A3000 restoration

Ok, some of you might have seen the board i got recently http://www.amibay.com/showthread.php?t=3079&page=126
It's a revision 9/03 mobo. First and notable defect is the U254 chip, an 74F646SPC Octal bus transceiver (by description). Although this is not a programmable IC, meaning it's of general use, i found quite a few variations of it. And not one of the various hires pics of an A3k mobo i found on the net had the exact chip. I've seen quite a few 74F646 ones, but not this particular one. So, without further ado, i'd like to know if i can use any one of the variations as an alternative.
Bought this mobo knowing that this chip was busted, so it has nothing to do with being cheated. ;)
Once i get this cleared and order the appropriate chip, i'll have to do something with the lack of a psu. Awaiting a big delivery of power supply 15-pin sockets, due to the fact that there was a minimum order limit. :(
Also got me a rather nice condition A3000 case waiting to be populated :)

EDIT: Here's the 'chipped' chip :D

http://i298.photobucket.com/albums/m...ax54/CHIP1.jpg

http://www.onlinecomponents.com/fair...tml?p=11353365

one of these?

Exactly! "Important Notice: Fairchild products cannot be sold or shipped outside of the Americas." LOL
Thanks for the link anyway mate! What i want to know is if the alternative 74F646's are compatible, and why the heck i haven't seen another A3000 with one like mine... :unsure:

Here is mine!

http://img684.imageshack.us/img684/6...01011jb.th.jpg

I'm trying to see if I can get you the chip.

Quote:

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Originally Posted by salaxi54

Exactly! "Important Notice: Fairchild products cannot be sold or shipped outside of the Americas." LOL
Thanks for the link anyway mate! What i want to know is if the alternative 74F646's are compatible, and why the heck i haven't seen another A3000 with one like mine... :unsure:

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Did you see this link it's for fairchild in Greece..


http://www.fairchildsemi.com/cf/sc_Europe.html#Greece
:coffee:

Quote:

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Originally Posted by salaxi54

Exactly! "Important Notice: Fairchild products cannot be sold or shipped outside of the Americas."

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I daresay one of our fellow members on the other side of the pond might be willing to aid you here, if you genuinely can't get the part in Europe.

Quote:

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Originally Posted by salaxi54

Once i get this cleared and order the appropriate chip, i'll have to do something with the lack of a psu. Awaiting a big delivery of power supply 15-pin sockets, due to the fact that there was a minimum order limit. :(

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Nathan (AmigaManiac) sells ATX-to-A3000 PSU adapters, might be worth just getting one from him?

Quote:

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Originally Posted by ChrisUnionNJ

Did you see this link it's for fairchild in Greece..

http://www.fairchildsemi.com/cf/sc_Europe.html#Greece
:coffee:

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Yup! Nadda! Lookie:

a) Available Quantity 0

http://i298.photobucket.com/albums/m...54/74F6461.jpg

b) (translation) Attention! No relative components found

http://i298.photobucket.com/albums/m...54/74F6462.jpg

c) No results found

http://i298.photobucket.com/albums/m...54/74F6463.jpg

Andy, it don't have to be the exact chip if someone can verify the alternatives work.. I've sourced variations abroad that i can order. I know we have some wonderful people within the premises that would help indeed if need be :thumbsup:
As about Nathan's adapters i'm trully aware, but last time i had something come from down under it almost took between holidays :)

My friend, all mentioned parts are fully compatible with each other and will work.

On TTL world, what counts is the middle letters, not the suffix. So a 74F part can only be replaced by another 74F (or 54F, to complicate things a little, lol).

Explaining better: 74 is the prefix of ALL TTL chips, but those made to military specifications (insert MILspec jokes here), which then receive the 54 prefix. Nothing much different, only military parts can work in a wider temperature range and have ceramic bodies.

Then the "families":

74xx (where xx are numbers): first of all TTL chips, they are common as mud.

S (Schottky), one of the elder series, it is faster than normal 74xx chips, but tend to consume too much power;

LS (Low-power Schottky): tried to "cure" the S faults, but besides the low consumption, they are only a bit faster than ordinary 74xx chips.

