What to do with a Grundy Newbrain?

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paulv
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What to do with a Grundy Newbrain?

Postby paulv » Tue Mar 21, 2017 7:22 pm

Hi Guys,

Today I received a Grundy Newbrain from my stepson's father in law as he found it in their loft and has no use for it. Clearly I have a reputation for collecting old computers and so it has found it's way to me....

The machine itself looks good but it's missing one key cap (The graphics key cap) and I've not done anything with it yet, including opening it up....

I've done some hunting around and I've found that the PSU has a BIG RIFA X2 cap in it (http://www.nightfallcrew.com/28/10/2015/filter-capacitor-rifa-removal-from-the-psu-of-a-grundy-newbrain/) that makes the Beebs X2's look like minnows so I know I need to pull that out and replace it with a new one before powering up without fear of the magic smoke....

Other than that, is there anything else I should look for before plugging it in and seeing if it actually works and does anyone know anyone who would have spares for a Newbrain such as a graphics key cap???

I couldn't find a Newbrain group of any kind whilst searching around and they really do seem to be museum pieces in more respects than Acorn kit so any and all advice is more than welcome...

Other links I've found that may serve useful up to now are...

http://www.8bit-homecomputermuseum.at/repair/newbrain/newbrain.html

http://www.newbrainemu.eu/

http://newbrain.hcc.nl/download/NewBrain_Handbook.pdf

Thanks

Paul

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FourthStone
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Re: What to do with a Grundy Newbrain?

Postby FourthStone » Thu Mar 23, 2017 12:39 am

Found a few listings on eBay, one of them was around US $120 which I guess is not too bad for a second unit as spares, there's also a kit with all the chips which is not too expensive which may be useful again as spares.

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.Xgrundy+newbrain.TRS0&_nkw=grundy+newbrain&_sacat=0

The emulator site looks good with some software you can use for testing etc.

If you don't plan to keep it, you might find a buyer on eBay as there does seem to be a small community of enthusiasts about but considering how it came to you maybe it's something to keep tucked away for a decade or two to see if it appreciates in value.

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paulv
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Re: What to do with a Grundy Newbrain?

Postby paulv » Thu Mar 23, 2017 12:54 am

I wasn't planning on selling it, I want to restore it and have a play because the machine has a bit part in the story of the BBC Micro in that it could well have been the BBC Micro and what we now call the BBC Micro would have simply been the Acorn Proton.

I've checked the PSU and the X2 cap was in a reasonably good state so I've powered it up for a couple of minutes. The VFD has flashing, garbled characters so there's some repair work to do but from what I've found online, it should be relatively easy to fix that.

I'm more interested in finding resources and enthusiasts so I can ask newbie questions etc. But even the Dutch Newbrain enthusiasts sites are 4-5 years old with no discernible updates.

There just doesn't seem to be a community for the machine, vibrant or otherwise :(

Paul

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daveejhitchins
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Re: What to do with a Grundy Newbrain?

Postby daveejhitchins » Thu Mar 23, 2017 7:04 am

paulv wrote:There just doesn't seem to be a community for the machine, vibrant or otherwise
Then we'll all have to chip-in with whatever we can. First off, Is there a schematic we can have a gander at?

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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hoglet
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Re: What to do with a Grundy Newbrain?

Postby hoglet » Thu Mar 23, 2017 8:03 am

daveejhitchins wrote:First off, Is there a schematic we can have a gander at?

Some holiday reading for you Dave:
http://www.goffart.co.uk/museum/schematics/newbrain.pdf

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Re: What to do with a Grundy Newbrain?

Postby CanonMan » Thu Mar 23, 2017 9:37 am

I could be wrong, but I seem to remember reading somewhere that Newbrains were notorious for being full of poor quality electrolytic capacitors, which cause all kinds of weird behaviour. If that is the case, you might want to think about doing a blanket replacement of all the electrolytics to see if that improves things.

EDIT: Maybe this will help! http://www.8bit-homecomputermuseum.at/r ... brain.html

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Re: What to do with a Grundy Newbrain?

Postby Commie_User » Thu Mar 23, 2017 9:54 am

I've heard the Newbrains were useless when they worked anyway, so I've no doubt user groups are relics now. As far as I am aware, Newbury were one company who hopped on the micro bandwagon, rather than make a tailored machine for a certain need, like Acorn or Sinclair or Commodore.

But that just makes an old computer a challenge. When it's working, I hope someone can rig it to send tweets or something, as you can with the ZX Spectrum. Or make funny noises enough to sample for music, as I'd be interested in.

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Re: What to do with a Grundy Newbrain?

