You can better take contact with this man because he does all the repairs for Jobo Germany.
    http://www.fotolaborservice.de/
     
  10. arigram

    arigram Member

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    Thank you.
    I have sent an email with the close up photo to both Jobo and Mr.Seynsche.
    It comes in a bad time when I need the jobo because I shoot a lot and need to be able to develop a lot of film as conveniently as possible. With hand tanks, I can only do four rolls of 120 at once and of course its more work. At least I can use the rest of the machine and because its summer, I don't need the warming function yet.
     
  11. glbeas

    glbeas Member

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    A good thermometer and a handy hot water tap and you can keep the processes pretty close. The tanks are pretty good at holding temperature for the short times the developer will be in them.
     
  12. Frank Szabo

    Frank Szabo Member

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    Ari - these blasted little chips, for all the PITA they are, are sealed. Nothing can get inside (at least not photo chemistry - anything that would melt that plastic would destroy your CPP). Perhaps a short as the liquid does appear to have run between the components.

    I'd be more worried about the components in the far-left of your red circle. It certainly looks as though the magic smoke has been let out of those with all the apparent discoloration.

    (a couple hours later) Looked at the catalog of the electronics supply outfit I normally use (Mouser Electronics, Texas, USA) - The IC chip is a voltage comparator and they sell them for $1.23US singly.

    The blue critter appears to be a tantalum capacitor - from your description it is a 6.3wvdc and 10%tolerance of value but can't tell anything else from the numbers. About $1.25US

    The yellow guy may be a resistor. If there's voltage sensing going on (the IC voltage comparator), this may be to drop voltage to an acceptable voltage level running the IC with the blue capacitor in parallel acting as a ripple filter.

    Your friend at Tech may be your best way out - as the other fellow said, he can trace the circuit and check the in and out voltage of the resistor (if that's what it is) and figure the value that's supposed to be there rather easily.
     
    Last edited by a moderator: Jul 20, 2008
  13. arigram

    arigram Member

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    Yeah, temperature control is not a big problem, especially since my times are usually under 6 minutes and I have an air conditioner right above the Jobo. Lowering the temperature of the water is a -lot- more of a hassle than warming it up and keeping it there.
    The thing is that if I need to send the machine or the circuit back to Germany, that means that for a considerable amount of time I would have to do without it, old skool dev-ing!

    Yes, you are probably right Frank.
    I have already contacted a friend who works in the Institute of Technological Research of Crete (kinda like our own MIT, one of the top in Europe) and told him about my problem and he will take it to one of the technicians there to take a look at it.
    I was wondering, if one can replace the chips, if needed, by ordering replacements from somewhere. I am sure an electronic technician can replace those bulbous components which seem much more common.
     
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  15. tim_walls

    tim_walls Member

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    I can't quite read the marking from your photograph, but it looks like a 74 series logic chip - look for a number starting something like '74LS...' to identify it.

    In any event, if it is 74 series logic, it will cost literally pence to replace; although I'd concur that the chip itself is unlikely to be damaged, it's more likely to be a pin corrosion problem. In any event, if you can find someone with basic soldering skills and a decent parts tray, they should be able to eliminate the possibility that chip is a problem in a matter of minutes.

    (Even if it's not 74 series, it is 99% certain to be a standard part not made of unobtainium, and should be reasonably easy to replace.)


    The 'bulbous component' looks like a tantalum capacitor; given its location it's probably a decoupling or smoothing capacitor used to eliminate ripple from the power supply to the chips; again, the component will be pence to replace (and in fact there's a good chance the board will work fine without it, although you'd not exactly recommend that as good practice :wink:.)
     
  16. arigram

    arigram Member

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    Allright then, we are getting somewhere!
    Tim, if you are interested, the writing on the parts is:

    Chip: 23AY35M, SN74LS85N
    Yellow Capacitor: K1K
    Blue Capacitor: +10, +6.3V

    I did a test and plugged it in, being careful for the heating element not to touch anything. I twisted the first knob where 3 should be (for 30 degrees) and noticed two things:
    - The heating element doesn't seem to get warmer
    - There is a component in the board that looks to have some sort of enclosed in plastic switch of two parts that come together or separate with a click when the temperature knob is twisted in certain parts. I am not sure what it does exactly though, nor did I notice any difference in the heating when it was closed or opened.

    The thing is... what if that's not the problem?
     
  17. glbeas

    glbeas Member

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    Sounds like the control circuit is working, thats a relay you are looking at. Seems the power to the heater or the heater itself is at fault.
     
  18. arigram

    arigram Member

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    So, the chip and capacitors are ok then?
    What should I look for?
    The rest of the circuit looks fine (for a layman).

    Funny, but I even thought that maybe the first knob doesn't point to 30 or 20 degrees which means that the thermometer (which is working fine along with the LED display) wouldn't let the heating element work as the ambient temperature is above twenty degrees celcius.
     
  19. glbeas

    glbeas Member

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    Final cut- let your friend at the Institute check it out with a meter. That person should be pretty familiar with circuit tracing and should be able to pinpoint where the power disappears.
     
  20. hka

    hka Member

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    Try to use some contactcleaner maybe the pins make contact true the corrossion.
     
