Hello all, I was hoping someone more experienced might be able to help this Atari guy.
I have an Amiga 500 that had a Vampire V2 on it. It worked fine until recently and then stopped booting up. The screen on the RGB was just yellow.
I also have an Amiga 2000. Using that machine I've checked to be sure the gary, paula, denise, cias, cpu and fat agnus were all good. And they all are.
I ordered diagrom and couldn't get it working. Nothing at all. I figured out eventually that I need an adapter for a rev 5 board which I ordered. Still no dice. I tested diagrom on my Amiga 2000 and it works perfectly and gives output out the serial which proves the diagrom works as well as my usb serial setup.
After getting the diagrom the bus activity in the 500 looks very much exactly like the 2000. You can see lots of activity. All the ram chips have activity on the outputs. The lows have a sawtooth pattern to them which I was alarmed by but it looks like my 2000 does the same thing. I've replaced all the data path IC's on the 500. Still even with diagrom in the screen just stays yellow and the serial port is completely silent.
PSU was replaced with a meanwell and I've checked that all voltages are (and were) correct.
I'm just not sure where to look next. What else fails? Resistor packs? Capacitors? I checked all data and address lines for shorts and they all read the same resistance. I checked the rom for connectivity to the cpu and all pins seemed good. I'm at a total loss. This thing just doesn't want to work. Meanwhile my 2000 just chugs along.
A yellow screen usually denotes a RAM error. Either Chip or Slow RAM (Fast RAM on other Amiga systems). Sometimes this could be a red herring and something else could be causing it such as an add-on card not playing nice.
Do you have any extra RAM expansion connected to the under belly connector? If so, try removing that first.
