Amiga 2000 Green Screen

[Acill]

I would recommend you run John Hertells diagrom and see what it tells you. If you dont have an eprom burner to make one I can help you out for the cost of the eprom.

http://www.diagrom.com/index.php/download/

[Acill]

John and I are very good friends and talk nearly every day. If you PM me a list of results and questions I will be happy to pass them on and review them myself. I am in Japan this month on a job, but have internet access thats quite good. The time change just gets in the way some is all. For now I have passed on your last post with the serial output.

[Acill]

If you look at the address  the first 512K of chipmem is not detected..  so I would check the output on serial port to see if there are biterrors.

Since  the kickstart actually had a greenscreen  it is unable to allocate chipmem at first memoryblock (it does it in blocks of 16k if I remember correctly)
while the test rom searches the complete 2MB area for memory.

Post the serial dump here and I will review it.

[Acill]

Interesting.

Looks like a 2000 needs a 27C4000?  http://www.mouser.com/Search/Refine.aspx?Keyword=27C400

Where do you find yours?

27c400 and I get them from China off ebay. Here is the ones I use and also the same seller.

http://www.ebay.com/itm/10pcs-IC-AM27C400-150-IC-DIP-40-512K-x-8bit-256K-x-16-bit-COMS-EPROM-AM27C400-/191274549477?hash=item2c88da00e5:g:PoYAAMXQKLdRy-xJ


As for the A2000 serial dump I can see the first 512k is totally dead.. so I'd guess power to memory bufferchips or something. Look around for bad traces near them. Check U451 as the fist thing and I expect its bad too, it handles _WE and _RAS1 and RAS0, CASL och CASU. Thats the first thing I would replace. Its an  LSF244 and all memory select signals go through it. Here id data sheet: http://www.mouser.com/ds/2/149/fairchild%20semiconductor_74f244-608438.pdf

[Acill]

Hopefully, this is all it is. The fact you can get the diagrom working and are getting a green screen is actully a good thing. It means the KS rom is at least executing its first command.

[Acill]

The trace going to Pin 8 was making no connection.  This is _RAS0, which I can only assume stands for Row Address Strobe 0.  Memory Access...of course!

The pic I posted was AFTER I picked at it with an X-acto knife.  There was just the tiniest bit of green fuzz there at the pin that was totally obscuring the broken trace.  

Repaired that trace, and....TA DA!!!!

GREAT JOB!!! Even from Japan, I was able to get you in the right location. Damn, I am good! hahha.. No, but in all seriousness, you did all the work and great job finding that trace and fixing it!

Now get some pure lemon concentrate and kill off all the rest of that leaking battery crap, get some GOOD board cleaner and flood the crap put of it, blow it down and inspect it thoroughly for any more weak traces.