Search found 5156 matches
- Tue May 28, 2024 12:32 pm
- Forum: Hardware
- Topic: Timex Sinclair 2068 - Troubleshooting
- Replies: 2
- Views: 208
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: 1
- Views: 157
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: 691
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: 691
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: 691
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: 691
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: 691
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: 1319
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
- Tue May 14, 2024 11:41 am
- Forum: Hardware
- Topic: Spectrum 128 Toastrack Mishap
- Replies: 5
- Views: 485
Re: Spectrum 128 Toastrack Mishap
ZTX651 and ZTX653 are suitable replacements for the ZTX650 normally found in TR4 position and when I last checked earlier this year, were still in production.
TR4 normally only dies if there is a short circuit or other overload on one of the outputs of the DC/DC converter.
Mark
TR4 normally only dies if there is a short circuit or other overload on one of the outputs of the DC/DC converter.
Mark
- Tue May 14, 2024 9:49 am
- Forum: Hardware
- Topic: Spectrum 128 Toastrack Mishap
- Replies: 5
- Views: 485
Re: Spectrum 128 Toastrack Mishap
The colour encoder chip is not involved with the RGB output.
Are the +5V and +12V supplies for the video section okay?
Mark
Are the +5V and +12V supplies for the video section okay?
Mark