How far gone must a BBC be to be unfixable?

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Commie_User
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How far gone must a BBC be to be unfixable?

Post by Commie_User » Thu May 31, 2018 4:43 pm

I'd like to throw this question open to the Acorn users especially. Their dedication to repairs and maintenance are probably second-to-none, coupled with such high technical literacy. What is the worst condition Acorn machine which users have repaired and restored to any kind of glory and what's the limit? Can I hear your stories?

With Commodore people, it seems to be when the board tracks have utterly perished.


In my universe, they've even successfully mended Commodore computers that have been stored under water or absolutely saturated with machine grease during their lives: http://www.lemon64.com/forum/viewtopic. ... fc510bc6f8

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Re: How far gone must a BBC be to be unfixable?

Post by danielj » Thu May 31, 2018 5:13 pm

The limit has to be when the parts to fix it cost more than a new machine? They're fairly robust. Anything with a complete circuit diagram and built mostly from off the shelf components is mostly going to be fixable with the time/inclination.

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Re: How far gone must a BBC be to be unfixable?

Post by geraldholdsworth » Thu May 31, 2018 5:56 pm

danielj wrote:
Thu May 31, 2018 5:13 pm
The limit has to be when the parts to fix it cost more than a new machine?
Surely that is still fixable...just uneconomical to fix?
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Re: How far gone must a BBC be to be unfixable?

Post by 1024MAK » Thu May 31, 2018 6:19 pm

Over at Sinclair ZX World, various members have created new PCB's and new ULA equivalents. ZX81 and ZX80 keyboard membranes are available. So in theory, as long as the case is okay, an entire machine can be recreated.

It's the same with ZX Spectrums, except ULA equivalents are harder to get.

For a BBC model A or model B, if someone wanted to, it would be possible to create a new PCB, so then it's a case of obtaining all the chips. The glue logic (74 series logic) should not be a problem, but some of the others may be hard to get at a reasonable price.

Of course, the Video ULA/VideoProc is now not a problem thanks to a member on here :D

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Re: How far gone must a BBC be to be unfixable?

Post by CMcDougall » Thu May 31, 2018 7:11 pm

Probably when they have been is salt water or when a old battery has leaked it's guts.

then the PCB is beyond fixing, unless your want to sit for hours re making tracks with jumper wire....
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Re: How far gone must a BBC be to be unfixable?

Post by duikkie » Fri Jun 01, 2018 9:40 am

i think if the PCB board is gone. by fire . all other thinks are fixable. allmost every chip is to buy :)
but if there are no tracks left you have a problem. new board oke , but still the old board is gone then

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Re: How far gone must a BBC be to be unfixable?

Post by Coeus » Mon Jun 04, 2018 3:49 pm

Given the talk of creating a replacement PCB from the circuit diagram, the question of Trigger's broom (or the Ship of Theseus) seems relevant. When do you consider that you have fixed a machine and when do you consider that you have created a new work-alike one?

Is there a reimplemention of the Serial ULA?

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Re: How far gone must a BBC be to be unfixable?

Post by 1024MAK » Mon Jun 04, 2018 4:09 pm

Coeus wrote:
Mon Jun 04, 2018 3:49 pm
Given the talk of creating a replacement PCB from the circuit diagram, the question of Trigger's broom (or the Ship of Theseus) seems relevant. When do you consider that you have fixed a machine and when do you consider that you have created a new work-alike one?
That is a fair question, but like the answer 42 in a certain sci-fi drama, it depends on the question...

The PCB itself is just one component, it's no different than say the OS ROM chip. Is a computer still original if the ROM/EPROM is replaced with a new one?

What about in the Master, where the OS has been modified to overcome the limitation of the date range?

Everyone will have their own opinions. To a (purest) collector who does not use the machines, (normally) everything must be as it came out of the factory, even if it does not work.

But to a hobbyist, keeping it working so it can be used is more important than all the parts being original...

In reality, with the amount of work needed, the size and cost and while the used market is very active, I can't see anyone actually creating a new Beeb PCB anytime soon.
Coeus wrote:
Mon Jun 04, 2018 3:49 pm
Is there a reimplemention of the Serial ULA?
I have not heard of one, or a project for this.

