Hi,

New member. Did a bunch of searching and got some things resolved. Down to a no sound condition left to sort out.

Black Knight - all lamps, solenoids, and switches appear to be working.

The Sound Board test points show correct voltage (+14v, -14v, and 5v). I get a hum from the speaker, and when I turn the speaker pot up I get a really loud hum. I get no sound during gameplay, or in diagnostic mode.

One guide mentioned that pin 1 on 10J1 should have 18v AC. I get 11v on all the pins from this connector (to ground). I still have 11v after the two fuses on the sound board. This leads me to think I may have a transformer problem, but I am asking for advice before I start messing with it.

Also, I have owned this game since 1993. It was working well for several years. I had a no sound problem in 2000, and bought a replacement sound board (looks like an original System 7 board). This took care of the problem. I moved, and the game started to get a bit flaky after I moved it (in 2003), but still worked most of the time. I have done nothing else to this game other than clean/adjust the blade switches and clean and wax the playfield (which is in bad shape, btw) over this time. It has started to do things like lose track of how many balls are in play (switches not being made) which I can usually get cleared up. The no sound popped up again about a year ago and I am finally now taking the time to look into it.

Thanks for any suggestions you may have.

DJ Roberts

Thanks! That should keep me busy for a while. I'll report back when I get a chance to poke at it some more.

DJ

Hi again,

Cody's guide says there should be 18V on J1, but I only get 11 V. It also mentions that this voltage supplies the other voltages and if the only problem is sound being out the voltage is probably ok. With that in mind, I moved on to the next checks.

Dug out a logic probe and did some more poking around. The volatges on IC9 were correct. I had pulsing on pin 9 when I depressed the diagnostic switch, and on a couple other. Most of the pins 9-29 did not show pulsing. Cody's guide says this indicates a bad 3.58 MHz Crystal. Great Lakes has those in stock, so I'll put in an order.

If the oscillating crystal is bad, why do some pins pulse and others not? This will be my first soldering / desoldering on a circuit board, so wish me luck! Should I worry about the 11V on J1?

DJ

Test points are all good:
#1: 13.5
#2: -13.7
#4: 4.95

For JC 1, I get 22 V from pin 1 to 9. A little high. Is this anything to worry about?

Going back to IC9. Is it odd that some pins are pulsing and others not?

Thanks again,

DJ Roberts

I did not swap those chips. I'll re-check the pins and swap the chips next time.

Gotta go out of town until Thursday, so it will be a few days before I can get to it. I'll be thinking about this pinball machine instead of the work I am travelling to do. Funny how things work like that sometimes.

I'll report back when I get a chance to probe some more.

DJ

Got this working, thanks for the help.

When I swapped the chips it started to work. Ordered a new chip, installed it, and I have sound!

I had turned the pot way up during troubleshooting. When the sound came it, I thought my kid (11) was going to jump out of his chair. "Dad, that's way too loud!" Got it adjusted, and the balance between normal sounds and speech where I want it.

DJ