Jobo CPP-2 malfunction

[eunkefer]

CPP-2 units have two styles of circuit boards, old style – new style, this is the new style. The chip is IC53 on schematics and is a 74LS85N. The chip interfaces the output of the BCD switch (the rotary switch for tenths digital, "binary coded decimal") into the circuits that regulate temperature. From the corrosion in your picture very likely this could be your problem. Inexpensive part but you need a tech that can remove the chip without destroying the circuit board, this type of corrosion can weaken the lands on the circuit board. It should be repairable.

Best regards,

Ed

 

[Raphael]

Refreshing an old thread... Sorry

Hi Ari,

Have you solved your CPP-2 heating problem, since July ?

I run yesterday in the same problem, on a Jobo ATL-1 (which use the CPP-2 as base) before I discovered that the "canceled-hidden-secret" thermal switch went off. It take long minute between the moment when I find the clue on the Net, and the moment I actually discovered the switch...
Of course, I presume you had checked that a long time ago.

Otherwise, as a electric engineer from my student days, I confirm all the things already said, your problem came certainly from the corroded printed circuit board around the 74LS85 IC. This binary comparator checks the consigned temperature against the real bath temperature (binary converted) and order the heating element goes on or off, IMHO.

It's a pity that buttons and human interfaces on these Jobo processor are not really waterproof, and at reach of any corrosive chemical spilled. On my side,
I discovered too traces of chemicals in the electronic head of my ATL-1, but hopefully without impact on PCBs.

BTW, I changed the exhausted Ni-Cd cell used for processing programs backup by a new one (in fact a more current, adapted), and the thing seems to working well.

I am interested of any experience on Jobo fixing and tinkering ;-)

Regards,

Raphael

 

[ic-racer]

Just saw this thread. If you are still working on this, you could try cleaning around the IC chip or just replacing it. Here is the technique I use: http://www.largeformatphotography.info/forum/showpost.php?p=324377&postcount=59

 

[arigram]

I haven't done anything the the Jobo, truth be told.
I was swept into an abyss of personal matters and photography has been put on hold and while I plan to send the machine to Germany every week, I keep postponing it.

Raphael, if you are right, I only need to replace the chips and this is a job that can be done here by a technician and won't need to send it away. Are you sure about it?

 

[Raphael]

Hello Ari,

Raphael, if you are right, I only need to replace the chips and this is a job that can be done here by a technician and won't need to send it away. Are you sure about it?

Sorry, I can't be sure of anything, without the actual schematic, my assertions are just guesses based on the pictures and IC reference.

However, if the technician does a correct job, it won't harm to clean and check this part of your Jobo, given the pictures you'd showed us.
Maybe, it is not the Integrated circuit itself, as said sooner, it's rather hard to die, but certainly the Printed Circuit Board tracks that connect it. Are the PCB tracks look corroded around the 74LS85 chip ? Have you tried to clean gently it and around it ? With isopropyl alcohol, by example. After unplugged it from the outlet, of course !

If you know how to use a multimeter, you can check tracks continuity yourself, starting from the chip pins using the multimeter "ohmmeter" setting. Sorry if I seems to talk chinese, here...

If you are used to work with electricity, with a multimeter, you can even check if the chip does its job, with checking its output going up (about 5v) or down (about 0v)...

The technician can do this for you, an can be a good option. Of course, if he will take big bucks for the work, or if your Jobo is still under warranty, may be the return at Jobo AG will be preferable.

You writed sooner, you heard relay clicking when you rotated the temperature knobs, but was water bath filled ? Because, if you power up your CPP-2 without water, the overwarm of heating element will trigger automatically the "thermal protection switch" off, and the Jobo don't warms water (but all LEDs are still lit) until it's armed on again.

I discovered it a few day ago, when I powered up my ATL-1 without water in it, for testing my CPU battery mod, the thermal protection switch in the CPP2 part goes off, cutting the heating element power, maybe in the 30 seconds...

Don't hesitate to PM me if you have any questions or need help I can bring to you.

Regards,

Raphael