dahnz
New member
Hi
I need some help with Robotron-era Williams power supplies (the ones with the OV protection built in). I had one that I did a cap kit on (except for C10 - the 18,000 mfd cap). It was working okay until the 5 volts went out and the -12 volts unregulated went up to about -30 volts. BR1 was new and read okay but I replaced it anyway, but that didn't help. Ken gave me some advice via PM but I never did figure it out and in the meantime I replaced it with another PS I had. That one also was recapped (again, I left out C10 because I didn't have any onhand).
Now that one has gone the same way. Was working fine, then the 5v went out and the -12 is now reading -42. I'm a noob when it comes to these things but apart from BR1 I can't see anything in the circuit diagram that would be affecting the -12v in this way.
We have 230v AC down here but the transformer is wired correctly for that and the voltages coming off the transformer measure out okay (pins 8 and 9 on 4J1 show 25v instead of 20v but all the rest are closer and, if anything, lower than they should be).
Any help would be much appreciated.
Dominic
I need some help with Robotron-era Williams power supplies (the ones with the OV protection built in). I had one that I did a cap kit on (except for C10 - the 18,000 mfd cap). It was working okay until the 5 volts went out and the -12 volts unregulated went up to about -30 volts. BR1 was new and read okay but I replaced it anyway, but that didn't help. Ken gave me some advice via PM but I never did figure it out and in the meantime I replaced it with another PS I had. That one also was recapped (again, I left out C10 because I didn't have any onhand).
Now that one has gone the same way. Was working fine, then the 5v went out and the -12 is now reading -42. I'm a noob when it comes to these things but apart from BR1 I can't see anything in the circuit diagram that would be affecting the -12v in this way.
We have 230v AC down here but the transformer is wired correctly for that and the voltages coming off the transformer measure out okay (pins 8 and 9 on 4J1 show 25v instead of 20v but all the rest are closer and, if anything, lower than they should be).
Any help would be much appreciated.
Dominic
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