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@karl: At the moment I have got two power rails on the PCB, one is +5V directly from the Zeddy board and the second is +3.3V rail for the CPLD. The video output of the CPLD is connected to a transistor buffer. The transistor is fed off the +5V Zeddy rail to avoid any CPLD switching noise on the +3.3...
In my case I create +3.3V for the CPLD from the Zeddy +5V rail using LM11117-3.3V plus 4 capacitors (100nF & low ESR 10uF) at both sides (in & out). However, for video output buffers I've decided to go for +5V which is noisy. So, it is time to change and don't use +5V rail from the Zeddy board for a...
Hi Andy, Looks interesting. I'd added and tested the ferrite bread + caps (0.1uF and 10uF) in similar fashion as you shown above, but it didn't help much in my case. I think the issue is with the noise coming to the ULA PCB from the Zeddy mainboard. It seems that the +5V and GND are the carriers. So...
I've tried all these enamels with various brushes ... it was a waste of time and money. Yes, indeed, you can match nearly every colour what you can think of but final results are not as good as you expect. Using the oil based marker makes your works easy and stress free with painting just the top of...
You can use an oil based marker with a fine tip. I used this method on raised letters on Zeddy's case when I did a refub last time. Red is not as deep as the Sinclair one but looks good.
- Mon Mar 19, 2018 10:57 pm
- Forum: Development
- Topic: do we still use UHF modulators ?
- Replies: 17
- Views: 313
I all Zeddys that I've got the NEC Z80 clone is sitting. The uPD780C datasheet is referring to:
- Address lines 50pF
- Data lines 200pF