Retrocomputer, Heimcomputer und Videospiele der 80er

VTech Laser 210 repair

Broken keyboard (many keys not working) and only a black/white picture on the monitor and tv output. 
Vtech Laser 210 repair The broken keyboard was an easy fix, after a few measurements with my multimeter one broken trace was found. Vtech used a nice pcb for the first layer, but a kind of printed graphite for the second layer... and over time the graphite layer became non-existent.

I soldered a small wire in => keyboard works!

Vtech Laser 210 repair Still i only got a b/w display and not the nice green one :-)

The "color-part" is located on a small extra pcb, after i got hold of a shematic i quickly found, that the color-circuit needs 12V to operate, which where not present...

So i started with the simplest things: I measured (and changed) the electrolytic capacitors, mesaured all diodes and even checked the transistors => no use

The circuit uses an oscillator-coil and two transistors to generate 12V from the 5V input.

Vtech Laser 210 repair I checked the coil at last, because i thought coils do not easily fail (and i did not know anything about the inards of an osczillator coil, i even thought they could not be opened).

But, after i desoldered the 2 outer pins i could remove the top!

And what did i find on the inside?

Vtech Laser 210 repair After looking very closely i recognized, that one wire was broken!

You can see it in the picture (left bottom).

So coils do fail!

Vtech Laser 210 repair After very carefully lifting the wire i tied a knot around it with one strand of wire, soldered it on and connected it to the pin at the bottom.
Vtech Laser 210 repair That's how it looks...
Vtech Laser 210 repair So after putting everything back together...
Vtech Laser 210 repair I got a nice colourfull Display!

In the picture you see a little color demo running.

Autor: Thomas Gutmeier