This printer needs a PSU with a 24V 1A AC output.
Mark
Search found 3118 matches
- Thu Apr 18, 2024 2:51 pm
- Forum: Hardware
- Topic: Timex Sinclair 2040 printer question
- Replies: 5
- Views: 128
- Thu Apr 18, 2024 2:46 pm
- Forum: Hardware
- Topic: black plus 2 keyboard fault
- Replies: 3
- Views: 131
Re: black plus 2 keyboard fault
Okay, that's weird... The keyboard matrix is pure hardware and what program is running shouldn't make any difference to the hardware. Having said that, BASIC and some games will ignore a key if two of the normal keys are detected to be pressed simultaneously. That may explain why the symptoms are di...
- Thu Apr 18, 2024 2:26 pm
- Forum: Hardware
- Topic: DC-DC mod query
- Replies: 5
- Views: 194
Re: DC-DC mod query
So, over the lifetime of the Spectrum, there were various changes to the circuitry including that of the DC-DC converter section. The website/blog you linked to is mine BTW. On your board, you may have either an earlier version or it has just been implemented differently. The service technicians tha...
- Tue Apr 16, 2024 2:16 pm
- Forum: Hardware
- Topic: black plus 2 keyboard fault
- Replies: 3
- Views: 131
Re: black plus 2 keyboard fault
It may be that the problems with the keyboard existed before you opened the case. Were you able to test it before opening it? The keyboard uses a membrane, which itself is wired as a matrix of "switches". The "normal" keys (those that are the same as in a rubber key model) use a ...
- Mon Apr 15, 2024 9:11 am
- Forum: Hardware
- Topic: +2B with a non responsive keyboard
- Replies: 37
- Views: 5497
Re: +2B with a non responsive keyboard
With faults, I much prefer members to start a new topic. This saves confusion. However, I'm not an admin or moderator here.
Mark
Mark
- Mon Apr 08, 2024 5:26 pm
- Forum: Programming
- Topic: Bank switching issue
- Replies: 32
- Views: 1081
Re: Bank switching issue
So, just the few instructions needed to switch banks then I guess? I was expecting a bigger speed penalty to bank switching. The latch chip that stores the extra address bits for the memory is just as quick as the Z80. The limiting factors are what you have to do in your software routine and the OU...
- Sun Apr 07, 2024 10:40 am
- Forum: Hardware
- Topic: Question about 48K composite mod
- Replies: 5
- Views: 250
Re: Question about 48K composite mod
I assume you were using an original Sinclair power supply unit (model UK1400 9V 1.4A). This is not a universal mains voltage type, as it requires a nominal 240V AC 50Hz mains input voltage. It will not produce enough output voltage if connected to a 110V – 120V 60Hz mains supply. The good news is th...
- Sat Apr 06, 2024 1:53 pm
- Forum: Hardware
- Topic: Question about 48K composite mod
- Replies: 5
- Views: 250
Re: Question about 48K composite mod
Yes, it has definitely been modified. The (phono) output connector on the modulator (what was the UHF TV output) will now output a composite video signal. I can't tell which version (there are more than four...) of the composite video modification has been done. If you want to know, you need to care...
- Tue Apr 02, 2024 9:49 pm
- Forum: Hardware
- Topic: Hardware diagnostics interface (Pico based)
- Replies: 4
- Views: 183
Re: Hardware diagnostics interface (Pico based)
Oh, and during the RAM check that the ROM does, it may be possible to check for some RAM faults that the ROM code does not test for. It's not possible to pick up all RAM faults, because the intention of the ROM routine is to simply work out how much RAM is fitted, NOT if it works correctly. Hence th...
- Tue Apr 02, 2024 9:45 pm
- Forum: Hardware
- Topic: Hardware diagnostics interface (Pico based)
- Replies: 4
- Views: 183
Re: Hardware diagnostics interface (Pico based)
Nice 8-) The next step would be an instruction trace, Often knowing at what point the Z80 is no longer executing the expected sequence can help identify the problem, or at least narrow it down. If there is no input from the user, the machine should make it to the "copyright" screen with th...
- Tue Apr 02, 2024 5:33 pm
- Forum: Programming
- Topic: Bank switching issue
- Replies: 32
- Views: 1081
Re: Bank switching issue
It's called bank switching or paging, but at the hardware level, the value on the data bus from the OUT is stored in a latch (register). Then some of the bits are used as extra address lines to the memory (ROM and RAM). The effect of this is that as described above, the Z80 can only see a "wind...
- Sun Mar 31, 2024 8:49 pm
- Forum: Programming
- Topic: Zilog's Z80 opcode choice
- Replies: 20
- Views: 516
Re: Zilog's Z80 opcode choice
CP/M became a big thing and certainly helped make the Z80 successful. I don't know if during the design of the Z80 CP/M was considered. But it may have been. As far as I can recall, the 6502 did not have a direct equivalent to CP/M back then. There was FLEX for the 6800, and then later on a version ...
- Sun Mar 31, 2024 4:37 pm
- Forum: Programming
- Topic: Zilog's Z80 opcode choice
- Replies: 20
- Views: 516
Re: Zilog's Z80 opcode choice
To be fair, the 6809 came along a lot later, and because it was late to the party, and hence not established (so not as cheap) only made it into a small number of computer models.
