Re: 264 Series and their chips

On 08/14/2011 08:05 PM, Bil Herd wrote:
>
> Quick story about how we figured stuff out on the fly:  We were getting
> black dots on the display of the early  TED/264, seemed to have shown up
> when we married a PCB with keyboard early on.  I threw a scope on the
> master clock and it was "freezing".  I licked my finger and went around
> the pins of the ted chip and found a pin that would cause a beat pattern
> of black dots on the display (clock was freezing at a 60 hz rate) when I
> touched it with my other hand on the monitor itself.   I strapped the pin
> to VCC with a Germanium diode to keep the pin from pulling higher than VCC
> and the symptoms stopped.

I remember that one and you can find pictures on the web showing a 
prototype board with a TED plus 2 diodes. The ceramic TED I have doesn't 
have them which suggests that it's a later revision (thanks to a glued 
on heatsink the chip came with I have no way to read the lettering).

The same story mentioned that in the original design there was no 6529B 
for the keyboard but the unbuffered data lines just connected to the 
matrix which resulted in problems with the joystick ports.

The only place I have seen the 6529B was the 264 series. Was this chip 
another quick fix?

  Gerrit


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