Search found 6754 matches

by 1024MAK
Sun Dec 10, 2017 5:43 pm
Forum: hardware
Topic: Only the Break key works on Keyboard
Replies: 7
Views: 123

Re: Only the Break key works on Keyboard

The 1MHz signal and the KB EN signals are very important. If you have a 'scope or logic probe, check these on the input pins of the relevant chips (see the schematic above).

Mark
by 1024MAK
Sun Dec 10, 2017 11:10 am
Forum: hardware
Topic: Only the Break key works on Keyboard
Replies: 7
Views: 123

Re: Only the Break key works on Keyboard

The most common problem with keyboards (well, apart from the keyswitch contacts tarnishing and/or getting dirty) is the cable between the main board and the keyboard failing. One or more connections may have failed. The break key is an independent circuit as it is connected in parallel with the posi...
by 1024MAK
Sun Dec 10, 2017 1:50 am
Forum: hardware
Topic: Problem Beeb MotherBoard
Replies: 68
Views: 1147

Re: Problem Beeb MotherBoard

Assuming the keyboard is not connected, or has no links fitted, a BBC Micro starts up in MODE 7. MODEs 0, 1, 2 and 3 are not available if there is only 16k bytes of RAM configured. The reason being that they need more RAM than is available to the system (because a machine with only 16k bytes availab...
by 1024MAK
Sun Dec 10, 2017 1:37 am
Forum: hardware
Topic: Problem Beeb MotherBoard
Replies: 68
Views: 1147

Re: Problem Beeb MotherBoard

Ed, when fault finding, in order to be able to work out the cause of the fault(s), you have to follow a logical sequence. Note that if you find a problem, it's helpful to list the current status of the machine, so that readers can clearly understand what's fitted and what is not fitted. In order to ...
by 1024MAK
Sat Dec 09, 2017 3:25 pm
Forum: for sale / freebies
Topic: BeebSCSI mini
Replies: 84
Views: 5417

Re: BeebSCSI mini

Mine arrived today (see here) :D

Thanks Jason and Simon =D> =D> =D>

Mark
by 1024MAK
Sat Dec 09, 2017 3:23 pm
Forum: hardware
Topic: BeebSCSImini
Replies: 5
Views: 325

Re: BeebSCSImini

Thanks Simon. A fair amount of bedtime reading there :mrgreen:

Mark
by 1024MAK
Sat Dec 09, 2017 3:17 pm
Forum: general
Topic: Today I received.....
Replies: 4308
Views: 249895

Re: Today I received.....

In the post today... :D
IMG_5833.JPG
Beeb SCSI mini other side
IMG_5832.JPG
Beeb SCSI mini component side
Thanks Jason =D> and of course, thanks to Simon for the project, design and support =D> =D> =D>

IMG_5831.JPG
ZX Max 48

Mark
by 1024MAK
Thu Dec 07, 2017 3:49 pm
Forum: hardware
Topic: BBC Micro: writes to ROM?
Replies: 10
Views: 348

Re: BBC Micro: writes to ROM?

But keep in mind that most chips can only output up to around 25mA into a short circuit, or sink a similar amount. Hmm. I may have misconstrued. I thought those limits meant the chip would break if you ever tried to source/sink more, not that it would current-limit! Well, strangely enough, the vari...
by 1024MAK
Thu Dec 07, 2017 3:24 pm
Forum: general
Topic: Today I received.....
Replies: 4308
Views: 249895

Re: Today I received.....

Lardo Boffin wrote:A very interesting looking game!

Snap!

IMG_5824.JPG
White Light

Mine arrived today :D

Thanks to Sarah and to Dave =D> =D> =D>

Mark
by 1024MAK
Wed Dec 06, 2017 7:24 pm
Forum: hardware
Topic: BBC Micro: writes to ROM?
Replies: 10
Views: 348

Re: BBC Micro: writes to ROM?

The combined output impedance of the two chips that are trying to both drive the bus limits the current. Whichever has the higher drive (lowest output impedance) will override the weaker chip. Modern CMOS memory chips are likely to win against an NMOS CPU for example. But keep in mind that most chip...
by 1024MAK
Wed Dec 06, 2017 6:01 pm
Forum: hardware
Topic: BBC Micro: writes to ROM?
Replies: 10
Views: 348

Re: BBC Micro: writes to ROM?

Despite what the various text books say, it not uncommon for there to be no read/write control in ROM control circuits. The BBC is indeed a computer that is like this. So yes, a write will result in a bus clash for the duration of the memory bus cycle.

