Search found 253 matches

by johnkenyon
Sat Nov 28, 2020 5:39 pm
Forum: 32-bit acorn hardware
Topic: RISC PC 120v Power supply
Replies: 7
Views: 108

Re: RISC PC 120v Power supply

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...
by johnkenyon
Tue Nov 24, 2020 11:47 am
Forum: 8-bit acorn hardware
Topic: Help identifying this Model B
Replies: 16
Views: 368

Re: Help identifying this Model B

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.
by johnkenyon
Fri Nov 20, 2020 1:45 pm
Forum: 32-bit acorn hardware
Topic: Acorn A3010 and Serial WiFi adapter
Replies: 8
Views: 214

Re: Acorn A3010 and Serial WiFi adapter

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...
by johnkenyon
Wed Nov 18, 2020 7:54 am
Forum: 8-bit acorn hardware
Topic: Loose ROM sockets
Replies: 12
Views: 272

Re: Loose ROM sockets

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...
by johnkenyon
Mon Oct 26, 2020 4:54 pm
Forum: 8-bit acorn hardware
Topic: Someone's pinched my econet! (Not Mine Any More!)
Replies: 30
Views: 1762

Re: Someone's pinched my econet! (Now repair help!)

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...
by johnkenyon
Wed Oct 14, 2020 1:14 pm
Forum: 8-bit acorn hardware
Topic: Unknown rom
Replies: 27
Views: 813

Re: Unknown rom

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 ~...
by johnkenyon
Fri Oct 09, 2020 11:06 pm
Forum: 8-bit acorn hardware
Topic: Unknown rom
Replies: 27
Views: 813

Re: Unknown rom

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...
by johnkenyon
Sat Aug 22, 2020 8:19 pm
Forum: general
Topic: Today I received.....
Replies: 6056
Views: 640363

Re: Today I received.....

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...
by johnkenyon
Thu Aug 13, 2020 4:09 pm
Forum: other vintage hardware, software and languages
Topic: Picked up some unusual equipment today
Replies: 16
Views: 1247

Re: Picked up some unusual equipment today

[*]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...
by johnkenyon
Tue Aug 11, 2020 4:16 pm
Forum: 8-bit acorn hardware
Topic: Clearing EPROMS/EEPROMS
Replies: 52
Views: 1602

Re: Clearing EPROMS/EEPROMS

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 ...
by johnkenyon
Tue Jul 21, 2020 8:31 am
Forum: 8-bit acorn hardware
Topic: Model B - possible faulty cassette interface?
Replies: 30
Views: 1836

Re: Model B - possible faulty cassette interface?

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...
by johnkenyon
Sun Jul 12, 2020 4:00 pm
Forum: 8-bit acorn hardware
Topic: Faulty ROM sockets
Replies: 9
Views: 548

Re: Faulty ROM sockets

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...
by johnkenyon
Thu Jul 09, 2020 10:53 am
Forum: 8-bit acorn hardware
Topic: Econet High Pitched Squeal
Replies: 3
Views: 339

Re: Econet High Pitched Squeal

If you want more randomness ;)

Code: Select all

   10 M%=&800
   20 REPEAT
   30 FOR A%=0 TO 47
   40 B%=RND(256)-1  
   50 M%?A%=B%
   60 NEXT
   70 UNTIL FALSE
by johnkenyon
Thu Jul 09, 2020 10:42 am
Forum: 8-bit acorn hardware
Topic: Unreliable ROMs / sockets in BBC B
Replies: 12
Views: 668

Re: Unreliable ROMs / sockets in BBC B

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...
by johnkenyon
Sun Jun 28, 2020 10:17 pm
Forum: 8-bit acorn software: other
Topic: Writing a service rom - it's not recognized
Replies: 21
Views: 1323

Re: Writing a service rom - it's not recognized

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 \ ...**... \ ..****.. \ ..****.. \ .******. \ .******. \ ........ \ .******. \ .....
by johnkenyon
Sun Jun 28, 2020 3:33 pm
Forum: 8-bit acorn hardware
Topic: Model B - possible faulty cassette interface?
Replies: 30
Views: 1836

Re: Model B - possible faulty cassette interface?

