Search found 14 matches
- Mon Oct 18, 2021 12:59 am
- Forum: SALES
- Topic: vLA81 Availability
- Replies: 4
- Views: 6588
Re: vLA81 Availability
Thanks Mark, good to be back in action.
- Mon Oct 18, 2021 12:49 am
- Forum: SALES
- Topic: vLA81 Availability
- Replies: 4
- Views: 6588
vLA81 Availability
Hi All, As most will know there have been a few changes to import rules for both the UK and the EU over the past year. As a result I (and a few other makers) have had to jump through a few hoops in order to keep selling the stuff we make. My eventual response to this was to create two separate onlin...
- Wed Aug 11, 2021 9:47 am
- Forum: Hardware
- Topic: VLa81 noisy video signal
- Replies: 19
- Views: 4137
Re: VLa81 noisy video signal
I presume you include plenty of supply rail decoupling capacitors on the module There's a 100nF in close proximity to each IO rail and I do remember spending a bit of time minimising the noise from both the LDO regulator and CPLD itself. The law of diminishing returns stepped in however and adding ...
- Wed Aug 11, 2021 3:56 am
- Forum: Hardware
- Topic: VLa81 noisy video signal
- Replies: 19
- Views: 4137
Re: VLa81 noisy video signal
Hi, Just in case some members don't know, I make the vLA81 (and a few other retro things). As with a lot of CPLD designs (due to their very fast switching speeds) there is going to be some impulse noise that will make it to the analogue domain with some resultant frequencies appearing in the video s...
- Sun Aug 08, 2021 6:14 am
- Forum: Hardware
- Topic: ZX81 RAM pack Issue 3 (ULA 1H035E) DRAM refresh
- Replies: 12
- Views: 3502
Re: ZX81 RAM pack Issue 3 (ULA 1H035E) DRAM refresh
I think I may be able to shed some light on this (and thanks to those who have previously managed to trace the pinouts, it saved quite a bit of time). The only way to see what is really happening is to hook up a logic analyser and so that is what I've done. Once the relationships can be seen clearly...
Re: ZX81 ULA
The “standard” that has developed is for composite video (also known as baseband video) to be fed via co-ax cables that have a characteristic impedance of about 75Ω, hence most have an input resistance of 75Ω (as when dealing with video frequencies, every part of a circuit should have the same impe...
- Fri Aug 16, 2019 3:13 am
- Forum: SALES
- Topic: I missed the hot cakes...
- Replies: 26
- Views: 19886
Re: I missed the hot cakes...
Hi and a warm welcome. Looks like a great product. Since you, by magic, just create one ULA after the other, :) how about a ULA for the Lambda 8300? It’s a little different than the ZX81 and has the charset (ROM) build into the ULA. :) Just when I thought I had run out of things to do :) Is there a...
- Fri Aug 16, 2019 1:21 am
- Forum: SALES
- Topic: I missed the hot cakes...
- Replies: 26
- Views: 19886
Re: I missed the hot cakes...
I prefer my internal RAM upgrade detailed here :D Hello Bloodnok, welcome :D I must admit, I could not resist buying one of your vLA81 Sinclair ZX81 ULA replacements. When it arrives (and I can find some time) I’ll try hooking it up to the Zeddy that I used in the article on the site I linked to ab...
- Fri Aug 16, 2019 1:15 am
- Forum: SALES
- Topic: I missed the hot cakes...
- Replies: 26
- Views: 19886
Re: I missed the hot cakes...
QUOTE. " It looks like you sold about 6 of these since moggy pointed them out yesterday. :D Happy days." I WANT 10% !!!!!!!!!! :lol: Seriously, welcome aboard Bloodnok ( A Goons fan perhaps?) and really excellent work. :D Thanks Moggy. Bloodnok is an old gaming tag which has sort of stuck - and yes...
- Fri Aug 16, 2019 1:09 am
- Forum: SALES
- Topic: I missed the hot cakes...
- Replies: 26
- Views: 19886
Re: I missed the hot cakes...
Thanks for the RAM heads-up Charlie. I’m looking at the video output section. Does this have a native composite video output like Andy’s? Just not sure of the terminology. :D Yes - the video output is designed to drive a 75 ohm monitor input directly (or through a capacitor if desired). Here's the ...