Search found 29 matches

by MJS
Fri Dec 04, 2020 5:36 pm
Forum: 8-bit acorn hardware
Topic: Replacement black plastic BBC keyboard surround
Replies: 11
Views: 270

Re: Replacement black plastic BBC keyboard surround

I'd be interested too, if only because if they can be die cut and screen printed to the same standard, then they'd make nice replacements for a certain HiFi company's front fascias from the same era.
by MJS
Tue Oct 20, 2020 8:47 pm
Forum: 8-bit acorn hardware
Topic: Cub 1431 Red Screen
Replies: 16
Views: 457

Re: Cub 1431 Red Screen

You're also seeing lines when the beam should be blanked (those diagonal lines). In my experience this sort of thing is caused by leaky capacitors so I'd go for a full recap first. Interestingly, and nothing whatsoever to do with Cub monitors, it turns out that if you set the Chroma to minimum on a ...
by MJS
Sun Oct 18, 2020 11:52 am
Forum: 8-bit acorn hardware
Topic: The Master Lives!
Replies: 13
Views: 547

Re: The Master Lives!

I'd be interested to know where you got your cleaning disk from. I have a Canon MD220 disk drive that's a pain to disassemble to get to and clean the heads.
by MJS
Tue Oct 06, 2020 9:47 am
Forum: 8-bit acorn hardware
Topic: Help! Master 128 Resurrection (hopefully)
Replies: 20
Views: 1190

Re: Help! Master 128 Resurrection (hopefully)

I had some keys that would not work, or did so intermittently. I have a big can of de-oxit that I use for audio work and tried that to see if it'd work. It worked perfectly literally within a couple of presses.
by MJS
Tue Oct 06, 2020 9:44 am
Forum: 8-bit acorn hardware
Topic: Master 128 Power supply caps are blue?
Replies: 2
Views: 169

Re: Master 128 Power supply caps are blue?

I think the OP referring to the blue caps in between the line and neutral input and next to the varistors. Mine is the same. I don't think they need replacing - the Rifa branded ones are the ones to be worried about because their resin case cracks over time and lets moisture in hastening their demis...
by MJS
Sat Sep 19, 2020 7:51 pm
Forum: 8-bit acorn hardware
Topic: Master startup beep question
Replies: 6
Views: 285

Re: Master startup beep question

I got my MultiOS ROM today (after the postman had not bothered trying to deliver it a week ago and taken it back to the depot without leaving a card - grr - and thanks Mark for helping me find it). It turns out all the different MOS ROM images cause different beeps with 3.2 being the most inconsiste...
by MJS
Sat Sep 19, 2020 7:28 pm
Forum: 8-bit acorn hardware
Topic: Master 128 CMOS Fault - SOLVED
Replies: 7
Views: 406

Re: Master 128 CMOS Fault

Mine did some of the symptoms you're having (no keyboard, often saw TERMINAL). I went straight for IC8 - the VIA that handles keyboard/sound etc and that was the culprit. I ordered a new, compatible, one here: https://www.ebay.co.uk/itm/164245883607 It's worth putting a socket in if you replace it o...
by MJS
Fri Sep 18, 2020 3:03 pm
Forum: 8-bit acorn hardware
Topic: Master startup beep question
Replies: 6
Views: 285

Re: Master startup beep question

Thanks, that all explains a lot.

I know the second beep is essentially the OS saying 'I've initialised everything' but if the registers are random, why does my model B always make the same first beep? I'm guessing the surrounding circuitry initialises at different rates.
by MJS
Fri Sep 18, 2020 2:31 pm
Forum: 8-bit acorn hardware
Topic: Master startup beep question
Replies: 6
Views: 285

Master startup beep question

Should the Master128 make exactly the same startup beep as the model B? I ask because although I've got my dead one working again, it doesn't always startup with the same beep. The first part is often a different note or what sounds like a chord, but the second one is always correct when we get the ...
by MJS
Wed Sep 16, 2020 7:42 pm
Forum: 8-bit acorn hardware
Topic: BBC Master 128 slow to startup
Replies: 17
Views: 781

