stardot.org.uk

Depends on if you will actually want to erase them. If not, one time programmable EPROMs are slightly cheaper (that’s what BeebMaster uses).

Mark

Well, normally for key registering reluctance, hitting the key lots and lots of times often helps, as you wear through the tarnish and dirt on the contacts.

A large group of non-functional keys could be a broken row, or column line.

Mark

Going on the photos you posted, me thinks you’ve been using LCD TVs / monitors for too long... They look fine to me, I only see a little bit of distortion. Some CRT displays do ‘pinch’ a little bit, as the pincushion distortion circuit can’t fully cope with the difference between most dark pictures ...

You have to keep in mind that the actual position of the image is relative to the sync signals. So if different programs or modes change the timings of the video signal with respect to the sync signals, the image on the screen will start / end in different positions. Can’t say I’ve noticed too many ...

Yes, there should be a preset (variable resistor) to adjust the displayed horizontal position. However, it may be that a component fault is causing this symptom. Cameras, especially those with small diameter lenses (or larger diameter lenses when zooming in) curve the image inwards at the sides and ...

It’s unwise to speculate on how many products were produced or which still exist on the very small number of samples available via a forum. Not everyone who still has or still uses Acorn machines is on here, and even if they are a member, they may not post about their devices. The ZX Spectrum scene ...

Have a look at the tools linked on this page

Mark

IBM PC and compatibles need a twist in the cable, as the wiring for the disk drive interface is slightly different to the Shugart Associates interface used by the Beeb (and other computers before IBM moved the goalposts). So that means you want a cable without any twist. It is possible to make up a ...

As C1 and C2 are not made by Rifa, you can choose if you wish to replace them or leave them. The reason that C1 and C2 are normally recommended to be replaced, is because the capacitors used in these positions were made by Rifa and this type are known to self destruct. When they develop cracks, mois...

BBC BASIC may not use IN as a reserved word, but some other BASICs do where it is a function that returns the (8 bit) value from a 8080/8085/Z80 I/O port address. Although it’s use is not universal as some BASICs use INP instead. I’m sure I have seen ‘AS’ used (as a reserved word) in a BASIC somewhe...

http://www.ebay.co.uk/itm/382795937202
Nice to see they checked the description matches the product in the pictures...!


Mark

PS Yes, I ordered one for fun, and no I did not get a FPGA

Yes, check the transistor packages, if they have heatsink tabs or fixings or metal cases, which terminal is connected to the heatsink tab/fixing or transistor case? Does it have to isolated from the metal heatsink? What insulator was used? Is it damaged or missing? Where you have a ‘dual channel sco...

There is also the Sell My Retro site

So far, I’m managed 124 transactions on this site since 2011

Mark

Lardo Boffin wrote: ↑

Fri Nov 08, 2019 1:03 pm

Nice! And very good luck with it.

Agreed.

Good luck Ian

Mark

Welcome on board Chris! :D :D :D I’m glad that you are enjoying the forum :D Put yourself on the map by sticking a pin in it at this link (although I do know where Keynsham is, as I was there about two weeks ago! :P ) You can make your confession here :mrgreen: You can list your Acorn machines vita...

If this thread continues to feature Psions, I’ll have to post up photos of mine.... I started with a Series 3 many, many years ago. Then moved to a Series 3a, a Series 3c, a Revo, a Series 5mx. Since then I have got a Series 5. With the 3c, I had great fun walking into my manager’s office, and ‘hove...

Replace capacitors C702 and C703. I didn't replace them, but I did test them, and they seem to be ok. Also tested C701 with no issue noted. The reason I suggested replace rather than just test, is that in similar circuit designs in CRT TV or monitor sets, sometimes high voltage capacitors like thes...

Welcome on board Grant! :D :D :D Enjoy the forum :D You can make your confession here :mrgreen: Put yourself on the map by sticking a pin in it at this link :P You can list your Acorn machines vitals here I’ve been visiting your site for many years, and often I have had to search for it, as you hav...

Dead! No no he's not dead, he's, he's restin'!



Err, moving on...

In the PSU, the capacitors that need replacing are C1 and C2. It is also recommended that C9 be replaced at the same time.

See this web page

Mark

Have you tested for any other short circuits? Replace capacitors C702 and C703. Test the various resistors in Q702 base circuit. Do the same for R702 ... R704. Test diodes D703 and Zeners ZD703, ZD704. If you have a ‘scope, see what waveform you get at Q701 base (with the collector circuit disconnec...

Welcome on board Dave!



Lurk alone no more...

Enjoy the forum

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

Mark

It’s likely to be a USB<>RS232 chip with interface circuitry to connect to a RS423 port. I’ve certainly in the past sent text (including BASIC programs) and commands over serial connection between a PC and a Beeb (well, a Master 128). As its possible to connect a RS232 port to a RS423 port. So it sh...

Please note that I have edited my earlier post to clarify what I was trying to say. A 180°phase shift between the same frequency of two different square wave signals (but derived from the same oscillator) can simply be due to the different signals going via a different number of logic stages, some o...

The 6845 CRTC can operate on the Beeb at two clock speeds - 1MHz and 2MHz - according to bit 4 of the Video ULA. I assume this controls not just its character clock rate, but also the rate at which its registers are accessed (I don't see two separate clock inputs). No. The clock direct from the vid...

Keep in mind that the clock signal seen by the VIA (pin 25 on the 6522 VIA called PHI2 on datasheets, but called 1MHZE on the BBC schematic) is from the circuitry that feeds the CPU clock circuit (specifically IC34). This 1MHZE 1MHz clock signal is in fact is a 2MHz clock that has been divided so th...

And what happens when you press [Escape]?

Mark

Good that everything worked okay

Mark

Lee, try this: Wire up as per this table: D terminal Function Wire colour Joy 1 Wire colour Joy 2 1 +5V N/C N/C 2 D.GND / 0V N/C N/C 3 D.GND / 0V N/C Black 4 A.CH3 Up/Down N/C Green 5 A.GND N/C Orange 6 D.GND / 0V Black N/C 7 A.CH1 Up/Down Green N/C 8 A.GND Orange N/C 9 /LPSTB N/C N/C 10 PB1 Fire N/...

Can you post some more photos from more angles. My eyes aren’t as young as they used to be, and even if they were still young, I can’t see around corners

Are both the joysticks wired the same?

Which one do you want to be joysticks 1?

Mark

Yes, that confused me when I first tried to download from GitHub. I also often check a file using a hex and ASCII file viewer / editor on the PC to make sure I have the correct file.

Mark