EPC 902S missing output (voltage or current)

Greetings
J have EPC 902S controller. I have no DC sognal (voltage or current) on outputs A2 and A3.J have oreginal usermanu.J tried everything that is written inside, described and suggested but no positive result.J opened and checked the hardware module for DC voltage but it looks quite straight.J need help or idea what to take it further.

Thanks a lot
Alexandar
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  • Bob Anderson (Technical Support Engineer) February 26, 2014 13:58
    Hello Alexandar,

    It appears you have a hardware failure with the DC output card.

    This will need returning to your local Eurotherm Service Repair Centre.
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  • Thanks for the answer.
    Bad thing is that J have not Eurotherm Service Repair Centre in my neighborhood. J have sufficient knowledge, experience and practice specifically for hardware services but sometimes it is necessary to consult with someone. On the DC output card J detect a portion of the output with transistor 3B (BC846), which certainly does not work correctly, but I can not understand how this part works correctly.Here really J need help from someone who knows more about this part.
    If you have a good suggestion for assistance J will be very grateful.

    Thanks a lot
    Alexandar
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  • Bob Anderson (Technical Support Engineer) February 27, 2014 16:57
    Hello Alexandar,

    Due to the age of the controller electrolytic capacitors can sometimes dry out,
    may be it is worth trying to replace these.
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  • The scheme is hand made.It is 95% of the DC output section.It is downloaded from a PCB.The electrolytic capacitors is ok. The problem I see in the lower right corner on the transistor 3B (BC856).On its collector is amplitude of 8Vpp.After the resistor 104 J have only 2Vpp amplitude.It remains the same in all circumstances.Even to cut a line which goes to pin 10 of the CD4013, amplitude remains the same.This level of 2vpp can not affect the pin 10 of the CD4013 (reset pin). But if pin 10 of the CD4013 freely switched between GND and VCC output voltage appears between 0 and 10Vdc, depending on the frequency of the oscillations.With the exception of resistors, capacitors and rectifiers everything else has been replaced with a new parts.Obvious that the information from the previous section are transferred by changing the frequency or changing duty cycle or some type of phase shift.But I really can not understand how work the section with transistor BC856 (3B).On the other hand at the entrance of DC PCB (that is not the pattern) there is a clear command rectangular signal with a constant frequency that does not change with the change of temperature. I have no idea what else to do.

    Thanks a lot
    Alexandar
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  • Bob Anderson (Technical Support Engineer) February 28, 2014 08:43
    Hello Alexandar,

    For your info,

    The 818 controller maintenance manual has the circuit diagram and description of the DC output brd which may help you, link below.

    http://www.eurotherm.com/downloads/do...
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  • Thanks a lot.I hope this will help me. I'll try something later this evening.
    Greetings Alexandar
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