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Lardo Boffin wrote: ↑

Tue Dec 24, 2019 11:40 am

A new ULA for a ZX81. In an A4 sized postal box!


F248CAEC-73B7-487C-B2BF-0D56CB0E6735.jpeg

One way of stopping a postman from ramming a package through a letter box..

Keep in mind that if you have say a three input NAND gate and you are only using two inputs, the third input should be tied to the appropriate logic level, in this case a logic high. states don’t matter (unused gates), you can tie the inputs to either logic level. If you are using a "spare" 3 input...

Hi, I know the BBC Master has 4 banks of sideways ram. I have two pascal roms, if I install them (for some reason they appear as one in the *ROMS list) will they occupy one of the banks of sideways ram - leaving me three left? I've tried to get the ROMS to appear at position 0, but I cant. I think ...

You might find it easier/cheaper to get hold of 27256 devices compared to 27128. If you "double up" the image, you can use a 32k device in a 16k sockets on the BBC B mainboard and IC27 on the Master. In both cases, A14 is tied to +5v so only the upper half of the device is used. Your mileage may var...

i did buy it for 1 euro but how to use it :) someone know this E(E)promer 3.0 : (c)2000 parallele poort. DIY PROJECT from which book ? ( elektor/elektuur?) , pc ?? My google fu yielded this link https://www.taringa.net/+hazlo_tu_mismo/programador-eeprom-burner-batronix-hagalo-usted-mas-facil_1hv7r7...

One other question - I'm unsure which 6850 chip would be suitable. There's loads listed on ebay: MC6850 MC6850P MC6850S MC6850L F6850P Maybe there all the same an the first letters are the manufacturer and last letter is package type? Also there seems to be some newly manufactured ones from China a...

Use a separate MIDI port. If you don't: 1) You will have to modify the clock to the 6850 (Midi uses 31250 baud, so you'll need a 31250 x whatever multiplier Hz clock) That will stop you from using the serial port "normally", and will also break the tape interface 2) You will have to mess around with...

If I was going for a 5.25"+Gotek solution my shopping list would be: 1x Dual floppy case with one working FDD 1x3.5" floppy mounting bracket kit 1xGotek Either 1xcard edge to IDC adaptor, or a ribbon cable with the right connectors and without a twist. 1xBBC floppy power lead 1xMolex disc drive powe...

Does any one happen to have information on the rgb socket layout of the AKF17 ? Does this 9-pin-male socket differ from the common Commodore/Philips monitors then ? Or did just the Acorn 9-pin-RGB cable sort out those connections the right way as the Acorn being known for off-standards pin outs ? I...

That's part of the psychic abilities. How does the person writing the program know that there's a filing system number 73 which is selected with the *ZEEBAR command, but must be selected with the *XEBURE command to prevent it attempting to electrocute nearby cats on selection? How did that get out ...

The proper way is to use Service Call 18 and cycle through all filing system numbers 1-255, unfortunately, DFS 0.90 doesn't respond to Service Call 18, and (if configured) ADFS tries to mount a disk. You then have to fall back on *commands, which means requiring psychic abilities, dealing with Bad ...

cmorley wrote: ↑

Tue Aug 13, 2019 8:09 am

80 column text.

You can do that in Mode 3.

Thanks for the extra info 🙂 I've now tested with RF and get white text in modes 4 and 7 so moved on to look at the board. There are no obvious signs of dry joints or damaged tracks in those areas so I'll look at swapping the transistors out and go from there. If the drive transistors were weak/dyin...

Not sure off the top of my head if the composite out on a Master is supposed to have colour but if you have an RF lead do you get colour on the UHF output? If so then the problem is with the resistors/RGB socket. If that is green too then it is the Red & Blue buffer transistors or upstream of that....

Hi guys I just revived an old bbc master 128 and when I opened the case I was treated to the lovely surprise that there was a 2nd processor board fitted. I am wanting to do the modification to add a 470pf capacitor so as to make composite video into colour. As the board is perilously close to the a...

