Back up here! 3 giant steps!
Like I posted before, if you pop in the 5881 tubes and then as you say they idle at 27ma, if you than play thru the amp you will see the tubes draw over 100ma as they try to drive the shorted OT.
If the OT was good even with only two 5881s in the amp and drawing 80ma the sound thru the speakers would be clear and quite loud!
JCM 900 - power tubes not drawing enough current.
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Stevem
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Re: JCM 900 - power tubes not drawing enough current.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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beasleybodyshop
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- Location: East Texas (Yee Yee!)
Re: JCM 900 - power tubes not drawing enough current.
Steve, When I install two 5881s in the two middle sockets (V5 and V6) and power the amp up, i get no sound and idle at 27ma. if I try to install them in the outer two sockets, it pops the cathode fuse for that pair. I did some more swapping around last night, and that's what ive come up with.Stevem wrote:Back up here! 3 giant steps!
Like I posted before, if you pop in the 5881 tubes and then as you say they idle at 27ma, if you than play thru the amp you will see the tubes draw over 100ma as they try to drive the shorted OT.
If the OT was good even with only two 5881s in the amp and drawing 80ma the sound thru the speakers would be clear and quite loud!
Still a bit confused about the -43 voltage coming off of the LT rectifier. If I measure outer winding to outer winding i get 43 voltsAC, which from what i understand is correct (20-0-20) while the other side is something like 17 volts.
"It's like what Lenin said... you look for the person who will benefit, and, uh, uh..."