Re: 6569 luminances

From: Gerrit Heitsch <>
Date: Mon, 14 May 2012 07:37:45 +0200
Message-ID: <>
On 05/14/2012 12:51 AM, wrote:
> On 2012-05-13, at 22:16, Gerrit Heitsch wrote:
>> Sure... I think I posted it before, but a bit of ASCII-graphics won't hurt:
> Great, thanks all the info! I moved it into less ASCII - something like:

He... considering that the original circuit was an image published on 
the website. I just made it into ASCII so it can be easily 

An important detail... On the 250466 I tried this on, I had thought 
about using the modulator supply, but there it does not run on +5V but 
the unregulated +9V. So I grabbed +5V from trace feeding the expansion 
port. This means it will not really be possible to put it into the 
modulator housing unless you also add a 78L05 plus support.

> Now I shall need the actual dimensions of the modulator case (I am out of my place) and I can quickly lay a pcb out of this. One that would go exactly in place of the modulator and connect directly to its solder points.

I just removed the modulator completly and put a small handwired PCB in 
its place. I never thought about making a PCB for something as small as 
this circuit.

>> R5      = 470 Ohm (TED manual suggests 1 KOhm)
> Tried what works better in such case? Or is it 470 for VIC and 1k for TED?

So far I have only built one for a C16 and there the 470 Ohm seem to 
work. Feel free to check with 1 KOhm, it means TED will have to sink 
less current.

>> Do _not_ use metal film resistors,
> Why?

Because they are a metal film with a spiral groove in it. Which is 
sufficiently close to a coil that it will act as one once the frequency 
gets high enough (This circuit goes up into the MHz range). The effects 
are not very big but enough to influence the picture quality.

>>>> Now you only need to replace 2114 color RAM with a CMOS version
>>> I have never thought of/measured it - is the difference worth the effort?
>> The original 2114 is NMOS and gets noticably warm. The CMOS-Version (LC3514A or MB8414) does not.
> I checked Conrad, Reichelt, Segor. None seem to have those in theri catalogues.. Will have to google outside of Germany probably.

Well, the 2114 and derivates are old chips that are not made anymore and 
no one uses in new designs anymore... So you have to look where old 
chips are sold.

Like here:

 From what I found via Google, the UL224D is a CMOS-Version of the 2114 
made by ZMD in the GDR when it still existed.


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Received on 2012-05-14 06:00:04

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