I have posted this before within other threads, but in a blatant attempt to get in the compendium again it is posted here in it's own thread. Fingers crossed! Oh, and if you find any corrections let me know and I'll edit them in.
Black Knight Sound Board Repair
The following information was written specifically for a Williams Black Knight (’80) pinball machine. These procedures may also be used for other WMS games like Firepower. However, some signals may or may not be used for your model.
If you are reading this document, it is assumed that your BK sound board is not working. It is further assumed that there is NO sound AT ALL to begin with. If your board works somewhat, the fix may be mixed in with the procedures and you will have to pinpoint the failure with deductive reasoning. This document may be practically useless.
Complaint
My Black Knight will not make any sound during game play or sound diagnostic. (It is assumed that the game functions properly other than no sound).
The Basics
Before you even pick up a screwdriver, adjust the remote volume inside the lower cabinet on left side to center position. Also locate the adjustment knob on the Speech board and set it to the center position. The Sound/Speech boardset will be located at top right inside the backbox. A larger, square sound board (with four connectors along the top and a plug on the left) and a smaller, rectangular speech board connected to the sound board via 40 pin ribbon cable to the above-mentioned plug.
Check the orientation of the connectors on the sound board. Top left is J3, the select lines from the driver board (J9). Next is J4, the remote volume connector (the shield [bare wire] should be on left). J2 is the speaker connector. J1 at top right is the AC input for the sound board operational voltages (Gray wires). Make sure J2 and J4 are not swapped. There should be no open chip sockets on the sound board or speech board for BK (other games may have open sockets on speech board). All chips on the sound boardset are oriented with pin 1 (divot in corner of chip) pointing downward. Check all socketed chips for bent legs and straighten or replace as needed. If your meter is handy, check the two fuses on the sound board. If not, we will check them soon enough.
OK, so our cursory look in the backbox didn’t turn anything up. Now we need to check the lower cabinet. Open the door, release and remove the lockdown bar and slide the playfield glass out. Reach in the door, on the right (a few inches inside of the lockdown release lever), and work the ball release solenoid by hand to eject the three balls into the trough. Use caution not to mangle trough switches. Place the balls in a safe place. Lift the playfield and rest it against the backbox (you may want to secure the field so it can’t fall). Now inspect the remote volume potentiometer (pot) lugs. Gently tug on each of the three wires and resolder as needed. Inspect the two lugs on the speaker itself and resolder as needed.
Jumpers
Sound boards must be configured for the model machine they are being used in. This is accomplished with hardwired jumpers installed at locations around the board. The jumpers could be a piece of wire or a Zero-Ohm resistor, which is normally gray or tan with a single black stripe around the center. Black Knight should have the following configuration (please refer to game manual for other models):
W1 Not Installed (with Speech Board; if no speech board present, install W1)
W2 Installed
W3 Not Installed
W4 Not Installed
W5 Installed
W6 Not Installed
W7 Installed
W8 Not Installed
W9 Installed
W10 Installed
W11 Not Installed
W12 Not Installed ***Edited 12/26/15 this is "PB7 Status Control, with W13 never used. Can someone confirm on their BK sound board? Confirmed W12 NOT INSTALLED***
W13 Not Installed
W14 Installed (This is a foil trace jumper that is always present. It is located directly underneath R30, and ties one leg of that resistor to ground)
ROMs
The sound ROM for BK should be a White Label Sound ROM 5. The speech board should be fully populated with four ROMs.
DIP Switches
Located at top left corner of sound board by the diagnostic switch is DIP switch bank one (DS1). It consists of switch one and switch two. Factory settings with speech is switch one (on bottom) set to Off, and switch two set to On.
Capacitors
Black Knight sound board electrolytic capacitor list
C12/C30/C36 1 ų @ 63 Volt C26 1000ų @ 25 Volt
C14 800ų @ 16 Volt* C27 12,000ų @ 16 Volt
C15 500ų @ 15 Volt** C29 10ų @ 25 Volt-Low Leak
C25 100ų @ 10 Volt
It is recommended that all electrolytic capacitors on the sound boardset be replaced. C27 (12,000 microfarad @ 16 volt) should be replaced regardless.
Black Knight speech board electrolytic capacitor list
C12 10ų @ 25 Volt-Low Leak
Refer to game manual for component location.
Troubleshooting
Note: If the sound board is jumpered for a speech board (W1 out), it must have the speech board connected to work, and it is possible for the speech board to kill all sound. If you are unsure if the speech board is good or not, disconnect it, install W1 and repair. Then rejumper sound board and reconnect speech and repair.
The quickest form of troubleshooting is substitution. If you are fortunate enough to have another like-model game that works, you can swap boards to determine exactly what board is causing the failure. Furthermore, once that is done, you can swap socketed chips to eliminate those and prove they are good. Socketed chips can also be quickly replaced to eliminate them as suspects.
The underside of the connectors on all the boards in the game should be checked and the solder reflowed as needed. The header pins should be inspected and replaced if the pins are delaminating or pitted. Connector pins should be replaced along with the header pins.
