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Post by rootspicker on Sept 3, 2023 13:53:54 GMT -7
Good day, it’s been awhile since I’ve posted anything but am looking for the Z-Talk‘s community input.
Recently, my beloved Jetta amp started making a low level hissing sound after the amp is fully warmed up and generally when I start cranking up the volume or applying OD from my pedal board. It’s been fairly “non-intrusive” up until but over the last few days the hiss and become louder and more persistent, and a cracking noise is now accompanying the hiss. (Again, none of this happens until the amp is fully warmed up, after approx 20 minutes minimum)
From past experience, this sounds to me like the preamp tubes may be wearing out. I do have a supply of 12AX7 tubes on hand, and also some spare JJ 7591S power tubes if need be. My question is, when swapping out tubes to test, do I need to turn the amp fully off and then fully on or can I simply flip the standby switch while I switch preamp tubes? Also, how about for power tubes? (Just in case)
Any coaching or experience from my fellow forum members would be appreciated! Thanks!
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Post by purpletele on Sept 3, 2023 16:21:54 GMT -7
Good day, it’s been awhile since I’ve posted anything but am looking for the Z-Talk‘s community input. Recently, my beloved Jetta amp started making a low level hissing sound after the amp is fully warmed up and generally when I start cranking up the volume or applying OD from my pedal board. It’s been fairly “non-intrusive” up until but over the last few days the hiss and become louder and more persistent, and a cracking noise is now accompanying the hiss. (Again, none of this happens until the amp is fully warmed up, after approx 20 minutes minimum) From past experience, this sounds to me like the preamp tubes may be wearing out. I do have a supply of 12AX7 tubes on hand, and also some spare JJ 7591S power tubes if need be. My question is, when swapping out tubes to test, do I need to turn the amp fully off and then fully on or can I simply flip the standby switch while I switch preamp tubes? Also, how about for power tubes? (Just in case) Any coaching or experience from my fellow forum members would be appreciated! Thanks! rootspicker, You need to turn the amp off completely to be safe.
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Post by RickJames on Sept 3, 2023 19:24:10 GMT -7
When I added the voltage regulator/line conditioner, all those sounds stopped……..for under 150 bucks
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Post by Don A on Sept 3, 2023 19:34:39 GMT -7
I've seen people swap tubes with the amp on standby. That doesn't make sense to me. The heater is the highest current in the amp. Hot swapping tubes has to cause arching that would negatively affect the contacts in the sockets.
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Post by RickJames on Sept 3, 2023 19:37:20 GMT -7
Stock tubes , overt 2-3 years
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Post by Chilly Gibbons (Todd T.) on Sept 4, 2023 7:31:55 GMT -7
If it’s a frying pan sound, it’s usually tubes. It’s usually tubes anyway…
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Post by RickJames on Sept 4, 2023 7:44:21 GMT -7
For me, and to my surprise………adding the Tripp Lite did the trick…….it moved my voltage from 116 to 120, and cleaner current..
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Post by rootspicker on Sept 4, 2023 10:03:20 GMT -7
If it’s a frying pan sound, it’s usually tubes. It’s usually tubes anyway… Hmmm, I hadn’t thought of describing it that way, but a frying pan is very much what the sound is like. It’s a rainy, dreary holiday Monday here in Calgary, and today I plan on removing the Jetta chassis, perform a yearly maintenance check (as per the “good Dr’s” video), and safely switch out some tubes to see if I can pinpoint the issue. Stay tuned!
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Post by rootspicker on Sept 5, 2023 7:11:05 GMT -7
Yesterday was a cool and dreary Labour Day Monday here in Calgary, so it seemed like a perfect day to troubleshoot my Jetta and see what I might do to remedy this noise.
First off, I watched a couple of Dr Z’s YouTube tutorial videos on amp maintenance. There is some very good (and frankly, common sense) information contained in these clips! So I did what the ‘good Dr’ suggested; I removed the chassis from the cabinet, checked the tightness of all connectors and controls. Then I carefully sprayed contact cleaner on the areas where components grounded to the chassis, as well as into the tube sockets and pins. Finally, I switched around the V1 and V2 preamp tubes and tightened up the retainers and silicon dampeners that secure the two 7591S power tubes in place.
After reassembling the amp, I played the crap out of it for a good hour and a half with a number of guitars. (To the point where my wife warned me about going deaf!…) I dimed the volume & tone controls, turned the MV way up and made sure to play some loud distorted power chords on the lower strings to try to induce resonant vibrations. I’m happy to say that after fully warming up the power tubes and giving the amp a pretty strenuous workout, any hiss or crackling that was present before seems to be gone. I will apply the lessons learned from this experience and be more diligent in maintaining my gear. I will perform a similar maintenance routine on my Victoria Vicky Verb combo.
Again, thanks to everyone for your comments and suggestions!
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Post by frankie on Sept 7, 2023 12:30:13 GMT -7
Yesterday was a cool and dreary Labour Day Monday here in Calgary, so it seemed like a perfect day to troubleshoot my Jetta and see what I might do to remedy this noise. First off, I watched a couple of Dr Z’s YouTube tutorial videos on amp maintenance. There is some very good (and frankly, common sense) information contained in these clips! So I did what the ‘good Dr’ suggested; I removed the chassis from the cabinet, checked the tightness of all connectors and controls. Then I carefully sprayed contact cleaner on the areas where components grounded to the chassis, as well as into the tube sockets and pins. Finally, I switched around the V1 and V2 preamp tubes and tightened up the retainers and silicon dampeners that secure the two 7591S power tubes in place. After reassembling the amp, I played the crap out of it for a good hour and a half with a number of guitars. (To the point where my wife warned me about going deaf!…) I dimed the volume & tone controls, turned the MV way up and made sure to play some loud distorted power chords on the lower strings to try to induce resonant vibrations. I’m happy to say that after fully warming up the power tubes and giving the amp a pretty strenuous workout, any hiss or crackling that was present before seems to be gone. I will apply the lessons learned from this experience and be more diligent in maintaining my gear. I will perform a similar maintenance routine on my Victoria Vicky Verb combo. Again, thanks to everyone for your comments and suggestions! Great resolution and really goes to show you what a little troubleshooting and light maintenance can do. Good on you to take it into your own hands.
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