Search found 7522 matches

by 1024MAK
Fri Jul 20, 2018 5:45 pm
Forum: general
Topic: *TAPE baud rates
Replies: 4
Views: 29

Re: *TAPE baud rates

No, no, no, no!
It's actual purpose is so you can enjoy the longer time for the program to load :mrgreen: :lol:

Mark
by 1024MAK
Fri Jul 20, 2018 1:25 pm
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 36
Views: 524

Re: BeebSCSI 7_7

Duncan, all joking aside, good luck with the various projects.

If everything works out, are you intending on posting up your BOMs?

Mark
by 1024MAK
Fri Jul 20, 2018 1:22 pm
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 36
Views: 524

Re: BeebSCSI 7_7

Elminster wrote:
Fri Jul 20, 2018 10:15 am
Nearly finished putting together parts order list for v7.7. 2 questions, all to do with holes.

What do I need to order for:

Fiducials:Fiducial_0.5mm_Dia_1mm_Outer
Tipex? :lol:
by 1024MAK
Thu Jul 19, 2018 7:59 pm
Forum: general
Topic: "Outline specification for the BBC MICROCOMPUTER system"
Replies: 203
Views: 16187

Re: "Outline specification for the BBC MICROCOMPUTER system"

Yeah, except having a 'custom' chip did not stop all clones. For example, there were unlicensed clones of the ZX81 and of the ZX Spectrum. The most widely available clone of the ZX81 had it's own ULA that included features beyond that of a real ZX81! Of course, as laws changed and original manufactu...
by 1024MAK
Thu Jul 19, 2018 7:47 pm
Forum: for sale / freebies
Topic: Worth Taking a Look At
Replies: 2655
Views: 218610

Re: Worth Taking a Look At

One for Acorn System enthusiasts: a large quantity of Vero Eurocard racking, collection only from Devon: https://www.ebay.co.uk/itm/Vero-Eurocard-racking-and-enclosures-for-electronic-equipment-and-PCBs/153103738578 I'd be bidding if it weren't so far away... Well, being a bit nearer, I'm taking a ...
by 1024MAK
Thu Jul 19, 2018 7:06 pm
Forum: hardware
Topic: RGB to HDMI using a Pi Zero and a small CPLD
Replies: 223
Views: 7711

Re: RGB to HDMI using a Pi Zero and a small CPLD

I've always thought that the TV uses the centre of the pulse. No. In most analogue CRT TVs, the synchronisation pulses are used to synchronise two free running 'oscillators', one for the horizontal defection system and one for the vertical defection. Note that each 'oscillator' is actually a curren...
by 1024MAK
Thu Jul 19, 2018 1:04 pm
Forum: hardware
Topic: Fake 6502As
Replies: 4
Views: 161

Re: Fake 6502As

I get the impression that old chips that are no longer in production, but for which there is some demand, attract the interest of unscrupulous recycling companies. Due to the low cost of labour in parts of the Far East, we already know that they are good at "pulling" used chips (either from sockets,...
by 1024MAK
Thu Jul 19, 2018 9:25 am
Forum: hardware
Topic: SCART image quality
Replies: 9
Views: 203

Re: SCART image quality

Dave has hit the nail on the head. Please disregard the over simplified 'digital' is better perception that gets pushed by marketing people and others who jump on bandwagons. All LCDs are digital. It does not matter if the signal is analogue or digital, conveying information electronically always ha...
by 1024MAK
Wed Jul 18, 2018 5:53 pm
Forum: for sale / freebies
Topic: Worth Taking a Look At
Replies: 2655
Views: 218610

Re: Worth Taking a Look At

If you want to discuss copyright, please find a more suitable thread, or start a new one.

Mark
by 1024MAK
Wed Jul 18, 2018 3:42 pm
Forum: hardware
Topic: Model B paged ROM breakout board. Interest?
Replies: 43
Views: 2841

Re: Model B paged ROM breakout board. Interest?

