Hi all, Hoping someone can help me out here.

I have a Black Knight that came with a new Rottendog MPU 327 board. I have had no major problems for the past 2 or 3 years until recently I noticed the game settings had reset to the defaults. I assumed the battery on the MPU was dying or dead. I had to order the special button style battery and after a couple weeks they arrived. I switched the machine on in preparation for changing the battery and the machine would not boot up. No attract mode lights. No score displays. Just GI lighting.

The Rottendog board has two red LED lights that are on steady. I have checked all the fuses I can find with a meter. I have removed and replaced all the cables from the MPU and the power supply board. I disconnected the display board. I also pulled the game ROM and tried different game dip switch settings. I'm having trouble finding troubleshooting advice for my particular combination of the Rottendog and the original Williams System 7 stuff. If anyone knows some existing articles I can check out let me know. I did try searching the forum before posting. I don't know where to go from here.

*Not sure if this is relevant but I had completed the suggested rectifier mod to add a fuse for each rectifier block in the back box. The other day one of those fuses blew. I replaced it and got my ball trough solenoid to work again. I noticed a couple days later that one of those fuses was again blown and that is about the same time the "no-boot" issue appeared. I have since replaced that fuse but the no-boot issue remains.

**I also noticed some white residue around a couple of the ROM chips including the main game ROM. This stuff wipes away easily and looks almost like battery acid corrosion. The battery is a button style battery and it has never been leaking so I'm not sure what this residue is, what's the best way to clean it, and if it is affecting the game.

Any advice is greatly appreciated

Thanks in advance! , Rob

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The coin door switch is bypassed. Is there something about that high voltage circuit that affects boot up? I would have expected it to boot up and at least be in attract mode even if no solenoids were active. I did try flicking power in and off a few times fast but no change.

I'll have to find the instructions for a new rottendog startup procedure. If anyone has that link it would be awesome!

I will definately look at the rectifiers as its own issue. For the no-boot issue I'm thinking I may be on the right track with going through the startup procedure for the rottendog mpu. I think I let that battery die and I hadn't powered the machine up in a while. Hoping the board just reset if that's even possible. I found the setup procedure online so I'll try it this afternoon.

No luck with the rottendog setup procedure. The two led's don't flash like they should when you remove battery and all cables except the top right and set dip switches to 1's per the diagnostuc instructions. They lights just glow steady. I will move on to the rectifiers and other voltage checks coming out of the power supply.

Thanks, I tried the installation sequence with no luck. I'll contact Rottendog.

I called the contact number listed on the rottendog website but got no answer. I checked voltage the best I could based on the schematic and it looked like its putting out 5 and 12 volts (more or less). If anyone knows a good step by step check for the system 7 power supply let me know. The bullet proofing links are great but I haven't seen one for just diagnosing. I'll do some research on the rectifiers. I need to rule them out.

While working with the rottendog board I noticed what looked like corrosion around some of the chip sockets and a couple resistors and connections. It looks like a fine white powder, or like dried up salt. The only battery in the board was a button battery that had no signs of leakage. Is this stuff just some sort of mold spores, or what? Does anyone think this could be interfering with the board? I'll post a couple closer pics.

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The powder wipes away easily. I cleaned it up and it looks fine. I replaced all the caps on the power supply but not the large blue cap mounted to the bottom of the backbox (not sure if that's the 30k cap). I suppose it could be spewing something.

I spoke to Jim at Rottendog by email (very helpful and responsive by the way). I had stated my power supply was 5v "more or less", assuming that the 4.8v it was putting out was within a tolerable range. But Jim said that will not be enough to boot. So, I have to figure out why my power supply is falling short.

Good points on the corrosion issue. I'll look into that further and hopefully the ic sockets aren't bad. I just ordered a new switching style voltage regator (supposedly a modernized and direct fit replacement of the old linear type), the one mounted to the giant heat sink that controls the 5v side. That is one of only a few items I didn't replace when I "rebuilt" the power supply. At $8, I'm going to try it out. I also have an old computer in my basement. I will have to strip the power supply out to use as a bench testing tool. I'll see if the board boots with a clean solid 5v. BTW, I'm sorry for the long gaps between updates, I work too much and lose track of my Pinball stuff now and then. Thanks to everyone for giving me some advice and helping me learn. I will definitely post the final fix when I get there so others can also learn from it.

Installed the new voltage regulator and still no boot. In fact, there was some odd clicking as if some solenoids were attempting to close and then a slight burning smell. I have heard that clicking at random times since this problem began, but the burning smell is definitely new. It went away, but that doesn't make me feel much better. Couldn't locate the origin of the burning. I'll have to take a closer look tomorrow. I am losing hope at this point. There is just too much I don't know yet about repairing these machines. I still cannot find a good straightforward description of where to test for the different voltages that should be present at the power supply and then at the Rottendog CPU. If anyone can walk me through that part of the diagnostics I would be grateful. I really want to make sure it's a 5v issue. That burning smell has me worried. Wondering if I have a stuck solenoid somewhere, but would that cause booting issues?

I know this is an old post but I'm just adding that I have a brand new power supply installed and I have a brand new rottendog mpu327 plus an all in one rectifier/fuse board ready to go in. The old rottendog board was cooked. I'm looking for some guidance on what voltages should be where before I hook anything up and risk burning up my new $300 MPU. If anyone can give me a hand in checking the various key voltage pins on the MPU that would be great. This machine has been down too long

All set. New board is in and everything works great. For the record my replacement board from Rottendog was an MPU327-2 (an updated version of the one I had before) and it did not work with my Black Knight. NONE of the version 2 boards will likely work in any BK. Jim at Rottendog is working to identify the bug. So, I returned it and found a used version 1. That's what's in there now.

Im pretty sure the sound issues are very limited and probably not noticable by the vast majority of BK fans. I think there's a laugh that's missing in attract mode after the BK taunts you to challenge him. The background music also runs after the game is over for a few seconds. No big deal. Not sure what else is off. Sounds good to me when I play.