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If the Pi is always going to be powered by the BBC, then the easiest option is to cut the +5v USB connection. You only need ground, D+ and D- to send data, and a computer won't complain when an enumerated USB device draws zero current. One method is to cut the track on the PCB (not the method I woul...

Do you reckon you could also have a stab at my AlphaTantel which is the precursor to the TD2500? It's not a password crack this time but merely trying to locate the key that enters programming mode. There's a switch on the back that physically enables config mode but how you then enter new phone nu...

Latest discovery - a possible reset password. Found a subroutine which compares text pointed to by ($40) against that pointed to by ($42). The first call to this subroutine loads ($40) with $7A1E which contains the our previously identified "RESET!" text. So I suggest when prompted for a p...

Attached the ROM from Tony. The ROM must map to &C000-&FFFF for the reset vector to be found, but this then jumps to &6100, so ROM must also be at &4000-&7FFF. I've started disassembly of the code. From my findings so far: The R6501 has several bus modes, and the code switches b...

A Google for R1702-12 will yield a datasheet for the CPU. It has onboard RAM between 0040 and 00FF. 0040 to 005F gets battery backed, and probably holds the password. There's no obvious "factory default" link, so my money is on a "hold down a key and power on to reset" style meth...

Flat grey square capacitors with a purple top are un-polarised ceramic capacitors - identify the value and replace with any same value ceramic capacitor. Tantalum capacitors are polarised (the PCB will have one pin marked with a "+"), and are usually dark yellow or orange (really old ones ...

How do I make the cable up? What do I need to buy and where? Will only use the thing once to copy my discs and I’m done with it!! Usually a length of 34way IDC ribbon cable, and three 34way female IDC connectors. The connectors are crimped onto the cable (in a factory: using a specially designed pr...

To identify which pins, I would take the lid off the modem and see how the serial connector is wired. If it is panel mounted, with wires to the PCB, the PCB might even have markings telling you which wire/pin is which. An examination of the PCB+connector should reveal the ground pin (usually to a la...

Mandatory health warning: The input reservoir capacitors on a switch mode PSU will have high voltage DC (>300v) present which may persist for some time after the equipment is disconnected from the mains supply. It may be possible to modify the existing PSU. It may have provision for a link on the PC...

Is there any chance that the ROM labelled "BASIC" is actually the OS+BASIC ROM?

It wouldn't do any harm to move the BASIC ROM to the OS socket and see if it boots, and if it doesn't come up in BASIC see whether *BASIC works or not.

The A3000 has a weird non-standard DSR/DTR handshaking arrangement so I imagine the A3010 is the same... I worked it out with some help from serial wiring diagrams on the internet (A30x0<>PC) but don't remember what you need to connect to what. I sold my A3000 too so didn't bother to commit it to m...

I keep having reliability issues with my Beeb. Mostly it manifests itself as a reluctance to start up the first time every day. Once it is up it is stable for hours on end. I am reasonably convinced the problem is loose / sloppy ROM sockets, since pressing down on the ROM tends to fix things. I sho...

If you want some spade terminals for your beeb, PM me. I bought a sack load a while back. Bear in mind they are 'fun' to fit. Well, the 'fun' has been had! Thank you very much, @Colday - really appreciate it. Given the hard life this board has had I'm amazed (but happy) to say it has survived surge...

You can get them from Farnell's. Likely cheaper than eBay, And their delivery is superb. https://uk.farnell.com/murata/rder71h333k0m1h03a/cap-0-033uf-50v-mlcc-radial/dp/2990806?st=33nf Based on my experience over 30+ years - RS wins hands down for delivery. RS - next day ~99% - - Farnell next day ~...

And what this is, there are lots all over the board, marked A, this one has broken off . Decoupling capacitors - they are wired between 5V and ground, and (put simply) provide a local reservoir of energy when the IC nearby temporarily pulls more current from the 5V line. If these capacitors weren't...