IIRC some of those you mention are alternative positions for SMD parts. If you look at the schematic, these resistors are in parallel pairs. They are all optional so IIRC, no need to fit them unless you experience problems. The resistor for the LED (R1 or R2, but not both) depends on which colour an...
by 1024MAK
Tue Jul 17, 2018 4:06 pm
Forum: hardware
Topic: I2C 4 U
Replies: 169
Views: 12172

Re: I2C 4 U

Removing the resistor is easier, just put a soldering iron bit (a 3mm to 5mm chisel bit) nearly touching one side of the resistor, apply solder between the tip and each pad of the resistor, then use the iron to "flick" the resistor off the board... if needed, clean up any solder. Then clean the boar...
by 1024MAK
Tue Jul 17, 2018 1:18 pm
Forum: hardware
Topic: I2C 4 U
Replies: 169
Views: 12172

Re: I2C 4 U

When using the RTC chips from Maxim, this is my general advice: The datasheet from Maxim is clear in showing how to connect a primary cell/battery (non-rechargeable). The positive connection of the cell/battery should only be connected to the chip pin identified as V BAT . There should be no other c...
by 1024MAK
Mon Jul 16, 2018 3:10 pm
Forum: hardware
Topic: Electron +Plus 1 + AP5 + MMFS question(s)
Replies: 8
Views: 206

Re: Electron +Plus 1 + AP5 + MMFS question(s)

Information on the ROM and the ROM socket inside the Plus 1 here.

Mark
by 1024MAK
Mon Jul 16, 2018 2:54 pm
Forum: hardware
Topic: 2nd User port for Beeb?
Replies: 96
Views: 6198

Re: 2nd User port for Beeb?

It's possible to use a 74LS138 (or a 74HCT138) in place of the 74LS42 in position IC4, but the pin-outs are different.

Mark
by 1024MAK
Mon Jul 16, 2018 11:54 am
Forum: hardware
Topic: 2nd User port for Beeb?
Replies: 96
Views: 6198

Re: 2nd User port for Beeb?

Yes you can connect multiple devices on the 1MHz bus. Each device must use a different address (or address range if more than one address required per device). Only the last device should have line terminating resistors fitted. The length of the total length of ribbon cable between the 1MHz connecto...
by 1024MAK
Mon Jul 16, 2018 7:33 am
Forum: hardware
Topic: I2C 4 U
Replies: 169
Views: 12172

Re: I2C 4 U

I have seen I2C RTC modules on eBay based on these: Mark
by 1024MAK
Mon Jul 16, 2018 7:07 am
Forum: hardware
Topic: Electron RGB to VGI
Replies: 6
Views: 213

Re: Electron RGB to VGI

The RGB DIN connector is the same on both BBC B/BBC Master and Electron machines. However, the Electrons with earlier issue PCBs don't produce such a bright picture compared to the Beebs and the later Electron machines.

Mark
by 1024MAK
Mon Jul 16, 2018 7:03 am
Forum: hardware
Topic: Need help figuring out how to fix a couple of Beeb PSUs
Replies: 21
Views: 398

Re: Need help figuring out how to fix a couple of Beeb PSUs

GadgetUK164 wrote:
Sun Jul 15, 2018 8:23 pm
Do you happen to have the secondary side of that diagram? Just for future reference!
See the text in the post of mine that you quoted! I have not finished it yet.

Mark
by 1024MAK
Mon Jul 16, 2018 6:59 am
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 36
Views: 524

Re: BeebSCSI 7_7

Just to add to the confusion, the normal description in the U.K., is that for the normal dual pin IDC connectors, the PCB mounting part is the male plug. The connector that fits the male plugs, that attach to ribbon cable are line sockets. I am not sure that is right... Isn't a PCB box header a rec...
by 1024MAK
Sun Jul 15, 2018 7:04 pm
Forum: hardware
Topic: BeebSCSI 7_7
Replies: 36
Views: 524

Re: BeebSCSI 7_7

There's really only one type of cable connector; so it's just the type of socket on the BeebSCSI that can be varied. Sounds like you have a plan now though :) Just to add to the confusion, the normal description in the U.K., is that for the normal dual pin IDC connectors, the PCB mounting part is t...
by 1024MAK
Sat Jul 14, 2018 6:11 pm
Forum: hardware
Topic: Need help figuring out how to fix a couple of Beeb PSUs
Replies: 21
Views: 398

