Einstein 50W problem?

  • Thread starter Thread starter Marvel
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Marvel

Marvel

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Hi,

I'm new to the forum. My name's Marcin and I'm from Poland.

A friend has just called me to ask for advice as the 500mA fuse on his Einstein blew during the gig. Any idea what could cause this? Is the amp biased too hot? A mechanical fault of the fuse? Unfortunately he only has a 3A spare replacement fuse and he's got no choice but to put it in as he's in the midde of a gig...

Regards, Marcin
 
Welcome Marcin,

your power tubes blow the fuse.

Please replace the power tubes and the fuse into 0,5 amp slow blow.
Finally bias the new tubes.
 
Thank you. So the power tubes, getting old, are drawing more current?

Any special considerations regarding setting the bias, or just standard 70% of tube dissipation power, calculated on the basis of the actual measured anode voltage?

Regards, Marcin
 
For Diezel's I've stuck with the 30-35mA setting for 70-75% MPD.
I have never blown a power tube in a Diezel !!!!
 
MARK2C":2w6x2pwv said:
I have never blown a power tube in a Diezel !!!!
Click to expand...
Thanks. But we're talking about blowing a fuse, not a tube. ;)

Marcin
 
Marcin,
if a tube is blowing a fuse with 0,5 amps it has a short.
The maximum current on a good EL34 in this case is 150 mA.
This fuse is build in to avoid damage to the components.
Go to 60-70mA bias for a pair.
 
Hello,

i'm this Einstein owner - Marvel set bias and it's 70 now but problem is the same... I will try to change power amp tubes now..


thanks,
Bart
 
After you replace the tubes bias on the colder side, if you want the tubes to last longer.
 
Of course, I read the post about replacing power tubes. But you can't buy them easily here and ordering from TAD takes some time. In the meantime I checked the bias and it turned out it was 82mA for two tubes. Which is a little strange, because the amp is about a year and a half old and still has original TAD tubes. I expected it to be well below 70mA. The tubes will be replaced soon. :)

Regards, Marcin
 
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