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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...

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

Mark

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...

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...

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...

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

Mark

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

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...

I have seen I2C RTC modules on eBay based on these:

• PCF8563 I2C RTC link to datasheet
• DS1307 I2C RTC link to datasheet
• DS3231 I2C RTC link to datasheet

Mark

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

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

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...

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...

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...

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

Mark

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...

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 ...

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...

Or use a Beeb / Master etc...

Mark

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

Mark

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...

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...

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

Welcome to StarDot Dave

Enjoy the forum

Mark

davidb wrote: ↑

Wed Jul 11, 2018 11:46 am

Welcome!

And another Dave, too! Are things getting confusing for non-Daves yet?

Note to self: must remember to turn off the Dave cloning machine

Mark

Welcome on board Erik!



A successful repair, great news

Put yourself on the map by sticking a pin in it at this link
You can list your Acorn machines vitals here
You can make your confession here

I hope you enjoy StarDot

Mark

I've found threads on here about combining 2 x 16K images into one 32K chip, but is it also possible to combine 2x8K and 1x16K ROM images? Yes, you can combine two 8K byte ROM images into a single 16K byte EPROM. And also combine 2 x 8K ROMs with a 16K ROM. However there is a big problem with both....

The lines from an exchange have a current limited 50V supply. The MODEM (or telephone on the same line) has to 'load' the line (called going off-hook, same as when lifting the handset of a normal two part telephone, the line voltage then falling to between 3V and 12V approximately) then dial the num...

MODEMs designed only for exchange line use normally need something to simulate the exchange... For an auto dialing modem this simulation would need to be more complete but without autodial I wonder if you could get away with connecting a pair of these back to back and just provide the DC 50V. Assum...

If the existing PCB translation header and the ribbon cable at that end is okay, you could cut the ribbon cable and fit an in-line male IDC plug like this type:- IMG_7445.JPG I found this on eBay ( link ) They should also be a available from the large electronic component suppliers, but finding the ...