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Post by Jericho on Jul 20, 2009 21:32:45 GMT -7
Is there anything besides tubes that can cause a loss of perceived power?
Not like a drop to transistor radio levels...but something less extreme.
This amp is pretty new, about 2 months. It is noticeably quieter. Almost like it switched from 45 to 20 watts. The tone seems the same pretty much, just with Bass/Treble at 9oclock it isnt very loud even at volume 1/2 way up. And it is already getting a decent amount of "hair" at that setting. Not nearly the clean headroom machine from before. Before I try a new set of tubes...is it possible that something else can cause this or is it most likey tubes?
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Post by Darkside on Jul 21, 2009 10:33:22 GMT -7
I'd have to suspect the tubes, but I guess you could check your speaker cables and cab wiring just in case something was wrong there. Try the EF86 first as this is the main gain stage pre amp tube, then if that's not the fault eliminate each one in turn. Good luck! Keep us posted.
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Post by Phil (aka Phil) on Jul 23, 2009 6:51:54 GMT -7
It's a tube for sure. I've had those exact symptoms with a bad power tube and bad preamp tubes (both EF86's and 12AX7's) including the phase inverter.
I just had the exact symptoms you described on my beloved MAZ Jr NR. I changed the power tubes and that didn't fix it. I was really running short on time as we were leaving for vacation, so I just swapped every preamp tube with my identical MAZ Sr Nr, and instantly the Jr was perfect. I still need to figure out which preamp tube it was and replace it so my MAZ Sr will be 100% again.
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Post by Jericho on Jul 30, 2009 13:33:35 GMT -7
First Update: Strike One - Replaced The 12AX7 and the EF86 Pre-Amp Tubes. No change. It fires up perfect. Sounds good for 15-30 sec. Then there is a "Pop" and the volume still cuts in half and gets dirtier. Guess I'll move on to the power tubes next and hope for better luck there...
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Post by Jericho on Aug 5, 2009 6:51:28 GMT -7
Whoa..BIG strike 2. I changed the power tubes next. Turned it on, and this time no sound at all. Hmm I said, and put the original tubes back in to see if Murphy's Law just was saying I got 2 bad new tubes. Turned it on and SMOKE starts coming out of whatever that Blue thing is inside the amp. Shut it down. I'm guessing this one is a job for the Doc?
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Post by jbgtr on Aug 6, 2009 21:55:41 GMT -7
That seems really unusual. The only "problem" I have had with my KT is a bad 12ax7. It caused some erratic pops and noise, but it has worked fine since replacing it. I would suggest calling Dr Z.
I believe the blue thing you are referring to is a capacitor. The smoke may be coming from a different part of the circuit. I am not an expert, but in a tube amp diagnostics class I was in, there was a silverface Fender (can't remember which model) which kept blowing one particular resistor. Whenever the resistor popped, smoke emitted from the amp.
I cannot remember off the top of my head what the problem was, but either way, contact Z. He is extremely helpful, he and Brent have answered every question I have asked.
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