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've now ordered replac...
by johnkenyon
Wed Jun 24, 2020 6:30 pm
Forum: 8-bit acorn hardware
Topic: Here are some scans of the Barson computers Electron Econet interface CCT and blank board
Replies: 33
Views: 1974

Re: Here are some scans of the Barson computers Electron Econet interface CCT and blank board

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.
by johnkenyon
Thu Jun 18, 2020 3:29 pm
Forum: 32-bit acorn hardware
Topic: AKF17 repair - whining noise, no screen
Replies: 13
Views: 1020

Re: AKF17 repair - whining noise, no screen

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 capacitors in series gives y...
by johnkenyon
Sat May 16, 2020 12:12 pm
Forum: 8-bit acorn hardware
Topic: ROMS - lots and lots
Replies: 39
Views: 2254

Re: ROMS - lots and lots

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 following * 2764...
by johnkenyon
Sat May 16, 2020 11:10 am
Forum: 8-bit acorn hardware
Topic: ROMS - lots and lots
Replies: 39
Views: 2254

Re: ROMS - lots and lots

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)
by johnkenyon
Sat May 16, 2020 8:22 am
Forum: 8-bit acorn hardware
Topic: 6502 and IC's on daughter board
Replies: 17
Views: 941

Re: 6502 and IC's on daughter board

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 actually a...
by johnkenyon
Fri May 15, 2020 5:56 pm
Forum: 8-bit acorn hardware
Topic: 6502 and IC's on daughter board
Replies: 17
Views: 941

Re: 6502 and IC's on daughter board

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 double density ...
by johnkenyon
Thu May 14, 2020 9:04 am
Forum: programming
Topic: Below page free space (DFS)
Replies: 27
Views: 1772

Re: Below page free space (DFS)

If you want the soft keys cleared before chaining the program, your !BOOT file becomes *BASIC *K.0*FX18|MCH."MYPROG"|M *FX138,0,128 I thought I'd tried that some time ago and I vaguely recalled that it didn't work. I just tried it again now in BeebEm and I can confirm that it doesn't seem to work: ...
by johnkenyon
Wed May 13, 2020 10:27 pm
Forum: programming
Topic: Below page free space (DFS)
Replies: 27
Views: 1772

Re: Below page free space (DFS)

*BASIC *K.0CH."MYPROG"|M *FX138,0,128 Rather than running the chain command from "inside" the EXEC loop, define a function key, and then insert it into the buffer for execution after the EXEC loop has ended. Thanks, that's a neat trick! @AJW, sorry for hijacking this thread, but if I may just add t...
by johnkenyon
Wed May 13, 2020 3:28 pm
Forum: programming
Topic: Below page free space (DFS)
Replies: 27
Views: 1772

Re: Below page free space (DFS)

I've seen something along the lines of

*BASIC
*K.0CH."MYPROG"|M
*FX138,0,128

Rather than running the chain command from "inside" the EXEC loop, define a function key, and then insert it into the buffer for execution after the EXEC loop has ended.
by johnkenyon
Wed May 06, 2020 7:25 am
Forum: 8-bit acorn hardware
Topic: BBC micro black linear PSU repair
Replies: 27
Views: 2433

Re: BBC micro black linear PSU repair

Perhaps the iss7 boards used a single rail PSU - a single 7805 with PNP power transistor to give a single 5V 3A power rail with multiple outputs to avoid high currents via the PCB traces.
by johnkenyon
Sat Apr 04, 2020 5:45 pm
Forum: other vintage hardware, software and languages
Topic: Atari 2600 - doesn’t like switching PSUs
Replies: 13
Views: 1140

Re: Atari 2600 - doesn’t like switching PSUs

A common fix for SMPS noise is to clean the SMPS output by feeding it into a linear PSU. For example, for a device expecting 12v regulated, feed 19v from a laptop PSU into a 7812 regulator+heatsink. Note that the laptop PSU will already have sufficient output capacitors to strip low frequency ripple...
by johnkenyon
Fri Mar 06, 2020 9:07 am
Forum: 8-bit acorn hardware
Topic: Sync issue with Master + Panasonic Viera TV
Replies: 10
Views: 710

Re: Sync issue with Master + Panasonic Viera TV

Does anyone know of a cable which goes from a 6 pin DIN to three phono connectors (see photo of an Atari compatible cable) for connecting to the rgb input of a TV? Have searched but can’t find one, which says to me that it can’t be done...? F8136A66-B6D3-4982-8EE8-95859151E026.jpeg If you want to u...
by johnkenyon
Thu Feb 20, 2020 2:49 pm
Forum: 8-bit acorn hardware
Topic: Re: BBC model b serious sound issue
Replies: 7
Views: 661

Re: BBC model b serious sound issue

If the computer is freezing then that indicates something on the "digital side" of the sound generator First port of call is the system VIA Then working your way from the CPU towards the speaker IC3 System VIA IC32 74LS259 IC99 (Speech processor - if installed, extract it to test) 76489 IC17 LM324 I...
by johnkenyon
Sun Feb 16, 2020 1:59 pm
Forum: 8-bit acorn hardware
Topic: Help Finding Replacement AC/DC Adapter
Replies: 4
Views: 388

Re: Help Finding Replacement AC/DC Adapter

Two "cheapo" suggestions: 1) Keep the original adaptor, and glue on a modified "socket protector"/"plug socket cover" (like: https://images-na.ssl-images-amazon.com/images/I/51Yob6yTRDL._AC_SX466_.jpg ) Find one that has an earth pin long enough to open the shutters, then do some trimming. The aim o...

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