A customer brought in a Kay model 703 for us. Only backstory and instruction on work order was to go through and make sure everything is a"as it should be". At first I thought it was an old widowmaker power transformer-less amp. While not completely isolated from the mains, there is a power transformer to isolate main power supply. Originally, all the heaters are run directly coupled to the mains supply.
This doesn't make any sense to me due to the potential fault from a heater shorting to any other node.
Anyways, the amp had had some service in the past. It had been fitted with a 3-conductor AC cord and the power transformer had been replaced with a triad N-68x isolation transformer. However, whoever did the wiring had no idea what they were really doing with really dangerous mains wiring grounding the neutral mains wire to the chassis/power supply ground making the chassis a mains current conductor and shorting the primary windings of the triad.
Here is a schematic for the Kay 703:
https://el34world.com/charts/Schemat...Kay/Kay703.pdf
here is the data sheet for the Triad N-68x:
http://catalog.triadmagnetics.com/Asset/N-68X.pdf
Triad's design uses 2 x 115 primary winding to be used with either 115V or 230V mains voltage with a single 115V secondary winding. Anyone see an issue with using connecting the mains to the single "secondary" 115V winding and using 2 separate isolated secondaries to supply the heaters and main power supply? I noticed that this transformer has a lead for a shield connection on the secondary.
I plan on leaving this unconnected if connected to the mains supply?
This doesn't make any sense to me due to the potential fault from a heater shorting to any other node.
Anyways, the amp had had some service in the past. It had been fitted with a 3-conductor AC cord and the power transformer had been replaced with a triad N-68x isolation transformer. However, whoever did the wiring had no idea what they were really doing with really dangerous mains wiring grounding the neutral mains wire to the chassis/power supply ground making the chassis a mains current conductor and shorting the primary windings of the triad.
Here is a schematic for the Kay 703:
https://el34world.com/charts/Schemat...Kay/Kay703.pdf
here is the data sheet for the Triad N-68x:
http://catalog.triadmagnetics.com/Asset/N-68X.pdf
Triad's design uses 2 x 115 primary winding to be used with either 115V or 230V mains voltage with a single 115V secondary winding. Anyone see an issue with using connecting the mains to the single "secondary" 115V winding and using 2 separate isolated secondaries to supply the heaters and main power supply? I noticed that this transformer has a lead for a shield connection on the secondary.
I plan on leaving this unconnected if connected to the mains supply?
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