Search found 6569 matches

by 1024MAK
Tue Sep 26, 2017 6:52 am
Forum: hardware
Topic: Watford Electronics 13 ROM board
Replies: 7
Views: 530

Re: Watford Electronics 13 ROM board

I don't think I've ever seen current ratings for stamped pin DIL sockets. But some DIL chips used for power switching are rated at up to about 800mA for intermittent use. A lot of the 0V and +5V tracks on the Beeb are fairly wide, but I have not actually checked in detail with the thought of the cur...
by 1024MAK
Mon Sep 25, 2017 7:28 pm
Forum: hardware
Topic: Acorn A305 Mouse repair...
Replies: 6
Views: 85

Re: Acorn A305 Mouse repair...

=D> =D> =D>

Mark
by 1024MAK
Mon Sep 25, 2017 7:24 pm
Forum: for sale / freebies
Topic: Games on EEPROM
Replies: 22
Views: 3084

Re: Games on EEPROM

You said that it's built into the OS ROM, so does this mean I don't need to install anything to load/launce code from RFS ROMs? Yes. A basic machine can load from ROM. Including a standard Beeb and an Electron with just a Plus 1 expansion. Also, I'm still not sure what advantage this has over a ROM...
by 1024MAK
Mon Sep 25, 2017 6:08 pm
Forum: hardware
Topic: BBC Model B takes up smoking
Replies: 24
Views: 498

Re: BBC Model B takes up smoking

How long could a BBC PSU capacitor hold a charge for? When I did the ones in my Master I left it turned off for a day, flicked switch on and off etc. I'm still very wary of working on electronics. In general, there isn't a simple answer to this, as it depends on the circuit, the voltage and the cap...
by 1024MAK
Mon Sep 25, 2017 2:30 pm
Forum: hardware
Topic: 5.25" Floppy drive write-protect fault
Replies: 12
Views: 293

Re: 5.25" Floppy drive write-protect fault

Claim down everyone. As with most interfaces, the floppy drive Interface has some variation between different manufacturers. And there are signal and interface differences between 5 1/4in drives and 3 1/2in drives and also 3in drives on various signals. So yes, the write protect signal is an output ...
by 1024MAK
Mon Sep 25, 2017 7:30 am
Forum: for sale / freebies
Topic: Games on EEPROM
Replies: 22
Views: 3084

Re: Games on EEPROM

I think you mean the ROM Filing System (ROMFS or RFS). Although it can also use sideways RAM as well as sideways ROM. The ROM Filing System is built in as part of the OS ROM. It treats suitablely programmed sideways ROM (or RAM) as a read only storage system. It "loads" data from a suitabl...
by 1024MAK
Sun Sep 24, 2017 4:48 pm
Forum: stardot.org.uk
Topic: Notification problem
Replies: 7
Views: 64

Re: Notification problem

I can now see what the problem is. I was not getting notifications to this thread: http://stardot.org.uk/forums/viewtopic.php?f=25&t=13772 I now notice that even though I have posted in the thread, I have not been subscribed to it. My subscriptions do seem to be updating for other threads I hav...
by 1024MAK
Sun Sep 24, 2017 4:44 pm
Forum: stardot.org.uk
Topic: Notification problem
Replies: 7
Views: 64

Re: Notification problem

IMG_5328.JPG
Rubbish...
by 1024MAK
Sun Sep 24, 2017 2:22 pm
Forum: hardware
Topic: BBC B / Datacentre Fault
Replies: 12
Views: 207

Re: BBC B / Datacentre Fault

jgharston wrote:
danielj wrote:I really recommend dropping ...

On reading the first few words I fully expected it to continue: your machine from about one inch onto the desk. Sometimes a quick fix for intermittantly socketed ICs.

It's gone metric. It has to be 25mm... :lol:

Mark
by 1024MAK
Sun Sep 24, 2017 2:18 pm
Forum: upcoming and recent events & exhibitions
Topic: ABUG EAST MIDLANDS (Winter Warmer) 17-19 November 2017 (Leicestershire) BOOKING THREAD
Replies: 32
Views: 474

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

Yay! It's a go :D I was getting worried that the radio silence meant there was problems...

