Huge voltage drop on PSU

[AndrewT]

The Mains bulb tester is in the mains feed to the equipment.

 

[42001]

Yes.

 

[42001]

Bulb tester

Something like this, but on the 25VAC side

 

[42001]

It is a 25Watt / 230V lamp. I only get 11.8 volts AC out of the bulb.

 

[AndrewT]

post83 is correct.
That is the safe way to power up your project.
EVERY TIME !!!!!!!!

You plug the bulb tester into the wall socket.
You plug the mains power project into the bulb tester outlet socket.
You stand back and switch on.
If the bulb goes out then you can start measuring voltages.

All the earlier voltages should have been measured using the bulb tester in the mains feed.

repeat the test in post56 and post results.

 

[42001]

ok, but in post 69 you are clear about the 25VAC side.... so I'm puzzeled now.

I wil connect the bulb tester to the mains and measure again.

 

[AndrewT]

post69 asks if you know what the Mains bulb tester is?

It now appears you don't.
Even though you confirmed that you knew.

So back to post56 where you were told to power up with a Mains bulb tester.
That is where you ask:
"what is a Mains bulb tester?"

 

[42001]

Ok, you are right. Sorry.

Now I connected the bulb tester. the mains AC after the bulb dropped to 206 VAC. The voltages of the toroid are:

1: 23,6 VAC
2: 23,6 VAC

 

[42001]

Connected the PSU. Light ON bright! Then flickering en then going in low state but NOT off....still burning lightly....

 

[AndrewT]

the PSU is faulty.

remove the smoothing capacitors and test the rectifier as in post58

 

[42001]

Still a faint light

 

[AndrewT]

remove the rectifier.

 

[42001]

How to remove......

That is not easy....

 

[AndrewT]

I keep repeating in many posts BUILD IN STAGES.
Test in stages.

Your own fault.

 

[42001]

It has worked for over 6 months. Then I modify some parts and made the misstake of reversing positive and negative.

I already changed the rectifiers..... So I guess I can begin rebuilding the PSU now....

Any tips on what might be faulty?

Kind regards.

 

[42001]

Andrew, thank you very much for the lesson!

Kind regards,
Sjoerd

 

[AndrewT]

Fit the protection diodes.
Always power up every modified project with the Mains bulb tester.

These will prevent damage even from a reversed PSU.
Both the PSU and the Amplifier will not be damaged.