Sinclair ZX80 / ZX81 / Z88 Forums

Hahaha, good one.


So they took UK computer to make the movie look more... mysterious & exotic?


Cool info anyway, heh.

Oh - a modern clone. http://www.nyangau.org/rememotech/rememotech.htm

Okay here are details of the secondary side of the transformer wiring for the Memotech MTX PSU.
This includes the pin-out of the 6 way DIN plug. And here is the regulator circuit that the PSU feeds (sorry about the quality but the original image is not so good). Note that on one of my machines electrolytic capacitors C51 and C56 needing resoldering as they had dry joints. Despite their reputation, Memotech's design was not always brilliant. The position and way they mounted these large electrolytic capacitors is poor. Large electrolytic capacitors should be mounted flat on the PCB or given extra support and they should not be fitted right next to hot regulators

Edit: Images cleaned up and edited

Mark

Thanks for that. From the diagram, it looks like a 12V-0-12V transformer should do the job, maybe with a bit of work to get something lower than 12V to power the 7805... Tell if I've overlooking something - wouldn't want to blow anything up

Mike

The power supply components in the MTX (I suspect it is the 5V current boost transistor) run hot already, so I suggest the following arrangement using two transformers: As far as I can tell, the unexpanded machine only uses the +12V line for the video circuits, the tape in circuit and the 16k video DRAM.
There is a lot of logic and memory powered from the +5V line, hence why I am suggesting a 50VA transformer for the 9V ac that feeds the 5V regulator circuit.
Suggested components:
T1 Chassis Transformer 230v 6VA 4.5v+4.5v, e.g. Rapid 88-3902
T2 Chassis Transformer 230v 50VA 9v+9v, e.g. Rapid 88-3929
F1 500MA 20x5mm Antisurge Ceramic Fuse, e.g. Rapid 26-0384
F2 400MA 20x5mm Antisurge Ceramic Fuse, e.g. Rapid 26-0383
And of course suitable fuse holders...

Mark

yerzmyey wrote:Hahaha, good one.


So they took UK computer to make the movie look more... mysterious & exotic?


Cool info anyway, heh.

I thought Memotech was an American company?

Anyway, the only part of that movie that got stuck in my head (if we're talking about the same movie) was when they were trying to decide which cup size they would giver her.... Vector graphics never looked so good in my childhood.

BrunoFlorindo wrote:Vector graphics never looked so good in my childhood.

Yes, we are talking about the same thing

BrunoFlorindo wrote:I thought Memotech was an American company?

Hmmm. Wiki sayz: "Memotech was a company based in Witney in Oxfordshire, England".
That's the only thing I can say now.

Thanks. I could swear I saw a U.S. address in one or more ads in the Sync magazine (an American publication). Memotech add-ons are known for their quality. One day I'll have to get my hands on a Memotech keyboard and HRG interface.

I was reading a little bit more about these computers this morning, and looks like one of the founders is still active in electronics today. Geoffrey Arthur Coleridge Boyd seems to be working for New Transducers Ltd in Huntingdon, Cambridgeshire.

edit:

http://www.anvil-ict.co.uk/memotech/mtxsite/mtxfact.htm

Nice.

Update time

Since the activity in this thread , things have moved on.

Here is a web site page that includes lots of information about the MTX power supply arrangements.

And here on Memorum is a new PSU design for the MTX that can be built using off the shelf, currently available parts . If any one builds one, please do let use know how you get on .

Mark