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I wonder if a previous owner got a bit too aggressive with an upgrade/expansion, or when working on the board.
Resistors don't normally cause problems in Beebs, let alone break like you have described...

Mark

Interesting idea Tony

Mark

Good progress

Well done

Mark

Mark

Yeah, it's a CMOS type. Datasheet available from here

Mark

Ok, thanks Mark. Maybe you’ve previously robbed the 6522 from that Master for another fix because it’s almost as if it doesn’t have one fitted! 😜 Hah ha! You should know that pinching bits from a Master 128 is most likely too much like hard work, as in most Masters, everything except the ROMs are s...

I tested the Master 128 and the Plus 1 out of curiosity. I was not surprised by the results for the Plus 1, but was by the results on that Master.
I have some other Masters that I can test later.

Mark

There are two main types of mains fed primary SMPSU (Switch Mode Power Supply Units): Fixed input voltage types Wide range multivoltage types The wide range multivoltage types can normally run from any 90V to 250V, 50Hz to 60Hz mains supply without problems. They will only have a single large 400V o...

S25 question - Yes, it's detailed in the fault finding index thread, as well as elsewhere in the hardware section. The 'teletext' chip, IC5, an SAA5050 may cause a failure of the MODE 7 screen. It is also affected by link S26. I doubt it has failed in the OP machine though, given the problems with t...

Link S25 determines how much memory the system can see, and which bank of RAM the system sees at address 0000 hex onwards. Link S26 has to be correct for the actual chip fitted in IC6 position. There are two different manufacturers, and at least two different revisions of the chip from the two manuf...

Martin, some more data for you... :wink: DT-4000ZC Fluke DT-4000ZC Fluke Computer Board Serial number Pin 10 Pin 10 Pin 10 Pin 10 Pin 13 Pin 13 Pin 13 Pin 13 issue normal rev. normal rev. normal rev. normal rev. BBC B ??? 01-ANB04-6011871 1.140k 1.193k 1.146k 1.189k 1.121k 1.170k 1.125k 1.167k BBC B...

Nice work! This is the latest version of your own design, I take it? Just a small evolution, 374 buffers replaced with 574's to make the layout easier. Swapped the 245's around so I can use R/W signal from podule bus rather than having to invert it, saving a GAL pin. Clock pins for the latches are ...

Welcome to our forum :D You may want to introduce yourself . We are a very friendly community. Which version board do you have? I can't be certain from the photos you posted due to the black crock clip being in the way. From what you say, you have two faults. One is definitely a fault with one bank ...

But a little less than the amount in this thread

I prefer hot air...

The pitch of the pin-headers (links / jumper shunts) is 2.54mm or 0.1 inches. The same as used as selection links of all manner of older computer hardware...

Mark

Great to hear that it's working

Mark

Although I did not own any Acorn computers until well after the 1980s, at school, in terms of software, BBC BASIC was the primary interest for me. At home we had a ZX Spectrum and I loved programming in BASIC on it. But BBC BASIC was up another level. Especially the structured programming elements (...

There are at least four variations in Z80 CPU cores (not including the various later versions that had deliberately extended, reduced or different official instructions): Zilog NMOS and officially licensed manufacturer versions (for example Mostek, Synertek, SGS) - these should all be the same, as t...

From Zilog's own documention: Z80 Manual RESET. Reset (input, active Low). RESET initializes the CPU as follows: it resets the interrupt enable flip-flop, clears the Program Counter and registers I and R, and sets the interrupt status to Mode 0. During reset time, the address and data bus enter a hi...

@Jonathan - that looked horrible. I hope everything is now sorted and that you are okay now.

Mark

@Daniel - time to add spoiler tags?
Don't know if you can hide pictures in a spoiler though.

Mark

What Jonathan says about reset also changing register contents is true and I never intended to imply otherwise. In terms of decoding program flow though, for most systems, I don't think it is critical to know if the execution from 0000 was due to a reset or a jump to that address. And most of the ti...

Welcome back to Acornville and Beebland :D I glad that you are doing okay 8) Err, I feel a bit boxed in on this... (sorry :lol:) If I say it will be okay, it may not be! At my workplace we use monochrome CCTV systems, the CRT monitors typically run 24 hours a day every day (although there is always ...

Maplin used to sell them, but that's not much good to us now

In the past, I have just hacked off cables and connectors from old PC PSUs. Or got cable splitters or similar from online sellers.

BeebMaster may know more, as at one time he was making up floppy drive power cables.

Mark

Despite what the Zilog documents say, there is actually two different resets. But outside of the world of geeks trying to use the 'special' reset, all production products use the normal reset. All resets always restart the CPU to address 0000. So I don't think there would be any need to monitor the ...

Dave, can you please remind us which analyser you are using. Earlier in the year (or was it last year) I was reading one of your previous threads where you figured out that you could decode the 6502 without having to connect to the CPU chip pins. I remember thinking that I must get hold of the devi...

The text of your previous post appearing when you press "reply" is due to the save quick draft feature. Just delete the text and then write your new post. I think it's when composing your earlier post, it auto-saves your post at the same time as you hit "submit". For moderators and administrators, w...

Yeah, the notebook style (NC100 and maybe the other similar computers) are likely to use SMD chips. Not had a reason to open mine. Dave, sounds good :D. The point I was trying to make (and I forgot/got distracted), was that as the Z80 CPU clock is not needed for bus control, it often is not availabl...

Some very useful information on the ZX80 and ZX81 available here

For a more in depth explanation of the video system, read this

Mark