F (FAST!): as name hints, those are only used when switching speed is really needed because its (for the era) high price.

HC/HCT: those in fact are ordinary CMOS chips with TTL pinouts for drop-in replacement with the advantage of very low power consumption. HCT is the attempt to reach higher speed operation. Both are the current "equivalents" are pure crap in my opinion. Avoid like the plague for anything more than drive a LED.

Thanks for the details Rogerio! What i've found abroad is an 74F646N. I guess that'll do the job :)

Yes, pretty much any 74F646 will do. 54F646 will do, also, but I think Doomy take all of those for his A2000 machines.

Quote:

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Originally Posted by rkauer

Yes, pretty much any 74F646 will do. 54F646 will do, also, but I think Doomy take all of those for his A2000 machines.

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Lol, i knew Doomy had a high level of quality criteria, but i didn't know it was a Mil-spec level... :lol:

These just came in today:

http://i298.photobucket.com/albums/m...54/SOCKET3.jpg

http://i298.photobucket.com/albums/m...54/SOCKET2.jpg

Brand new psu sockets! More than enough, so i guess i'll release them to the public soon. By the way, i located an 74HC646 locally, but Rogerio advised to stay clear of the HC kind.. Looks like i'll be ordering from abroad after all. :)

Mate - Shove the HC chip into a socket on the mainboard & if you get any troubles then I'm sure I can find & send one to you from the UK

(PS have you tried Futurlec ;))

Regards
TC :cool:

Thanks for the offer TC, i'll keep that in mind! :thumbsup: Tomorrow's the day. I'll do just that; get me a socket and try the HC chippy lol
Meanwhile, here's another part of the puzzle :

http://i298.photobucket.com/albums/m...ax54/CASE2.jpg

http://i298.photobucket.com/albums/m...ax54/CASE3.jpg

So, the pieces are coming slowly :)

It reminds me my Towerization operation: A3000D to A3000T, with Micronik A3000 (6910).

Good luck with this puzzle :thumbsup:

Thanks mate, i'll do the best i can :thumbsup:

Nice A3000 project, looking foward many more pictures :D


@rkauer
thanks for the refresher on 74xx chips rkauer :thumbsup:, you would`t have linky to any pics of the TTL 74xx series of chips would you, the ones I find never live up to my expectations

something like
http://138.37.35.209/staffinfo/davew...chips/7404.gif

but for most of the series and that will fit one or 2 bits of paper. sorry salaxi back to you now... ribbits

Nope, never needed. When I'm in doubt I search for the datasheets.

Got this stuff today. Might as well go ahead and experiment with it.

http://i298.photobucket.com/albums/m...54/74F6464.jpg

Couldn't find a 24-pin socket, so i got two 22-pin ones to custom-make one.. Things can only get better :)
Will also experiment with a spare power socket and see if i can cut hand-made protective caps for the cables, due to lack of availability on the market. :thumbsup:

Sounds like a plan :cool:

Quote:

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Originally Posted by cosmicfrog

Sounds like a plan :cool:

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Oy, indeed! :)
Now, first things first! Battery removal time...

http://i298.photobucket.com/albums/m...x54/BAT1-1.jpg

http://i298.photobucket.com/albums/m...x54/BAT2-1.jpg

http://i298.photobucket.com/albums/m...x54/BAT3-1.jpg

http://i298.photobucket.com/albums/m...lax54/BAT4.jpg

http://i298.photobucket.com/albums/m...lax54/BAT5.jpg

Then came the chip removal..

http://i298.photobucket.com/albums/m...54/SOCKET4.jpg

Here's a shot while cleaning the holes :)
http://i298.photobucket.com/albums/m...54/SOCKET5.jpg

So, you could easily tell i've been busy.. Next up will be socket time :thumbsup:

You can also take the opportunity for the A3000 "_INT2" modification.

