Nothing springs out as being wrong with the Z80 clock part of the circuitry.
Mark
Search found 3141 matches
- Tue May 14, 2024 3:54 pm
- Forum: Hardware
- Topic: CPU not starting
- Replies: 23
- Views: 400
- Tue May 14, 2024 2:49 pm
- Forum: Hardware
- Topic: CPU not starting
- Replies: 23
- Views: 400
Re: CPU not starting
Can you please disconnect the power, then remove the ULA (I presume all chips are in sockets). Power up again and retest the voltages that you did in your last post. Next, power off again. Now use a test lead to connect R73 left lead to a 0V/ground point. Please ensure you have the correct lead of R...
- Tue May 14, 2024 12:43 pm
- Forum: Hardware
- Topic: CPU not starting
- Replies: 23
- Views: 400
Re: CPU not starting
Here's some screenshots from my PicoScope of one of my ZX Spectrum boards. https://i.postimg.cc/TLQ6DTqJ/ZX-Spectrum-Z80-clock-circuit-waveforms-1.png https://i.postimg.cc/145PZNsC/ZX-Spectrum-Z80-clock-circuit-waveforms-2.png Blue waveform is TR3 base. Voltage scale is shown on the left of the scre...
- Tue May 14, 2024 11:42 am
- Forum: Hardware
- Topic: CPU not starting
- Replies: 23
- Views: 400
Re: CPU not starting
It looks like your waveform is swinging from positive to negative, which surely can't be right, can it? I suspect that AC coupling mode is selected. For this circuit DC coupling mode should be used unless the 'scope used cannot process DC signals with a negative component. Also the timebase needs t...
- Tue May 14, 2024 11:15 am
- Forum: Hardware
- Topic: CPU not starting
- Replies: 23
- Views: 400
Re: CPU not starting
ZX Spectrum Z80 clock circuit. This is the circuit: https://i.postimg.cc/7J55WJf6/4-E0-FBB34-ED60-4049-9-B62-BF7-FBC900461.png https://i.postimg.cc/XNMLH8DD/4-E0-FBB34-ED60-4049-9-B62-BF7-FBC900461.png?dl=1 The reason why this circuit is used is because the ULA cannot output a rail to rail signal (m...
- Mon May 13, 2024 10:56 am
- Forum: Hardware
- Topic: CPU not starting
- Replies: 23
- Views: 400
Re: CPU not starting
Also a 'scope waveform of the base and the collector of TR3 if you have a dual channel oscilloscope. Note that the 'scope must have a bandwidth of 25MHz or better, ideally 50MHz or better.
Mark
Mark
- Mon May 13, 2024 10:39 am
- Forum: Hardware
- Topic: CPU not starting
- Replies: 23
- Views: 400
Re: CPU not starting
The type of transistor used in the clock circuit (TR3) is critical. If the turn off time of the transistor is too long, the voltage at the collector will stay low or the output pulse will be short and distorted. ZTX313 have been obsolete for years and the other main substitute is also discontinued. ...
- Sat May 11, 2024 12:15 pm
- Forum: Website
- Topic: QAOP bust again?
- Replies: 18
- Views: 218
Re: QAOP bust again?
Last time I tried on a iPad mini, the site would not work (it did earlier in the year). I no longer have this iPad. On the device that I am currently using, it does work (the link that Peter provided) and just going to the site via its URL so that you drop into BASIC. https://i.postimg.cc/JswcC1cn/S...
- Sat May 11, 2024 12:00 pm
- Forum: Website
- Topic: Issues changing email address on other site (WoS)
- Replies: 31
- Views: 667
Re: Issues changing email address on other site (WoS)
Okay, here's screen shots of those pages: https://i.postimg.cc/Z9pQz7dk/Screenshot-20240511-115151-kindlephoto-1591083851.png https://i.postimg.cc/0MvBkYYz/Screenshot-20240511-115226-kindlephoto-1591218515.png https://i.postimg.cc/wykb7120/Screenshot-20240511-115249-kindlephoto-1591176133.png Mark
- Sat May 11, 2024 10:12 am
- Forum: Website
- Topic: Issues changing email address on other site (WoS)
- Replies: 31
- Views: 667
Re: Issues changing email address on other site (WoS)
Have I got the correct user for each of you on WoSf?
Paradigm Shifter - https://worldofspectrum.org/forums/prof ... gm_Shifter
Timmy - https://worldofspectrum.org/forums/profile/5530/Timmy
zx81 - https://worldofspectrum.org/forums/profile/5549/zx81
Mark
Paradigm Shifter - https://worldofspectrum.org/forums/prof ... gm_Shifter
Timmy - https://worldofspectrum.org/forums/profile/5530/Timmy
zx81 - https://worldofspectrum.org/forums/profile/5549/zx81
Mark
- Fri May 10, 2024 4:26 pm
- Forum: Website
- Topic: Issues changing email address on other site (WoS)
- Replies: 31
- Views: 667
Re: Issues changing email address on other site (WoS)
Sorry if my poor English doesn't completely understand what you are saying. Are you suggesting me to DM/PM you? If Lee does communicate with me, he is very likely to want to know your old email address and your new email address. It is entirely up to you if you want to do this. I am just trying to ...
