Amiga 4000 New Build!

[johntayloruk]

Long post here, but hopefully someone will find it useful

Background

So I've been looking for a while to do something like this, but found getting a PCB and then working through the BoM quite daunting. The lockdown gave me plenty of time to go through things in more detail, research, refer to my original A4000, research more and then eventually get confident enough to start and ultimately finish.

I'd got the bug from watching a couple of YouTubers:
- "Building the Worlds Newest Amiga" series for the 500++ by RetroManCave
- "Commodore Amiga A4000 Repairs" by GadgetUK164
- "Building my own Amiga 4000" by TechJump

My own original A4000 had died on me and I'd exhausted my troubleshooting skills, so while it was off with someone to take a look at I bought a new PCB and got going.

BoM

I used the A4000 BOM list from Acill (https://github.com/Acill/A4000RevB) and Tbtorro and built my own list of items to buy from Digikey, AmigaKit, UTSource, Analogic and ebay. This isn't to say their list was wrong in anyway, I just found it easier for me to add some additional information. This included:

- Categorising the parts into something that made more sense to me
- Flagging where an item could be bought from
- Specifying the Digikey part number
- Specifying the Manufacturer part number (to see if other sites sell it)
- Flagging if an item has been substituted
- Flagging if an item can be socketed (optional to do this in most cases)

I've uploaded the BoM sheet I put together - please share, change, amend and use - I hope it helps others!

MASSIVE THANKS TO Acill and extended thanks to tbtorro and of course Chucky, just because

My Approach

I started with the smaller things then worked up. There are over 600 capacitors and resistors to do, so I just worked down the BOM doing one component group at a time, marking off each as I went. I only had the components I was working on out. I was checking traces as I went along and really focused on the pins around my IC's.

I decided to socket as much as possible. Mainly because I didn't want to go through the hassle of it not working and then trying to unsolder IC's and made a mess. Soldering the sockets was actually a lot easier than I expected, given the space and size of pins.

I didn't record how long I was spending on this, but It must have been over 40 hours give or take. My thoughts were that if I took my time and checked traces/continuity as I went it would be a lot easier than having to troubleshoot at the end.

Tricky Bits and the Final Hurdle

So after many hours and it being completed it was time to boot up. I put in the Diagrom chips, hooked it up to Power and my 1085S and....nothing. Fan was on, but the screen was grey. I checked socketed IC's, changed Ram, voltage from the PSU and all seemed ok. I played around with the brightness and noticed that I could see some text, but it was very faint and hardly visible. A bit more research and I came across an Issue raised for the build whereby the ADV7120 IC was not getting 5V's as there was an issue with a trace to L500.

The BoM I picked up from Acill said to put a fixed inductor in L500 and a 10k resistor at R465. In order to fix this, I removed the 10k resistor at R465 and replaced it with a 1 ohm resistor. More info can be found here (https://github.com/Acill/A4000RevB/issues/2)

When I made this change, the lights came on and it worked! It really worked and I'm happy

So I added a gotek drive, an Amiga 4000D case and have it setup running WB 3.1.4.

My Experience Going Into This

I've some soldering experience and have repaired the odd PSU and replaced capacitors on my other retro systems, like my A600, A1200, CD32, SNES, Nes, Saturn, Master System, Megadrive, 32X, MegaCD, N64, Jaguar and my X68000. I'd never done anything like this before though and I've got average equipment.

My Secret Weapons

Amiga PCB Explorer

http://amigapcb.org/ - it's amazing. Truly brilliant and helped me a lot with the checking and validation.

Flux!!

I used MG Chemicals 8341 No Clean Flux Paste and just Fluxed the Fluxing Flux out of it! Seriously, crappy solder point, just add flux and reflow. Too blobby, just add flux and wick off the excess.

I'm fortunate to have an ultrasonic bath, so after I'd done a lot of the major soldering (and before adding the IC's and ALU Caps) I cleaned it off in there.

My Thoughts on This Build

It's amazing that people are spending the time creating and sharing new hardware in 2020 for a machine that was released in 1992. Keeping the Amiga scene alive is important and we're all lucky there are some talented people out there making this happen, so big thanks to anyone who has been involved in this.

From my perspective, this was a big learning experience. It also wasn't cheap. If you want to know how much, then work it out yourself because I daren't check

My soldering could be better, particularly on the smaller resistors and capacitors (maybe should have used thinner solder), but other than that I'm really happy with what's been done and if anyone has any questions or comments please feel free to post.

My next project is to work on a batch of A3660 PCB's I've had made up so I'm sourcing the parts and will get building when I can. If that works I'll add another post.

