Memotech ZX81 keyboard + ZXPand

Discussions about Sinclair ZX80 and ZX81 Hardware
palmheads
Posts: 40
Joined: Thu Apr 30, 2009 8:15 am

Re: Memotech ZX81 keyboard + ZXPand

Post by palmheads »

Hi All

OK so finally my Memotech keyboard arrived!!! (WOO!)

Its a lovely bit of hardware!

Unfortunately the H-J-K-L keys don't work. It weird 'cos the '81 cursor blinks when I press the keys, but the characters don't appear on the screen.

On the I/F connector, I noticed with the 2 isoloted prongs on the left (while looking at the connector), the 2nd from the left prong are a little bent. Could that be the problem? If they went making a connection to the edge connector, does it make sense those 4 keys wouldn't work?

Here is a piccie:
IMG_20150121_222511.jpg
(1.57 MiB) Downloaded 492 times
cheers
Daryn
RWAP
Posts: 1348
Joined: Thu May 08, 2008 8:42 am
Location: Stoke-on-Trent, UK
Contact:

Re: Memotech ZX81 keyboard + ZXPand

Post by RWAP »

I see the spacer is missing which means it would be easy to misalign the interface which could cause any sort of problem and even wreck some chips on the ZX81... Make a new one from a piece of cassette case and glue it in place before proceeding...
Moggy
Posts: 3231
Joined: Wed Jun 18, 2008 2:00 pm

Re: Memotech ZX81 keyboard + ZXPand

Post by Moggy »

Good grief A missing key way!! :o

Please do as Rich says and make a key-way at once before connecting again, as for the bent pins the bit of the pin that makes contact looks to be ok but perhaps closing the gap between the contact part of the pins wouldn't hurt, the part that's bent at the front doesn't make contact anyway so no worries there. :D

Should any of the gubbins inside the module be blown they are as far as I'm aware replaceable IE no custom chips etc.
palmheads
Posts: 40
Joined: Thu Apr 30, 2009 8:15 am

Re: Memotech ZX81 keyboard + ZXPand

Post by palmheads »

Cheers for the advice Moggy & RWAP!

Ok so put a wee plastic key-way/spacer in the gap, so that should be good now.

Still no go with the keys. I realised the Newline/Function key also is not working. So that makes 5 keys (H-J-K-L-NL).

Seeing there are 10 keys in a row, could this be a keyboard matrix issue? Maybe something on the PCB?

Funny, I wanted the Memotech keyboard to safeguard the membrane failing oneday (also have a membrane replacement stored away), but the keyboard has the failing keys issue! haha

cheers
Daryn
palmheads
Posts: 40
Joined: Thu Apr 30, 2009 8:15 am

Re: Memotech ZX81 keyboard + ZXPand

Post by palmheads »

HOLD THE PHONE!!!!! :)

I recalled seeing some memotech documentation on zx81.de.

http://www.zx81.de/memotech/_frame_e.htm

Clicked on the Keyboard I/F link

Read this:

"IS THE ORDER OF THE MEMOPAKS IMPORTANT?

Not terribly, but the 'big' Memopaks containing 16K, 32K, or 64K should
come last. If you've got a Memopak HRG (High Resolution Graphics),
it's best to put that first, next to the ZX81. All Memopaks come with
extender boards at the back, so adding on to your add-ons is no problem."

I had been putting the Memotech 16k RAM first, then the I/F. So just tried switching them....

IT WORKED!!! haha. WOO HOO!!!

How weird.

But anyway, all the keys work now!!! :)

Thanks all!

cheers
Daryn
User avatar
1024MAK
Posts: 5103
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Memotech ZX81 keyboard + ZXPand

Post by 1024MAK »

The keyboard not working when the keyboard I/F "buffer" is connected behind the RAM module could just be a dirty contact on one of the edge-connector contacts (or another type of poor connection, like a dry solder joint). Or it could be a minor fault with the RAM module (it has circuitry to control any interfaces behind it to help prevent problems when more than one RAM module is connected up).

At least you now know that your your Memotech keyboard works okay :D

And you have learnt that the most important part of a edge-connector is the locating peg / pin :mrgreen:

Many Sinclair ZX Spectrums have been killed when the locating peg / pin has broken or been lost from interfaces :cry:
It happened to me when I was school age :(

Happy retro computing :D

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
Moggy
Posts: 3231
Joined: Wed Jun 18, 2008 2:00 pm

Re: Memotech ZX81 keyboard + ZXPand

Post by Moggy »

Also if the ram pack DIP switches are set in a certain fashion anything, behind the ram pack tends not to be recognised.

The positioning seems more to do with the physical shape of the modules, small ones at the front with the larger ram pack fitting snugly behind.
Last edited by Moggy on Fri Jan 23, 2015 12:30 pm, edited 2 times in total.
Moggy
Posts: 3231
Joined: Wed Jun 18, 2008 2:00 pm

Re: Memotech ZX81 keyboard + ZXPand

Post by Moggy »

1024MAK wrote:

Many Sinclair ZX Spectrums have been killed when the locating peg / pin has broken or been lost from interfaces :cry:
It happened to me when I was school age :(



Mark
Take heart Mark it still happens to me and I'm retired!! :oops:
palmheads
Posts: 40
Joined: Thu Apr 30, 2009 8:15 am

Re: Memotech ZX81 keyboard + ZXPand

Post by palmheads »

Really happy with this set-up now. Don't think I need anything more! :)

Image

cheers
Daryn
rune
Posts: 174
Joined: Thu Sep 04, 2014 8:35 am

Re: Memotech ZX81 keyboard + ZXPand

Post by rune »

A blue memotech keyboard :o Never knew they made then in anything other than black.

Enjoy!
Post Reply