Search found 6842 matches

by 1024MAK
Tue Jan 16, 2018 10:47 am
Forum: hardware
Topic: BBC B Running slow
Replies: 11
Views: 382

Re: BBC B Running slow

There is also the possibility that there is a strange fault with the circuitry that selects between 2MHz and 1MHz for the CPU clock.

Do you have an oscilloscope, or are you able to borrow one?

Mark
by 1024MAK
Mon Jan 15, 2018 4:09 pm
Forum: off-topic
Topic: How many people found computer self-assembly annoying?
Replies: 10
Views: 292

Re: How many people found computer self-assembly annoying?

I think there are a number of things to consider here. Speaking from a perspective of being in the U.K., here are my thoughts. It could well be a different story elsewhere in the world. The computer kits were initially mainly aimed at the electronic hobbyists. Various electronics and radio enthusias...
by 1024MAK
Sun Jan 14, 2018 8:26 pm
Forum: hardware
Topic: Which replacement parts are available new?
Replies: 5
Views: 249

Re: Which replacement parts are available new?

6522 CMOS versions are indeed still being manufactured. As are various Z80 support chips. It's highly unlikely that any of the older display controller, sound chips or floppy disk controller chips are still being made. As there is significant no market for them. Most 74 series logic is still availab...
by 1024MAK
Fri Jan 12, 2018 2:11 pm
Forum: off-topic
Topic: Decoupling capacitor for ic
Replies: 10
Views: 242

Re: Decoupling capacitor for ic

There is lots of information on decoupling capacitors in this thread and further on, here . In general, a 100nF capacitor is used. But the value is not critical in most cases. So a 47nF or 220nF capacitor may well be okay. Manufacturers can sometimes use smaller values, as they can either use wider ...
by 1024MAK
Fri Jan 12, 2018 12:58 am
Forum: off-topic
Topic: Internet of Strings
Replies: 8
Views: 269

Re: Internet of Strings

It's amazing what types of electrical signal you can actually send over a relatively short section of poor quality cable... (and for AC communication signals, a wet salty "conductor" for 2 metres is equivalent to a "poor quality cable"). It's been known for a weak, but usable sig...
by 1024MAK
Thu Jan 11, 2018 9:46 pm
Forum: upcoming and recent events & exhibitions
Topic: ABug NORTH User Group meeting | 19-21 JAN 2018 | MANCHESTER *BOOKING INFO*
Replies: 72
Views: 2946

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

On the Friday , numbers gradually fall during the afternoon. Leaving very diminished numbers after 16:30. Mark From the intro text, on Friday , we have the room from 5pm. Sunday, people start to drift away from about lunch time. Sorry, brain fart :oops: #-o [-X :lol: I was indeed thinking of Sunday...
by 1024MAK
Thu Jan 11, 2018 7:14 pm
Forum: upcoming and recent events & exhibitions
Topic: ABug NORTH User Group meeting | 19-21 JAN 2018 | MANCHESTER *BOOKING INFO*
Replies: 72
Views: 2946

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

On the Friday, numbers gradually fall during the afternoon. Leaving very diminished numbers after 16:30.

Mark
by 1024MAK
Wed Jan 10, 2018 10:56 pm
Forum: upcoming and recent events & exhibitions
Topic: ABug NORTH User Group meeting | 19-21 JAN 2018 | MANCHESTER *BOOKING INFO*
Replies: 72
Views: 2946

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

I once came across a 8 bit computer where someone had glued a broken connector back on :shock:. Never mind about these bits of broken and unjointed metal pins... Unsurprisingly, anything plugged into said connector did not work :lol: As the connector was obsolete, I had to get a spare from a shop th...
by 1024MAK
Wed Jan 10, 2018 5:03 pm
Forum: hardware
Topic: Electron cassette counter revolution rate
Replies: 26
Views: 548

Re: Electron cassette counter revolution rate

Not with the same motor as driving the capstan as there is no single gear ratio between the captan and the take-up spool that would work, hence the slipping clutch. I guess so. Though I think only very early decks relied on a single motor. I came to the party rather later. If tape recorders/players...
by 1024MAK
Wed Jan 10, 2018 1:42 pm
Forum: hardware
Topic: Electron cassette counter revolution rate
Replies: 26
Views: 548

