Pass "DeLite" Amp from BAF

[nicoch58]

Ok , this is for the Power Jfet , as built for now , going to listen
With R5 = 1 M and setting V at the Drain = half the rail , obtained is 1.5 Amps of current through the device , and R-light bulb = 18 ohm .
Thanks

Hi Stefano on schematics T1 is 75Vac....the correct one 36/40 Vac ?

 

[stefanobilliani]

Hi Stefano on schematics T1 is 75Vac....the correct one 36/40 Vac ?

Hello ! can you please link me to the schematic for reference?

thanks

 

[Puffin]

OK, tried that, still no joy

Next question. In the schematic in post 715, is the TAB of the IXYS shown by the solid line to the left of the 3 borken lines?

 

[stefanobilliani]

OK, tried that, still no joy

Next question. In the schematic in post 715, is the TAB of the IXYS shown by the solid line to the left of the 3 borken lines?

Hope this helps , the metal part in the back of the Transistor is connected to the Drain pin .

 

[Zen Mod]

yes - and you must have insulator between metal part of transistor and heatsink

as insulator use ready made mica or silicone pads

 

[Puffin]

Hope this helps , the metal part in the back of the Transistor is connected to the Drain pin .

Yes, that's what I thought. Thanks for the confirmation. So, I appear to have it wired correctly.

I am getting 82v to the bulb, but it doesn't light and the safety bulb mains lead glows brightly when I insert the bulb, suggesting a fault. Everything is ok until I fit the bulb. Bulbs are 300W - 130v.

 

[stefanobilliani]

the safety bulb mains lead glows brightly when I insert the bulb

what is that ?

 

[Puffin]

what is that ?

A 60W bulb in the live mains feed.

 

[Zen Mod]

give us pictures ;

of everything in amp

in "enough" resolution .

then we can help

 

[Puffin]

Are these any good?

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[stefanobilliani]

The big 1 ohm resistor that stands for R4 ( 50 watt I guess ) is it connected to the chassis ground ?

 

[Puffin]

The metal cased 1 ohm resistor is not wired up at present the PS is a CRC with some wirewound resistors. I was going to use these if the others got too hot.

 

[stefanobilliani]

The metal cased 1 ohm resistor is not wired up at present the PS is a CRC with some wirewound resistors. I was going to use these if the others got too hot.

OK , what is there for R4 ? I am using 30w metalfilm on heatsink

 

[Puffin]

R4 is the wirewound resistor on the amp board with IXYS.

 

[stefanobilliani]

R4 is the wirewound resistor on the amp board with IXYS.

that is probably too small in power to be working well , or at all . Check it , it may be broken

 

[Puffin]

OK. What does rating does Nelson suggest?

 

[stefanobilliani]

OK. What does rating does Nelson suggest?

Can't remember right now , the circuit will need 10W min.

 

[Puffin]

OK. Thanks for all your help. I'm off to bed now. Will tinker with it again and report back

Regards

Rob.

 

[Zen Mod]

P=I^2 x R

if current is , say , 2A then - dissipation P= 2^2 x 1 = 4W

that calls for at least 10W resistor ; preferably heatsinked

 

[Roscoe Primrose]

I think there may be some confusion on the Gate & Source. What looks like an internal connection between the gate and source in the MOSFET graphic is NOT an external connection. The source pin should ONLY be connected to R4.

Roscoe