Postby vanpeebles » Thu Mar 23, 2017 10:01 am

Throw it into a ditch :lol:

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hoglet
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Re: What to do with a Grundy Newbrain?

Postby hoglet » Thu Mar 23, 2017 10:19 am

Paul,
paulv wrote:Other than that, is there anything else I should look for before plugging it in and seeing if it actually works and does anyone know anyone who would have spares for a Newbrain such as a graphics key cap???

I have one spare key cap that I believe came from a Newbrain.
IMG_0868.JPG

IMG_0869.JPG

If this is any use, you are welcome to it.

Just PM me your address and I'll pop it in the post.

Dave

RobC
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Re: What to do with a Grundy Newbrain?

Postby RobC » Thu Mar 23, 2017 1:54 pm

Commie_User wrote:I've heard the Newbrains were useless when they worked anyway, so I've no doubt user groups are relics now. As far as I am aware, Newbury were one company who hopped on the micro bandwagon, rather than make a tailored machine for a certain need, like Acorn or Sinclair or Commodore.

To be fair, I think the Newbrain concept pre-dated the UK home computer boom by several years. Its Wikipedia entry has the project starting in 1978 so it would have been a very early entry to the UK market if it had been delivered on time.

It was originally intended to be used as the "BBC Micro" but delays and production issues meant that Acorn's Proton was chosen instead. And the rest is history... :D

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1024MAK
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Re: What to do with a Grundy Newbrain?

Postby 1024MAK » Thu Mar 23, 2017 3:29 pm

I'd recommend renewing all the electrolytic capacitors anyway...

Mark
For a "Complete BBC Games Archive" visit www.bbcmicro.co.uk NOW!
BeebWiki‬ - for answers to many questions...

Commie_User
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Re: What to do with a Grundy Newbrain?

Postby Commie_User » Thu Mar 23, 2017 5:06 pm

RobC wrote:To be fair, I think the Newbrain concept pre-dated the UK home computer boom by several years. Its Wikipedia entry has the project starting in 1978 so it would have been a very early entry to the UK market if it had been delivered on time.


Ah, yes! I got it mixed up with the Jupiter Ace! (Though the Ace tried to be innovative with its choice of OS.)

I still think the Newbrain, too, looked more a vehicle than any particular solution. It was a good idea for both Labour and Conservatives to invest in getting young people moving in the microelectronics industry. And it paid off with stepping stones like the Newbrain and springboards like the BBC.

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paulv
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Re: What to do with a Grundy Newbrain?

Postby paulv » Thu Mar 23, 2017 8:55 pm

Wow, what a great response :D

Thank you all =D> =D>

The NewBrain I have is an AD model with the VFD display on the front of the machine and it's currently displaying junk in a very similar fashion to the ones described here: http://www.8bit-homecomputermuseum.at/repair/newbrain/newbrain_ad_repair.html.

In the next couple of weeks, I'll have my workstation back in the utility room and I was planning to go through the info on that page and relate it to my example as it looks so similar in its fault.

I can see that when I press certain keys the display sometimes changes and stops flashing when the cursor keys are in use so I'm pretty confident that the basic machine is actually working but I don't have a TV to hook up to atm because that too is in storage at the moment so I'm just hoping that the TV out is reasonable.

In terms of repair for it as Mark had suggested, I was planning to replace the electrolytic caps straight away and then do a general once over for dry joints before then inspecting IC 402 and IC 412 as the primary suspects in the issue with the display.

Hopefully after that, it'll be up and running so it'll then be a case of making a cable for a tape player as the only thing that came with it was the PSU and a thermal printer which looks like it takes loo rolls.

A quick search online for an image gave me this...

Image

I have no idea what I'm going to do with that :-o

Paul

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1024MAK
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Re: What to do with a Grundy Newbrain?

Postby 1024MAK » Thu Mar 23, 2017 9:34 pm

I wonder how close it is inside to the version for ZX81, TS1000, TS1500, ZX Spectrums etc... linky
Image

These can take normal fax machine or till roll white thermal paper (but the roll may need cutting to size).

Mark
For a "Complete BBC Games Archive" visit www.bbcmicro.co.uk NOW!
BeebWiki‬ - for answers to many questions...

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Re: What to do with a Grundy Newbrain?

Postby paulv » Fri Mar 31, 2017 9:08 pm

Just a quick update.

Dave sent me his spare key cap last week which arrived last Saturday, I've finally got around to fitting it so here's a before and after shot...

Before:

NewBrain-NoKey.jpg


After:

NewBrain-NewKey.jpg


It might not be the correct key cap for the key in question but any key cap is better than no key cap :D

Thanks very much Dave :D =D>

Now all I have to do is strip it down and start investigating the prime suspects for its current state of wonkiness...