Re: Electron cassette counter revolution rate

the missing piece of the puzzle is that the take up spool has a clutch, often comprising a spring and a piece of felt, that enables it to slow down as the circumference of the tape wound into that spool becomes greater I thought cheap decks just used a motor with low enough torque not to stretch th...
by 1024MAK
Sun Jan 07, 2018 3:49 pm
Forum: hardware
Topic: Broken Beeb - strange memory issue, what to try next?
Replies: 12
Views: 544

Re: Broken Beeb - strange memory issue, what to try next?

Well, there goes the Beeb's build reputation :lol:

Well done =D>

Poor connections can cause all manner of hard to trace weird and not so wonderful fault symptoms :twisted:

Mark
by 1024MAK
Sat Jan 06, 2018 6:24 pm
Forum: hardware
Topic: Floppy switch configs
Replies: 41
Views: 670

Re: Floppy switch configs

Don't enter extra spaces... and check any separators are correct.

Mark
by 1024MAK
Sat Jan 06, 2018 6:18 pm
Forum: hardware
Topic: Floppy switch configs
Replies: 41
Views: 670

Re: Floppy switch configs

Post above edited.
by 1024MAK
Sat Jan 06, 2018 6:13 pm
Forum: hardware
Topic: Floppy switch configs
Replies: 41
Views: 670

Re: Floppy switch configs

BBC BASIC, link to JGH's site

Acorn MOS versions are here ;-)

Mark
by 1024MAK
Sat Jan 06, 2018 2:47 pm
Forum: hardware
Topic: Floppy switch configs
Replies: 41
Views: 670

Re: Floppy switch configs

You may also need to install a later OS chip. If you are not able to program an EPROM or EEPROM chip, buy a ROM chip from Mark of RetroClinic. Contact him via PM (if PM's have been enabled on your account) or via his web site . If you can program chips, you need a 27128, 27C128, 27256 or 27C256 EPRO...
by 1024MAK
Sat Jan 06, 2018 2:38 pm
Forum: off-topic
Topic: CPU International Crisis - Are We All Doomed?
Replies: 16
Views: 420

Re: CPU International Crisis - Are We All Doomed?

The only long term solution that I can see, is for a different architecture. Maybe splitting different code between different CPU cores that each have their own cache and therefore run completely independently from one another. The system to copy main memory to the various cache memory would however...
by 1024MAK
Fri Jan 05, 2018 6:46 pm
Forum: off-topic
Topic: CPU International Crisis - Are We All Doomed?
Replies: 16
Views: 420

Re: CPU International Crisis - Are We All Doomed?

It's simple. Just dedicate web browsing to a computer that has absolutely no private information on it and keep your private information on a separate system that has no internet connection :wink: Oh, and all 8 bit, and a lot of older 16 bit/32 bit systems have no, little or ineffective protection t...
by 1024MAK
Fri Jan 05, 2018 1:34 am
Forum: other vintage computer hardware, software and games
Topic: Early 70s Calculators
Replies: 43
Views: 2400

Re: Early 70s Calculators

fordp wrote:I had a Fx-451 at sixth form. Very good except the Flexi to the fold out keyboard breaks after a while.

Yeah, as soon as I noticed signs of cracks appearing, I stopped folding it. It has laid open and flat ever since.

Mark
by 1024MAK
Thu Jan 04, 2018 9:49 pm
Forum: hardware
Topic: What's the worst that could happen?
Replies: 16
Views: 514

Re: What's the worst that could happen?

Thanks for the advice. It would be great if you could elaborate on a few points... 74LSxxx and 74ALSxxx chips are relatively hardy and can survive brief short circuits on their outputs What does "brief" mean? Are you talking about a 10ns transient glitch, or ten seconds while I notice som...
by 1024MAK
Thu Jan 04, 2018 9:35 pm
Forum: hardware
Topic: Think I'm loosing my (beeb) memory
Replies: 22
Views: 489

Re: Think I'm loosing my (beeb) memory

JannievanZyl wrote:I'll collect faulty RAM chips and send to you at some point. Have a few 64Kx1 chips from a bunch of C64's I repaired. I'm sure the collection will grow....

