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Philiphifi
20-02-2020, 15:46
hi - could i please ask an experienced person to look over this diagram to see if the connections are correct? I bought the boards from the Diyaudio + a 500AV, 2x18v transformer. I am puzzled as to where to connect the IEC and the transformer ground? I presume i need to join 2 wires on the transformer to create centre tap. Where would this go ? do i ground this to the chassis?

Thank you very much in advance for your help

Philip
Made in 1968
20-02-2020, 16:20
Everything is here

https://guides.diyaudio.com/Guide/Firstwatt+F5+amplifier+v3/6?lang=en
Philiphifi
20-02-2020, 16:36
thank you. Unfortunately, they provide the build with external rectifiers and a 115v transformer. I don't know why considering the rectifier is part of the psu board they sell
Made in 1968
20-02-2020, 17:35
If they did not use Bridge Rectifier Packages they might have considered putting Diodes on the PSU board. I guess its easier to design the PSU Board if they are off..
Philiphifi
20-02-2020, 17:40
is it not the two black blocks? monolithic bridge rectifier?
Made in 1968
20-02-2020, 17:41
Yes they are Bridge Rectifier Packages with the four legs sticking up..
Patrick Dixon
20-02-2020, 18:42
Connect the transformer as per the diagram in the 240V box. The secondary connections are as per the 110V box above it. Chassis ground doesn't go anywhere near the transformer: the transformer doesn't have a ground and you should make sure that the bolt through the center of the transformer is only connected to the chassis at one end, otherwise you will create a shorted turn through the transformer (which is not a good idea). I'm assuming it's a toroidal transformer.

The bridge rectifiers should have two terminals marked AC or ~. It doesn't matter which way around you connect these to the transformer secondaries.

The +ve output of one bridge will connect to the -ve output of the other to give your 'centre tap' signal ground (the other ends of the bridges will be the positive and negative rails with respect to the signal ground). The signal ground then references to the chassis ground via a thermistor.