@LTAC: I think it has been done before i got the board, but i'll study it :thumbsup:
Here's the final result:

http://i298.photobucket.com/albums/m...54/SOCKET6.jpg

Last two pins of the socket are cut from an additional socket, because i couldn't find a 24-pin one.
I'll take a few pics of the bottom tomorrow to show the cable mod (perhaps INT2)

Here's the promised pics of the bottom of the mobo:

You can see the blue wire held in place with hot glue. It was bought this way.
http://i298.photobucket.com/albums/m...ax54/back1.jpg

A closer look at the one end of the cable,

http://i298.photobucket.com/albums/m...ax54/back2.jpg

And the other end of the cable:

http://i298.photobucket.com/albums/m...ax54/back3.jpg

Now i'll have to compare this mod to the link LTAC has provided to understand if it's actually the same thing..

---------- Post added at 22:27 ---------- Previous post was at 22:23 ----------

Ok, it seems a little different! Although the lower end is soldered to the same place (pin 82 of CN606), the other end is not. Anyone know if this makes a functional difference?

There's more than one place you can pick up the INT2 signal. The 'starting point' for it is on one of the CIA chips (you'd have to look up precisely which pin of which CIA) but you can also pick it up from somewhere on the Z3 backplane connector. That's the recommended place because the cable run is shorter.

So, it just might be the same thing! I think i'll just leave it like it is. After all, i have no intention to 'push' this miggie any more than a 3630.. It's not intended for AOS anyway, if all goes well it will end up as an AMIX platform. :)

Quote:

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Originally Posted by salaxi54

So, it just might be the same thing! I think i'll just leave it like it is. After all, i have no intention to 'push' this miggie any more than a 3630.. It's not intended for AOS anyway, if all goes well it will end up as an AMIX platform. :)

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It certainly looks like it. There is a wire from a pin on the CPU socket going back to one of the CIA chips. It's almost definitely an INT2 mod.

Okie dokie, an update!
I had a friend (thanks Skyrunner) lend me his A3000 psu so i could do some tests.
So, without wasting time, i fixed a 'temporary' insulation to go beneath the motherboard. That took a rather mightier friend, Chuck :lol:

http://i298.photobucket.com/albums/m...4/A3000MB4.jpg

Now, it appears the socketed chip works! But there's a detail. I can't manage to operate the A3000 with an 030 cpu.. Either the onboard, or the 3630 one. I tried everything possible with the jumpers, but i get a white (actually light grey) screen. No flashing, no Caps Lock problems.
I've only the onboard 2MB Ram, but i also tried a 4MB Zorro board, to no avail.
The funny thing is that the motherboard is working fine with a 3640.
Here's a historical moment :D

http://i298.photobucket.com/albums/m...4/A3000MB3.jpg

So, what would make all the difference? A possibility may go with the onboard crystals! The 3640 has it's own, while the 3630 doesn't...
Any idears?

OH, NICE ONE! We do love the purple 'begging' screen. :)

If you're not working with any '030 but the A3640 does work, then I'd guess along the same lines as you, check the 25MHz Xtal is good and behaving itself.

Of course, the worst case scenario is you have to use an '040 instead of an '030. It's a hard life, isn't it? ;)

But yeah, excellent stuff so far, keep it coming. I really do love the A3000 and know just how much hard work they can be to get working, but they are so worth it!

:thumbsup:

Thanks for your comments Andy! :thumbsup:
Now, i was thinking, should i swap both onboard crystals? The one is the 50 Mhz one (most probably for the cpu, as it is a multiple of 25), and the other one is a 28.37516 Mhz one.. Now, that second one, i couldn't trace anywhere easily.
Under normal cicumstances, i'd just go with the 3640, and have this over with. But an 040 does not cooperate with the AMIX OS :(

The 28.37516 is the PAL timing crystal, necessary for the board operation, as all custom chips depends heavily of it.

NTSC machines uses a 28.6363 crystal.

I'd be most curious about the 50.000MHz one. As rk says, the 28.blah is a PAL timing Xtal. If you're getting PAL video output, it's probably behaving itself.

You could do a lot worse than pinch the one off the A3640.

Oh, and just to sanity-check, you are remembering to switch J100 and J104 back to INT when you take the A3640 out, right?

