Search found 6561 matches

by 1024MAK
Sun Sep 24, 2017 2:22 pm
Forum: hardware
Topic: BBC B / Datacentre Fault
Replies: 12
Views: 136

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: 5
Views: 50

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: 513

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: 136

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: 24
Views: 677

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: 179

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: 348

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: 521

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: 521

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: 19
Views: 1062

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: 99

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: 215972

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: 348

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: 348

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: 897

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: 215972

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: 215972

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: 96

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: 222

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: 222

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: 10
Views: 395

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: 10
Views: 395

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 ...
by 1024MAK
Sat Sep 16, 2017 5:41 pm
Forum: hardware
Topic: Troubleshooting my latest BBC B
Replies: 70
Views: 897

Re: Troubleshooting my latest BBC B

Argh, it was listed, but out of stock. What about the SN74HC259N vs the SN74LS259N? As I understand it, the HC is a direct replacement for LS, based on CMOS. No. 74HCxxx types are high speed CMOS versions and are not officially TTL compatible as they have different input switching thresholds (level...
by 1024MAK
Sat Sep 16, 2017 5:01 pm
Forum: hardware
Topic: Troubleshooting my latest BBC B
Replies: 70
Views: 897

Re: Troubleshooting my latest BBC B

Simple answer: "yes". Long answer, the part number 74LSXXX defines only the logic function and normally the pin-out. But not the actual circuitry used. In most applications, parts from different manufacturers (and sometimes from the same manufacturer) are equivalents and work okay. But in ...
by 1024MAK
Sat Sep 16, 2017 2:18 pm
Forum: hardware
Topic: Troubleshooting my latest BBC B
Replies: 70
Views: 897

Re: Troubleshooting my latest BBC B

RS also have trade counters, which come in very handy if you have one in your area.
Some other suppliers also have trade counters, but only a small number.

Mark
by 1024MAK
Sat Sep 16, 2017 10:30 am
Forum: hardware
Topic: Troubleshooting my latest BBC B
Replies: 70
Views: 897

Re: Troubleshooting my latest BBC B

I'm not at home, so can't check on my Beeb. However here are some details that may help. IC32 is a 74LS259 "high-speed" 8-Bit addressable latch used as a "port expander" to get more input/output pins. The schematic of the keyboard is here : http://mdfs.net/Info/Comp/BBC/Circuits/...
by 1024MAK
Sat Sep 16, 2017 8:40 am
Forum: for sale / freebies
Topic: VideoNuLA boards
Replies: 20
Views: 1001

Re: VideoNuLA boards

Hi Rob

If you have some VideoNuLA boards left, and don't have any new first time customers interested, then I would like another one please.

Mark
by 1024MAK
Fri Sep 15, 2017 10:00 am
Forum: hardware
Topic: BBC Model B takes up smoking
Replies: 22
Views: 465

Re: BBC Model B takes up smoking

There are resistors (R2, R3 & R5) that will discharge the two 200V electrolytic capacitors (C6 & C8 ), but no separate discharge resistor for C1 and C2. However, they should discharge via R2, R3 & R5 if the bridge rectifier (DB1) is okay. Schematic of the primary side here :wink: It is a...
by 1024MAK
Fri Sep 15, 2017 7:48 am
Forum: for sale / freebies
Topic: Acorn Electron Bundle for Sale also BBC IO Relay Board and now Raspberry Pi
Replies: 10
Views: 394

Re: Acorn Electron Bundle for Sale and also Voltmace 14b Joystick

Bryce wrote:
1024MAK wrote: or screw thermal block...
Mark


I pretty sure you mean a screw terminal block... Unless it's getting hot? :D

Bryce.


:lol: That's another "correction" by the auto-suggest/auto-correct that I did not notice :lol:

Mark
by 1024MAK
Wed Sep 13, 2017 4:22 pm
Forum: software: new games
Topic: ZOMBIES ATE OUR ROADIES!
Replies: 28
Views: 634

Re: ZOMBIES ATE OUR ROADIES!

lurkio wrote:Or a PC with OmniFlop installed and working -- which is rarer, if anything.

Ha! I'll have to remember that if I sell a "retro" PC on fleabay... :lol:

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