The images at http://mdfs.net/System/ROMs/AcornMOS/Compact510/ and http://mdfs.net/System/ROMs/AcornMOS/Compact511/
are both 65536 bytes in size.

Bear in mind that the 64K ROM contains ADFS, Basic, Utils, plus MOS.
Are you sure you haven't just got the MOS bit?

In the PC zone, thinking of 1.44Mb floppy discs, but bear with me Back in the mists of time, you bought blank unformatted floppies. Then (in the PC age), you bought preformatted floppies Then after nearly 20 years later, along comes the gotek, and everyone goes back to using "unformatted floppies" a...

If I don't have any spare resistor/<insert any other radial electronic component here> legs lying around the bench, I would reach for the reel of insulated single strand insulated copper wire, strip one end, cut link size+1cm, then strip the other end. Bend neatly with pliers and insert. For links l...

Elminster wrote: ↑

Tue Jun 11, 2019 9:48 am

I guess to get them as good at the ones you get in the kit you would want to heat shrink some heat shrink in the middle of your resistor leg.

Or increase the leg length (if inserted in an IC socket), or solder with an air gap between wire and PCB if being soldered in...

Take a couple of resistors from that pack of 1000 you got cheap on eBay, clip the leads off, bend to the right spacing with your pliers, trim to length, install....
That's the cheap way...

Now here's a thing... Tried !Rat (!Pirat) on my A5000 last night and it crashed out and wouldn't copy the Touch Window disk. Copied the program to my A3000 and it worked perfectly making a virgin 'Master' disk which then would register to my A3000. :D Is this because the A3000 has an 800K drive and...

I would suggest a small AVR or PIC device.
Then you could code whatever parameters you like - delayed spinup, delayed spindown, with no rummaging around the parts bin looking for resistors or capacitors when you want to change.

B+ Doesn't have the HAZEL RAM that the Master uses for filing systems... d. See: http://beebwiki.mdfs.net/ANDY There's a job there for someone who wants to rewrite/extend the B+ MOS to support service calls &21, &22, &24, and supports HAZEL for calls &0F, and possibly &12. Then they'd have to tweak...

I've also found out that the A3010 used a UM1662. Unfortunately the A3010 doesn't have a composite video output, so I can't see how the UM1662 video in differs from bog standard CVBS out. I'm struggling to find a useful Atari circuit diagram. I think I will just suck it and see. My expected problems...

Whilst rummaging around a box of spares I've found a UM1662 RF modulator - It modulates video+mono sound onto channel 36 with the sound on the former UK standard 6MHz subcarrier. I can find a couple of photos of the first page of the datasheet, and absolutely nothing else. I then thought of searchin...

I just saw an announcement on the local BBC news that the RCM is going to be on "Inside Out" East Midlands tonight as they cover the "craze" of collecting old home computers. I'm guessing that the show will appear on the following link sometime after 8:30pm tonight (11th March) for everyone that do...

1. IC76 You need to fit a 74LS163 (BBC B Circuit diagram and others here: http://mdfs.net/Info/Comp/BBC/Circuits/ look for bbc.gif ) Note that the header from the daughterboard may have spread out the contacts making an IC a loose fit. The fix is either to replace the socket, or if you want to avoid...

What's the 40 pin device?
(Edit: Cancel that question - found this https://www.mirrorservice.org/sites/www ... manual.pdf
and it says "Large Scale Integrated Circuit BASF 81041-001")

And have you located a replacement?

I replaced the BNC connector on one of my Beebs with a chassis phono socket. BNC connectors are reserved for test gear and 10base2 as far as I'm concerned. Unhappy memories of numerous broken composite video cables at school, and spending half your lunchtime trying to get a working picture...

Mine kept shutting down about 45 seconds after being powered up. Problem was caused by a botched/leaky battery pack. The battery pack died, and electrolyte from the batteries wicked up the lead and rotted the molex contact. It then continued to rot a track on the PCB. Luckily I could trace where it ...