ZX81+35 Clone

[Paul]

Sorry, I didn't want you to change your mind!
I just wanted to explain that wobbly ram packs aren't an issue anymore. And if anybody has an unreliable interface it might be a solution to exchange the plug with a modern type as sold by reichelt. It has two metal pieces per contact and uses high quality steel instead of cheap stuff that only plugs in three times and then breaks.
And the zeddynet example was meant as an successful example of using a different, more reliable plug a long time ago.
Please don't change your design. It's very neat and well planned.
kind regards Paul

[mahjongg]

Thanks for the appraisal

[mahjongg]

I have created a component overview drawing of the ZX81+35 Rev 2.2

ZX81+35 silkscreen overview.png

(84.09 KiB) Downloaded 377 times

next up the BOM (Bill of Materials)

[mahjongg]

OK during the sixth anniversary of of Revelationspace, (my maker space) the bill of materials file I made for the ZX81+35 Revision 2.2, was readied.

I can' t seem to upload it (as pictures) here, it seems I have reached an "upload limit" here, but the pictures and the .ODF spreadsheet and the spreadsheet as a .pdf can be downloaded from Revspace, here: https://revspace.nl/ZX81%2B34_ZX81_clon ... nuary_2016

Total price for the components of the base unit is just over €40, when sourced from Farnell, so probably cheaper elsewhere. The PCB should not cost more than say something like 20 euro's from a Chinese PCB house. But I will wait to release gerber and drill files only after I have certified my design is working, that could take a few months.

[mahjongg]

My own favorite PCB manufacturer now sells "naked proto boards" for lower prices, a 10cm x 10cm 2-layer PCB is € 28.68, ready in seven working days.

http://be.eurocircuits.com/shop/orders/ ... rator.aspx

Although such a PCB is without solder masks, it unfortunately is also lacking a silk screen.
Still I think I will use this for my next proto PCB, as it is fast cheap and easy, and it resembles the "naked" ZX81 board, although those had solder-masks on their bottoms (which for me is almost totally unnecessary because I will hand solder the board, and its mostly SMT anyway).
But the ZX81 (as all Sinclairs boards) had a silkscreen on top, which is very necessary when selling the boards as kits, but mine will be "bare", which isn't a problem for me, although it will look different from a regular ZX81.

I'm thinking to create a "backup package" of the CAD and design files, and upload it at revspace, just for security.

[mahjongg]

The idea to upload a backup to Revspace was thwarted, as Revspace does not allow the upload of a .ZIP.
I was however able to upload the schematic by giving it a false .SCH extension.

I'm looking for an alternative.

[1024MAK]

Google Drive?
https://www.google.com/intl/en/drive/

Mark

[mahjongg]

I was thinking of dropbox, but google drive sounds good too.
I want a system where I not only can drop files into, but also share them with a select few.
Google drive sounds the way to go, will make an account.

[RWAP]

I have some spare capacity on a dropbox account which I would not mind sharing...

[mahjongg]

Yes, that would be an acceptable solution, Thanks for the offer! Not only are all the design files backed up, but in one fell swoop I also found a person who will safeguard them in case something happens to me, not that I expect that, but you never know.

today I ordered parts, and one PCB. I also found out that almost to the day the parts and PCB(s) for the first version were ordered exactly a year ago! Even through the actual PCB was finished a year earlier, I was almost a year out of commission due to a bad leg wound which needed to be operated upon.
From experience I have learned that I don't need three PCB's, so I ordered just one.

previously I thought to order "naked proto" PCB's, but when trying the design files did not get through Eurocircuits "design rule check", it seems that "naked proto" PCB's need very slightly more copper around their holes (outer layer annular rings). I did not have the patience to fix that, so I went for the normal "PCB proto" PCB's with solder masks and silk screen, just like the first PCB, price is almost double, but for a single PCB I don't really care. The solder mask might even help prevent soldering errors.
The PCB will arrive in seven working days, the (farnell) parts probably tomorrow, both parts and PCB though the company I work for, so I don't have to pay taxes.

RWAP, would you please send me a PM, so we can talk about the details?

Thanks.