The displays on my Black Knight at dead. The game goes into attract mode, all GI and controlled lamps work as well as sound. I have 100v at the displays. I am using a new Rottendog MPU327. The problem occurred when I inadvertently plugged the 5v connector from the power supply into the IJ6 connector. I am guessing something on the MPU is damaged? From the original board schematics 1J6 connect to IC29 and IC 6 decoder.

The Rottendog board passes the diagnostic test.

Thanks for your help.

I pulled the MPU327 from my Blackout and installed it in the Black Knight. The displays still do not work which would suggest it is not a board issue.

Thank you for the replies.

I was able to install a new Rottendog power board to test voltages. Voltages to the displays are correct but no displays. Not even a glow or ember light. This only leaves either the displays or the MDB that are damaged. I have never worked on a MDB so don't know where to start to trouble shoot.

Thanks,

Here is what I have done so far.

1) I checked voltages to the display board and all are correct
2) glass displays 3 & 4 emit a small dot orange/amber glow. Displays 1, 2, and the credit glass display do not
3) The "keep alive" resistors all check out to spec except for R20 which registers 70 volts.
4) I installed glass displays from 1 & 2 into player 4. Glass displays 1 & 2 emit a small orange/amber dot when installed in player 4.
5) I installed the glass credit ball in play display into player 4. It does not emit a small orange/amber dot when installed in player 4.
6) I probed the input side pins 2-8 of the ICs. ICs 7, 8,12, 13 pins 2-8 all stuck lo. ICs 1 & 2 pins 2-8 pulse.

Based on pinwiki it would seem that ICs 7,8,12,13 are bad. How do I know if the glass displays are also bad? I can find a used working MDB but if the displays are bad I might as well buy a whole new LED display set.

Thanks,

Schwaggs,

Thanks for the reply.

On the CPU board I plugged IJ2 into IJ6 and IJ6 into IJ2.

Yes, I am probed in the input side of the ICs on the MDB. IC 7, 8, 12, 13 pins 2-8 stuck hi.

No pulsing on the input side of IC9, 10,11. Each pin stuck either hi or lo

Correct. I installed the MPU327 from my Blackout board. I set the DIP switches on the board to BK and the game goes into attract mode but no displays.

All pins on IJ6 and IJ7 stuck hi

I am going to reinstall my other board one more time.

I reinstalled the blackout MPU. I must have not had the switched set correctly. It boots into attract mode and the displays work. Displays 1 and 2 have a lot of missing segments which wasn't the case prior. If IC6 that is an easy replacement. Do the missing segments also mean something is probably damaged on the MDB?

I found a 75154 on an old board and replaced the bad IC6 on the rottendog . The board is now working, but still have display problems for players 1 and 2.

Checked R1- R7 and all look okay. Tested Ic3 9-15 with probe and the pins cycle from hi to lo during display test. The UDN7180 gets voltages all over the place. Only two of,the pins are -97v. Other pins are anywhere from -21 to -47 v

In business. Had a udn7180 on an old system 11 display. Installed and all is well. Now to see if I can get the game to play thank you!

Could not have done it without your guidance.

Now back to addressing the original issue with the board. It seems Rottendog had some troublesome boards with the latest revision - I posted another thread about it and several folks were experiencing the issue. In BK the ball in play will not advance - plays the first ball but will not advance to the second ball - and there is no sound. Jim sent me an IC replacement - that is when I screwed up the displays reinstalling the board after putting in the IC. Unfortunately the problem still persists. The new IC did not fix it. If I install my Blackout MPU327 game works fine.

Thanks,