Can anyone identify my 16K Rampack?

[sheddyian]

I have a RAMPack that I bought around October 1982 in the UK, probably from WH Smiths but may have been somewhere else. It's not a Sinclair one.

The case was a flat rectangle in black plastic, I think the manufacturer name was a stick on label. It was assembled with double sided foam pads, no screws as I recall.

I long ago took it out of it's case and that has been lost, but I still have the board intact. It currently doesn't work, but there are some suspicious things to look at, not least being one of the edge connector pins being bent, as well as the dodgy solder joints around the connector itself. I suspect I swapped the connector or modified it in some way many years ago.

Does anyone recognise it or hazard a guess as to who made it? Or indeed have any comment to make on it's design?

[Trevor_B]

Reminds me of my old one - a Big Byte I think it was called. Had a huge box around it which made it more unstable than the sinclair version (if such a thing was possible)

I'll see if I can dig out a picture [edit - a quick google search shows that our own Lardo Boffin has the Byg Byte pack too - though it's not the same]

[Moggy]

I would say it's one of Yarmouth's finest, KAYDE.


A picture of mine albeit with the chips and a cap removed but the same board I would say.

Only my opinion,but just like their keyboard shoddily made rubbish.

Strangely enough there was at that time also in Yarmouth another company called DK or phonetically DEKAY who also made keyboards and other accessories for the Sinclair range albeit of a better build quality. They did use the same key caps and stick on transfers as KAYDE I seem to recall but not aware of any connection between the two companies.



Kayde Electronic Systems
48/49 Exmouth Road, Great Yarmouth, Norfolk NR30 3DP

dK'tronics
23 Sussex Road, Gorleston, Great Yarmouth, Norfolk

Their two respective keyboards.

[Lardo Boffin]

I think I have / had a similarly large boxed RAM pack. It was in a large shiny black box which I think was just glued together.

I will have a look.

[1024MAK]

Reminds me of my old one - a Big Byte I think it was called. Had a huge box around it which made it more unstable than the sinclair version (if such a thing was possible)

Bug Byte?

Mark

[1024MAK]

Or indeed have any comment to make on it's design?

Looking at the photos, it was hand soldered. Hence the brown deposits of flux on the underside of the board.

It uses eight 16k bit (16k x 1 bit) DRAM chips, with each chip providing one of the eight data bits (hence eight chips to make one byte per address), each of which looks like they have a date code of 1982 week 21.

It must be an early design, as it uses four multiplexer chips (74LS157), two to switch between the address from the Z80 and a refresh address generator, and two to convert between a 14 bit address and the 7 bit multiplexed address wanted by the DRAM chips. Later designs of RAM pack dropped the refresh address generator, As it was found not to be needed.

The refresh address generator is formed from a 74LS393 counter chip.
The ‘glue’ logic and address decoding is being done by the 74LS32 (4 x OR gates) and 74LS00 (4 x NAND gates).
A 741 op-amp looks like it is being used as an oscillator / charge pump to generate the -5V bias voltage supply (essential for the DRAM chips). It uses the nominal +9V from the Sinclair UK700 or UK1200 PSU to supply the +12V rail that the DRAM chips require.

Moggy, someone stole your chips!

Mark

[sheddyian]

Thank you all for the swift response!

It is indeed a KAYDE rampack, I recognised the picture of it in its case instantly.

Regarding the shoddyness, I had no problems with it for the few years that I was using it, not even any wobble as such. And the hand soldering along the edge connector is likely my own bodging years ago, though why I don't remember. The soldering on the other chips looks much neater.

I would agree to the shoddyness in one aspect, that being how the case was just stuck together with double sided foam pads!

I've got a 32K chip to put inside one of my 81s, so I don't yet know if I will try to get this ram pack working again. What do you think, is it worth it? My electronics fault finding skills aren't great, I have a DMM but no other test equipment, for example.

Thanks

Ian

[Moggy]

Or indeed have any comment to make on it's design?

Moggy, someone stole your chips!

Mark

It's how I got it Mark ( yes it is a 741 used for the oscillator which is all I wanted for a pre-amp!)

[Moggy]

Thank you all for the swift response!

It is indeed a KAYDE rampack, I recognised the picture of it in its case instantly.

Regarding the shoddyness, I had no problems with it for the few years that I was using it, not even any wobble as such. And the hand soldering along the edge connector is likely my own bodging years ago, though why I don't remember. The soldering on the other chips looks much neater.

I would agree to the shoddyness in one aspect, that being how the case was just stuck together with double sided foam pads!

I've got a 32K chip to put inside one of my 81s, so I don't yet know if I will try to get this ram pack working again. What do you think, is it worth it? My electronics fault finding skills aren't great, I have a DMM but no other test equipment, for example.

Thanks

Ian

Only my two pennorth as I'm not known for my tech skills but I would have thought the one chip(give or take) RAM mod you want to do would be far easier than trying to restore a multi chip 30 odd year old RAM pack which if still faulty could, as they sometimes do, take the ULA out as well.

Best take advice from any one of the forum guru's,Mark being one of the most active and ready with good easy to follow advice, if not sure.

As for KAYDE they went tits up fairly early around 83 I think whereas DK did rather well for themselves.

[1024MAK]

Is it possible to repair a RAM pack? Yes.
Would you want to? Not sure.

There are two problems, as I see it. The first is that the DRAM chips used have been out of production for a long time now. And they are not very reliable. Any ‘new’ ones are still going to be old. And everything ages including silicon chips, even if not used.

The second problem is that this type of DRAM chip really, really does not like it if the +12V power rail is powered up before the -5V rail. And that is exactly what happens with this design. So before doing anything else, you have to check (by testing) that the -5V supply system works. Preferably with no DRAM chips fitted. But all the chips on this board are soldered in.

So it may be rather a lot of work.

If it is important to you (sentimental) and you really, really do want to repair it, you will get help. Otherwise, my feeling is, you are better either using a more modern expansion that includes more RAM, or fitting a modern SRAM chip on the ZX81 board (internal RAM upgrade).

The choice however is yours...

Mark