Re: Need help figuring out how to fix a couple of Beeb PSUs

i am a old men pc's are to moderne for me :) i can only work with paper , pencile and so on :shock: i even have plastic things with symbols #-o to draw :) Yeah, but I often work with paper and pen or pencil. It's only when I intend to publish or make a PCB board that I go to the effort of using a s...
by 1024MAK
Sat Jul 14, 2018 5:16 pm
Forum: acorn atom
Topic: new to atom: ram rom mmc joystick power
Replies: 23
Views: 380

Re: new to atom: ram rom mmc joystick

Phill (Prime) is a regular here, so PM him. Alternatively he is on Facebook.

Mark
by 1024MAK
Sat Jul 14, 2018 5:10 pm
Forum: hardware
Topic: BBC Master weirdness
Replies: 2
Views: 192

Re: BBC Master weirdness

AFAIK, all 3 1 / 2 " drives use an optical sensor or microswitch to sense track zero. And I believe nearly all 5 1 / 4 " drives do the same. For most drives, there is however no sensor to detect the last track (40 or 80). So if the system is trying to step beyond track 41 to 42, or 81 to 85 (depends...
by 1024MAK
Sat Jul 14, 2018 6:55 am
Forum: hardware
Topic: Electron +Plus 1 + AP5 + MMFS question(s)
Replies: 8
Views: 206

Re: Electron +Plus 1 + AP5 + MMFS question(s)

It's well worth while reading the Acorn Electron Expansion Application Note . Especially the bit about using ROMs. The Plus 1 ROM is ROM 12 (decimal). Note that the ROM socket on the Plus 1 PCB is not wired up so that a standard EPROM can be used. An alteration is needed if you want to fit a device ...
by 1024MAK
Sat Jul 14, 2018 6:30 am
Forum: hardware
Topic: Need help figuring out how to fix a couple of Beeb PSUs
Replies: 21
Views: 398

Re: Need help figuring out how to fix a couple of Beeb PSUs

This one: https://stardot.org.uk/forums/download/file.php?id=24205&mode=view :?: That's something I doodled. In the service manual there is a schematic diagram of the Beeb PSU. But there are some differences to the actual real life PSUs. Hence why I reverse engineered the important primary side. I h...
by 1024MAK
Fri Jul 13, 2018 11:09 am
Forum: hardware
Topic: Electron overheating video
Replies: 24
Views: 415

Re: Electron overheating video

Or use a Beeb / Master etc...

Mark
by 1024MAK
Fri Jul 13, 2018 11:07 am
Forum: hardware
Topic: FreeFi-232 v2
Replies: 71
Views: 1544

Re: FreeFi-232 v2

If the software can individually control the spare RS232 outputs (DCD, RING etc), they can be used as status outputs if connected to a LED via a current limiting resistor. Gotta have some Blinkenlights =D>

Mark
by 1024MAK
Fri Jul 13, 2018 10:52 am
Forum: hardware
Topic: Electron overheating video
Replies: 24
Views: 415

Re: Electron overheating video

And a Rigol 1102E. Set up the 'scope on the composite output (monochrome mode) on a working Elk with some chunky graphics showing on screen. E.g. Coloured vertical bars. So that you can actually see the diffent voltage levels for the differently coloured bars on the 'scope. If available, set the tr...
by 1024MAK
Fri Jul 13, 2018 6:51 am
Forum: hardware
Topic: Electron overheating video
Replies: 24
Views: 415

Re: Electron overheating video

In the event of fire and/or smoke, call BeebMaster, I mean, in the event that you don't have any 'electronic' freezer spray, if you have a can of air, aka 'air duster', turn the can upside down and spay this on the chip you suspect. Failing that, put the whole naked board in the air path of a powerf...
by 1024MAK
Wed Jul 11, 2018 9:29 pm
Forum: hardware
Topic: Music 500 mod
Replies: 4
Views: 108

Re: Music 500 mod

Also, where exactly were you measuring from and to? And I trust that the power was disconnected and the 1MHz bus connector was not connected at the time.

Mark