Re: BBC Master 128 slow to startup

Sounds like a timer issue and could be a leaky tantalum capacitor C21 in the reset circuit. Its time constant is about 1.3 seconds and should be fully charged to 5v in about 6 seconds. The Schmitt inverter IC19 pin 8 should flip before that though. I'm just guessing though - but I've seen this sort ...
by MJS
Sun Sep 06, 2020 7:01 pm
Forum: 8-bit acorn hardware
Topic: Model A Issue 7 Constant beep no keyboard
Replies: 13
Views: 517

Re: Model A Issue 7 Constant beep no keyboard

I've just fixed a Master with almost exactly the same symptoms and it was, in fact, the 6522 that controls keyboard, sound etc. I found it by probing the I/O pins of the 6522 and saw that some were not logic 0 and 1, i.e. 0 and 5v but various voltages in between. I also had a series of broken wires ...
by MJS
Sat Sep 05, 2020 5:47 pm
Forum: 8-bit acorn hardware
Topic: Master 128 won't boot
Replies: 3
Views: 210

Re: Master 128 won't boot

Success.

I borrowed a 6522 from my working model B and it boots. Now to play, and find a new VIA.
Once I'm happy this is working properly I'll add it to the hardware fault fixing guide.
by MJS
Sat Sep 05, 2020 5:13 pm
Forum: 8-bit acorn hardware
Topic: Master 128 won't boot
Replies: 3
Views: 210

Re: Master 128 won't boot

Of course, if the data direction register hasn't been set yet then the pins could be inputs or outputs and floating. Am I barking up the right tree here?
by MJS
Sat Sep 05, 2020 4:50 pm
Forum: 8-bit acorn hardware
Topic: Master 128 won't boot
Replies: 3
Views: 210

Re: Master 128 won't boot

I've established that port A on IC8, the 6522 handling the RTC, sound chip and keyboard encoder has logic levels anywhere between 1 and 3 volts. Definitely not right, so it's coming out.
by MJS
Fri Sep 04, 2020 6:45 pm
Forum: 8-bit acorn hardware
Topic: Master 128 won't boot
Replies: 3
Views: 210

Master 128 won't boot

Hi guys. Not content with getting a single model B I went and bought a 'non-working' Master 128 believing it'd be a simple power supply fix. It's a slippery slope once you've bought one... Well, it's got the dreaded long beeeep and a flashing cursor on screen. First fault was lots of broken connecti...
by MJS
Tue Sep 01, 2020 6:43 pm
Forum: 8-bit acorn hardware
Topic: BBC B+/Master graphics upgrade?
Replies: 28
Views: 1591

Re: BBC B+/Master graphics upgrade?

With interlaced displays the problem occurs when you have a hard horizontal edge. It only exists on one one scan line and that line is only displayed 1/25th of the time. Similarly if the object drawn has a horizontal line that's drawn on the other field line then it will appear to jump up and down 2...
by MJS
Sat Aug 29, 2020 5:18 pm
Forum: 8-bit acorn hardware
Topic: BBC Model B - new keyboard connector?
Replies: 25
Views: 952

Re: BBC Model B - new keyboard connector?

Make them long and flexible so that you just pull the keyboard forward when changing ROMs. :wink:
by MJS
Sat Aug 29, 2020 4:35 pm
Forum: 8-bit acorn hardware
Topic: BBC Model B - new keyboard connector?
Replies: 25
Views: 952

Re: BBC Model B - new keyboard connector?

Another option is the use of the dirt-cheap header cables sold for the likes of arduinos and Raspberry Pis, e.g. https://www.ebay.co.uk/itm/40pcs-Dupont-Jump-Wire-M-F-M-M-F-F-Jumper-Breadboard-Cable-Lead-For-Arduino-https://www.ebay.co.uk/itm/40pcs-Dupont-Jump-Wire-M-F-M-M-F-F-Jumper-Breadboard-Cabl...
by MJS
Sun Aug 23, 2020 11:53 am
Forum: 8-bit acorn hardware
Topic: Metal Paint to match BBC Micro
Replies: 2
Views: 237

Re: Metal Paint to match BBC Micro

Thanks, that looks just the ticket.
by MJS
Sat Aug 22, 2020 4:03 pm
Forum: 8-bit acorn hardware
Topic: Metal Paint to match BBC Micro
Replies: 2
Views: 237

Metal Paint to match BBC Micro

I purchased a disk drive off eBay and the drive itself is pristine, but the metal case around it has rust in one corner and looks a bit unsavoury. I want to re-spray it the colour of the BBC Micro - it's more yellow than cream. I'll probably need to treat the rust first unless there's a good rust pa...
by MJS
Mon Aug 17, 2020 1:22 pm
Forum: 8-bit acorn hardware
Topic: Safe archiving of 5.25" floppies?
Replies: 6
Views: 408

Re: Safe archiving of 5.25" floppies?

