pfrischmann
Member
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- 3,457
Hi guys,
I've been working on a super bass that I converted ti '69 SLP specs with a Metro amps board. This amp had an oscillation problem before the conversion and unfortunately, still has it.
With the presence beyond 12:00 and the treble channel up past 10:00 I get a squeal. I can control the squeal by turning the presence knob up and down and/or by putting my hands near the tubes (ala theremin)
I have so far replaced the circuit board, fitler caps and rewired a good portion of the preamp. I also added 5.6K swamp resistors.
The problem still exists.
I checked the layout to the bes of my abilities following the Ken Fisher tips in Gerald Webers book.
Any ideas.
I'm running out of places to look. I'm trying to see if I can figure it out before I spend money sending it to a pro.
Thanks,
Paul
I've been working on a super bass that I converted ti '69 SLP specs with a Metro amps board. This amp had an oscillation problem before the conversion and unfortunately, still has it.
With the presence beyond 12:00 and the treble channel up past 10:00 I get a squeal. I can control the squeal by turning the presence knob up and down and/or by putting my hands near the tubes (ala theremin)
I have so far replaced the circuit board, fitler caps and rewired a good portion of the preamp. I also added 5.6K swamp resistors.
The problem still exists.
I checked the layout to the bes of my abilities following the Ken Fisher tips in Gerald Webers book.
Any ideas.
I'm running out of places to look. I'm trying to see if I can figure it out before I spend money sending it to a pro.
Thanks,
Paul