If you are thinking of doing this yourself, my advice is GO FOR IT! You can't beat the sense of achievement when it's done. Just remember to take your time, have plenty of breaks (and beer ready) and stick to it. Oh, and For Flux Sake, Flux!

[torsti76]

Very nice writeup and result! I second a lot of the things you said from my experience of building a NOS A4000T pcb.

What I found extremely helpful for soldering the birdseed is a hotair rework station (I've got one that's at least 15 years old and cost about 40 EUR back then, so no great investment).
Applying solder paste by hand is a pain though, so I also bought a small cut plotter (150 EUR on eBay) and created stencils out of old overhead projector sheets by using Gerber files for the board and a free tool named gerber2graphtec. Since you need about 4 A4 sheets to cover the board (front and bottom), I then did one sheet at a time, leaving out all electrolytic caps and PLCC chips first. For those, I used a regular soldering iron and drag soldering at the very end of the build. For that, looots of flux are very helpful indeed...

[DanyPPC]

Congratulations !

[nogginthenog]

Looks amazing!

[Valken]

Awesome work!

[Avrovulcan]

Lovely stuff there mate
I bought myself a set of A4000T boards off ebay last month. Looking forward to starting my own build. Still need to get the CPU board though.

Again, nice work. Very professional build

[ElectroBlaster]

Spot on

Wish I was brave enough to go for it! I want a new A4000D board myself.

Also this same thought comes up every single time I read posts like this, years ago I went to our local Maplins. I grabbed a tonne of soldering stuff, connectors bits bobs etc. I asked can you get decent amounts of flux! The staff were laughing at me, said you dont need flux ha ha ha etc...

From that day I never bothered with Maplins again! they actually believed that flux was useless, bunch of fools! lol.

[Jope]

Originally Posted by ElectroBlaster

From that day I never bothered with Maplins again! they actually believed that flux was useless, bunch of fools! lol.

Well, it really depends what you are doing. A high density QFP - yes, you'll need flux. A through hole cap or pin header? The flux inside the solder wire is totally enough.

If you solder a SOIC pin by pin with thin solder wire? The flux inside the wire is again totally sufficient..

[Avrovulcan]

For all the stuff they used to sell, I never found Maplins staff particularly helpful. Agree with the sentiments above about flux. I've almost always found the flux in solder sufficient, that says though I still keep a bottle of flux handy should I need it. I also only use leaded solder as I find it far easier to work with.

Regards
Andy

[johntayloruk]

For a newbie to soldering, flux just gives you the bit extra ability to have another crack at it.
I used a 60/40 tin/Lead core solder with rosin core and that’s fine in most cases, but it does burn of quickly so adding extra flux and reflowing for me made a huge difference, particularly with the smd components. IC’s too, I used a lot of flux and that just made drag soldering across pins a doddle. I couldn’t have done.
When you’ve done a few hundred through hole pins and you want them to look better, add flux and reflow every pin, just sweep the iron against the pin and you’ll be amazed how much better a finish it gives to the end result.
Everyone’s has their own technique but just go with what works for you.

[gdonner]

Very nice work indeed!

You mentioned a few videos that inspired your A4000 work; earlier this month, Retromancave started a nice series for the A4000 worth taking a look at (if you haven't already):

"Commodore Amiga 4000 Trash to Treasure (Pt1) - Meet the A4000"
"Amiga 4000 - "Damn you Mehdi Ali" & PSU Repairs - Trash to Treasure (Pt2)"

[johntayloruk]

Taken a bit longer than expected, but finally finished the first of the A3660 cards.
Getting the right Gal and data files for this burnt was a real pain, hence the sockets.
I’ve 9 more PCB’s so will put up a post to sell a couple and I’ll make a few more cards to sell while I have the parts. If anyone’s interested drop me a PM.

Some pics can be found at.

http://imgbox.com/Sqr7ANha
http://imgbox.com/AtnZKxgm
http://imgbox.com/VEFPrdor

Cheers,

John

[hooverphonique]

Originally Posted by johntayloruk

Taken a bit longer than expected, but finally finished the first of the A3660 cards.
Getting the right Gal and data files for this burnt was a real pain, hence the sockets.
I’ve 9 more PCB’s so will put up a post to sell a couple and I’ll make a few more cards to sell while I have the parts. If anyone’s interested drop me a PM.

Some pics can be found at.

http://imgbox.com/Sqr7ANha
http://imgbox.com/AtnZKxgm
http://imgbox.com/VEFPrdor

Cheers,

John

If price is reasonable, I might be interested in a A3660 board.

[johntayloruk]

If anyone's interested I'm selling a couple of A3660 PCB's here:
https://eab.abime.net/showthread.php?t=103586