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Post by 195db on Jan 11, 2019 16:40:45 GMT -7
Got a '13 8 head late Sept and immediately sent it in for updates. Been using it since roughly late Oct the without issue. Yesterday volume starting to fluctuate and sounds like garbage. Then plays ok for a bit. Almost like the power tube is going. When I unplug from the fx loop, everything seems ok. I experimented with using a buffer a few weeks ago but actually sounded worse so I figured the buffer was bad. So I haven't been using one since I got the amp. But I plugged in the T1M again anyway to see if that would help and seems ok at the moment. I also did the Deoxit cleaning of the inputs. Here's a quick recording I did. The only thing I did was unplug from the loop. Except at the end I hit the knobs on the guitar and clicked pedals.
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Post by premiumplus (Dave) on Jan 11, 2019 18:28:53 GMT -7
Sure sounds like a tube is getting funky on you. What happens when you go from Pentode to Triode? Anything seem wrong there?
If you've got a good EL-84 I'd try changing that first,there's only one of them.
Next thing I'd do is go down the line and pull and re-seat each tube to eliminate a possible bad/oxidized tube pin. Then take a known good 12AX7 and start at V1, run down the line substituting the known good one.
Follow the tube troubleshooting sheet on the Z amp site and let us know how it goes.
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Post by 195db on Jan 12, 2019 6:36:58 GMT -7
Sure sounds like a tube is getting funky on you. What happens when you go from Pentode to Triode? Anything seem wrong there? If you've got a good EL-84 I'd try changing that first,there's only one of them. Next thing I'd do is go down the line and pull and re-seat each tube to eliminate a possible bad/oxidized tube pin. Then take a known good 12AX7 and start at V1, run down the line substituting the known good one. Follow the tube troubleshooting sheet on the Z amp site and let us know how it goes. Tube was my first thought too because the vol drops to almost nothing at times. The curveball is when I unplug from the loop it's fine. And I would think the tube would be dead by now. But I was going to start swapping tubes anyway. It's happening in triode. Not sure about pentode.
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Post by premiumplus (Dave) on Jan 12, 2019 7:39:09 GMT -7
Maybe the switching jack on the effects loop has gotten oxidized. Have you tried plugging a short cable between the effects in/out jacks? Another thing to check would be that the jacks are good and tight on the chassis. Strange things start happening when a bad ground connection happens. You've probably heard about problems being solved just by tightening up the pots, switches, jacks...everything that's bolted to the metal amp chassis. Just a thought. Some DeOxit on a Q-tip will help clean up the inside of the jacks, just make sure that the cotton is tightly wound on the tip and you don't leave any strands in the jack.
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Post by 195db on Jan 13, 2019 19:04:32 GMT -7
Maybe the switching jack on the effects loop has gotten oxidized. Have you tried plugging a short cable between the effects in/out jacks? Another thing to check would be that the jacks are good and tight on the chassis. Strange things start happening when a bad ground connection happens. You've probably heard about problems being solved just by tightening up the pots, switches, jacks...everything that's bolted to the metal amp chassis. Just a thought. Some DeOxit on a Q-tip will help clean up the inside of the jacks, just make sure that the cotton is tightly wound on the tip and you don't leave any strands in the jack. Figure I start with the obvious and looks like it's a patch cable. A new one no less. Thought it would be a dirty jack in the pedal before a new cable. Cleaned it but acted up again. Changed cable, so far so good. Hopefully that's that. Thanks.
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Post by premiumplus (Dave) on Jan 13, 2019 19:14:23 GMT -7
Cool. Reminds me of a time years ago when I worked fixing TV sets. I found a bad capacitor in the vertical oscillator circuit and replaced it. Same problem. I went round and round with that stupid TV for two days and it kept leading me back to the brand new capacitor I had just replaced. So I pulled the new cap out and put another new one in. TV fixed. The new cap was shorted. You can't take anything for granted!
I now test every part I replace before installation.
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