Huge voltage drop on PSU

[42001]

Hi Andrew,

Cannot decouple the capacitors. So the earlier measurements are with capacitors.

 

[AndrewT]

now add on a resistor to load one side.

try 470r 5W Can you see the bulb filament brightening very slightly?
measure VDC on loaded side and unloaded side.

Swap 470r to the other side and repeat the two measurements.

 

[42001]

Hi Andrew,

435Ohm 4 Watt: (gets really hot during this process)

When load on positive side: Load side 35.27
Unloaded side 35.15

When load on negative side: Load side 35.05
unloaded side 35.25

 

[42001]

PS: I have no bulb in place

 

[AndrewT]

post56 said

Power up the transformer Alone using a mains bulb tester.

 

[AndrewT]

35V² / 435r = 2.8W !!!!!!!!
very hot very quickly.

 

[42001]

I guess you mean on the 230VAC side? Or the 25VAC side?

 

[AndrewT]

now add protection diodes across the amplifier supply rails.
+ve to power ground
-ve to power ground.

In normal use these are reverse biased and run cold.

With a faulty PSU, or faulty wiring, they turn on the bulb tester and the worst voltage any part of your amplifier can ever see is 1Vdc in reverse.

Now power on and measure your supply rail voltages.

 

[AndrewT]

I guess you mean on the 230VAC side?

No, you are working on the isolated low voltage side.

Are you asking about the mains bulb tester?
Do you have one?
Do you know what it is?

 

[42001]

Just made one

Starting over now.....

 

[42001]

Andrew, I have one bulb tester..... I have 2 x 25VAC... Just one side for now? Or both sides separately?

 

[AndrewT]

Mains bulb tester

Do you know what it is?

 

[42001]

Something is off.... with bulb I get only 11.87 VAC and -12.34 VDC

I only connected the negative side of the PSU. So only one winding of the toroid is connected.

 

[42001]

I know how it is made. Don't quite understand it....

 

[42001]

Voltage into bulb is 25, out is half... is that correct?

 

[AndrewT]

Mains bulb tester

Do you know what it is?

I know how it is made.

Show a pic of your bulb tester.
Show us the mains plug at one end.
Show us the mains socket at the other end.

 

[TonyTecson]

Ac both 25VSC

DC Both 35VDC

Note that DC measurement is on the output of the PSU.

this seems normal as normal can be....

 

[42001]

pictures

See pictures

 

[42001]

pic 2

another picture

 

[42001]

only phase goes in and out of the bulb....