Electronics > Repair
Fluke PM6666 counter freezing after 3 seconds from turning on.
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FransW:
Pages 30 t/i 35
khs:
Is there an interrupt line from the GPIB board to the CPU??
pizzigri:

--- Quote from: khs on October 08, 2020, 11:59:42 am ---Is there an interrupt line from the GPIB board to the CPU??

--- End quote ---

No, there are only three lines going to the IEC (GPIB) Bus: 5MHz clock, SCL and SDA. Power is supplied via an unregulated 12V, which an LDO onboard the GPIB PCB then converts to 5V reg.
What is interesting, is that the PM6666 has the whole PSU always on, transformer, rectifiers, big levelling capacitors etc; what the power switch does is only to connect the already powered on unregulated rail to the LDOs and the rest of the circuit. So, since the GPIB is powered thru the UNREG rail, it is always on, even if the rest of the counter is "off".
khs:
If you take a look at IC105 (on page 7 of the service manual) the option signal of the GPIB board  (BU102 on page 15) is connected to the interrupt input of IC105.

Is there a way to check (or cut) the option wire?
pizzigri:
Yes I see it, I can monitor the line using the BU102 connector. It’s what I used for I2C anyway since it replicates all lines for diagnosing purposes
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