Mark

PS, at the recent ABUG meeting, of those machines had their case tops off, most had at least one 'expansion' PCB fitted/connected...
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Re: How far gone must a BBC be to be unfixable?

Post by dgrubb » Fri Jun 08, 2018 5:09 pm

Commie_User wrote:
Thu May 31, 2018 4:43 pm
With Commodore people, it seems to be when the board tracks have utterly perished.
That's probably my personal limit as well. I'm game for repairing a small number of traces, but if a leaked battery has corroded through several layers and damaged a large number of traces then it's probably beyond my ability to repair.
Commie_User wrote:
Thu May 31, 2018 4:43 pm
In my universe, they've even successfully mended Commodore computers that have been stored under water or absolutely saturated with machine grease during their lives: http://www.lemon64.com/forum/viewtopic. ... fc510bc6f8
I saw that video by the 8-bit guy when he first posted it and was deeply impressed. He did a great job, although I wonder if he would still have been able to complete the repair if the board itself took more damage. He was lucky that most of the electronics repair consisted of swapping out ICs.

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Re: How far gone must a BBC be to be unfixable?

Post by tricky » Fri Jun 08, 2018 5:33 pm

For me, if the PCB was gone, I would probably put in an FPGA with options to switch between different beeb models.
This would be more useful for me and as I have quite a few "real" ones, I would feel OK.

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Re: How far gone must a BBC be to be unfixable?

Post by steve3000 » Sat Jun 09, 2018 7:39 am

All depends on time/effort you are willing to put into repairs and if you are treating it as a hobby/learning exercise.
dgrubb wrote:
Fri Jun 08, 2018 5:09 pm
Commie_User wrote:
Thu May 31, 2018 4:43 pm
With Commodore people, it seems to be when the board tracks have utterly perished.
That's probably my personal limit as well. I'm game for repairing a small number of traces, but if a leaked battery has corroded through several layers and damaged a large number of traces then it's probably beyond my ability to repair.
Over the past 18 months (often with weeks/months in between sessions) I've been repairing track-by-track an early A3010 with Adelaide (ARM2) mezzanine board. It has lots of battery leak-damage and corroded tracks on it's PCB, all around the sound, video, CPU and keyboard circuitry. Even now I'm not sure of the full extent of damage yet, but so far repaired about 30 tracks! The computer itself is working, disc drive loads OK, external keyboard and mouse work, but the internal keyboard decoding circuitry isn't working yet and video output (which was working well at one point) stopped working about 3 months ago... I've learnt so much about the circuitry of the A3010 in the process, and every little improvement in function feels so rewarding! I'll get there one day :)

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Re: How far gone must a BBC be to be unfixable?

Post by sydney » Sat Jun 09, 2018 7:58 am

This has made me think is a redesign of the PCB a good idea, maybe using a large ram ic instead of the large number needed now, built in 1770 controller instead of the Intel one. Built-in mmbeeb, beebsid/beeopl , pitube connector, smallymouse ... Etc.

Probably not but its an interesting thought exercise. What would you add and remove to make the ultimate beeb PCB?

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Re: How far gone must a BBC be to be unfixable?

Post by Elminster » Sat Jun 09, 2018 8:12 am

De ja vu, I think we discussed this before. Certainly for Electron. And looks like Roland might have been persuaded to do a new Atom fun.

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Re: How far gone must a BBC be to be unfixable?

Post by Commie_User » Sun Jun 10, 2018 2:36 am

1024MAK wrote:
Thu May 31, 2018 6:19 pm
Over at Sinclair ZX World, various members have created new PCB's and new ULA equivalents.
Ah yes, The UK micro world's Shelbyville against the BBC crowd's Springfield! :D (Or perhaps that's Amstradland.)

I would imagine servicing Sinclairs would be less economical in the long run if the boards were less robust than the Acorn ones and needed mending all the time.

Probably much more rewarding though, if new upgrades could make a more greatly marked difference.

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Re: How far gone must a BBC be to be unfixable?

