Recreating the Bywood Scrumpi

[Karen O]

That's brilliant, Phil.

You even have a vintage power transistor!

[Timbucus]

Originally Posted by Karen O

That's brilliant, Phil.

You even have a vintage power transistor!

That is an actual real one - he has been sent materials by the owner of the SunMoonStars one - glorious like a teacher marking our homework

[Timbucus]

The owner Mike as well as taking the above extra pictures has also kindly scanned his original letter and documents for Phil and I and said it was fine to share them. I have put them in order as the original PDF had an error for editing they have ended up quite big but, here they are on my Google drive for those interested:

Original BYWOOD SCRUMPI 1 document scans

[Slothie]

Well this allows you to check your deductions against the circuit diagram! A brief look over it seems to show you for most of the important stuf right, and the interface to keyboard and ETI 560 VDU is interesting.

[Timbucus]

Indeed I am pleased -chilling how close the assembly instructions are I wrote! I have been reading the VDU docs and thinking I might build one as it may give some insight into the thinking for the 3 although it is obviously a totally different design it will also make a cool addon.

[philoupat83]

Hello
yes thanks to Mike he came out are scrumpi and it still works.
damage the pcbs are in manufacturing I can no longer modify them.
we were not far from the original.
consolation it works I hate to play with.
the differences seems to be the resistance r5 which is not the pullup of D of the 74c74 but of the Out of the NE555 the scales used are not the same and Mike to solder under the PCB the pullup of D.
it is expected to be sent to TIM for KAREN SLOTHIE AND SIRIUS a PCB
may be that I will redo the pcb closer to the original now we have everything to redo it.
it is necessary to find how to make of the transparent epoxy the Chinese do not and with the good serigraphy and the etamage
for sc rumpi2
I have reflected on the circuit I do not understand the number of CI needed for addressing two are enough and the one behind the CPU seems to be the 74ls00 of the NADS and RDS/WDS the rom is an MM5403Q so alim -12v.
I finish a programmer for this type of eprom the monitor is maybe ETIBUG.(jim can give us the solution)
for Scrumpi 3 a lot of questions?
what do you think?

[philoupat83]

It’s fake I love this stone age thing too cool

[philoupat83]

I like the breakers

[philoupat83]

pcb dimensioning according to Mike
126mmx166mm
or 5"x6.5" as predicted by TIM

[Timbucus]

Originally Posted by philoupat83

pcb dimensioning according to Mike
126mmx166mm
or 5"x6.5" as predicted by TIM

Only slightly bigger than a Eurocard... supports my thinking of Vero case or S68 origin. Actually I found reference to the term S68 much earlier so ETI must have had a 6800 in their mind as a machine basis. When JMK was asked to assist he probably abandoned his similar design idea and just used elements.

Also Ha Ha that is funny that was my prediction from the photo but, I settled on 5 1/2" by 6" which you used as it said so in his advert in Dec 1976 ETI - he got his own size wrong. No wonder you were squeezed in space slightly.

I am currently working out why he used such a resistor network for the 555 it does not lead to the 1Hz in Step 12 he says and we have produced. I also cannot work out why there is a pullup on the 555 Pin 3 -> Clock input on the 74C74 it is not needed as far as I can see.

[Timbucus]

Originally Posted by philoupat83

may be that I will redo the pcb closer to the original now we have everything to redo it.
it is necessary to find how to make of the transparent epoxy the Chinese do not and with the good serigraphy and the etamage
for sc rumpi2
I have reflected on the circuit I do not understand the number of CI needed for addressing two are enough and the one behind the CPU seems to be the 74ls00 of the NADS and RDS/WDS the rom is an MM5403Q so alim -12v.
I finish a programmer for this type of eprom the monitor is maybe ETIBUG.(jim can give us the solution)
for Scrumpi 3 a lot of questions?
what do you think?

