Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Amplifier Short Circuit

Status
Not open for further replies.

Menticol

Active Member
Hello!

Again, my "DIY spirit" messed everything- Trying to change the case of an old Pioneer compact system to a custom one, I made a short circuit (I assumed the system was disconnected from mains).

A spark jumped, the fuse didnt blew up.

Now, the amplifier is on silence. When I do connect the amplifier to any signal source, I start to hear a loud hum (even only connecting the cable with no load). The hum changes with the tone controls and balance, so this section survived.

The Radio and Aux functions didn't worked before, So I have no way to know anything about the healt of the amplifier

Some data:

- There is a big ceramic capacitor between the two poles of the master switch
- The master switch was off during the short
- Maybe the short was on the 120 / 240 selector, I'm not sure because I see no burns
- My home's mains is 120 v

I hope someone could get the model number looking this pictures

Please, Any suggestion?

**broken link removed**
 
Last edited:
Wow that's an old amplifier!

It's hard to tell from the information you've given us, this is like asking "I plugged my 120V amplifier in to the 240V mains and it's broken", lots of thing could have gone wrong with it. You say that you assumed it wasn't connected to the mains, was it? Even if it wasn't connected to the mains you still could have damaged one of the semiconductors by discharging a capacitor where it shouldn't be discharged.

Are there any burnt components?


You could check all the transistors and diodes using a multimeter.
 
You are totaly right, with my text I gave to understand wrong thing (I'm sorry, my english is bad). The true story is:

I have forgot to disconnect the amplifier from the mains before attempting anything (very stupid), and a short circuit ocurred in the 120 / 240V selector, in the back of the radio (maybe it touched the metal frame).

I dont think the amplifier was exposed to overload, because my home's mains is only 120V, the minimum setting on the selector.

The "power" switch between the transformer and the PCB was in OFF position, but maybe the current made their way trough the frame, not the switch.

Well, is not only "it doesn't work", it does :D , but instead of music it only generates hum when a wire is connected to phono in, even if the other side of the wire is without load. And with load, for example my computer, the hum goes much more louder.

Even if they seem undamaged, I'll follow your tip and check the diodes and condenser from the +42 volts line that enters into the pcb. I'm worried about the mains wich could touch the metal frame (the ground of the amplifier) and the damage is beyond repair.

Thank you very much by your help, Hero999. Any other suggestion will be extremely apreciated.
 
Update

Putting the volume knob on the minimum, very distorted music can be heard,and the loud hum stays. Tried to change transformer, but It didn't worked. I have connected the metal frame to ground (on the wall outlet) and the hum reduced, but when appling load returned and louder. I don't know what to do!
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top