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Re: A2000 Replica Build

Posted: Tue Feb 25, 2020 5:56 pm
by nadoom
Na its all good,

I did actually find a resistor by the keyboard port that was only half soldered when i was trying to find out what was wrong. :-D So it didn't hurt that i had to check my sloppy work

Re: A2000 Replica Build

Posted: Tue Apr 07, 2020 9:30 am
by grshaw
It's been a long time since I posted an update on this subject. First thing to say is that I am still trying to get this A2000 to work. Second thing to say is that I am getting closer ( I think ). :D

Acill took a look at the board and then I asked him to post it back. Mainly because I wanted the Custom Chips from it and also because I got to thinking that having someone else complete it for me would not be ideal.

So - I have been fault finding on and off for the last few months.

I found a couple of really dumb things that I had done wrong. Firstly, the Electrolytic Capacitor at C317 was mounted with the incorrect polarity. Secondly, the 74F244 at U540 was also in the wrong way round. I have corrected both of these two problems. I have also done a fair bit of re-flowing. Guess I have more time on my hands recently, what with the lock down and all.

The situation I have now is that it will boot into Diagrom maybe 30% -> 50% of the time. Additionally, if I boot with KS 1.2, I see a Solid Green Screen. From black screen to this is a big step forward I think. So I am feeling quite happy about this build at the moment.

Running the Extended Chip Mem test in Diagrom, I see this:
Anyone got any ideas what this is trying to tell me? Looks like this could hold the key to the problem if i knew how to interpret it.

I have already re-flowed the solder around all the RAM chips and the surrounding area. Also I have tried switching the CIAs around. Neither of these two things has had any postitive effect.

I wonder if have the 74F244 around the wrong way could have damaged it?

Re: A2000 Replica Build

Posted: Tue Apr 07, 2020 10:18 am
by Zippy Zapp
Yes you could have damaged the chip by putting it in backwards. Try a new one. Look around the RAM circuit and the supporting logic chips and check all those areas for any problems. Did you install sockets for all the chips?

Re: A2000 Replica Build

Posted: Tue Apr 07, 2020 1:32 pm
by obitus1990
Installing it the wrong way would swap the positions of ground and VCC...probably damaged.

Re: A2000 Replica Build

Posted: Wed Apr 08, 2020 3:48 am
by grshaw
So - I swapped out the 244 at U540. Still no dice. Then swapped the 244 next to it at U541 also. Making that change, suddenly everything started working. I guess that putting U540 in the wrong way round, not only blew that one, but also the one next to it too. Moral of the story? Don't be a dummy. Insert your chips the correct way round. :D

Diagrom is now booting successfully 100% of the time and Memory tests look good. I put in a Kickstart ROM and I was greeted with the following:
Back of the net!

I am pretty much feeling over the moon at the moment. Something I certainly need in these dark times that we are living in. I started the build back in October, so it's taken me near enough six months on and off. Totally worth every second though. :D

I would really like to say thanks once again to everyone who has helped me out along the way. Specifically, Acill, obitus1990, Olem, eugenenine, nadoom BloodyCactus, Zippy Zapp and intric8. You guys rock!

Next Steps for me?

1) Get a KS 1.3 Rom. No need for any other versions. :D
2) Install into my case and attach Floppy Disks.
3) Get a CRT monitor
4) SCSI Hard card + Drive

I already have an A1200 for WHDLoad. I intend to make this machine as similar as possible to my beloved A1500 which I owned back in the day. That will mean playing games from floppy or from Hard drive installation ( if supported ).

If you are considering attempting such a project yourself - I would totally recommend it. It was certainly something of a stretch for my hardware skills and it was touch and go for a long time whether it would be successful or not. I have learnt so much along the way, it's really amazing. Perseverence and help from clever people are the key. I totally have the bug for building Amigas now, so I expect there will be more builds in the future. :D

Re: A2000 Replica Build

Posted: Wed Apr 08, 2020 5:10 am
by obitus1990
<3 Congrats! <3

Your first one is always the biggest rush. Mine was an A4000D repro board. It took me 8 weeks on and off building, followed by feeling crushed that it didn't boot, then leaving it alone for 2 weeks, troubleshooting it with help of people smarter than me, then finding the error on my own and bringing it to life. My wife thought I was nuts when I exclaimed "IT LIVES!" when the Kickstart screen appeared!

Re: A2000 Replica Build

Posted: Wed Apr 08, 2020 12:43 pm
by Olem
Wow, so happy to see you got it running! Inspiring stuff - after seeing your posts about your build I decided to build an A2000 myself. Just need to get the 250466 C64 done first! It's a serious effort to build these amiga mobos, with solder points in the thousands, but for me it gives a peace of mind that's really needed, not least nowadays. Post more pictures when you get it cased and set up!

Re: A2000 Replica Build

Posted: Wed Apr 08, 2020 12:56 pm
by Olem
...and I specially liked the "no, wait, send it back, I want to fix it myself" part :D I totally get how you feel about that!

Re: A2000 Replica Build

Posted: Wed Apr 08, 2020 4:02 pm
by intric8
Congrats, grshaw! That's a massive achievement and one I totally envy! Just tremendous.

Re: A2000 Replica Build

Posted: Thu Apr 09, 2020 1:21 am
by grshaw
Thanks everyone for your kind words. :D