Re: Firepower resistor value

On Sep 26, 4:42 pm, Chris Hibler <ch...@xxxxxxxxxxx> wrote:
The best way to track something like this down is by using a logic
probe and testing logic-level signals along the path all the way back
to the PIA.

Use your probe, or DMM set to DC volts, to test the outputs of IC3 (a
7408) pins 8, 11, 6, and 3. These are the drives for solenoids 9, 10,
11, and 12. Compare your results. BTW, you can pick up ground at 2J8,
pin 1.

Now compare pins 10, 12, 4, and 1. The same results as the prior test
should be obtained if the 7408 is working properly.

Now compare pins 10, 11, 12, and 13 of IC5, a 6821 PIA. What does this
tell us?
--
Chris Hibler - CARGPB #31www.Team-EM.comhttp://webpages.charter.net/chibler/Pinball/index.htm

Solenoid number 12 (drives sound board) stays on.  I have taken the
boards out and replaced the transistor and predriver (both checked OK
when removed from board) and was looking for some other suspect before
I put the boards back in and test it.  Both the IC chip and the PIA
chip seem to test fine per Clay's website.  Just looking for the real
culprit since everything seems to check OK (except for this
resistor).  I'm open for suggestions...

Put the boards back in and still have have the grounded transistor.
Boards haven't been touched except for the transistor, predriver and
resistor I replaced. Chips are not socketed.

Here are the results:
IC3 8-.156v 11-.164v 6-.159v 3-2.15v
IC3 10-.074v 12-.075v 4-.076v 1-1.35v
IC5 10-.074v 12-.076v 11-.075v 13-1.55v

Not sure what this tells me?
.

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