Search found 6694 matches

by 1024MAK
Sat Nov 18, 2017 11:20 pm
Forum: hardware
Topic: Electron Joystick interface and 'pokable' ports
Replies: 16
Views: 380

Re: Electron Joystick interface and 'pokable' ports

It would be best if the CPU Phase 0 clock (shown in Acorn documentation as phase 2, but the actual signal on the expansion port has been found to be phase 0, it appears Acorn dropped the ball, as it should have been the phase 2 signal...) is included in the control logic. The reason being, is that t...
by 1024MAK
Sat Nov 18, 2017 2:32 pm
Forum: wanted
Topic: WTB: 5.25" Floppies
Replies: 15
Views: 170

Re: WTB: 5.25" Floppies

What type of disks are they? The last IBM/PC disks were high density and have a different magnetic coating. They are not normally suitable. Also I f a disk has a alien format, the quickest, easiest method is to erase them using a bulk eraser. But as not many people have one, stick them next to a pow...
by 1024MAK
Fri Nov 17, 2017 11:55 pm
Forum: wanted
Topic: WTB: 5.25" Floppies
Replies: 15
Views: 170

Re: WTB: 5.25" Floppies

There is another possible cause of trouble. If the disks were originally used with a 40 track drive, the width of the head on a 40 track drive is wider than the head in an 80 track drive. So the 80 track drive may not be able to override all of the magnetic field made by the 40 track drive... Mark
by 1024MAK
Fri Nov 17, 2017 9:26 am
Forum: for sale / freebies
Topic: Thinking of selling some of my collection...
Replies: 7
Views: 150

Re: Thinking of selling some of my collection...

Note that I have edited my post above...
by 1024MAK
Fri Nov 17, 2017 9:22 am
Forum: for sale / freebies
Topic: Thinking of selling some of my collection...
Replies: 7
Views: 150

Re: Thinking of selling some of my collection...

@Stephen It may help if you let people know whereabouts you are in the world, as some potential buyers may want to collect. While others may need this information in order to get an idea of postage costs... When adding attachments, you can use the "Place inline" button, then you can copy a...
by 1024MAK
Fri Nov 17, 2017 9:11 am
Forum: hardware
Topic: EEPROM - the Holy Grail of Sideways Rom?
Replies: 340
Views: 25489

Re: EEPROM - the Holy Grail of Sideways Rom?

In my case, it's more of a "not discovered the limitations due to being too lazy and or too busy, or distracted by other shiny new items"... So, with Martin's tools, I have never bothered with the softlock, as I use a physical write protect switch. I have also never tried the checksum comm...
by 1024MAK
Thu Nov 16, 2017 10:00 pm
Forum: upcoming and recent events & exhibitions
Topic: ABUG EAST MIDLANDS (Winter Warmer) 17-19 November 2017 (Leicestershire) BOOKING THREAD
Replies: 106
Views: 3170

Re: ABUG EAST MIDLANDS (Winter Warmer) 17-19 November 2017 (Leicestershire) BOOKING THREAD

lazarusr wrote:I’ve been here for hours now. Where is everyone?

Um, you did reset the date on your watches and clocks in accordance with day saving time? In October we put the date back one day...
by 1024MAK
Thu Nov 16, 2017 5:50 pm
Forum: for sale / freebies
Topic: For free: two boxes of Acorn mags
Replies: 10
Views: 278

Re: For free: two boxes of Acorn mags

Ah yes Mr. Lurkio, but due to the small print in my "beeb-time contract" that Mrs. leenew made me sign, I am not allowed to have the laptop in bed... but I *am* allowed to read a magazine.... so therefore I can get more done with the real mags :D Lee. That's not the reason you gave me for...
by 1024MAK
Thu Nov 16, 2017 4:23 pm
Forum: hardware
Topic: Sounds weird...
Replies: 10
Views: 279

Re: Sounds weird...

As an aside, the test file on this web site allows you to check your upper hearing limit. Well, assuming your playback device has a good audio system...

I could just about hear the 15kHz on an iPad mini.

Mark
by 1024MAK
Thu Nov 16, 2017 4:19 pm
Forum: hardware
Topic: Sounds weird...
Replies: 10
Views: 279

Re: Sounds weird...

