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Yeah, Dave’s basically summed up what I was gonna say. To put it very simply, all appears to do, is test the frequency of the interrupts from the Electron (which are generated by the ULA and acknowledged by the 6502 running the normal ROM code), then light a LED to indicate if the frequency is in th...

Here’s my version...
Mark

That reminds me, civil aircraft, air traffic control, airfield/airport tower, and the military aircraft all still use analogue radio. And you really, really don’t want OFCOM investigating if they complain about interference causing them trouble... There are also still plenty of people using AM (LW, ...

Yes, rechecking, I agree the silk screen for Q2 and Q3 does have the “e” in the wrong place. Maybe the board was originally intended to have NPN transistors and then they realised they had the wrong logic! Note also that the two different boards have transistors with different cases in positions Q2 ...

Aren’t all the silk screen LED polarity markings misleading? I can’t see a problem with Q2 though. With both Q2, Q3, R7, R10, LED1 and LED2, it is slightly unusual to have a 150 ohm resistor (to limit the LED current) in the collector) and a LED in the emitter circuit, for what is otherwise a common...

Thanks Dave

Mark

So, it'll work, but it's causing harmonic ripple and a lot of RF noise which you probably don't want. I think it's temping to think that the problem no longer exists now much radio transmission (including TV, WiFi etc) is digital and we don't directly see noise in the received signal. Remember, tho...

They aren't to filter the incoming mains, but rather to reduce the electrical noise the PSU produces. Well, there’s my assumption out of the water! Thank you, I didn’t realise that was their job. I’ve only ever seen them described as filter capacitors and didn’t even consider that noise going “the ...

In some BASIC versions, you can’t have multi-statement lines, hence an IF THEN will GOTO somewhere else to do whatever is needed. It’s going to the second line of the program for maximum speed (assuming the search for the correct line number starts from the beginning of the program). Also in some BA...

I would post up the partial schematic that I have drawn, but it’s currently on a piece of paper that is 20 miles away from where I currently am.... C2 and C3 are decoupling capacitors, but what value are they? I can see the values of C1 and C5, but what value is C4? Thanks to Dave for the photos, I ...

daveejhitchins wrote: ↑

Wed Oct 28, 2020 9:38 am

Now to soak my workaday Electron overnight . . .

Where I am at the moment, just leaving it outside in the open will result in it getting a good soaking.... and a wash and shower at the same time...

Mark

I ran the speed test on my Tatung Einstein TC01 using Z80 BBC BASIC: That's pretty close so suggests there problem isn't much if any memory access contention on the Einstein, very different from the Sinclair machines. The Tatung has 16K of dedicated video RAM outside of the 64K main RAM so presumab...

HDMI has evolved since it was first introduced, with it being extended multiple times. So there are now many different resolutions and frame rates available. Hence the available resolutions and frame rates supported by DVI are now a subset. Even some official HDMI TVs or monitor’s can’t display all ...

It’s always wise to check the chip markings and to check the datasheet.

There are many different chips, from many different manufacturers, and various different programming voltages for these various different chips.

Glad that you got it sorted out

Mark

The best way to speed up GOTO and GOSUB is to treat the referenced line as a label. As the program is entered, a dummy offset address (in binary) from the start address of the program is allocated in a table. Then when run, the first thing that the interpreter does is search for and populate the tab...

Yes, they should be okay.

Mark

The real question here, is how often do members unplug and plug in cartridges, interfaces or expansions? If the answer is not very often, then Enig may be acceptable. If the answer is regularly or often, then that’s when hard gold would have the advantage. Also the other option is to not use gold or...

The only 8-bit BASIC I can think of that actually requires LET is Sinclair BASIC There is definitely more than one U.K. microcomputer where it’s BASIC requires the use of LET when assigning values to variables. And I don’t mean a ZX80, ZX81 or ZX Spectrum (or any of their ‘clones’ or compatibles). ...

When cleaning the heads, it’s the small different colour ‘slit’ in the head that does the signal detection, it’s this that needs cleaning. Use IPA (not the drink!) and a chamois cleaning stick. Magnetic dirt from old or worn tapes can get stuck in the ‘slit’ and this really degrades the tape signal....

Before redesigning the ROM arrangements, what are you intending putting in the vacated memory map space? More RAM? Keep in mind that at the time the machine was designed, RAM was rather expensive. So if you can put your hindsight aside, I think the memory map that Acorn used was not only reasonable ...

Also how does it get 12V or 21V from the User Port. Is there some king of inverter in the box? thanks You are better off using a short test file when trying to ‘burn’ an EPROM on a suspect device. An empty ROM should read as 0xFF (that is all data bits return binary ‘1’). When a memory cell is prog...

I use a Willem EPROM EEPROM etc. programmer. Willem types are fine (I have one connected to a PC running Windows 2000), as long as you can remember which DIP switch settings to use (mind the software tells you about most of them). My comment above about using an external 12V supply still applies if...

Either 27c128's (whilst I can stil get them) and 27C64's / 27c256's These are all CMOS versions (hence the C in the middle of the type number). Please check with the data sheet for the actual chips you have, but most use a programming voltage of between 12V and 14V so should be fine with a TL866II ...

Which chips are you intending on using? For 12V EPROMs, EEPROMs, E 2 PROMs and flash memory, a modern TL866II Plus is good enough. It may be okay for 21V CMOS EPROMs. For programming older 21V and 25V NMOS EPROM chips, I recommend a programmer that can run on an external 12V power supply. Or buy a h...

LET is optional in some versions of BASIC, but required in some other versions. In the versions where LET is required, if it’s not present, you will get an error (often a syntax error). With BBC BASIC, LET is optional, so most programmers leave it out. But in listings designed for use on a wide vari...

So, in order to try to eliminate things, apart from AMX art, what other programs or ROMs have you used? Did any you tried work okay? Or did strange symptoms occur? The BASIC programs that get extra characters, are you now saying that these problems are unrelated? Have you worked out what this proble...

Just like the PSU for the BBC A/B then

And no, they were not intended to be serviced...

Mark

If you search, you should be able to find some schematic/circuit diagrams. There is a topic on this forum somewhere... Colour CRT monitors work by having three separate circuits to process the three video input signals (red, green and blue). These limit (clamp the maximum signal level) and then ampl...

You need to compare the red channel voltages to the green and blue channels. The electron gun for the red channel is being driven when it should not be. Do this when a completely black picture is being produced by the connected computer.

Mark

Each different storage system uses its own filing system. So you need the DFS (Disc Filing System) ROM in the system in order to access real floppy drives. DFS is the disc (disk) filing system (Acorn uses “disc”, well, most of the time). The cassette filing system is part of the OS. For systems with...