Thread: Zx81
View Single Post
Old 14th Mar 2020, 6:59 pm   #57
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 8,873
Default Re: Zx81

Turning the transistor pinout into a practical layout, this is how to physically wire everything up. (See attached). I've laid it out so that the incoming +5V and the incoming video-in arrive from roughly the right place and direction.

When you cut the incoming video-in and +5V wires do it about 5-7mm inside the modulator housing, the transistor's base and collector leads can then be soldered directly to the ends of the incoming wires.

The resistor can be soldered between the transistor's emitter and the inside of the modulator case which is a handy 0V point - if you do that, do it low enough down the inside so the modulator lid can still be fitted on afterwards.
Attached Thumbnails
Click image for larger version

Name:	zx81_composite_buffer.jpg
Views:	56
Size:	25.5 KB
ID:	200971  
SiriusHardware is offline