Thank you :D

Mark
by 1024MAK
Thu Jan 04, 2018 9:34 pm
Forum: hardware
Topic: Think I'm loosing my (beeb) memory
Replies: 22
Views: 489

Re: Think I'm loosing my (beeb) memory

Out of interest, how portable are your tests likely to be, and how easy might they be to apply to DRAM in situ via the CPU socket of a model B? It's intended to be a standalone tester for testing individual chips that are not connected to anything else. So would not be suitable for testing chips th...
by 1024MAK
Thu Jan 04, 2018 12:24 pm
Forum: hardware
Topic: Think I'm loosing my (beeb) memory
Replies: 22
Views: 489

Re: Think I'm loosing my (beeb) memory

It uses a PIC micro controller and the initial objective is to have sockets suitable to test common DRAM chips, such as 16k x 1 bit, 16k x 4 bit, 64k x 1 bit and 64k x 4 bit. That would include the very common 4116, the 4816 (used by the Beeb), 4164 and 4464 chips for example. Then, it would be poss...
by 1024MAK
Thu Jan 04, 2018 1:16 am
Forum: hardware
Topic: What's the worst that could happen?
Replies: 16
Views: 514

Re: What's the worst that could happen?

Err, first off, yes, it's better to use a Model B rather than a Master. Simply because most of the chips in a B are still available. Whereas, the Master uses a lot of custom chips. These are in a limited supply, and we don't have much data on them :-( 74LSxxx and 74ALSxxx chips are relatively hardy ...
by 1024MAK
Wed Jan 03, 2018 11:36 pm
Forum: hardware
Topic: Think I'm loosing my (beeb) memory
Replies: 22
Views: 489

Re: Think I'm loosing my (beeb) memory

Well done =D> It's not unusual for DRAM chips to fail in strange ways. If you have not yet binned the defective DRAM chip, would it be possible to send it to me please. I'm after faulty DRAM chips so that when I have made my prototype DRAM tester, I have some real life example DRAM chips to test the...
by 1024MAK
Tue Jan 02, 2018 7:39 pm
Forum: off-topic
Topic: mdfs.net offline
Replies: 14
Views: 803

Re: mdfs.net offline

Testing...

Yep, fine in my world :D

Mark
by 1024MAK
Tue Jan 02, 2018 7:35 pm
Forum: general
Topic: Don't have a desolder station or hot air gun!
Replies: 17
Views: 415

Re: Don't have a desolder station or hot air gun!

An electric paint stripper hot air "gun" works well if an appropriate nozzle is used. At least for desoldering. Both SMD chips and through hole chips.

Mark
by 1024MAK
Tue Jan 02, 2018 12:55 pm
Forum: off-topic
Topic: An odd collection
Replies: 12
Views: 489

Re: An odd collection

Hmm, I may have to use a computer to count my computers... :mrgreen:

Mark
by 1024MAK
Tue Jan 02, 2018 12:50 pm
Forum: general
Topic: Don't have a desolder station or hot air gun!
Replies: 17
Views: 415

Re: Don't have a desolder station or hot air gun!

Although, you want the heat to be a bit higher that those values, so that the solder flows better. Also, the material that the solder is soldered to makes a little bit of a difference.

Mark
by 1024MAK
Tue Jan 02, 2018 12:20 am
Forum: hardware
Topic: Only the Break key works on Keyboard
Replies: 15
Views: 454

Re: Only the Break key works on Keyboard

Another fine repair =D>

by 1024MAK
Mon Jan 01, 2018 11:56 pm
Forum: hardware
Topic: Random pixels on BBC Model B
Replies: 60
Views: 1115

Re: Random pixels on BBC Model B

Just so you know, the 74LS245 in position IC14 is a known cause of what appears to be RAM problems, but your problem at first did not appear to be a typical symptom of a faulty 74LS245....!

Anyway, I glad that you have fixed it :D

Mark

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