I thought that was a weird audio range. Given that human hearing tops out at around 20kHz to 22kHz (assuming you are young), why would they have a system that went as high as 62.5kHz?

Mark
by 1024MAK
Thu Nov 09, 2017 11:08 pm
Forum: off-topic
Topic: MiniPro TL866 Eprom Programmer
Replies: 11
Views: 178

Re: MiniPro TL866 Eprom Programmer

For a 2764 EPROM, the 5V supply current when active can be as much as 150mA alone. The programming current can be as much as 30mA (at 21V). Some EPROMs may need around 50mA. If the DC/DC step up converter was perfect (no losses), 30mA at 21V equates to 126mA at 5V. Assume that it is 75% efficient an...
by 1024MAK
Thu Nov 09, 2017 3:38 pm
Forum: hardware
Topic: WE 32K RAM Card Repair
Replies: 70
Views: 2099

Re: WE 32K RAM Card Repair

And the resoldering of a Watford Electronics PCB of the week award goes to....
























jms2
Well done =D> =D> =D>

Seriously, glad that you have it working okay now. Fancy a bit of reverse engineering to keep you busy... :mrgreen:

Mark
by 1024MAK
Wed Nov 08, 2017 11:09 pm
Forum: hardware
Topic: Beeb to SCART Aspect ratio switching?
Replies: 8
Views: 248

Re: Beeb to SCART Aspect ratio switching?

For testing (as in asking users to test their TV), you will see that I suggest using a PP3 9V battery. The aspect switching input should not be too current hungry. What does have a 75 ohm impedance, is the fast blanking / Composite/ RGB input on pin 16. But for RGB, that only needs 1V to 3V. Mark
by 1024MAK
Wed Nov 08, 2017 11:00 pm
Forum: off-topic
Topic: retro-kit.co.uk has gone SSL
Replies: 8
Views: 254

Re: retro-kit.co.uk has gone SSL

With Google Chrome and all the other browsers moving towards the target of forcing all sites to have some form of SSL on them even if it's just got a simple contact form on it, I've upgraded my site to SSL. I've put a couple of URL re-write rules into place so all non-SSL links should still work bu...
by 1024MAK
Sat Nov 04, 2017 1:17 am
Forum: hardware
Topic: Unable to Load on BBC B
Replies: 12
Views: 252

Re: Unable to Load on BBC B

I've not tried a 'modern' cassette deck with any of my machines. But it may be that the cassette deck that you have limits the volume at too low a volume level.

Mark
by 1024MAK
Fri Nov 03, 2017 9:12 pm
Forum: hardware
Topic: Electron Joystick interface and 'pokable' ports
Replies: 16
Views: 380

Re: Electron Joystick interface and 'pokable' ports

On some auto-fire joysticks, pin 7 is used for a +5V supply to power the electronics. On other designs of auto-fire joystick, the power is "stolen" from the fire button circuit via the pull-up resistor. But this arrangement can be unreliable if either no pull-up resistor is used, or the va...
by 1024MAK
Fri Nov 03, 2017 1:10 pm
Forum: hardware
Topic: Unstable display on issue 7 beeb
Replies: 14
Views: 303

Re: Unstable display on issue 7 beeb

There are two major chips that form (part of) the video system in a BBC Micro. The Video ULA/Video Proc (IC6) provides division of the master clock (square-wave) to provide various clock signals for the system, including the clock to the 6845 (IC2). The 6845 (IC2) provides all the video timing and t...
by 1024MAK
Thu Nov 02, 2017 9:37 pm
Forum: hardware
Topic: Electron Joystick interface and 'pokable' ports
Replies: 16
Views: 380

Re: Electron Joystick interface and 'pokable' ports

And this is the reverse engineered schematic from the other version (the version that uses a PAL).
First Byte Electron Joystick Interface (PAL version).png
First Byte Electron Joystick Interface schematic
Mark
by 1024MAK
Thu Nov 02, 2017 1:11 pm
Forum: hardware
Topic: Daisy-chaining 2 FDD
Replies: 7
Views: 163

Re: Daisy-chaining 2 FDD

There are two signals to select a floppy drive. The first is the 'motor on' control. With the Shugart interface (the type of interface used on Acorn BBC machines), this is a single control signal that goes to all the drives. So when the computer wants to access a disk, the same 'motor on' control is...
by 1024MAK
Thu Nov 02, 2017 12:56 pm
Forum: general
Topic: Today I received.....
Replies: 4270
Views: 235720

Re: Today I received.....

jonb wrote:
Lardo Boffin wrote:I now have more ZX81s than fingers.


