Williams rom board question

dahnz

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Can someone with a Robotron or similar tell me what voltages are meant to go to the rom board? Mine had one 5 volt wire connected to both the 4 and 6 pins of 2J2, but I thought from looking at the schematics that there should be 12 volts going in there (I'm probably just reading the schematics wrong). It's the 5771 09840 00 rev A board.

Also, I powered up my Stargate last night to test a CPU board and I got a really loud bang. Sounded like it came from the monitor but nothing seemed burnt or broken, there was no smoke, and the monitor was still working. I can't see any damage on any of the boards and I haven't recapped anything, so there are no the wrong way round. Any ideas what that might have been? Maybe something discharged somehow. It was a very cold night if that matters at all.
 
You can hook +5V to both pins 4 & 6. Pin 6 is not used. There was an errata sheet for the Robotron Drawing set that indicated that the +12V on pin 6 was supposed to be +5V or nothing. Of course, nobody bothers to keep errata sheets so it is a common wiring error.

It sounds like you may have triggered a fairly rare component normally called an NED (noise emitting diode). They are one shot devices so you may need to carefully check for cratering on any IC chips and diodes.

ken
 
It sounds like you may have triggered a fairly rare component normally called an NED (noise emitting diode). They are one shot devices so you may need to carefully check for cratering on any IC chips and diodes.

Hehehehe.

Also check for SER's - Smoke Emitting Resistors

-Ian
 
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