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Modern Saturn 128 redesign.

D

David_M

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Joined
Oct 1, 2016
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647
Location
Melbourne, Australia
Yesterday I completed the circuit design for a Saturn 128k compatible ram card and sent for 10 prototype pcb's to be made.

I still need to write the GAL code but that shouldn't be too difficult. It will probably be a couple of months away because I didn't elect to pay for expedited shipping of the prototypes.

I'm wondering how much interest there is in getting production boards once the prototyping is complete.
new_saturn.jpg
 
David_M said:
Yesterday I completed the circuit design for a Saturn 128k compatible ram card and sent for 10 prototype pcb's to be made.

I still need to write the GAL code but that shouldn't be too difficult. It will probably be a couple of months away because I didn't elect to pay for expedited shipping of the prototypes.
Click to expand...

My you're busy at the moment (TRS80 ICE, this, ...)

I'm wondering how much interest there is in getting production boards once the prototyping is complete.
View attachment 46398
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I too would be interested (going in a 2e). Do you have an estimate for price?

PJH
 
pjhacnau said:
My you're busy at the moment (TRS80 ICE, this, ...)



I too would be interested (going in a 2e). Do you have an estimate for price?

PJH
Click to expand...

I've had a few projects on my todo list but hand wiring kind of kept them on that list. Now that I've worked out how to use KiCAD and found a pcb manufacturer that makes good quality prototype boards at a competitive price some of those projects are coming off the todo list. This particular one came about because I have five Saturn cards and only one of them doesn't get random errors, the other four have had a full chip swap and the fault follows the board not the chips. So I suspect it might be a timing or layout issue with the original design. Rather than waste more time coming up with a workaround I decided to just make my own board using a single static RAM.

I'm hoping I can do bare boards for about $10 plus shipping, these ones will need gold edges which adds to the setup price so the more boards run the more likely I can keep to that price.

I decided the prototype board looks ugly and is larger than it needs to be (cost). So I changed the layout to a more compact design which I intend to use for the production run if the prototypes work as intended.
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$10 each sounds about right with true hard gold plating on a 50-contact edge connector. Several of us are using pcbcart.com for hard gold plating, I don't know if the shop you ran your prototypes with will do hard gold or not, but if there's any question, give pcbcart.com a try. They've delivered consistently good products for many years, even in hobbyist sized batches.
 
glitch said:
$10 each sounds about right with true hard gold plating on a 50-contact edge connector. Several of us are using pcbcart.com for hard gold plating, I don't know if the shop you ran your prototypes with will do hard gold or not, but if there's any question, give pcbcart.com a try. They've delivered consistently good products for many years, even in hobbyist sized batches.
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They have a gold option for enig boards, it is a fixed surcharge for enig regardless of quantity. I'd need at least 10 solid advance orders to make it worthwhile getting production pcbs. With small runs shipping is the killer, it pushes the price per board up about 50%.
I got the boards for the Z80 ICE back today and the quality is great, with expedited shipping it doubled the price for 20 board with a HASL finish but it was only 6 days from the time I placed the order and I didn't want to wait 3 or 4 weeks.
 
In case anyone doesn't know what the saturn cards are good for they are awesome for copying floppies with locksmith 5.0
Locksmith will read the entire floppy disk in one pass and write out the copy to either the same or a different drive in about 15 to 20 seconds.
It is also compatible with any software that uses a standard 16k memory card.
 
I expect they are weeks away from being ready.
The prototype boards have been made but are coming registered airmail, so probably about 3 weeks. I am also moving house in 5 weeks time so further development will probably have to wait until I unpack at the new house.

Who knows if I manage to pack my huge vintage collection of machines and parts ahead of schedule I may find time to complete a prototype and write the GAL code before I move. If I manage the impossible I should have production boards in hand about 10 days after that.

rjustice said:
I would be interested in one.

/Rob
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The prototype boards arrived today, it has highlighted a few minor issues with the original layout.
The card edge is a little too tight a fit in the slot for my liking so I'll adjust the cut lines for the production boards.
For the production boards I have angle the led footprint so the leds can be bent upward and towards the front for a better viewing angle.
The hole spacing for the .1uf caps has been changed to better suit the common monolithic cap size rather than the ceramic disc cap spacing.
The electrolytic cap holes have been rotated 90 degrees to allow it to be bent over horizontally so it is less likely to be damaged.

Some of the parts I need are at my sons house 400km away, I had them delivered there thinking they would not arrive before I moved.. the move is now delayed so I'll have to get him to send them to me.
Of course all of my Apple computers have been pack in preparation for the move, so I'll have to locate them and teach myself how to code the rules for GAL programming.
 
Minor setback, while writing the GAL rules I discovered that to be 100% compatible with the original Saturn one mode bit needs to be initialised high rather than low like the others.
The latches I was using to store the mode bits don't support any initialisation other than low. So I've had to use different latches which has increased the chip count by one.
New prototypes boards have been ordered, hopefully all problems are now resolved.
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The new prototype arrived and its working.
There was one glitch, when I updated the schematic in KiCAD one wire overlapped the IC pin and it looked connected to me but KiCAD didn't agree and the trace was missing from the gerber.
After running a jumper for the missing trace all was well. I've updated the schematic so the production run won't have the issue.

Now that the first board is working I'll assemble another to make sure they play nice with other cards, if I find any issues with that it will just be some tweaking of the GAL code.
For those that are wondering, yes it does work in a 2e.
Saturn.jpg

I'm still out of pocket some due to other pcbs I've had made so for this one I'll need to take advance payments before I do a production run.

edit: I assembled a second board and they run happily together in a 2e, I also tested with an original saturn card plugged into a slot.
 
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I got a quote on the production boards with a ENIG-RoHS finish and gold plated edge connector.
The boards measure 60mm x 66mm.

I can confirm the cost at US$10 plus $3.50 postage.
Once I have 6 prepaid orders I will have the boards made, I should have them in hand ready to ship 6 days from when I place the order.

PM me for my paypal details.

I'll put together a parts list in the next few days, I bought the parts for the prototypes on ebay and it cost me less than $10 per board.
 
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soviet9922 said:
Sorry for my ignorance, but what this card do ? :p
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It is a remake of the Saturn 128k memory card for the Apple 2.
I use it mostly with locksmith to fast copy disks. With the 128k ram card it can read a whole disk in a single pass, then write out a copy in a single pass. I just timed it and it copies a disk in 20 seconds flat.
It has the functionality of a 16k language card in a Apple 2+, so you can load integer basic into it or for an Apple 2 with integer basic you can load applesoft basic into it.

Here is the manual for the original Saturn card, this one duplicates its functionality with a lower power usage and lower chip count. Of course all the chips are easy to come by unlike some of the chips on the original card.
Saturn 64k/128k manual
 
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