ZX81 denigrated! (was Re: Approaches to projects)

[Gordon JC Pearce]

Jim Brain wrote:
> Glen Goodwin wrote:
> 
>> One transistor + one resistor + one monitor = rock solid display.
>>  
>>
> Any links?  A dormant unit sits on the shelf.

 From memory, desolder the resistor inside the UHF modulator that goes 
to the middle pin of the phono.  Poke one lead of a 75 ohm (or 
thereabouts, 68 is common and close enough) through the polythene 
through the polythene bush, and solder it to the socket instead.  Solder 
the emitter of a small NPN tranny to the other end. Solder the base of 
the tranny to the video lead, the other one that goes through the bush, 
and solder the collector to the +5 supply where it goes into the 
feedthrough cap.  Finally solder another 75 ohm resistor between the 
junction of the first one and the emitter, and ground.  You may need to 
adjust those values, I may be wrong.

>> Scraps from the junk box and 30 minutes time will yield a cable which
>> provides enough distance from the ZX81 to eliminate the "wobble"
>> problem.
>>  
>>
> Again, links?

Get a 2x23 edge connector, a bit of circuit board etched and shaped to 
match the edge connector on the ZX81, and a bit of ribbon cable.  Wire 
them together.

Gordon.