Paul

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Re: What to do with a Grundy Newbrain?

Postby Seldon2k » Sat Apr 01, 2017 1:49 am

Well done on the acquisition of the Newbrain AD.
There is a fair amount of information online on resurrecting these computers.
I have both the 'AD' and 'A' models of this machine.
They do use unusual connectors for Serial, Cassette etc.
Also in programming I/O they use Streams rather similar to the IEEE488/GPIB addresses used on Commodore machines.
The VFD display is a single line in a much larger screen, and it does have full screen editing.

I hope I have remembered all of that correctly as I have not touched mine in over 20 years!

Here is one being used to control a Robot:-
https://www.youtube.com/watch?v=2T6mNi2ula4
SD-Card for the Newbrain:-
https://www.youtube.com/watch?v=3G5fARz7HnM
Good Repair Tips:-
http://www.8bit-homecomputermuseum.at/r ... brain.html
Great AD repair tips:-
http://www.8bit-homecomputermuseum.at/r ... epair.html

Bye and good luck,
Terry, (Seldon2k)

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Witchy
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Re: What to do with a Grundy Newbrain?

Postby Witchy » Fri Sep 22, 2017 10:15 pm

*bump* :)

Apropos of a conversation last weekend at the Centre For Computing History in Cambridge I dug out my 'brains only to find both had expired temporarily. Also the RIFA delta network filter cap expired in one of the PSUs in their usual smelly manner so I replaced that tonight.

Cap replacement for the powerup and startup circuits brought one machine back to life but with caveats in that all the characters are shifted one pixel to the right and after a while the screen inverts and becomes unreadable. The VFD works fine however so the machine itself is OK. I've replaced all the 6.3V caps too but the screen still is unreadable. Hopefully a new batch of 25V ones will arrive tomorrow so I can do the rest.

Any help appreciated!

Pics:

newbrain-13.jpg

newbrain-14.jpg

newbrain-13.jpg
Attachments
newbrain-05.jpg
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Where RIFA capacitors come to die

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jonb
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Re: What to do with a Grundy Newbrain?

Postby jonb » Sat Sep 23, 2017 12:17 pm

Regarding the picture showing the BASIC prompt - looks to me like a vertical line of pixels is missing on the right hand side of each character. Check the character ROM / generator chip's output lines, as well as the shift register I assume it is using to clock characters to the screen.

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Re: What to do with a Grundy Newbrain?

Postby Witchy » Sat Sep 23, 2017 7:13 pm

It is, a 74LS166N which looks OK. In fact nothing looks out of the ordinary signal wise. I'm trying to find the name of the UK char ROM but no luck so far. I HAVE found a few different main boards in a box in the garage though, including an issue 2 which is totally different to the rest layout wise. I'll pull the char ROM from one of those. In fact I might as well pull the LS166s (there's 2) from one too.

The Newbrain Emulator contains all the ROMs but it isn't obvious which is the char ROM so I'll just examine them all in my EEPROM burner.

Cheers!
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Witchy
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Re: What to do with a Grundy Newbrain?

Postby Witchy » Sun Sep 24, 2017 10:20 am

Ah, the emulator just has a dump of the character set, no actual ROM. Right, time to fire up the desoldering station!
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Re: What to do with a Grundy Newbrain?

Postby Witchy » Thu Sep 28, 2017 5:34 pm

Just in case anyone else stumbles across this thread I fixed my AD the other night after tracing the video circuit backwards from the output with a logic analyser and verified outputs matched inputs etc. I got the to the 74LS166 shift reg that forms the byte stream from the character ROM* (SOVSR) and noticed it was regularly pulsing some data lines before RESET was asserted so the CPU wasn't doing anything. Replaced it with a new one and IT LIVES.

Time to fix my French one now!

newbrainWorking-6.jpg


*it looked fine with just a scope on each input

W
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jonb
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Re: What to do with a Grundy Newbrain?

Postby jonb » Thu Sep 28, 2017 6:31 pm

Nice one!

=D>

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Re: What to do with a Grundy Newbrain?

Postby Commie_User » Tue Oct 03, 2017 2:21 pm

That's fantastic, especially the BASIC. I heard it was supposed to have FOTRAN or something.

Now it's had a tune up, what's its remaining life expectancy? I've witnessed BBC and Commodore boards disintegrating and, of course, components go. I wonder how long before most original working micros become a memory. Though I would guess the tiny ones like the Grundy would last a whole while longer, especially with a good bloke putting the spanners to it as you have.


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