A4000TX ATX Amiga motherboard

Thanks for the link.
But I will modify the 56 pin connector.
10 connectors are too many to just use one.
In AliExpress I will order the 100-pin connector, they were no longer in Mouser when I made the purchase.

https://es.aliexpress.com/item/32968781297.html?spm=a2g0o.cart.0.0.20543c003PneUP&mp=1

My current progress
33pbn9c.jpg



Now, I'm waiting for the Chip memory that I ordered from AliExpress to arrive.
 
Thanks for the link.
But I will modify the 56 pin connector.
10 connectors are too many to just use one.
In AliExpress I will order the 100-pin connector, they were no longer in Mouser when I made the purchase.

https://es.aliexpress.com/item/32968781297.html?spm=a2g0o.cart.0.0.20543c003PneUP&mp=1

My current progress



Now, I'm waiting for the Chip memory that I ordered from AliExpress to arrive.


I see that you revomed the center support in the PLCC socket`s. this can give problems I belive when the chip is inserted and may push the contacts out of possition in the middle. I did also buy the plcc sockets
and is tempted of doing the same. But now I have ordered some low temp solder paste so I hope I will manage to solder them in with hot air. If I have to remove the center support I also have an idea of 3dprinting a frame
to fit arround the socket and give more pressure if needed. But it won`t be an nice fix for shure.

For the 54 POS connector I will try to modify the 56 POS connector some how. I may remove two of the end contacts and then add a 3D printed end stop so that the card will fit perfect. There is no problem with space on the edge between the 100 pos and 54pos even if you use a 56pos connector.

Im also looking for the 100Pos connector, mouser was out of stock.
 
I have removed the inner plastic of the socket to be able to weld better.
You can always put something inside and then the chip on top. But I think it is not necessary.


I have already modified the connector.


I have cut one end.

20200615_152812_resultado.jpg

and then I left it to the size of the 54 Pin

20200615_152837_resultado.jpg

And now you can solder it to the board.

20200615_214417_resultado.jpg




I have bought ten 100-pin connectors on Aliexpress.

https://es.aliexpress.com/item/32968781297.html?spm=a2g0s.9042311.0.0.186363c00XK6D4

​I will put five of them on sale when they arrive.
 
I ordered 10 of the 54pin edge connectors.
Guess its going to be some time before they show up, but I'm in surplus once they show up.....
 
I had my order cancelled too. Was told he could not send it to me due to covid 19 and being unable to post to me. I smell bullshit, but you never know.
 
If someone has one of the 54pin edge connectors and can ship it to the UK let me know.

I tried to order 100 pcs from Ebay and they didn't turn up, i got told by the seller they where stopped by UK customs and because i'd refused to pay the import tax they had been returned to the seller at his cost so there would be no refund.
Needless to say nobody ever contacted me to say that the shipment was held up by customs and that i needed to pay the import tax. i've now written this cost off but i'm still on the look out for some connectors. i had planned to offer the ones i didn't use on here at cost + shipping. but nevermind.
 
Hi :) just wonder on what PSU I should go for with this A4000TX board. I do not like to put a 500watt PSU in it since I belive that is just stupid but do anyone know if the board have any overcurrent protection? If there is a short it may blow more that just components, worst case tracks on the board if there is no protection. I do see some fuses but not shure what they are ment for. Hese do you have any thoughts on this?
 
Every high quality Power Supply should work, that means with Overvoltage, Undervoltage, Overcurrent and Shortcrcuit Protection.

Even a A4000 System with 64MB Onboard Ram, CS MK1 060 (128MB), Fastlane (64MB), Picasso IV, A2386SX, AriadneII, SCSI CD Rom, CD-RW and 128GB SSD with SCSI Adapter consumes significantly less than 100W.
But since an Amiga use almost exclusively the 5V Line 20A schould be the minimum the Powersupply can handle, the other Lines are completely uncritical.

As a Guide the The A4000 Powersupply Specs:
+5V 25A
+12V 10A
-5V 0,3A
-12V 0,3A
 
A4000D power supply hasn't got -5V. There is only +5V, +12V and -12V, see spec on it. A4000D motherboard power connector hasn't got possibility to connect -5V too, so A4000D itself doesn't need it and if any card on Zorro bus require -5V it has to have it's own DC/DC converter.
 
An A4000D the -5V is generated from the -12V line with an 7905 linear regulator (U198) and two parallel 20 Ohm Resistors.
This is a common cause of error if this line is loaded, since at 0,3A the Regulator is feed with 9V (3V voltage drop at the resistors) and generate 1,2W heat without a heatsink...
 
A4000D power supply hasn't got -5V. There is only +5V, +12V and -12V, see spec on it. A4000D motherboard power connector hasn't got possibility to connect -5V too, so A4000D itself doesn't need it and if any card on Zorro bus require -5V it has to have it's own DC/DC converter.


You're right. The A4000TX have a MC7905CD2TG for generating (1A) nagative 5v.
Hadn't seen that.
 
An A4000D the -5V is generated from the -12V line with an 7905 linear regulator (U198) and two parallel 20 Ohm Resistors.
This is a common cause of error if this line is loaded, since at 0,3A the Regulator is feed with 9V (3V voltage drop at the resistors) and generate 1,2W heat without a heatsink...

OK, You're right. I have missed it when I was checking it on www.amigapcb.org. But I still don't know why the spec says that the power supply has -5V.
 
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