Re: 6569 luminances

From: silverdr_at_wfmh.org.pl
Date: Tue, 15 May 2012 12:03:48 +0200
Message-Id: <A737D391-CA6B-4A16-A39D-6114029C20A4@wfmh.org.pl>
On 2012-05-14, at 12:56, Gerrit Heitsch wrote:

>> Your ASCII-art skills are remarkable in this context.
> 
> Thank you... Took a while to do it though as wasn't much fun in 'vi'.

Vi, and especially vim is an impressive tool in well-trained hands.. yes, I like emacs too! :-D

> Further on in the thread they got more fancy with tries to eliminate the vertical bars generated by the 8565.

One of the reasons I prefer 6569 for..

> Since I only wanted it for a 6569 I used this simple stage of the evolution.

Did they get to a point where the problem was eventually solved? While I don't use the C64 narrow boards with 8565, I find this effect quite annoying in the 128s. BTW - there are some pictures (photos) in the thread but despite that the description says e. g. 800x600, they are very small when clicked..

> Remember that this ciruit will only produce a Y/C-Signal. If you want composite, you'll have to add a capacitor of a few hundred pF between Chroma and Luma. Ideally this is done in the plug and not on the board so you can still use Y/C for monitors that have the proper input.

Since I want to keep the output over original socket, I think I would simply add a switch on that daughterboard I am going go make. I take typical 470pF would work as "few hundred", right?  Hopefully it would not affect signal quality much.

> 2) The PCB layout of the C16 board is broken, Chroma and Luma signals run side by side for quite a bit of distance. This results in enough Chroma being coupled into Luma that you get a color picture if you just connect the Luma signal to the monitor.

:-) I know. I recall myself wondering "WTF" many years ago.

> The ROMs run on +5V only, so messing with +12V won't help them.

I know. I was talking about VIC and SID.

> The SID uses the +12V for some of the output stage and since it's analog, changing the voltage might change the sound. So be careful what you do.

Yes - that's exactly what I meant when writing that I "have to check". For digital things there is not much of a problem replacing VRs with switching ones (potentially more noisy output) or going up / down with voltage and see whether it works or not. With analogue stuff things are much more subtle and less predictable, with possible side effects that may go unnoticed on first quick check.

> As for the ROMs... you could desolder all of them, and add a little adapter with a 74LS11 and a properly programmed 27C256 on it. Then you have all 3 ROMs in a single CMOS-EPROM which needs a lot less power, especially if in standby (_CS high).

As I wrote several times - I would very much like to replace all ROMs with the selectable, menu driven solution. In order to make it hardware compatible with all 6502 systems I imagine it going between CPU and the main board. Trigger can come from various places for different systems. In the most obscure version it can be a simple push-button type of switch that would have to be added somewhere (joystick fire button for an example or just a dedicated switch if nothing better is available on a particular system). Most appealing would be of course to tap on the key combinations.

> Setup: [...]

Well, if nobody makes that dream-solution of mine, I'll get back to this.

-- 
SD!
       Message was sent through the cbm-hackers mailing list
Received on 2012-05-15 12:00:09

Archive generated by hypermail 2.2.0.