Hello and welcome to our forum RS232!
I hope you enjoy this forum
Although I notice you actually joined some time ago
And thank you for contributing
Mark
Search found 5158 matches
- Wed May 29, 2024 12:37 pm
- Forum: Welcome Area
- Topic: Greeting from the UK. Coding again for the Zx81
- Replies: 4
- Views: 103
- Wed May 29, 2024 2:58 am
- Forum: Development
- Topic: Does a specy membrane work on a zx81?
- Replies: 2
- Views: 83
Re: Does a specy membrane work on a zx81?
No and yes. The keyboard matrix is the same, but the order of the signals on the membrane tails is different. Plus the location on the boards for the connectors for the tails is different. So if you use separate connectors and add your own wiring so you can change the order of the signals, yes. Mark
- Tue May 28, 2024 12:32 pm
- Forum: Hardware
- Topic: Timex Sinclair 2068 - Troubleshooting
- Replies: 2
- Views: 320
Re: Timex Sinclair 2068 - Troubleshooting
U1 (µA78S40), Q1 (D432C1), CR1 (1N5821), the inductor L2 and associated components form a buck converter (step-down DC-to-DC converter) which decreases and regulates the output voltage to a set amount. It has the limitation that often a fault with it will result in nearly the full input voltage bein...
- Tue May 28, 2024 11:44 am
- Forum: Welcome Area
- Topic: Hello everyone!
- Replies: 2
- Views: 222
Re: Hello everyone!
Hello and welcome to our forum Diegorand!
I hope you enjoy this forum
Mark
I hope you enjoy this forum
Mark
- Tue May 21, 2024 11:19 pm
- Forum: Hardware
- Topic: FIXED Spectrum +2 grey 5V and 12V power short
- Replies: 12
- Views: 735
Re: FIXED Spectrum +2 grey 5V and 12V power short
No problem
Good to know that you fixed it. Thank you also for reporting your findings
Mark
Good to know that you fixed it. Thank you also for reporting your findings
Mark
- Fri May 17, 2024 7:09 pm
- Forum: Hardware
- Topic: FIXED Spectrum +2 grey 5V and 12V power short
- Replies: 12
- Views: 735
Re: Spectrum +2 grey dead short
Oh, and the voltage source has to be a constant steady voltage, otherwise you are wasting your time.
Mark
Mark
- Fri May 17, 2024 7:02 pm
- Forum: Hardware
- Topic: FIXED Spectrum +2 grey 5V and 12V power short
- Replies: 12
- Views: 735
Re: Spectrum +2 grey dead short
Well, you could try using the voltage gradient testing to try to narrow down the area where the fault is. Every conductor (outside of superconductors) has a small resistance, including PCB tracks. Hence if there is a short circuit, there will be a gradual voltage loss (drop) between the source of th...
- Fri May 17, 2024 2:26 pm
- Forum: Hardware
- Topic: FIXED Spectrum +2 grey 5V and 12V power short
- Replies: 12
- Views: 735
Re: Spectrum +2 grey dead short
Shorts on the +5V rail are rather tricky to find, because almost everything is connected to it...
How good is your multimeter?
How many digits and what is the maximum count?
What is the lowest DC voltage range?
Mark
How good is your multimeter?
How many digits and what is the maximum count?
What is the lowest DC voltage range?
Mark
- Fri May 17, 2024 12:49 pm
- Forum: Hardware
- Topic: FIXED Spectrum +2 grey 5V and 12V power short
- Replies: 12
- Views: 735
Re: Spectrum +2 grey dead short
Which power rail? Do you mean the (nominal) +9V input?
It could be something simple like an item of metal or a solder splash. If a visual inspection under a good light does not find the problem, then if you mean the +9V, remove the 7805 and TR9. Then retest.
Mark
It could be something simple like an item of metal or a solder splash. If a visual inspection under a good light does not find the problem, then if you mean the +9V, remove the 7805 and TR9. Then retest.
Mark
- Wed May 15, 2024 10:21 am
- Forum: Hardware
- Topic: ZX81 Comp. Mod, no Video
- Replies: 16
- Views: 1387
Re: ZX81 Comp. Mod, no Video
They are only fitted on models sold in the USA. They are to reduce the level of EMI “leaking” out. They are not used on UK models. They do not affect the operation of the computer (well unless broken).
I don’t know the value of them.
Mark
I don’t know the value of them.
Mark