Event 20/20p studio speakers malfunction

[c5agan]

I just recently received the Event studio speakers 20/20P powered monitor from someone. I was told there might be an issue with them so I plugged them in to test them. After realizing there might be some issue, I took out the back panel to take a quick look at the speaker wiring. It seems that the previous owner had done some sort of hack job to the speaker cabling: they clipped the HF wire entirely (chanel B's circuit board) and rewired only the LF to both speakers.

I found a blown Cap and replaced it with the exact same rated cap and rewired the LF output to the larger speaker, and the HF to the smaller speaker. Ta-da, it worked.

Then I was shimmying the board back into the cabinet and tried it out again. This time the only sound you could here was some interference at 60Hz - I know this noise very well :0/.

I've gone through and wiggled every wire (with NO power of course) to make sure all solder conections were good. I then turned the speakers on and tested all of the power regulating chips, and they were all working perfect as rated.

The company Event's technical support sent me the wrong schematic when I inquired to them, and they are now ignoring any attempt I make to contact them (to no surprise).

From here, I'm not too sure where to go, for I'm 80% sure that this could be a small fix. I'd rather not just throw these away.

Thanks for any help, let me know If I can provide more info, I'll be close by here.

c5

 

[Nigel Goodwin]

Is the 60Hz hum pretty loud?, if so it's a common sign that the amplifier is blown.

 

[c5agan]

The Hum is not VERY loud. I actually barely realized it when standing 2 feet away from the speaker. I had to bend down and stick my ear near the speakers to confirm that it was indeed a hum.

Question: what does it mean when an "amplifier is blown" ? could it mean one of the small amplifier chips fried?

Thanks

 

[Nigel Goodwin]

The Hum is not VERY loud. I actually barely realized it when standing 2 feet away from the speaker. I had to bend down and stick my ear near the speakers to confirm that it was indeed a hum.

Question: what does it mean when an "amplifier is blown" ? could it mean one of the small amplifier chips fried?

It means the main amplifer is short circuit, all the output devices directly shorting across the supply.

 

[c5agan]

I'm at work right now :0o , but when I get back to the speaker, I will take photos of the circuit board and post them: if you could help point me into what you think is most likely the issue, that would be great.

 

[Tom7227]

I have just repaired this monitor in the shop today. The LM3886 amplifiers that I have been fixing, have all had similar issues. Sometimes the chip itself overheats or some random noise is produced with no input. In the case of this powered monitor, there are (3) 22uf 63v caps in the individual amplifier that need to be replaced. If you want to do it correctly, you will need (12) total, 3 for each amplifier. Another fault are the 10,000uf capacitors in the power supply. Keep it in mind when your trying to fix this amplified monitor

Tom

 

[Synthdr]

Hi I have been reading the info on the 2020p monitor thanks Tom7227 for the heads up been trying to isolate the noise issue for ages I replaced PSU caps first time for new chips and 22uf caps bye bye noise