maybe I'm stupid? bias stuck at 2.00 mA with el34 ?

  • Thread starter Thread starter stefvorcide
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stefvorcide

stefvorcide

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So today, I set up the bias on herbie with 6550 to 95 mA like advised. Then with my pair of el34 and el34b in pos 2&5 and 1&6 the bias is stuck at 2 mA ?? and if i just uses one pair alone the clean is distorted :scared:

Have i done something wrong?? :confused:

Also, if no guitar chord is plugged, it's not normal to have a hum (the same on all channel) right? defective preamp tube?

Maybe i just need to order all new tubes?? it's not really new tubes, I had some annoying hum (that got killed by the decimator) but I was looking for the best sound possible

Vielen Dank, Peter ist am besten!! Merci beaucoup.
-Stephane


btw: with the 6550 alone it sounds like MAGIC even without mid-cut:)
 
Try the 6550's in the outer position and the 34's inside.

Steve
 
Steve, I,ll try it first thing in the morning and I,ll let you know.

You should be the customer service for diezel :D
 
Sometimes the bias range is not big enough
for tubes that have an extreme bias rating.

Please go to 60-70mA for the pair of 6550 and try
to adjust the EL34´s again.

Thanks Uncle Steve for support :thumbsup:
Time for a meeting, the beer is on me !
 
1&6 6550 are biased right...
3&4 el34b are biased right
2&5 won't go higher than 50 mA... is it my tubes or the trim pot or something else?

Papa (or terry if you know) , it is a kinda unrealated question, could you tell me with preamp tubes would be "cathode follower" in herbie please ? is it just v5-v6 ?
 
Not V1, not V2, not V6.
V3 is a CF
V4 and V5 could be CFs.
AFAIK
 
I would be satisfied with 50mA.

If not buy a pair with higher plate current.

Or ................... there is a broken screen grid resistor
on power tube 2 or 5 !
 
Peter Diezel":nff17iwu said:
I would be satisfied with 50mA.

If not buy a pair with higher plate current.

Or ................... there is a broken screen grid resistor
on power tube 2 or 5 !
Click to expand...

Danke papa, I hope nothing ist broken
 
I had the same problem a couple of months ago. I also had the 6550 in the inner pair.

First turn the trimmers to the far left.
bias the 6550 for an x percentage
Bias the el34's for an x percentage
bias both again the sameway

after a view runs you should be up there. It took me some time but it worked.
 
Merci Olaf, it was for Mike Fortin

Thank you shadow, it seems correct now... ahh, electronics ;)
 
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