I've often wondered if such a thing were possible with modern materials, low noise electronics and software. The application I was thinking of was quadruplex video tape. This was the first successful video tape recording format but it relied on 2" tape written at right angles on heads that floated o...
by MJS
Sun Aug 16, 2020 5:58 pm
Forum: 8-bit acorn hardware
Topic: Help me understand my School Setup (35 years ago!)
Replies: 0
Views: 236

Help me understand my School Setup (35 years ago!)

A bit of a cheeky question but I'm curious as to how this was all interfaced and how it worked, and someone here must know. My school had a room full of Electrons connected to each other via ribbon cables and a home-brew interface plugged in the back. It was protected with cassette tape clear covers...
by MJS
Sun Aug 16, 2020 2:50 pm
Forum: 8-bit acorn hardware
Topic: Which Disk Controller to use?
Replies: 11
Views: 696

Re: Which Disk Controller to use?

I pulled the drive apart and cleaned it thoroughly, not that it needed it, the heads were pristine. So I've taken another close look at the disks - and they're not the best. Just because it floats around in the case, it doesn't mean it rotates! So, it's mouldy discs that are causing my issues. I hav...
by MJS
Sun Aug 16, 2020 1:50 pm
Forum: 8-bit acorn hardware
Topic: Which Disk Controller to use?
Replies: 11
Views: 696

Re: Which Disk Controller to use?

Thanks for the suggestions, I think Sideways RAM is my next upgrade.
by MJS
Sat Aug 15, 2020 9:55 pm
Forum: 8-bit acorn hardware
Topic: Which Disk Controller to use?
Replies: 11
Views: 696

Re: Which Disk Controller to use?

I can read the catalogue on most of the disks I’ve tried. A verify using the disc doctor often fails. Reading more about the drives it seems more and more likely that it’s dirt related so I’m going to have a good look tomorrow. I’m still new to using these drives (well, I’m not, but that was 32 year...
by MJS
Sat Aug 15, 2020 9:00 pm
Forum: 8-bit acorn hardware
Topic: Which Disk Controller to use?
Replies: 11
Views: 696

Re: Which Disk Controller to use?

The discs I tried all rotated freely and generally looked ok on the surface. The heads seem fairly deeply buried in the drive but the sled works perfectly as does the centre platter. It’s like a stutter, so I could believe it can be dirt causing the heads to vibrate, I’m just not sure the best way t...
by MJS
Sat Aug 15, 2020 7:09 pm
Forum: 8-bit acorn hardware
Topic: Which Disk Controller to use?
Replies: 11
Views: 696

Which Disk Controller to use?

I just bought my first Model B and was pleased when I found that it already had an 8721 FDC, DFS v1.2 and a Disc Doctor ROM installed. I then bought a disc drive and a bucket load of discs off ebay. The drive powers up perfectly and is Canon MDD 220 which I can find out very little about, but I did ...
by MJS
Sat Aug 01, 2020 1:17 pm
Forum: introduce yourself
Topic: Hello World
Replies: 9
Views: 472

Re: Hello World

I toyed with the idea of refurbishing them and selling on, but I think I need to get one for myself first.
by MJS
Sat Aug 01, 2020 12:56 pm
Forum: introduce yourself
Topic: Hello World
Replies: 9
Views: 472

Hello World

Hi All, I first used Acorns at School in the mid 80s. We also had a computer lab of networked Electrons running from an RM380z file and print server. It was all housed in a room that was formerly taught in by Nobel Laureate William Golding. If anyone else remembers the set up at BWS in Salisbury I'd...

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