Mark
by 1024MAK
Sun Sep 24, 2017 9:29 am
Forum: hardware
Topic: 5 pin din domino pcb mount sockets
Replies: 19
Views: 539

Re: 5 pin din domino pcb mount sockets

iii) I have to lose one of RI, DCD or DSR, which is least useful? Listed as least useful to most useful... RI is Ring Indicator and is only useful if you have a PSTN modem connected up and your software needs to know about incoming calls/connections. It is an output from the modem to the computer/t...
by 1024MAK
Sun Sep 24, 2017 9:14 am
Forum: hardware
Topic: BBC B / Datacentre Fault
Replies: 12
Views: 207

Re: BBC B / Datacentre Fault

Very strange.

Have you tested the +5V and the +12V outputs from the Beeb's PSU?

Mark
by 1024MAK
Sat Sep 23, 2017 6:32 pm
Forum: for sale / freebies
Topic: Test equipment for sale + CROs
Replies: 30
Views: 773

Re: Test equipment for sale

I'm declaring an interest in one "100MHz 2 channel, Rapid Electronics branded analogue CRO". If it's okay, I'll collect at the Abug meet-up. PC 'scopes and LCD storage 'scopes are fine as practical test tools, but just don't bring back the memories of my collage years working with a real C...
by 1024MAK
Sat Sep 23, 2017 9:32 am
Forum: hardware
Topic: Master CMOS checksum
Replies: 4
Views: 186

Re: Master CMOS checksum

jgharston wrote:
dominicbeesley wrote:Thanks JGH, I was misremembering "Bad Sum" as being config rather than ADFS...it's my age

Hey, I can barely remember what I was doing when I... what was I saying?

You may want to get the DRAM refresh system checked out... :lol:

Mark
by 1024MAK
Sat Sep 23, 2017 9:26 am
Forum: hardware
Topic: Challenge of the month - Troubleshooting?
Replies: 18
Views: 363

Re: Challenge of the month - Troubleshooting?

The "edge-connectors" are clearly visible on photos of model A boards.

I'm not sure whether these "edge-connector" pads were intended as edge-connector contacts, or for straight pin headers (or some other connector) fitted at 90o to the board.

Mark
by 1024MAK
Sat Sep 23, 2017 9:09 am
Forum: hardware
Topic: Acorn 3000 4mb Ram Expansion
Replies: 30
Views: 542

Re: Acorn 3000 4mb Ram Expansion

Greater amounts of RAM require more address lines, or more control lines (depending on the actual configuration used).

This is also partly the reason that RAM sizes go up in steps, 1, 2, 4, 8 etc...

Mark
by 1024MAK
Fri Sep 22, 2017 8:14 pm
Forum: hardware
Topic: Acorn 3000 4mb Ram Expansion
Replies: 30
Views: 542

Re: Acorn 3000 4mb Ram Expansion

@ Mark - I presume you have checked all the pin connections for the RAM connector including the solder joints? Both on the main board and on the RAM board. If not, it would be a good idea just in case there is dirt, corrosion or a dry solder joint :idea:

Mark
by 1024MAK
Thu Sep 21, 2017 11:33 pm
Forum: software
Topic: Archimedes Iomega ZIP drivers
Replies: 20
Views: 1103

Re: Archimedes Iomega ZIP drivers

Slightly off topic, but may still give an insight... MO discs ( Wikipedia page here ) can be formatted as either a "floppy" format or a "HDD" format on a Windows PC using the MO application software. But I think Windows own dialog only does the "HDD" format (it does not...
by 1024MAK
Thu Sep 21, 2017 1:26 pm
Forum: hardware
Topic: Testing RAM for a 4Mb A3000 Upgrade
Replies: 3
Views: 108

Re: Testing RAM for a 4Mb A3000 Upgrade

crj wrote:(Oh, and you'd also need a DRAM refresh circuit...)
Some DRAM chips can automatically refresh themselves. You will need to read the relevant data sheet...

Mark
by 1024MAK
Wed Sep 20, 2017 10:07 pm
Forum: general
Topic: Today I received.....
Replies: 4144
Views: 216306

Re: Today I received.....

What! You've removed the fairy dust, you bad boy [-X

What will the pixies play with now?

Takes all the sparkle out. And on the lead-up to Christmas as well...

