Hi AL666,
You may have already cured this but heres an answer. I have already sent an email to the designer of that circuit showing how to correct his design, it was due to a mix up of pins I think, hopefully he should amend his posting soon. Anyway back to your problem, heres the answer.
The way the relay is wired ( where b1 and b2 are the "arms" of the relays, as shown in the photographs) poses a problem. On the diagram for the double pole relay, if output from the Digidoc5 is off, then b1 (arm) would be connected to d1 (normally closed) and also b2 (arm) would be connected to d2 (normally closed). This would allow 7v (ie. 12v - 5v = 7v) to flow back into the Digidoc5 outputs, which may do harm. The fan would also
only be ON when the relay was activated by the Digidoc5 with 12v only.
To cure the problem:
a1 (arm) should be connected to c1 (normally open);
a2 (arm) should be connected to c2 (normally open);
the fan connection c1 should be on b1;
the fan connection c2 should be on b2.
The output you have blown on the Digidoc5 may be corrected, I think. I have not got a Digidoc5 yet but will in the near future. Devices like these usually have a switching component like a power transistor to control the output. Basically examine with an ohmmeter, with the Digidoc5 removed, each of the output circuit components near the output lead, comparing results between the different outputs. Each output should have identical readings. A component with an unusual value is most likely the cause of the problem.
Hope this posting is of use to you and anybody else.