Could anyone direct me towards a link for oscilator sockets? (the rectangle ones) It seems i can't trace any. evilbay (BINs) would do as well i guess..
Don't want to simply solder the crystal directly on the mobo.
Thanks :thumbsup:

Doesn't FANOS (the electronics gear store) in Exarhia have them? I'd be surprised if they didn't.
Never owned an A3000 but from the looks of it, you need a DIL-14 oscillator socket. Amigakit for example has them in stock.

Are they even soldered? On my A3000, the two oscillators aren't "socketed" but are easily removeable and replaceable. They just pull out and push back in again, I think the legs on them are slightly angled inwards to hold them in place.

Quote:

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Originally Posted by salaxi54

Could anyone direct me towards a link for oscilator sockets? (the rectangle ones) It seems i can't trace any. evilbay (BINs) would do as well i guess..
Don't want to simply solder the crystal directly on the mobo.
Thanks :thumbsup:

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I don't know the dimensions of the A3000 MB oscillator, but for the standard rectangular ones you can use a standard 14-pin DIP socket, and clip off all but the 4 corner pins. The smaller square oscillators fit in a DIP-8 socket. (Here's a pic from one of my project prototypes)

https://lh3.googleusercontent.com/-N...Oscillator.JPG

It seems i've been searching the wrong way! :blink: If i type either oscilator socket or crystal socket i get nada on fleabay. But after BLTCON0 described it as DIL-14, ta-dah! :D
Anyway, i might visit downtown soon to see if there's availabilty.
Andy, i'll disassemble the unit again, and find out tonight hopefully if the oscillator is just sitting there.
@jthiem: Any chance to tell us what that prototype is for? We all love geekery projects around here :thumbsup:

Now, another question that has risen! Which pin is #1 on the mobo power socket? I went reading here: http://pinouts.ru/Power/amiga3000power_pinout.shtml and the socket drawing is indulgently bad.

http://pinouts.ru/connectors/amiga3000dpower.gif

The top left corner doesn't look like the real thing...
I've found this interesting, http://www.te.com/commerce/DocumentD...pdf%7F172171-1

but would really like someone else's verification.. Thanks!

Quote:

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Originally Posted by salaxi54

@jthiem: Any chance to tell us what that prototype is for? We all love geekery projects around here :thumbsup:

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Aww shucks, if I _have_ to... :D Hint: the chip next to it is a 6581 :thumbsup:

Joe.

Joe, that is some amazing stuff you're building there mate! Keep it up! :thumbsup:

@Joe
Wow! SIDshield for Arduino!!! Awesome project mate. Those Arduinos are so nice... Will try fitting one Nano unit on my Gameboy LSDJ for MIDI funz0rz s00n.
For SID funz I'm almost ready to use an SammichSID :)

Quote:

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Originally Posted by salaxi54

Now, another question that has risen! Which pin is #1 on the mobo power socket? I went reading here: http://pinouts.ru/Power/amiga3000power_pinout.shtml and the socket drawing is indulgently bad.

http://pinouts.ru/connectors/amiga3000dpower.gif

The top left corner doesn't look like the real thing...
I've found this interesting, http://www.te.com/commerce/DocumentD...pdf%7F172171-1

but would really like someone else's verification.. Thanks!

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Pin #1 is marked as such on the PCB with a silkscreened "1" at one of the connector's corners (the one closest to the U103 chip).
Or you can look at the underside of the board, #1 has a square solder pad (vs round ones for the rest).
While looking at the underside you can also verify that the middle of the three rows (pins 6-10) is indeed all grounds.

The other link doesn't seem of particular interest with respect to pinouts as it's just the mechanical specifications of the plug, here's the mating connector PDF too as found on the A3000.

Will you provide circuitry for the tick signal too (I suppose you'll be using an ATX power supply, not a genuine one)?

Quote:

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Originally Posted by BLTCON0

Pin #1 is marked as such on the PCB with a silkscreened "1" at one of the connector's corners (the one closest to the U103 chip).
Or you can look at the underside of the board, #1 has a square solder pad (vs round ones for the rest).
While looking at the underside you can also verify that the middle of the three rows (pins 6-10) is indeed all grounds.