Mark
by 1024MAK
Wed Sep 20, 2017 4:44 pm
Forum: hardware
Topic: Challenge of the month - Troubleshooting?
Replies: 18
Views: 363

Re: Challenge of the month - Troubleshooting?

I have a project - photos later - that might, sort of, fit the bill. It's one of Mark Haysman's (RetroClinic) "I've now finished with this board" board :shock: Dave H :lol: p.s. I'll start a new thread when I have a few photos. p.p.s. this will be a loooooong project :D Do you need to bor...
by 1024MAK
Wed Sep 20, 2017 6:54 am
Forum: hardware
Topic: Challenge of the month - Troubleshooting?
Replies: 18
Views: 363

Re: Challenge of the month - Troubleshooting?

In my normal job, I'm a leader of a small team that maintains, fault finds and repairs electrical control systems. Hence in addition to tinkering with 1980s and 1990s computers and various other electronic and electrical items at home, I have a good understanding of investigating faults and failures...
by 1024MAK
Tue Sep 19, 2017 5:23 pm
Forum: hardware
Topic: Troubleshooting my latest BBC B
Replies: 70
Views: 900

Re: Troubleshooting my latest BBC B

@adrm good to hear that you have got it working :D Well done =D>

I thought a 74HC259 would work as a replacement, but had to point out the differences just in case it didn't :mrgreen:

Mark
by 1024MAK
Tue Sep 19, 2017 5:02 pm
Forum: general
Topic: Today I received.....
Replies: 4144
Views: 216306

Re: Today I received.....

:lol:

For £14.16 I could not resist...

See a review here :wink:

Most of my other meters are pictured here and there are close ups in a later post in this thread :D

I also have some analogue meters (sorry no photos yet) and at work I have an expensive Fluke meter.

Mark
by 1024MAK
Tue Sep 19, 2017 1:07 pm
Forum: general
Topic: Today I received.....
Replies: 4144
Views: 216306

Re: Today I received.....

So yesterday, two packets arrived. Thanks to Rob for the VideoNuLA board =D> The other item was a small and cheap multimeter from eBay:- IMG_5298.JPG IMG_5297.JPG IMG_5308.JPG IMG_5302.JPG IMG_5301.JPG IMG_5300.JPG IMG_5299.JPG It has the smallest cartridge fuses I have ever seen in a meter :shock: ...
by 1024MAK
Mon Sep 18, 2017 10:15 pm
Forum: other vintage computer hardware, software and games
Topic: Spectrum Currah MicroSource
Replies: 5
Views: 103

Re: Spectrum Currah MicroSource

Believe it or not, Currah actually made more expansions than just the microspeach. And they also made expansions for some other micros as well.

I can't remember if I have a copy of the ROM. I downloaded various ROMs from a web site a few years ago. If I have time, I'll see if I do have it.

Mark
by 1024MAK
Mon Sep 18, 2017 5:54 am
Forum: hardware
Topic: First ever BBC broken
Replies: 6
Views: 226

Re: First ever BBC broken

Well, at least you eventually fixed it :lol:

So well done on getting there in the end =D>

Mark
by 1024MAK
Sun Sep 17, 2017 9:36 pm
Forum: hardware
Topic: First ever BBC broken
Replies: 6
Views: 226

Re: First ever BBC broken

Yep, in order, things to check first are: ⋅ Power supply rails, which you have done. But have you checked the power pins of all the important chips? ⋅ The main clock circuits - as suggested above, check the clock output pins on the Videoproc / video ULA. Then check the clock on t...
by 1024MAK
Sat Sep 16, 2017 7:22 pm
Forum: hardware
Topic: Origins of the BBC keyboard layout
Replies: 11
Views: 439

Re: Origins of the BBC keyboard layout

More pictures of "dumb" terminals here.

Mark
by 1024MAK
Sat Sep 16, 2017 6:31 pm
Forum: hardware
Topic: Origins of the BBC keyboard layout
Replies: 11
Views: 439

Re: Origins of the BBC keyboard layout

A lot of the old computers took more hints on keyboard layouts from so called "dumb" terminal keyboard layouts than from other computers. But most of the old "dumb" terminals and their keyboards have disappeared into silicon heaven... And I expect that various people who went on ...

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