Mark
by 1024MAK
Tue Dec 05, 2017 12:05 am
Forum: hardware
Topic: Switchable/dynamic/expanded RISC OS
Replies: 25
Views: 594

Re: Switchable/dynamic/expanded RISC OS

crj wrote:(Do people mind the idea of powering up, waiting a mo, then hitting reset?)
Yes! We have Windows machines for that! :lol:

I don't think that many users are going to want more than two ROM images (but may be wrong). Especially if one is as up-to-date and bug free as is possible to make.

Mark
by 1024MAK
Mon Dec 04, 2017 12:11 pm
Forum: hardware
Topic: Switchable/dynamic/expanded RISC OS
Replies: 25
Views: 594

Re: Switchable/dynamic/expanded RISC OS

Elsewhere on other computers, SMD chips have been soldered to thin PCBs that have pins to insert into DIL sockets (some of these boards are not very tall, due to the limited height available in the computer). Both to replace 40 pin DIL chips and to replace a bank of eight DRAM chips. So it may well ...
by 1024MAK
Mon Dec 04, 2017 8:04 am
Forum: hardware
Topic: DMA on the Electron
Replies: 14
Views: 2142

Re: DMA on the Electron

Reading in between the lines, I would say that the bus drivers for the address bus in NMOS 6502 CPUs do not go to a tri-state hi-impedance mode when RDY is active. Otherwise why would the manufacturers of the more advance CMOS versions add an extra control pin (BE) for bus control. 3.2 Bus Enable (B...
by 1024MAK
Sun Dec 03, 2017 7:15 pm
Forum: general
Topic: Cars and Organs
Replies: 33
Views: 680

Re: Cars and Organs

Hey Mark I suppose you bought it to Memofest then? I would have thought a Mustang or 'Vette was more your thing, to be honest. Or a classic like the Lotus! Still, I guess your hands are full with electronics and answering stoopid Qs from the likes of me. :D Yep, but it was out of view on a side str...
by 1024MAK
Sun Dec 03, 2017 11:07 am
Forum: hardware
Topic: Using a ZIF socket for testing Chips in DIL board sockets
Replies: 1
Views: 84

Using a ZIF socket for testing Chips in DIL board sockets

The cheap textool and 3M clone sockets that you can get from China have rectangular pins and are impossible to fit into a turned pin socket. But if you apply a bit of force, they will push into a stamped pin socket. And then the stamped pin socket should fit in a turned pin socket. 33665523333_ff09c...
by 1024MAK
Sat Dec 02, 2017 11:51 am
Forum: general
Topic: Cars and Organs
Replies: 33
Views: 680

Re: Cars and Organs

Average 63 mpg indicated - nice. Note quite 63MPG on that journey. I have managed upto 70MPG for some parts of a journey before :D (Normally when the high voltage battery is fully charged and the petrol engine is warmed up, while driving on a good road at a nice constant speed between 50 and 70 MPH...
by 1024MAK
Sat Dec 02, 2017 11:16 am
Forum: general
Topic: Cars and Organs
Replies: 33
Views: 680

Re: Cars and Organs

@jonb - yeah, a Toyota Prius, 2009 year. It's a hybrid with an battery electric motor and a 1.8L petrol engine (136hp). Apart from the normal servicing items and a couple of recalls, it's had one new 12V battery, one set of new brakes (all wheels) and four new new tyres. It's not a sports car, but y...
by 1024MAK
Fri Dec 01, 2017 7:11 pm
Forum: hardware
Topic: Open Source Logic Analyzer Experiments
Replies: 97
Views: 3546

Re: Open Source Logic Analyzer Experiments

Yes, Ultra ATA cables are only useful for Ultra ATA drives :( Whereas the older, 40 way IDE (ATA) cables that had/have standard IDC (line) socket(s) (with no "pins" plugged) can easily be repurposed :D However, some 40 way IDE (ATA) cables do have "pin" 20 blocked, these are less...
by 1024MAK
Fri Dec 01, 2017 2:09 pm
Forum: hardware
Topic: A blitter for the beeb?
Replies: 38
Views: 1311

Re: A blitter for the beeb?

Zilog developed and introduced their Z8410 DIRECT MEMORY ACCESS CONTROLLLER in the 1980s. I think in 1983 but can't find a date with my internet search. http://www.zilog.com/force_download.php?filepath=YUhSMGNEb3ZMM2QzZHk1NmFXeHZaeTVqYjIwdlpHOWpjeTk2T0RBdmNITXdNVGM1TG5Ca1pnPT0 Z80 Family Product Spe...
by 1024MAK
Fri Dec 01, 2017 12:23 pm
Forum: hardware
Topic: Open Source Logic Analyzer Experiments
Replies: 97
Views: 3546

Re: Open Source Logic Analyzer Experiments

Some time ago there was a seller on eBay selling CD ROM cables. These were 40 way, 40 wire IDC cables and were great for use with older machines.

