amplifier Keeps blowing Fuses troubleshooting 101

If a Amplifier keeps blowing fuses where to start and how to start troubleshooting ?

How to use the Variac in this situation have to bring up the voltage but when you bring it up to the operating voltage it blows the fuse so what does a tech. do in this situation?

If i use the Variac at HALF the voltage then the output of the power supply and regulator is going to be HALF B+ supply voltage so how do i know whats drawing to much current? thats blowing fuses?

If Changing all the power Transistors and it still blowing fuses and drawing to much current what would be the next this that is drawing to much current and make the fuses blow?

The Regulator being open or shorted would cause this?
A Filter Cap in the power supply would this cause this?

How do i use the Variac to track down the current draw? and flow blowing?

You should be able to test the power supply with the amplifier disconected establish if it is OK.
The most commom problem with amlplifiers that devolope this type of problem is normaly the output stage.
If you have replaced the output devices have you setup the output stage standing current or bias. This always needs to be done when installing new power devices.
If none of the above works star disconnecting sections of the amplifier untill the fuzzes stop blowing.

Barrybear

to test the power supply with the amplifier disconected

How can i do this? how can i test the power supply with the amp disconnected?
do you mean to disconnect the power amp and preamp cut/break the traces?

setup the output stage standing current or bias.

How do i set the Current or Bias of the output stage by the trim pots? and what
voltages and current amps is it range around?

Search the internet for common questions like that. For example:
**broken link removed**
**broken link removed**

The simplist thig to do is just desolder the power pin of the op amp and lift it clear of the traces. This will remove power to the op amp and you can then determine if its the power supply or the op-amp.
THen resolder the power pin to the op amp and lift the output pin.
This will tell you if there is a drastic error with the op-amp.
If all goes this far and fuse is not blowing, measure the load on the op-amp output.
Then using ohms law and the data sheet verify you are not violating the specs.
Good luck, keep us posted as to where you are and what you've tried.

How can i Test the Power transformer for shorts or opens in the secordary to see if its causing the Fuses to Blow ?


Should i Disconnect Cut/Break the traces to the power supply to the unit to isolate the problem to see if the power supply output is putting out the voltages?

If i put the oscilloscope probe on the rectifier i see half wave. If the power supply is outputing 300DC volts the recitifier half wave should be 150volts DC or 300vdc on the oscilloscope displayed from the probe?

If i put the oscilloscope probe on the (+) positive side of the Filter cap. i see the ripple discharging if the power supply is outputting 300DC should the oscilloscope
display 150vDC on the (+) side of the filter caps

If i put the oscilloscope probe on the output of the Regulator it should be a FLAT line with 300VDC outputing?

You can't run before you know how to walk. Many users on this group and others that you are flooding with questions told you to master the basic principles of electronics first by reading or studying a good book or many online tutorials on the internet. You refuse to take that advise, in return you ask more meaningless questions. You end up knowing just enough to be dangerous. As one member said on the forum below.

https://www.electro-tech-online.com/viewtopic.php?t=17504

"walters, your interest and perseverance are commendable, but I fear you are attempting things that are beyond your present grasp. I am afraid you are only going to get hurt ( electrocution, ) or at the very least damage alot of gear and test equipment. When I see you post about testing a live chassis, then later post questions regarding how to make a very simple measurement it does not sound as though you have a good enough understanding of basic electricity to be doing what you are attempting.

I think you need to find some text books, or better yet, a structured electronics course."

sorry just trying to learn

We all learn something new every day but, you can only learn something new by understanding the principles that the new information was derived from. There is no point to attempt to repair a high power amplifier if you don't know how to make a simple voltage measurement, let alone how the amplifier works. That is plain dangerous. When you go to college you start learning basic electricity, physics etc. Only later, after you mastered the basic theory, rules and calculations you are able to understand and able to design or debug a basic circuit. Also there's no point in making any measurement if you don't have any idea what the result should be.

Here is a link on basic electricity and measurements found on Google. You should be able to find many more. Good luck

https://www.facstaff.bucknell.edu/mastascu/eLessonsHTML/BookIndexBasicEE.html

E-design

is there Measurements i can do to practice?
on a tube amp or transitor amps?

How can i start praticing measuring voltages on the tube pin sockets , biasing,
Chassis is LIVE how do i know these measurments ?

Can you guide me , give me some rules?

? ? ? I rest my case :? Anyone else?