Leaderboard

Even though most of it isn't my tech (and all of it goes over my head), I absolutely love reading your posts Bob.

Yep, it does make it an MPU2. They obviously made these before the MPU2 was released to give the extra functionality, and then developed it into the MPU2. Managed to get it working today.

This one came in as not booting. These are normally in quite good nick mainly due to the fact they don't have batteries. This model also had the later type of regulator using the TO3 device, like MPU3. The only other odd thing was that the ROM cart was an MPU1 version but running 'Rock on' which is an MPU2 game. First thing was to swap out the old cap. On a power up it would light one of the lamps but nothing else. Looking at the CPU it would start but after a few seconds all activity from the data and address busses would stop? Sometimes they would start pulsing again after 10 secs or so. All very odd. These boards use the 6800 CPU and I didn't have one to substitute and as it appeared to be sort of working I was reluctant to splash out on one until I'd tried everything else. So, after replacing all the 6821's and 6810 RAM I was getting nowhere. All the original chips were put back in and the board was put aside waiting for the CPU to arrive. After a few days it landed on the doorstep and it didn't look like a fake when inspected which was a relief. Putting it in and powering up resulted in still no boot but there was a noise from the speaker and some different lamps flashed. So it was out with all the 6821's again which made no difference. Then the 6810 and bingo she lives! All the original 6821's were OK too so they went back in.

That's funny, I sometimes think somebody's got my other half especially when I'm stuck on a fault!

That is a mask programmed ROM, which contains common code used in all the games. Normally they are SCM39199 which is a motorola device