Glad that you have found the problem and now have a working board
And it’s good to confess mistakes. It allows other members to learn. You are not the first and will not be the last to suffer from bent pins...
Mark
Search found 3145 matches
- Wed May 15, 2024 8:15 pm
- Forum: Hardware
- Topic: CPU not starting
- Replies: 31
- Views: 561
Re: CPU not starting
Thank you for reporting back
Glad that you have found the problem and now have a working board
And it’s good to confess mistakes. It allows other members to learn. You are not the first and will not be the last to suffer from bent pins...
Mark
Glad that you have found the problem and now have a working board
And it’s good to confess mistakes. It allows other members to learn. You are not the first and will not be the last to suffer from bent pins...
Mark
- Wed May 15, 2024 12:27 pm
- Forum: Hardware
- Topic: Issue 4B, 12V power missing
- Replies: 1
- Views: 39
Re: Issue 4B, 12V power missing
Most likely TR4 (ZTX650) has died. A ZTX651 or a ZTX653 can be used as a replacement. It's also possible that TR5 has died. The most common causes of TR4 becoming damaged are edge-connector abuse (expansion/interface being removed or fitted while the computer is powered on or other short circuit), o...
- Wed May 15, 2024 10:55 am
- Forum: Hardware
- Topic: CPU not starting
- Replies: 31
- Views: 561
Re: CPU not starting
In the last set of tests, the ULA is not fitted, hence there is no AC signal, the circuit is only operating in a static / DC state. This is primarily to confirm that in a static state it is working okay. It's much easier to pick up basic faults in a static state. As to what a digital meter will show...
- Wed May 15, 2024 9:51 am
- Forum: Hardware
- Topic: CPU not starting
- Replies: 31
- Views: 561
Re: CPU not starting
See comments in GREEN and RED No ULA R73 5.03 Right, 2.81 Left - Okay R24 2.93 Right, 0.87 Left - I would expect R24 right to be approximately the same as R73 left Base 0.83, collector 0, Emitter 0 - Okay Pin 6 CPU 0 - Okay R25 5.03 Right, 0.83 Left - R25 left should be 0V or very close to 0V Can yo...
- Tue May 14, 2024 3:54 pm
- Forum: Hardware
- Topic: CPU not starting
- Replies: 31
- Views: 561
Re: CPU not starting
Nothing springs out as being wrong with the Z80 clock part of the circuitry.
Mark
Mark
- Tue May 14, 2024 2:49 pm
- Forum: Hardware
- Topic: CPU not starting
- Replies: 31
- Views: 561
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: 31
- Views: 561
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: 31
- Views: 561
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: 31
- Views: 561
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: 31
- Views: 561
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: 31
- Views: 561
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: 37
- Views: 1402
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: 1455
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: 2081
- Sun Apr 21, 2024 3:03 pm
- Forum: Programming
- Topic: Goodbye,Z80
- Replies: 35
- Views: 2081
- Sun Apr 21, 2024 3:02 pm
- Forum: Programming
- Topic: Goodbye,Z80
- Replies: 35
- Views: 2081
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...