Post by 1024MAK » Sun Jun 10, 2018 7:18 am

People have mainly recreated boards as a learning experience, or to make a compatible computer without having to use a ULA (e.g. Harlequin) or to use modern memory (e.g. using modern SRAM instead of DRAM) or to add extra features, rather than just a like for like replacement.

Having said that, new exact copies of ZX80 PCBs have been made and new exact copies of Jupiter Ace PCBs have been made.

Although some versions of the ZX Spectrum PCB are more susceptible to damage, this is not normally a problem until an inexperienced person tries desoldering components. The PCBs don't normally die natural deaths, as although the recommendation is to renew the electrolytic capacitors, the originality fitted capacitors don't often leak. And there are no batteries in Sinclair computers.

And it's not hard to wreak any double sided (or multilayer) plated through board if you are not careful when desoldering.

Mark
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Re: How far gone must a BBC be to be unfixable?

Post by Elminster » Sun Jun 10, 2018 9:39 am

And some people have replaced the innards with a raspberry pi. Of course it is on legal to do this on a completely dead Beeb :twisted:

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Re: How far gone must a BBC be to be unfixable?

Post by sirmorris » Sun Jun 10, 2018 1:24 pm

Quite far gone I'd say, like this Atari 800 xl.

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Re: How far gone must a BBC be to be unfixable?

Post by Elminster » Sun Jun 10, 2018 1:25 pm

sirmorris wrote:
Sun Jun 10, 2018 1:24 pm
Quite far gone I'd say, like this Atari 800 xl.
Looks like someone drove a car over it. Ouch.

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Re: How far gone must a BBC be to be unfixable?

Post by Commie_User » Mon Jun 11, 2018 2:31 pm

My hat goes off to this guy. Don't know why but it does.

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Re: How far gone must a BBC be to be unfixable?

Post by dgrubb » Wed Jun 13, 2018 9:38 pm

steve3000 wrote:
Sat Jun 09, 2018 7:39 am
Even now I'm not sure of the full extent of damage yet, but so far repaired about 30 tracks! [...] I've learnt so much about the circuitry of the A3010 in the process, and every little improvement in function feels so rewarding! I'll get there one day :)
Highly commendable!

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Re: How far gone must a BBC be to be unfixable?

Post by DutchAcorn » Sat Jun 16, 2018 6:58 am

steve3000 wrote:
Sat Jun 09, 2018 7:39 am
Even now I'm not sure of the full extent of damage yet, but so far repaired about 30 tracks! [...] I've learnt so much about the circuitry of the A3010 in the process, and every little improvement in function feels so rewarding! I'll get there one day :)
I have an A5000 board under repair like that. Now fixed 21 tracks and it is booting to desktop but the FD and IDE HD don’t work yet.
Paul

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Re: How far gone must a BBC be to be unfixable?

Post by RobC » Sat Jun 16, 2018 8:21 am

DutchAcorn wrote:
Sat Jun 16, 2018 6:58 am
steve3000 wrote:
Sat Jun 09, 2018 7:39 am
Even now I'm not sure of the full extent of damage yet, but so far repaired about 30 tracks! [...] I've learnt so much about the circuitry of the A3010 in the process, and every little improvement in function feels so rewarding! I'll get there one day :)
I have an A5000 board under repair like that. Now fixed 21 tracks and it is booting to desktop but the FD and IDE HD don’t work yet.
How have you guys approached this sort of repair? I have a couple of A5000 alphas and a couple of Adelaide A3010s that won't boot or give POST and just wondered how you have done it. My intention was to try to make a 33MHz ARM3 A3010 system but I've abandoned the idea for now.

My R260 needed a similar sort of repair with a dozen or so damaged tracks but it was visually obvious where the problems were - however, after a few years of working fine, it's also refusing to boot now :(

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Re: How far gone must a BBC be to be unfixable?

Post by daveejhitchins » Sat Jun 16, 2018 8:38 am

RobC wrote:
Sat Jun 16, 2018 8:21 am
My R260 needed a similar sort of repair with a dozen or so damaged tracks but it was visually obvious where the problems were - however, after a few years of working fine, it's also refusing to boot now :(
More corrosion, probably sneaked under the solder resist :?

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