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Post by purpletele on Jan 20, 2018 2:27:40 GMT -7
Hi guys! Please I need your help. My new Z-Lux make a cracking sound only if I play a certain note on the guitar I made a short video here for Don (Dr.Z Repairs) and I'm waitin' for reply. You can ear better with headphones... photos.app.goo.gl/DX7z0OfYtWz6jHet1Sorry for my poor english during video. What do you think about? Thanks as usual!! littlegiop, My first guess would be the input jack and fx loop jacks having a build up on them, regardless if you are using the fx loop. I had a similar sound but not as prevalent. It's possible that you have a bad tube, but the static noise indicates the jacks with a build up on them. That's my 2 cent theory
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Post by zpilot on Jan 20, 2018 3:10:43 GMT -7
Microphonic tube. Do the tap test with your finger or a pencil with one of those slip-on erasers. If not that, my next guess would be a bad solder joint.
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Post by zpilot on Jan 20, 2018 4:42:54 GMT -7
Yes. V1 will be the most sensitive to vibration. Then V2 and so on.
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Post by Maddog on Jan 20, 2018 6:44:03 GMT -7
I agree, it's probably a bad tube.....next would be contact points like purple tele said. Also check your speaker connectors.....Check every electrical junction: switches, pots, jacks, etc and clean them with Deoxit...
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Post by zpilot on Jan 21, 2018 7:59:19 GMT -7
V4 definitely. That is the tube 4th from the right. It is the tube that recovers the sound from the reverb circuit and mixes it back in with the dry signal. The others don't sound bad.
Using a screwdriver to tap on the tubes is kind of risky. You stand a good chance of cracking the glass. Using something with some padding on it you can strike it harder without that risk. Like I noted previously, I much prefer a pencil with a slip-on rubber eraser. If I don't have one handy I use my fingertip. I posted a video awhile back of the RCA factory where they made tubes back in the '50's/'60's. They had a test fixture where they whacked the tubes pretty hard with something similar to that pencil to test for microphonics. I was struck by how hard they hit them.
Anyway, that tube need to be changed. If you don't have a spare tube handy, for test purposes you can swap V4 with V5. V5 is only for the oscillator for the tremolo so it won't be affected by the microphonics. I'm not sure what Z put in V4 in your amp but a 12AX7 will work for testing until you can get the preferred tube.
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Post by zpilot on Jan 22, 2018 8:37:56 GMT -7
Yes, check solder joints next. Chasing down a fault can be frustrating. You just have to start with the most likely and work your way from there.
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Post by purpletele on Jan 23, 2018 2:27:42 GMT -7
Yes, check solder joints next. Chasing down a fault can be frustrating. You just have to start with the most likely and work your way from there. Hi!! this is my last Z-Lux issue recording. I think the problem is reverb. In the attached audio file, I recorded four licks. The first and third licks are with the reverb set at none, while the second and fourth are with the reverber set at full. Even if in the recording is not heard, the problem is slightly present even when reverb is set to none ‘cause the module in never really bypassed. Z-Lux issue audio testlitttlegiop, I stand by original assessment, and that is that there is an input jack that needs to be cleaned well with a very light grit sand paper and even some deoxit. I would clean the two inputs as well as all of the jacks in the back. It takes 10 minutes to do the work and clean up. It sounds just like my Maz did about 6 months ago. The amp was about a year old, and I started having floaters, then it got a little worse but the sound was similar but not as acute as yours. That's my 2 cents, but I already gave my two cents, so that's a better part of a nickel.
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Post by zpilot on Jan 23, 2018 6:13:26 GMT -7
Hi!! this is my last Z-Lux issue recording. I think the problem is reverb. In the attached audio file, I recorded four licks. The first and third licks are with the reverb set at none, while the second and fourth are with the reverber set at full. Even if in the recording is not heard, the problem is slightly present even when reverb is set to none ‘cause the module in never really bypassed. Z-Lux issue audio testlitttlegiop, I stand by original assessment, and that is that there is an input jack that needs to be cleaned well with a very light grit sand paper and even some deoxit. I would clean the two inputs as well as all of the jacks in the back. It takes 10 minutes to do the work and clean up. It sounds just like my Maz did about 6 months ago. The amp was about a year old, and I started having floaters, then it got a little worse but the sound was similar but not as acute as yours. That's my 2 cents, but I already gave my two cents, so that's a better part of a nickel. My advice is worth every penny that you have paid for it.
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bradm
Junior Member
Posts: 74
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Post by bradm on Jan 31, 2018 14:43:08 GMT -7
Oxidation is a nasty and elusive little bugger. As a routine, I hit every point of contact with DeOxit when an amp with some age comes to my bench. Once found a Jaz with some very very subtle hum. (I'm a hater of hum and it just doesn't belong.) I use a nylon adjustment tool (same one I set bias with) to apply pressure to key areas to search for issues like this. The culprit in the Jaz? The speaker jack mounting to chassis for ground. I removed the jack...DeOxit to the jack...small piece of 440 grit cloth to the inside chassis where the jack mounts...reassembled...no hum.
Some people use popsicle sticks or chopsticks...be real careful using those...if you get some high humidity and they soak a bit of moisture...they can conduct. Use a nylon probe...won't have an issue.
If i'm not pulling the chassis and just want a fast assessment...I'll soak a 1/4 plug and insert & rotate...problem gone or lessens? You know what the culprit is. But, don't try loosening & retightening jacks without removing the chassis...twisted wiring is not your friend either.
i've had a half dozen or more Z's in for work...what I love?? Everything...good construction to get to anything you need...lightweight...no 30-40 lb head like many steel chassis Marshalls (I do a lot of vintage Marshalls in this SW Ohio area...Marshall Major has a weight!!). I was impressed enough with Doc's work that I swapped for a Galaxie a week back...love it. Yes, I'll mod a little, but love it.
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