• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Loud sudden rumbling when turn on amp

Status
Not open for further replies.
Jump to Latest
#5
Tube_Dude said:
So? :whazzat:
Click to expand...


Sorry for the delay. But I was looking at the schematic myself and the input stage doesn't look like a diff stage so I am not sure if they are supposed to be connected together.

I haven't gotten a chance to open up the amp and look at it yet. But I have a picture of the amp internally:
http://www.geocities.com/hai_vu1/mingda.JPG

I am not sure if the picture can tell.

By the way, the initial noise because I think I don't have any mean to slow down to initial inrush current at start up. So I have to come with a way to limit the current when turned on.

The simplest way is to use a thermister between the rectifier and the power decoupling caps.

Thanks.
 
#6
The input stage appears to want to be two triodes connected in parallel. So since you have plates tied together, grids tied together, you absolutely need to tie the cathodes together. Trying to use the capacitor as a ground return on that second section will definitely not benefit you!
 
#7
I suspect the error is in the schmatic only and not in the wiring of these amps. I also can not see how this would cause instantaneous startup noise since the strapping of both cathodes of the input 6SL7 is meaningless until the cathode reaches emission temperature which will take a good 8-10 seconds.

I am also aware of this problem and would like to know the sulution. A friend has it in his MingDa and is too far for me to get the amp to sort out on my bench. He has reported an accompanying flash inside one of the 300B tubes. Unfortunately he has ElectroHARMonix gold grid 300B's in his amp and in my experience with this brand 300B, they do this normally. Pure overhyped garbage IME.
 
#8
rcavictim said:
I suspect the error is in the schmatic only and not in the wiring of these amps. I also can not see how this would cause instantaneous startup noise since the strapping of both cathodes of the input 6SL7 is meaningless until the cathode reaches emission temperature which will take a good 8-10 seconds.

I am also aware of this problem and would like to know the sulution. A friend has it in his MingDa and is too far for me to get the amp to sort out on my bench. He has reported an accompanying flash inside one of the 300B tubes. Unfortunately he has ElectroHARMonix gold grid 300B's in his amp and in my experience with this brand 300B, they do this normally. Pure overhyped garbage IME.
Click to expand...

Could you be a little specific as to what problem he is experiencing? It could help me.

As for the tube flasing when turned on, is this normal or could signal some abnomality?

Thanks.
 
Status
Not open for further replies.
Top Bottom