Yes, it was a good and powerful microprocessor.
Mark
Yes, it was a good and powerful microprocessor.
Mark
- Sun Mar 31, 2024 7:34 am
- Forum: Programming
- Topic: Zilog's Z80 opcode choice
- Replies: 20
- Views: 516
Re: Zilog's Z80 opcode choice
This is probably more of a general Z80 question rather than applying to the Spectrum specifically, but do you think when Zilog designed and implemented the Z80's instructions and assigned them to either 1 or more byte opcodes that they always made the right choice? I'm not really talking about hypo...
- Wed Mar 13, 2024 11:13 pm
- Forum: ZX80 & ZX81
- Topic: WRX True High Resolution Graphics
- Replies: 5
- Views: 773
Re: WRX True High Resolution Graphics
For the game, see also
https://www.sinclairzxworld.com/viewtop ... f=11&t=289
and
https://www.sinclairzxworld.com/viewtop ... f=4&t=1317
For the details on how hires works, this site is a bit more readable (apart from the ASCII diagrams)
Mark
https://www.sinclairzxworld.com/viewtop ... f=11&t=289
and
https://www.sinclairzxworld.com/viewtop ... f=4&t=1317
For the details on how hires works, this site is a bit more readable (apart from the ASCII diagrams)
Mark
- Sun Mar 10, 2024 2:23 pm
- Forum: Hardware
- Topic: When tapes fail due to age
- Replies: 9
- Views: 471
Re: When tapes fail due to age
Sounds like a lack of volume issue.
Mark
Mark
- Tue Mar 05, 2024 2:12 pm
- Forum: Hardware
- Topic: very low 'volume' from 'speaker'
- Replies: 6
- Views: 188
Re: very low 'volume' from 'speaker'
That's diode D13 (1N4148).
Speakers unless the cone is damaged, either work normally or are completely broken.
Mark
Speakers unless the cone is damaged, either work normally or are completely broken.
Mark
- Thu Feb 29, 2024 3:31 pm
- Forum: Hardware
- Topic: New open lower RAM module design (photoessay)
- Replies: 98
- Views: 2778
Re: New open lower RAM module design (photoessay)
And the last part of that post appears to have got lost. It should have ended:
'It will be hard to work out exactly what the problem is".
Mark
'It will be hard to work out exactly what the problem is".
Mark
- Wed Feb 28, 2024 8:25 pm
- Forum: Hardware
- Topic: New open lower RAM module design (photoessay)
- Replies: 98
- Views: 2778
Re: New open lower RAM module design (photoessay)
Okay, best if we calm down. Right, so there are some points I want to comment on. First off, we now know far more about how high speed digital signals are affected on PCBs now, compared to the 1980s. And Sinclair did have problems. Yes, the ZX Spectrum was okay, but the QL board had to be redesigned...
- Sat Feb 24, 2024 2:50 pm
- Forum: Hardware
- Topic: Question... 2nd joystick button?
- Replies: 9
- Views: 260
Re: Question... 2nd joystick button?
I'm curious to know whether the Spectrum can make use of a 2nd joystick button (or Master System pad buttons for example)? As Andy says, it depends on the actual joystick interface. By this, I mean both the type and the actual revision/version. This is especially relevant for Kempston or Kempston c...
- Fri Feb 23, 2024 7:26 pm
- Forum: Hardware
- Topic: Composite to Scart - What am i doing wrong
- Replies: 8
- Views: 242
Re: Composite to Scart - What am i doing wrong
You might be able to fit a composite connector to that monitor, it has markings for cvbs input, on a lot of those rebadged Philips (cm8833) monitors you can. Will not help if it lacks the PAL colour decoder circuitry... Does scart need voltage for it to switch? "Notice the +5 volts applied to ...
- Fri Feb 23, 2024 9:22 am
- Forum: Hardware
- Topic: Composite to Scart - What am i doing wrong
- Replies: 8
- Views: 242
Re: Composite to Scart - What am i doing wrong
Although most TVs support composite video inputs on their SCART sockets, not all monitors do. So the first thing is to check any documentation for your monitor. The fact that you can get an monochrome red, green or blue image if you use one the red, green or blue RGB inputs without having to provide...
- Thu Feb 22, 2024 12:31 am
- Forum: Hardware
- Topic: Cant load anything
- Replies: 41
- Views: 1136
Re: Cant load anything
Thanks for reporting back
Have fun
Mark
Have fun
Mark
- Wed Feb 21, 2024 11:45 pm
- Forum: Hardware
- Topic: Recap Problem.
- Replies: 5
- Views: 267
Re: Recap Problem.
Beware, the thinnest hair width solder splash can cause utter chaos...
Mark
Mark
- Tue Feb 20, 2024 10:16 pm
- Forum: Hardware
- Topic: Diagnosing strange 'black screen' video issue
- Replies: 6
- Views: 244
Re: Diagnosing strange 'black screen' video issue
Replacing IC14 is unlikely to make much, if any difference to the dot-crawl. The real problem is a design limitation. The 16K/48K/+ uses two different oscillators to produce the pixel clock and the colour sub-carrier/encoder. Hence they are not locked to each other. That's the problem (well, the mai...