The other link doesn't seem of particular interest with respect to pinouts as it's just the mechanical specifications of the plug, here's the mating connector PDF too as found on the A3000.

Will you provide circuitry for the tick signal too (I suppose you'll be using an ATX power supply, not a genuine one)?

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Good-golie! you're right! Pin 1 is indeed silkscreened. Thanks :thumbsup:
Now, as about the pdf link, if you look at the top left corner, you will notice that the male socket actually has pin numbers stamped around the plastic. (see attached pic)
I visited a nearby electronics shop, but they didn't have DIL-14 sockets, and i bought some female-receptacle single pins. Have just now soldered them at the four corners where the oscillator will be plugged in.

@AndyLandy: Mine's deffinitely soldered. Or actually, was :)

Ah hadn't seen the numbers upon first look. I get your original idea about pin #1 now :thumbsup: that would have worked very well too :)

Well, there's good news! It was the crystal after all. Put there a half-can 50 Mhz oscillator, and she woke up! :thumbsup:
Here's the pins i used as a socket

http://i298.photobucket.com/albums/m...54/SOCKET8.jpg

And here's the square crystal in place, temporarilly for experiment's sake.

http://i298.photobucket.com/albums/m...54/SOCKET9.jpg

So, this is "crystal clear" now :lol: Next step is getting the full-size one. After that, it's psu work..

Grand :thumbsup:

While waiting for some stuff to arrive, i got me a couple of transparent plastic sheets A4 size, and cut them to fit as an insulating pad under the motherboard. No big deal, but a bit better than ol' Chuck :)

http://i298.photobucket.com/albums/m...x54/PATOS1.jpg

http://i298.photobucket.com/albums/m...x54/PATOS3.jpg


http://i298.photobucket.com/albums/m...x54/PATOS2.jpg

Left me a rather small area uncovered (about 3x3 cm) at one corner, but nothing an extra sheet won't fix.
I also took measurements of the physical dimensions of the original psu, so i can "replicate" it as much as possible. That means some metal works up ahead..

Been a little busy these days... LTAC has sent me the 74F646 chip, plus a SCSI chip as a bonus! THANX dude! :thumbsup:
So, i am going through some metal works lately :)

Here's an old useless ATX psu

http://i298.photobucket.com/albums/m...4/LAMARIN1.jpg

Slowly transforming into:

http://i298.photobucket.com/albums/m...4/LAMARIN2.jpg

http://i298.photobucket.com/albums/m...4/LAMARIN3.jpg

http://i298.photobucket.com/albums/m...4/LAMARIN4.jpg

http://i298.photobucket.com/albums/m...4/LAMARIN5.jpg

http://i298.photobucket.com/albums/m...4/LAMARIN6.jpg

http://i298.photobucket.com/albums/m...4/LAMARIN7.jpg

http://i298.photobucket.com/albums/m...4/LAMARIN8.jpg

I hope it looks close to the original..
http://i298.photobucket.com/albums/m...4/LAMARIN9.jpg

I did some preliminary measurements before anything else :)
http://i298.photobucket.com/albums/m.../LAMARIN10.jpg

Stay tuned!

Really good work! :thumbsup:

You should ask for a job at COMMODORE USA to show them how to build a real AMIGA :lol::D:)
I'm impressed! It is fantastic and magical to see an unborn AMIGA like this! :bowdown:

Got the crystals from Cosmos today, and replaced the square one for a rectangle. But, i went out of luck!
Turned the machine on, after a few seconds of normal light-grey screen, the psu went BAM!.. :(
Needless to say, that i doubt it has anything to do with the crystal.
So, i opened the psu, and did a visual inspection. At first it seemed like nothing was burnt. But on a closer look, i noticed a charcoaled resistor on the pcb. It's R7. If anyone knows the value of this resistor i'd appreciate it.
The glass fuse is intact, measured it ok. Caps look good, solder side of the pcb is intact, no black spots etc..
I couldn't find the psu's schematics anywhere, just the main A3000 are the ones i could trace. The psu has a sticker saying "Serviced by DART Computers Services", which means it's been refurbished i guess..