Amiga 2000 Green Screen

[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.

[Frankencelery]

OH!  

Acill, you are the MAN!

Tonight, I decided to unsolder U540 and U541 and put in sockets.  My replacement chips are supposed to be here on Friday.  

Then I looked closer at U541....do you see it?

[Frankencelery]

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!!!!

[vince_6]

Great news!

[paul1981]

I love that white screen!

[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.

[Frankencelery]

I haven't had any time to get it back together yet, but I hope to this weekend.  

This all started when I bought another A2000 a couple weeks ago.  The seller gave the ever popular "it worked when I used it X years ago, but now I have no way of testing it", and I fell for it because I thought he was a stand up guy.  Anyway, it was an early model with a rev 4.4 motherboard, and it had pretty severe battery damage, which he also failed to mention.  That one has a yellow screen.  But I figured if I was going to get this thing going, it would be a better bet to fix my spare rev 6 board, and put that one in the machine.  

So now I might try my hand at fixing the old 4.4 board.  If I need help (which I probably will) I will start a new thread.  

Thanks again for your help everyone!

[Hanzu]

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

A2000 REV 4.1 here. History: Battery leak, battery removed, was given to me faulty, I repaired lots of old leak damage, tested all socketed chips in a working REV 6.2, changed CPU, ROM and Agnus sockets, still grey screen, yesterday found missing contuinity between CPU pin 64 and RP900 pin 10, repaired that today and got green screen now.

Since there are no no schematics for A2000 REV 4.1 (only REV 6.1 that has different number and type of RAM chips) and https://www.amigapcb.org/ is still missing any A2000 models, I googled Amiga 2000 green screen for ideas and came to this topic.

After reading Acills good tips (BTW Japan jet lag took its toll  , since it is U541 not U451 and it is 74F244 and not LSF244) I was encouraged by Frankencelerys success on finding U541 pin 8 track cut. After extensive measuring I concluded my U541 tracks are ok. Did find out U540 pin 15 is routed different on REV 4.1 than REV 6.2. Read on about that.

But since U540 is closer to old battery place, it is more likely to get leakage and after measuring last four lines I found it. U540 pin 8 track was cut on its first via ring tracing that track to Agnus pin 46. That place is located battery length on right side of CPU pin 1. Very notorious place for leakage damage with all those non masked vias.

Thank you for both of you for making my repair easier. Will repair that track soon and maybe notice there are still more faults. I just hope I don't have take on RAM chips since on REV 4.1 there are 32 of them compared to better REV 6.2 with only 8 of them.

How is your older REV 4.4 doing now Frankencelery?

Here are my notes to help some A2000 green screeners to start with:

U540 74F244
1 GND
2 DRA0 U101 AGNUS 43
3 RP500 9
4 DRA1 U101 AGNUS 44
5 RP501 2
6 DRA2 U101 AGNUS 45
7 RP501 6
8 DRA3 U101 AGNUS 46
10 GND
11 DRA7 U101 AGNUS 50
12 RP500 7
13 DRA6 U101 AGNUS 49
14 RP500 6
15 DRA5 U101 AGNUS 48
16 RP500 4
17 DRA4 U101 AGNUS 47
18 RP500 2
19 GND
20 +5 U500 21

U541 74F244
1 GND
2 DRA8 U101 AGNUS 51
3 RP502 10
4 _CASL U101 AGNUS 54
5 (SPARE)
6 _CASU U101 AGNUS 55
7 RP502 6
8 _RAS0 U101 AGNUS 57
9 (SPARE)
10 GND
11 GND
12 RP502 2
13 _RAS1 U101 AGNUS 56
14 RP502 4
15 REV 6.2 GND / REV 4.1 _WE U101 AGNUS 21
16 RP501 10
17 _WE U101 AGNUS 21
18 RP501 4
19 GND
20 +5 (FOR EXAMPLE U500 21)