Nice pizza box Stephen! They do come up occasionally for reasonable prices. I scored an IPX with keyboard and Sun monitor for postage as the owner was moving house and wanted rid. It's ex Bath Uni Maths department. Just needed a battery hack for the NVROM and it's a good 'un. I was given an UltraSp...

[*]the monitor socket looks like nothing I've ever seen before - certainly a cross between DVI and something else). A 13W3 ? Popular on Sun and SGI back in the day https://en.wikipedia.org/wiki/DB13W3 Note: Sun and SGI DB13W3 to VGA adaptors are not compatible with each other, despite having identi...

That could explain why it doesn't work at all in any beeb.... So I need to write the test ROM code to 0xC000 instead of 0x4000? Ok, I'll give that a go next. I do not think this is going to make any difference with the dishwasher beeb. But we shall see. My personal rule is to program N images into ...

https://en.wikipedia.org/wiki/Crystal_earpiece My tool of choice when trying to trace where a low level audio signal has disappeared. Use the tip of the 3.5mm plug as a probe, the thing is so sensitive, you don't need to provide a return path. Play a signal (an audio cassette will do) into the casse...

Test with the power switched off using the 200 ohm range on your multimeter. You are looking for a resistance of less than 1 ohm. Always test with a ROM chip fitted in the sockets and test the very top of the IC leg/pin. Pinging off at a tangent (as is my wont)... I'm a bit paranoid about using the...

If you want more randomness

After that, I was able to remove the pins and clear the holes individually, by standing the board vertically, applying the soldering iron to the underside and pulling the pin out with pliers from the top side. That was much easier than trying to get all 28 holes clear before moving the socket. My t...

I believe the Acorn data lives here in the Electron MOS ROM: \ Electron Acorn bitmap for Ctrl-Break \ ------------------------------------ .LC42B EQUB &18:EQUB &3C:EQUB &3C:EQUB &7E EQUB &7E:EQUB &00:EQUB &7E:EQUB &3C \ ...**... \ ..****.. \ ..****.. \ .******. \ .**...

OK. Thanks. Since my last post, I've run the following test program: 10 CLS 20 *MOTOR 1 30 PRINT "ON" 40 FOR N=1 TO 5000: NEXT N 50 *MOTOR 0 60 PRINT "OFF" 70 FOR N=1 TO 5000: NEXT N 80 GOTO 20 On running the program, I can confirm there is NO motor light OR sound ('click'). I'v...

No collision detection I note.
The circuit between the 68B54 and the Econet socket is more or less a direct lift from the original ("issue 1") Master Econet module.

Watch out for the 4.7uF 50V bipolar electrolytic! These seem to be NLA. I've chucked a poly film cap on my order to try in place of it. You can make a bipolar electrolytic from two "normal" electrolytics wired in series, wired "like to like". Remember that two identical capacito...

Possibly an adaptor to put two 2764's into a single 27128 socket. What would be the reason to do this? Probably one of * The mask programmed ROM 's won't be along for a few weeks. * "We have to ship 1.00 now, and then replace with the 1.20 ROM when it's finished." and/or one of the follow...

Colday wrote: ↑

Sat May 16, 2020 9:14 am

Or this...

image.jpgimage.jpg

The part number (203,011) looks like a Acorn product.
Possibly an adaptor to put two 2764's into a single 27128 socket.
(i.e. "top half" in one socket and "bottom half" in the other)

I presume this is some sort of disc controller8DC2E9E6-DE8C-4830-9493-C9E9DBA68AB7.jpeg The "8272" marking on the board seems to tally with a double density controller. So if this an 8272 why does the chip have what looks like a covered window as one might expect on an EPROM? Is the 8272 ...

I presume this is some sort of disc controller8DC2E9E6-DE8C-4830-9493-C9E9DBA68AB7.jpeg Microware DDFS? Looks like the item pictured on page 9 of Beebug Jan/Feb 1984 available at http://www.computinghistory.org.uk/downloads/14544 The "8272" marking on the board seems to tally with a doubl...