Vectorbeam 1977 Vectorbeam 1977 Monitor Modifications :
There are a few physical modifications that should be performed on Vectorbeam monitors and also on older revision Cinematronics monitors in order to make them more reliable. These modifications are very easy to perform and are well worth the effort.
The first and most well known modification, adding the 1N4148 (or 1N914) diode to the LF13331 chip. A Cinematronics monitor may already have this diode labeled as D200. If your monitor doesn't have this diode (A Space War will not have it), it is highly recommended that you add this diode asap. This diode performs a power supply clamping function during power-up and power-down that can prevent destruction of the LF13331 chip in the event that the negative supply voltage is sufficiently higher than the positive supply voltage. Such a condition can also occur if the positive circuit breaker (CB1) pops and cuts off the positive supply.
The diode must be connected to LF13331 (VB U3, or Cine IC1) such that the cathode (banded end) is at pin 4 and the anode is at pin 5. Add the diode to the bottom of the PCB.
The next modification adds current limiting to the DAC chips analog outputs. This is done by cutting a trace to separate DAC chip pins 15 and 18 and by adding a 820 ohm resistor between them. Cine monitors may already have these resistors labeled as R130 and R230. A Space War monitor will not have these two resistors so you should add them.
Cut two traces on the top side of the PCB near U1 and U5 respectively as shown...
Next, add two 820 ohm resistors, one at each DAC chip (VB IC1 & U5, or Cine IC101 & IC201) respectively across pins 15 and 18.
Add the resistors to the bottom side of the PCB as shown...
| Space War : The Story & Documentation | Space War : Control Panel Help |
| Space War : Picture Library | Space War: Key Switch Problems & Solutions |
Top ....... Game List ....... Bill's Classic Arcade Home ....... Biltronix Home