Mark
by 1024MAK
Fri Dec 01, 2017 12:19 pm
Forum: off-topic
Topic: Virgin TiVo PIN
Replies: 5
Views: 198

Re: Virgin TiVo PIN

The Sky+ boxes also annoy me when I'm (trying) to play back a programme, but part of it is an overlap with an age restricted film that was on earlier, so I have to enter the PIN to continue :twisted: You should be able to change the PIN to a number that is easy to remember and enter, like 1234 or 11...
by 1024MAK
Fri Dec 01, 2017 12:12 pm
Forum: general
Topic: Cars and Organs
Replies: 33
Views: 680

Re: Cars and Organs

IMG_5796.JPG In the photo, TRIP A 154.5 Mi is showing the distance of that journey, CONS. 55.0MPG is the actual overall average distance/fuel consumption figure for that journey, AVG. 63MPH is the average speed for that journey and the bar graph is showing the MPG figure per minute, for the last 15...
by 1024MAK
Thu Nov 30, 2017 3:00 pm
Forum: upcoming and recent events & exhibitions
Topic: ABug NORTH User Group meeting | 19-21 JAN 2018 | MANCHESTER *BOOKING INFO*
Replies: 27
Views: 946

Re: ABug NORTH User Group meeting | 19-21 JAN 2018 | MANCHESTER *BOOKING INFO*

I do intend to attend :D Just waiting for conformation that my boss will let me have time off... I will be arriving Friday and leaving Sunday afternoon. I will be traveling by train this time, but will be bringing some bits and pieces, so half a table should be fine. I can confirm that I now have t...
by 1024MAK
Thu Nov 30, 2017 10:19 am
Forum: upcoming and recent events & exhibitions
Topic: ABug NORTH User Group meeting | 19-21 JAN 2018 | MANCHESTER *BOOKING INFO*
Replies: 27
Views: 946

Re: ABug NORTH User Group meeting | 19-21 JAN 2018 | MANCHESTER *BOOKING INFO*

I do intend to attend :D
Just waiting for conformation that my boss will let me have time off...
I will be arriving Friday and leaving Sunday afternoon.

I will be traveling by train this time, but will be bringing some bits and pieces, so half a table should be fine.

Mark
by 1024MAK
Wed Nov 29, 2017 2:15 am
Forum: upcoming and recent events & exhibitions
Topic: ABUG SOUTH 1 to 3 June 2018 (Hampshire) BOOKING THREAD
Replies: 17
Views: 543

Re: ABUG SOUTH 1 to 3 June 2018 (Hampshire) BOOKING THREAD

Hi Robert

Please put me down as a provisional attendee for the full weekend (Friday to Sunday) - full table. I'll confirm later once I know for certain about my calendar for next year.

Mark
by 1024MAK
Tue Nov 28, 2017 11:04 pm
Forum: hardware
Topic: BBC Master PSU capacitors - watchful waiting?
Replies: 5
Views: 221

Re: BBC Master PSU capacitors - watchful waiting?

ZX Spectrum 16k, 48k and plus models use boards that have small transformers (the "coil"). On some boards, it is this that people can hear "buzz" and not the speaker. It affects mostly the issue 1 through to some issue 4 boards. It is the noise of the transformer vibrating at the...
by 1024MAK
Mon Nov 27, 2017 9:51 pm
Forum: hardware
Topic: BBC Master PSU capacitors - watchful waiting?
Replies: 5
Views: 221

Re: BBC Master PSU capacitors - watchful waiting?

Hello aqarius. Welcome to StarDot :D Sometimes school computers were serviced by good engineers, and so the problem capacitors may well have already been replaced. I have two Master 128 machines where the problem capacitors are not originals. But without opening the case of the computer, then removi...
by 1024MAK
Mon Nov 27, 2017 10:40 am
Forum: hardware
Topic: Open Source Logic Analyzer Experiments
Replies: 97
Views: 3546

Re: Open Source Logic Analyzer Experiments

I agree that the buffering should only be applied for the Electron. So yes, another jumper option... With the Electron especially, the Phi0 clock line can pick up lots of crosstalk with multiple expansions plugged in :( Oh, not that it helps, but other communities have similar problems where manufac...

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