I think the current PCB (your second version) is great for people to own and operate an SC/MP2 based unit that is very close to the original - that is possible for people to build easily. As you say a redone absolute original one may be a good idea - I am tempted to clean up an image from the original - print it on a laser, iron it on and etch my own PCB - I wonder if the chemicals in my dad's shed are still usable... You can still get copper clad SRBP and I still have one or two pieces perhaps big enough from BITD.

On SCRUMPI2 I have stopped looking at it as I think it is worth waiting for photos from Jim. That news item you found in PE says:

"The PROM can be supplied blank or programmed by Bywood to customer specification for an extra £20,"

So I don't think he supplied any kind of OS - that did not arrive until SCRUMPI3.

On that as I have said it just does not seem to exist anywhere so I am carrying on doing the reverse engineering - I have a good sense of the board layout and memory map but, I accept a lot will be guesses. My first task is to get the Keyboard running and interfaced to my veroboard SCRUMPI 1.5 which I am adding an EPROM to I can then get the code developed - I will initially hook it up the MK14 VDU until I can engineer one. If one turns up in the meantime then I will have had fun anyway like this project so far.

[SiriusHardware]

Originally Posted by philoupat83

Hello
it is expected to be sent to TIM for KAREN SLOTHIE AND SIRIUS a PCB

While I watch this with great interest I do not intend to build a SCRUMPI at this time, but the thought was greatly appreciated, thank you Phil.

[Timbucus]

Originally Posted by SiriusHardware

While I watch this with great interest I do not intend to build a SCRUMPI at this time, but the thought was greatly appreciated, thank you Phil.

Just you wait - when I have it as a plug in diagnostic board for the MK14 the time will have come...

[philoupat83]

well maybe you’d like to build the scrumpi 2 or the 3
or maybe you like mk14 too much

[Timbucus]

Originally Posted by philoupat83

well maybe you’d like to build the scrumpi 2 or the 3
or maybe you like mk14 too much

This is going to get like the Spectrum / C64 playground war in a minute

[Mark1960]

Originally Posted by Timbucus

I am currently working out why he used such a resistor network for the 555 it does not lead to the 1Hz in Step 12 he says and we have produced. I also cannot work out why there is a pullup on the 555 Pin 3 -> Clock input on the 74C74 it is not needed as far as I can see.

I think the high level output voltage of the 555 with 5v supply does not meet the minimum high level input voltage of a cmos input. Typical is only 3.3v, but minimum is 2.75v

[philoupat83]

the famous ETI560_VDU

https://www.dropbox.com/t/CIbaPOYsKpenQCAy

[SiriusHardware]

Originally Posted by philoupat83

maybe you like mk14 too much...

I have owned my original issue II MK14 since 1978 and so yes, I definitely have an emotional or nostalgic attachment to the MK14 which I do not feel for the Scrumpi - I learned things from the MK14 then which I still use in my job and my hobby - both the same thing really.

I remember the adverts for the Scrumpi at the time but I am sorry to say I thought they looked very crude and unprofessional, especially compared to the much more professional looking adverts for the MK14.

This does not mean that I am not interested in the Jurassic-Park like activity (….bringing back dinosaurs) going on here, but I am quite content just to admire rather than engage with the activity.

[philoupat83]

don't be mad where's the English humor
of course scrumpi is not a successful system a little amateur low cost I think it has made a little bit of success
to program in binary what a galley and to light leds!
I think that the creator of this series was with a small team at the very beginning of computers.
He didn't have the support that Clive Sinclair had much more business with two genius engineers and the way was paved for the idea of a hobbyist kit.
but I love my MK14 martin.
And finally it's giving MJK back some of the glory.
maybe the scrumpi3 would have surpassed the mk14 it was already announcing the zx80
but then that's English history.

Translated with www.DeepL.com/Translator (free version)

[SiriusHardware]

Don't be concerned Phil, I have a very, very 'dry' way of 'speaking' so it is not always easy to tell when I am being serious or when I am joking even when you meet me face to face. I should be more careful to use emojis or more obvious language when I write here.

I am not mad at you or anyone, and as I said I admire what everyone here is trying to do. It is a great pity that MJK did not go on to fulfil his full potential, I agree.