  21. Steve Smith

    Steve Smith Subscriber

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    If the relay is clicking on and off when you twist the temperature control either side of ambient room temperature then the heat sensing and control circuit is working. It is more likely that the heating element itself is broken. Someone with a multimeter should be able to tell you if it has gone open circuit.

    I have a CPP-2 in my shed which is just gathering dust and I don't expect I will ever use (I think it's a CPP-2, I will check when I get home). If you can determine what part is broken you are welcome to have that part from mine and/or any other circuit boards and parts for spares.

    Another option for temperature control is to get something like this: http://www.screwfix.com/prods/61083/Plumbing/Central-Heating-Controls/Danfoss-ATC-Cylinder-Stat# from a plumbing supply store and fit it to the outside of the tank. Use it to control the heating element via a relay or if your element is broken, perhaps a submersible heater possibly from an aquarium supplies company. Be sure to get one that goes down to 20 degrees c though. As they are intended for domestic hot water clamped to the outside of the hot water cylinder, some of them start at 40.


    Steve.
     
  22. tim_walls

    tim_walls Member

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    If the relay turns on/off as you adjust the target temperature setting, the chances are high that the circuit is working (you would expect the point at which the relay flips to be around the current ambient temperature - i.e. if the water is currently at 21 celcius, you'd expect that the relay would flip as you move the target temperature setting past 21C.)


    For what it's worth, the chip you identified - a 7485 - is a 4-bit comparator; this is, it compares two digital numbers and outputs an indication of which is higher (or if they are equal.) It very likely is a part of the thermostat circuit, therefore (the output of the comparator would be what turns the relay on/off to turn the heater on when the sensed temperature is less than the set temperature.) If the relay isn't behaving as described above, then this chip is therefore implicated; it sounds more likely though that it's all working as intended from what you describe.


    In which case, if the relay is operating correctly, that more or less leaves the heating element, which is sad - if the element is buggered you're going to need Jobo to provide the replacement.

    As far as I know (I have a CPE rather than a CPP, but I assume the element is the same) the element is of the nichrome-heating-wire-inside-a-ceramic-pipe variety. The two main failure modes are the heating element breaking, or the ceramic cracking.

    Presumably, the ceramic hasn't cracked. If it had, the earth-leakage circuit breaker (which you do use, I hope) would trip as soon as the heating element turns on. A cracked element means the water in the bath is connected to the mains when the heater turns on (if the appliance wasn't connected to earth for some reason, this would make it a real hazard) - an RCD/GFCI breaker will detect this as earth leakage and trip.

    If the wire has just broken, there's not a lot you can do other than replace the element though :-(.


    There is some good news though:
    A fault with the heating element is easy to diagnose for anyone with a multimeter. With the element disconnected, use the resistance checker to check continuity through the element (there should be a high resistance, but not open circuit.)

    To check for a crack in the ceramic, fill the bath with water and then check resistance from the heater element to the outer layer (which is normally earthed.) It should be open circuit if the ceramic isn't cracked.

    There may be some other components in the heater element circuit other than the relay and the element itself; there may be a separate fuse for the heating element, there may also be a thermal fuse which will blow if the thing has ever overheated (e.g. by being operated with no water in the bath,) it could even just be a loose wire. So don't panic yet :wink:.
     
  23. tim_walls

    tim_walls Member

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    Oh, incidentally, in the unlikely event that the 7485 chip is buggered, it costs less than 50 pence and is readily available - I probably even have one in my parts tray I can send you if you need one in case it's tricky to get hold of in Crete.
     
  24. arigram

    arigram Member

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    I just got word that the technician is on vacation.
    I also got an email from the German technician with his address to send the jobo too.
    I think I might wait a bit, to finish a couple photoshoots I have planned and either try the local guy or send it over to Germany. Since its just the heating, it can wait.

    Thank you Tim for all the detailed description.
    Are you an electronics professional? Because it looks like you're having fun fiddling with it. :smile:
     
  25. tim_walls

    tim_walls Member

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    Ha, no, just a hobbyist - although I used to write embedded software back in the day when programming was a skill and understanding the hardware was considered an advantage (just throwing a faster processor or more memory at your bad code is not an option when your processor has a princely 256 bytes of internal RAM and you've run out of IO pins to attach any more...)

    I still keep my hand in by designing/building microcontroller boards and keep old computers (I have a DEC PDP-11 which has sadly been in storage too long waiting for me to move into a bigger house...)


    The problems people keeping older computers and electronics up and running face are not dissimilar from the problems people face keeping 'old' photographic techniques alive; parts are hard to find if not unobtainium, information is locked up in company research libraries if it hasn't been lost completely, and the general knowledge just seems to be rarer and rarer in an age where 'repair' means 'replace entire boards until the thing seems to work again'. Thank God for the Internet - APUG and its equivalents are a godsend for making sure the information that is out there doesn't get lost forever.

    (Err, sorry, started rambling there...)
     
  26. Steve Smith

    Steve Smith Subscriber

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    Further to my previous post: The processor I have in the shed is not a CPP-2 but is a CPE-2 Plus. However, I assume that the heater and its controller are similar, if not identical.
    If you want any parts from it you are welcome to them.

    Steve.