- Thu May 09, 2024 5:21 pm
- Forum: ZXDB Discussion
- Topic: Manic Miner/Jet Set Willy no longer available
- Replies: 30
- Views: 1203
Re: Manic Miner/Jet Set Willy no longer available
- Tue May 07, 2024 4:43 pm
- Forum: Website
- Topic: Issues changing email address on other site (WoS)
- Replies: 31
- Views: 667
Re: Issues changing email address on other site (WoS)
I don't know any details on the forum software used by WoS, but on phpBB forums, the powers between moderators and administrators can be very different. Even the powers given to the moderators can vary. A standard moderator can only ban users, not change their details. But the administrators can giv...
- Tue May 07, 2024 4:36 pm
- Forum: Programming
- Topic: Bank switching issue
- Replies: 38
- Views: 1444
Re: Bank switching issue
Well, it all depends on what you are trying to do. Which takes up the most space, executable code or data?
The all RAM mode is only available on the +2A, +2B and +3 models and was presumably intended for CP/M use.
Mark
The all RAM mode is only available on the +2A, +2B and +3 models and was presumably intended for CP/M use.
Mark
- Tue May 07, 2024 4:32 pm
- Forum: Website
- Topic: Issues changing email address on other site (WoS)
- Replies: 31
- Views: 667
Re: Issues changing email address on other site (WoS)
I'm happy to add other users that are unable to log in to the WoS forums to my topic on WoS forums.
Please quote your WoS forum user name. And it helps if you PM / DM your old and new email addresses in case Lee or another WoSf admin asks for them.
Mark
Please quote your WoS forum user name. And it helps if you PM / DM your old and new email addresses in case Lee or another WoSf admin asks for them.
Mark
- Tue May 07, 2024 3:19 pm
- Forum: Website
- Topic: Issues changing email address on other site (WoS)
- Replies: 31
- Views: 667
Re: Issues changing email address on other site (WoS)
The problem is that Lee does not appear to visit the WoS forums very often now.
I posted a topic about a new user wanting to join back at the beginning of the year, but there was no reply to the topic...
I'll add you to the same topic later once I've found it again.
Mark
I posted a topic about a new user wanting to join back at the beginning of the year, but there was no reply to the topic...
I'll add you to the same topic later once I've found it again.
Mark
- Thu May 02, 2024 9:02 am
- Forum: Website
- Topic: Did I mention the search is bad?
- Replies: 15
- Views: 685
Re: Did I mention the search is bad?
No
You can however use a search engine:
Code: Select all
site:https://spectrumcomputing.co.uk/forums/ QL- Wed May 01, 2024 11:34 am
- Forum: Website
- Topic: Did I mention the search is bad?
- Replies: 15
- Views: 685
- Mon Apr 22, 2024 12:59 pm
- Forum: Programming
- Topic: Goodbye,Z80
- Replies: 35
- Views: 2072
- Sun Apr 21, 2024 3:03 pm
- Forum: Programming
- Topic: Goodbye,Z80
- Replies: 35
- Views: 2072
- Sun Apr 21, 2024 3:02 pm
- Forum: Programming
- Topic: Goodbye,Z80
- Replies: 35
- Views: 2072
Re: Goodbye,Z80
What does it exactly mean? Brand new Z80 MPUs and the support chips for it that were still available will no longer be manufactured. Yes, there are plenty of used Z80 MPUs on the grey market. But as with many things on the grey market (including trading sites like eBay) what you actually get may no...
- Sun Apr 21, 2024 2:45 pm
- Forum: Hardware
- Topic: black plus 2 keyboard fault
- Replies: 6
- Views: 387
Re: black plus 2 keyboard fault
And if course, the joystick ports are part of the same matrix...
Glad you found the problem
Mark
Glad you found the problem
Mark
- Sat Apr 20, 2024 9:36 am
- Forum: Website
- Topic: "Most users..."
- Replies: 7
- Views: 1043
Re: "Most users..."
Currently:
MarkIn total there are 292 users online :: 12 registered, 0 hidden and 280 guests (based on users active over the past 15 minutes)
Most users ever online was 1411 on Tue 19th Mar 2024 09:18
- Thu Apr 18, 2024 2:51 pm
- Forum: Hardware
- Topic: Timex Sinclair 2040 printer question
- Replies: 5
- Views: 239
Re: Timex Sinclair 2040 printer question
This printer needs a PSU with a 24V 1A AC output.
Mark
Mark
- Thu Apr 18, 2024 2:46 pm
- Forum: Hardware
- Topic: black plus 2 keyboard fault
- Replies: 6
- Views: 387
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...