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PP7A and PP7B does NOT use a 7905 fixed voltage regulator for -5V. A radarscope board would really be pushing it for that kind of fixed regulator.

If you want a ttl replacement for the AM25LS2519 I can sell ya a blank board. I made them a while ago and never got around to offering them for sale. I tested it on @Dillweed's pengo board that he loaned to me for this project.

I think I am going to call it fixed™. The crashing and more "random" failures were likely caused by 74ls373 that were acting as buffers for the DRAM. After replacing those, the crashing stopped happening. The RAM failure on startup I have not observed since I replaced the 22uF capacitor in the...

DACs are not ADC. DAC08 is a digital to analog converter. ADC is a analog to digital converter. So they are not compatible by principle.

From today's workday: Game: Atari Centipede Symptoms: Game resetting and audio is really crackly Troubleshooting Steps: First step is always reseating the card edge connector and pushing down on the socketed chips. That ended up fixing the issues with booting. I started with the audio issue by...

Just got a RAM 32 error upon a cold start after sitting for half an hour. I guess there still might be something going on. What's weird is that the background was yellow, I would think that a ram failure would have had a black background. I guess I might have some more work to do, but I'll keep...

I messed around with it tonite, I ended up replacing the caps but like one would expect it didn't resolve the issue. I was goofing around with the RAM test again, and I was occasionally getting bank 3 and bank 1 RAM errors. On a whim I replaced the 74LS373s associated with it and that seems to...

I didn't even notice that uses the "12V Unreg". I gotta pay more attention to these things.

One thing I noticed is that SOMETIMES on a cold start, meaning it hasn't been on for several hours, it will throw a random RAM error code (I've seen 13, 21, and 37). It will boot after displaying the error code and crash shortly after (presumably because RAM didn't get properly initialized)...

Which is still a good thing to experience. Someone who wants to repair their own boards should know how to fix their screwups (both troubleshooting and bodge work). It is incredibly valuable to learn how to do this kind of work. It also keeps ya humble. I work on boards just about every other...

The bottom of the machine was covered in dirt. I still have to do a better job cleaning this but I was itching to get it working.

It was one of my requirements for a bench setup, I made it using a lot of piece of scrap material I had in the garage. Eventually I wanna make an actual sheet metal enclosure, but that is a down the road project...

I sure hope not. I have no idea what it was. One thing I noticed on this board is that there are a couple spots with corrosion. Not sure if it was bugs or mice or whatever. I spent a lot of time cleaning this cabinet... I've cleaned it off since there hasn't really been anything severe. This...

Game: Sega Head On 2 (Slimline/VIC Dual PCB) Symptoms: Accelerator button always pushed in Troubleshooting Steps: This was a pretty straight forward repair. When troubleshooting input stuff like this, you will usually have one of 3 failure points: Cold solder joints on the pin headers/harness...

The Gorgar pinball used the same sound and speech board. I figured it would be funny to put that because they are both hungry.

I think you nailed it. I piggybacked one and it ran a whole hour without crashing. As soon as I pulled it, next time it went into gameplay it crashed. I went ahead and swapped the 74ls373 at 3H and am gonna let it run for a while. I also put a fun message on the title screen, it's neat that I...

Nothing serious. Little bit of green on the holder solder points and the holder was trashed. I made myself a remote battery pack to keep em off the board from now on.

That could make sense. I didn't consider it because I figured I'd have more problems being it is with the dram. But I suppose the occasional miss with latching would cause problems. I'll take a peek after work today. Thanks.

Managed to get this exactly once. Odd that the background was yellow for this. Sometimes if I run the RAM test, through the coin door buttons it will say ram 21 or 22 (they are both new), once it said 24.

Here's what I tried this evening: Replaced the sockets for the decoders and CPU, those were a bit yucky. No change. Burnt a new ROM set for the off chance something goofing around. No change. I am going to start poking around tomorrow, I'm gonna start by poking the 153s, I've had terrible luck...