Black Knight lighting problem? Troubleshooting help please.

1500points

New member
Joined
Sep 2, 2011
Messages
5,706
Reaction score
107
Location
Iowa
Black Knight lighting problem? Troubleshooting help please.

I am having an issue with the lights for numbers 2 through 9 on the lower playfield.
(The center line of lights in the sword).

They are always slightly on and have about twice the brightness of the other lights.
They do go on and off at times but it appears they are in sync with the Lock lights at the very top of the playfield.
The upper right drop target timer light seems to be in sync with the number 4 light.

I've put a meter on the lamps and they aren't much different than the dimmer lights. they surge up to 13Vdc at times.

Where do I start troubleshooting this?
I don't see any physical contact points, shorted wiring, or anything visually wrong with harness or connectors.

Diode bad somewhere?
Transistor on a board?

I haven't pulled out the schematics yet, wanted to see if this is a common Williams issue that others have noticed.

Thank you.
 
Check the driver transistors for that circuit of lamps on the driver board. Probably have a shorted one. Check the big resistors on the driver board too.
 
attachment.php


Looks like the transisitor driving col 7 could be an issue?
 

Attachments

  • bk_lamps.jpg
    bk_lamps.jpg
    22.4 KB · Views: 55
Gotcha!
Thank you all for the fast replies.
I saw those grids in the little handbook but was unclear how to read them.

I just started posting but I've been lurking about this site for a little while.
Nice resource this place is.
 
update.
changed q74 and q75 in the column 7 lamp circuit.
now lights 2 through 9 don't stay lit in sync with the specials.
Thank you again for the clarification of that williams t-shooting table.
 
Back
Top Bottom