I will assume you do not have another game to swap your board into (or another board to install in your game), and that the connectors look great. So let’s isolate the sound board by disconnecting J3. Now press the diagnostic switch on the sound board. If sound is restored, there is a locked signal on the driver board and it should be repaired. If still no sound, verify operational voltages are present at the test points on the sound board:
Set multimeter to AC Volts. Probe from J1 pin 8 to J1 pin 2. Then from J1 pin 1 to J1 pin 9. Each time you should see about 18 Volts AC. If this voltage is missing or incorrect, trace the gray wires back to the transformer, and verify it is correct coming off the transformer. Remember that this voltage is also used to generate the +5, +12, and –12 used elsewhere in the game, so if only the sound is out, the AC should be correct.
Set meter to Volts DC, 20 Volt range. Connect black lead to TP3 (ground). With red lead, probe:
TP1 = +12 Volts DC (positive reading)
TP2 = -12 Volts DC (negative reading) – If either TP1 or TP2 are incorrect or missing, make sure fuses and clips are good, then replace BR1.
TP4 = +5 Volts DC – If TP4 is incorrect or missing, but TP1 and TP2 are correct, replace IC8 and C27.
IC13 Pin 3 = -12 Volts DC – This is an input voltage originating from TP2, so find the broken trace between the two if missing.
If you have verified that all operating voltages are correct, you have gone about as far as you can go with a meter. Time to pick up a logic probe and/or scope probe. These two items are extremely useful, but still fall short of an oscilloscope for troubleshooting. However, the inexpensiveness of probes makes them affordable, and even if you can’t determine the cause of failure and have to send the board out for repair, you’re not out too much money.
Using the Logic Probe
The logic probe is one of the most efficient (CHEAP!) tools that can be used for troubleshooting logic problems. I do not claim to be an expert in the use of one, but I do know how to use one to help.
We will be using the sound board’s own diagnostic for these tests, so the first thing we need to do is verify the switch signal makes it to the CPU.
Disconnect sound board J3.
Connect the black clip lead of the logic probe to TP3 (ground).
Clip the other lead (red or traced) to TP4 (+5V).
Set logic probe to “Pulse” and “DTL/TTL” (not CMOS).
Power up game and make sure it enters attract mode.
Carefully apply the logic probe to IC9 pin 6. It should read “HI”.
Depress the diagnostic switch. The line should drop LOW when the switch is depressed. If it does, the diagnostic switch and logic probe are operating properly. If not, find the problem with the diagnostic switch through continuity tests, or the problem with the logic probe (does it show a HI if you touch TP4?)
Let us assume that the switch and probe are operating properly, and that the NOT NMI line at IC9 pin 6 goes low when the diagnostic button is pressed. Now we need to check for pulsing on the sound CPU, IC9.
NOTE: When probing signals with a logic probe you can accidentally short two IC signal pins together, which can “crash” the board. It is suggested to cycle power between tests to make sure the sound CPU is running and not crashed/locked.
Verify game is in attract mode.
Depress sound diagnostic switch.
Probe IC9 pins 9 through 20 (address buss outputs), and 22 through 33 (data buss two-way signals).
If you see pulsing on all of these lines, the Crystal and CPU should be fine. Since the CPU is socketed, it would not be a bad idea to swap it into a working board or with a known working component if suspect.
If you still get no pulsing, verify operational voltage is on the chip. Set meter to DC Volts and probe black lead to pin 1or 21 and red lead to pin 8 or 35. You should read +5 Volts. If you do not, verify TP4 is +5 Volts, then locate and repair break in continuity to IC9.
If +5 Volts is present, replace the 3.58 MHz crystal.
The NOT NMI signal is a manual override that commands the CPU to initiate the memory test. So…
Verify game is in attract mode.
Depress sound diagnostic switch.
Probe IC11 pins 17 through 23 and IC12 pins 1 through 8. They should all be pulsing. If not pulsing, locate and repair break in continuity to IC9.
IC11 (6810 RAM) and IC12 (Sound ROM) will interpret the above inputs and feed them out on their data lines.
Verify game is in attract mode.
Depress sound diagnostic switch.
Probe IC11 pins 2 through 9. All should be pulsing. If not replace IC11.
Probe IC12 pins 10,11, and 13 through 17. All should be pulsing. If not replace IC12.
So we have the CPU at IC9 pulsing and the RAM and sound ROM are pulsing. This information is then fed to the PIA at IC10.
Verify game is in attract mode.
Depress sound diagnostic switch.
Probe IC10 pins 26 through 33. If not pulsing, locate and repair break in continuity to IC11/IC12.
If pulsing, probe outputs of IC10 at pins 2 through 9. If one or more lines are locked HI or don’t pulse, replace IC10, PIA 6820/6821.
The data is then fed to the Digital-to-Analog Converter (DAC) at IC13.
Verify game is in attract mode.
Depress sound diagnostic switch.
Probe IC13 pins 5 through 12. If not pulsing, locate and repair break in continuity to IC10.
The DAC takes the digital data and converts it to analog information that the amplifier can understand. It is fed through the 2N4401 transistor at Q2.