Not sure why you would have so many of them, but hats off to you!
=D>

One for each of the nuclear turbine-generators in the back garden.... :lol:
by 1024MAK
Wed Nov 01, 2017 3:54 pm
Forum: general
Topic: Today I received.....
Replies: 4270
Views: 235720

Re: Today I received.....

Oh my! Calculatorfever is catching....!
by 1024MAK
Tue Oct 31, 2017 9:27 pm
Forum: general
Topic: Who saw the BBC II Micro?
Replies: 8
Views: 323

Re: Who saw the BBC II Micro?

As far as I can remember, 3.5 inch drives were available as 40 track single sided, 80 track single sided and 80 track double sided. And no, the 3.5 inch disks were not officially reversible/flippable.

Mark
by 1024MAK
Tue Oct 31, 2017 9:24 pm
Forum: general
Topic: Who saw the BBC II Micro?
Replies: 8
Views: 323

Re: Who saw the BBC II Micro?

3 inch disks are double sided. But the 3 inch drives fitted in the Amstrad CPC 664, CPC 6128, PCW 8256, ZX Spectrum+3 and the Tatung Einstein TC-01 computers were 40 track single sided. To use the other side of the disk, you ejected it, flipped it over and slotted it back in :wink: The Amstrad PCW 8...
by 1024MAK
Sun Oct 29, 2017 2:38 pm
Forum: hardware
Topic: Display issue on my spare beeb
Replies: 15
Views: 239

Re: Display issue on my spare beeb

It may be worth a try, with swapping the 6845. However, it is doing something, as you do appear to be getting some kind of display. If the 6845 was completely failed, there would be no DRAM refresh (all programs including the OS code would crash) and you would get no picture of any kind (black scree...
by 1024MAK
Fri Oct 27, 2017 5:50 pm
Forum: hardware
Topic: Turbo MMC ROM
Replies: 59
Views: 1291

Re: Turbo MMC ROM

OK I'll try that later, but it's a long winded affair to get the rom image into the beeb. I wont bore you with the details. I only have a TurboMMC interface to work with. Sorry about the upside-down pics, I'm taking the pics on my iPad, and I could have sworn I had it up the other way for the last ...
by 1024MAK
Fri Oct 27, 2017 2:23 pm
Forum: software: other
Topic: Running 8-bit Acorn kit with no OS
Replies: 9
Views: 370

Re: Running 8-bit Acorn kit with no OS

I think Tricky means, the code runs from ROM and does not need any RAM to run. If there is a fault with the RAM used for the display, this will been seen as corruption on screen. If the RAM used for the screen is okay, then there will be no on-screen corruption. Normally, with defective RAM, the OS ...
by 1024MAK
Fri Oct 27, 2017 2:17 pm
Forum: hardware
Topic: BBC B psu ok now has issues and cant get it onscreen
Replies: 22
Views: 419

Re: BBC B psu ok now has issues and cant get it onscreen

If you type

Code: Select all

*HELP

the machine will list any ROMs that include a list of the basic commands for that ROM chip. Most (but not all) will print at least something.

Mark
by 1024MAK
Thu Oct 26, 2017 9:27 pm
Forum: hardware
Topic: Electron Joystick interface and 'pokable' ports
Replies: 16
Views: 380

Re: Electron Joystick interface and 'pokable' ports

Ahh, there must be more than one version, here's mine:
IMG_5505.JPG
First Byte Electron Joystick I/F Tape & Case
IMG_5504.JPG
First Byte Electron Joystick I/F Case
IMG_5503.JPG
First Byte Electron Joystick I/F PCB top
IMG_5502.JPG
First Byte Electron Joystick I/F PCB bottom


Mark
by 1024MAK
Thu Oct 26, 2017 9:05 pm
Forum: hardware
Topic: BBC + Torch Z80 Help
Replies: 19
Views: 534

Re: BBC + Torch Z80 Help

Link to the Schematic in this thread :wink:

Mark

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