Two things:
The Opus has its own bank switched / paged ROM/RAM system, so there must be a switch or something to prevent clashes between them.
The MF1 looks to be missing a lot of logic chips.
Mark
Search found 5118 matches
- Sat Mar 23, 2024 8:19 pm
- Forum: Hardware
- Topic: how to verify if a multiface 1 is working correct ??
- Replies: 18
- Views: 1836
- Sat Mar 23, 2024 2:14 pm
- Forum: Hardware
- Topic: how to verify if a multiface 1 is working correct ??
- Replies: 18
- Views: 1836
Re: how to verify if a multiface 1 is working ??
I'm guessing, but I would have thought that if the RAM was faulty, you would get different symptons. Is it really permanently soldered to the Speccy :shock: That makes it awkward... Have you checked for solder splashes and short circuits? Also open circuit / bad connection issues? This site has some...
- Sat Mar 23, 2024 2:10 pm
- Forum: Hardware
- Topic: What to do with an unusual ZX81?
- Replies: 7
- Views: 563
Re: What to do with an unusual ZX81?
If it's any help, the ZX Spectrum issue 1 (and some early issue 2) boards that have a different "dead bug" daughter board tend not to be modified (unless they were back in the day). You don't need to snip any wires. Just desolder the two wires going into the modulator from the PCB and secure them so...
- Sat Mar 23, 2024 11:11 am
- Forum: Hardware
- Topic: ZX Spectrum 16K keyboard issue - not all keys works
- Replies: 4
- Views: 526
Re: ZX Spectrum 16K keyboard issue - not all keys works
Hello and welcome :D The first point is that the keyboard is a matrix of eight half rows (five keys in each half row) and five "columns" (eight keys in each column). Hence there are two groups forming the connection to PCB (one of eight and one of five). A hairline fracture in one of the metal layer...
- Fri Mar 22, 2024 11:49 pm
- Forum: Hardware
- Topic: What to do with an unusual ZX81?
- Replies: 7
- Views: 563
Re: What to do with an unusual ZX81?
Hmm, being the electronics nerd that I am, I was thinking that those are a useful source of a couple of 74 series logic chips... :ugeek: :twisted: :lol: Mark PS i have plenty of run of the mill issue 1 and issue 3 boards to tinker with. A long time ago in a universe far, far away, I bought around 5 ...
- Fri Mar 22, 2024 4:29 pm
- Forum: Hardware
- Topic: how to verify if a multiface 1 is working correct ??
- Replies: 18
- Views: 1836
Re: how to verify if a multiface 1 is working ??
Either by design or by mistake, the NMI handler in the BASIC ROM will result in the Z80 jumping to the reset vector. With a MF1, it should switch out the BASIC ROM (forcing /ROMCS high) and page in its own ROM. Hence during the NMI it's the MF1 ROM that should be in control.
Mark
Mark
- Fri Mar 22, 2024 4:25 pm
- Forum: Hardware
- Topic: ZX Spectrum Issue 6a short
- Replies: 17
- Views: 732
Re: ZX Spectrum Issue 6a short
Sounds (!) like you are nearly there with a working machine. Well done
Mark
Mark
- Thu Mar 21, 2024 3:41 pm
- Forum: Hardware
- Topic: ZX Spectrum +2a issue with all expansion cards
- Replies: 8
- Views: 626
Re: ZX Spectrum +2a issue with all expansion cards
Okay.
All those require the machine to page out the internal ROM chips. Do you have any other expansions/interfaces to try, such as a Kempston (or compatible) joystick interface?
Mark
All those require the machine to page out the internal ROM chips. Do you have any other expansions/interfaces to try, such as a Kempston (or compatible) joystick interface?
Mark
- Wed Mar 20, 2024 10:01 pm
- Forum: Hardware
- Topic: Spectrum modded / composite question
- Replies: 19
- Views: 1046
Re: Spectrum modded / composite question
Some important things you need to know about the type of Ferranti ULA chips used in Sinclair computers: They use a type of bipolar transistor technology. This is very different to the other large chips used in the ZX Spectrum. The matrix cells (that provide the logic functions) are CML (current mode...
- Wed Mar 20, 2024 7:31 pm
- Forum: Hardware
- Topic: ZX Spectrum +2a issue with all expansion cards
- Replies: 8
- Views: 626
Re: ZX Spectrum +2a issue with all expansion cards
Which expansion cards / interfaces have you tried?
Mark
Mark