Spectrum Computing

Last update... I have bought the following composite video to HDMI converter for about 10 USD: https://www.aliexpress.com/item/Mini-1080P-Composite-AV-RCA-to-HDMI-Video-Converter-Adapter-Full-HD-720-1080p-UP-Scaler/32826053126.html?spm=2114.search0104.0.0.2cc4504eOIkcBs It works, there are no synchr...

Thousand thanks to artVan an 1024MAK for your scope traces . Now I have all the information I need. For those who might be interested: a) The amplitude of sync/black/white on the Y signal is similar between 5C102 (issue 1), 5C112 (issue 2) and 6C001 (issue >2): 3.4-3.6V for sync, 2.2-2.5V for black...

Hey, nobody can help? :shock: In the meantime, I have found a video of somebody repairing a ZX Spectrum 48K with a 6C001 ULA. A some point, an oscilloscope trace of the ULA's Y output is shown, and the signal levels are the same as my 5C112 ULA produces and not at all what is described in the ULA bo...

Yes, but it would be even nicer if a nice person would measure those voltages in an issue 2 Spectrum and tell me the results...

OK, guys, after some more measurement and reading Chris Smith's great book "The ZX Spectrum ULA: How to design a microcomputer" (incredible work, I recommend it), I'm a little less stupid. If you are interested in the book, look at http://www.zxdesign.info/book/ Now it's clear that all unm...

... and that the burst is commanded by the U or V output of the ULA, which is output once all ca. 60us even during the field blanking.
Seems to be the normal way of working of the Speccy... and maybe not much appreciated by modern digital TV sets...

... just noticed that the ULA's Y signal (luminance) does not go into the LM1889 at all... only the chrominance signals U and V. How does the LM1889 when to generate the chrominance subcarrier and when not?

It would be great, thank you! After 36 years I should be able to wait until the weekend ;) What I'm interested in, when displaying the start screen ("(c) Sinclair...") with pale white and some black characters: - output of the ULA, DC voltage of sync level, black level and white level (if ...

Thank you 1024 MAK. Yes, I'm aware of these facts but actually, digital processing could allow a modern TV to be much more tolerant to a bad composite signal with almost no costs at all. But it's probably not in the objectives of Samsung's R&D department! --> Could anybody tell me if what I'm ob...

Hello I have juste bought again my first computer on ebay... a Speccy 48k. Just had to replace TR4 and it worked. I have made the composite video modification, simple (wire), with capacitor (100uF), with transistor (BC547), but my TV (Samsung UE40H6400) has difficulties to lock on the video signal: ...