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Post by LuckyBlackCat on Jan 12, 2018 20:56:40 GMT -7
Figured I'd tap into the collective expertise here on something funky that just happened with my Maz 18 NR.
I've had my share of tube problems over the years, but the symptoms have alway been either noise or volume drops.
Today I was playing at very low volume and for some reason my volume increased for a short time. No noise, just a notable volume increase like I turned up.
Any idea what may have caused this? Can a funky tube be at fault here?
I did change out the power tubes to see if by chance the "regular volume" was lower than it should be due to bad tubes, thinking that the louder volume I got was the "correct" sound and i had just become accustomed gradually to the fade, but the volume was "regular" and not louder with the other tubes as well.
I did notice that one preamp tube, V3, wasn't glowing as bright as the two in V1 and V2. The V3 is a sovtex 12ax7 while the others are JJs, so I assume that's just due to the difference in tubes. I did put another JJ in V3 to try, but noticed no sound difference. It did glow like the others, so maybe the sovtek just doesn't glow as brightly.
It's back to "normal" now, so I'll keep an eye on it, but any insight my fellow Z bros may have would be appreciated!
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Post by BritInvasion on Jan 13, 2018 8:04:37 GMT -7
A Sovtek 12AX7-LPS which is commonly used in the phase inverter position (V3) doesn't glow as much because the spiral filaments are enclosed in the plates. A failing power tube can sometimes cause a jump in volume but in my experience is accompanied by noise / distortion. Only thing I can think of is if one of the volume pots on the amp is a little dirty / worn. Might try spraying it out with some contact cleaner like Deoxit.
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Post by benttop (Steve) on Jan 15, 2018 14:31:23 GMT -7
If you haven't recently, try cleaning all of your input and output jacks, especially the loop.
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Post by pcns on Jan 15, 2018 17:39:50 GMT -7
If you haven't recently, try cleaning all of your input and output jacks, especially the loop. I was thinking the same thing Steve, something might be dirty, clean your cables too
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Post by LuckyBlackCat on Jan 16, 2018 7:14:17 GMT -7
Thanks, all. Don't have any deoxit, so can't clean the pots. Probably should get some. Isopropyl alcohol and a Q-tip should do for the jacks and plugs, yes? Any tips would be appreciated!
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Post by Maddog on Jan 16, 2018 7:24:37 GMT -7
Yes alcohol will work. I too really feel this could be a corrosive contact issue. Deoxit is much easier to get into a pot than alcohol w qtip, but do your best. Also, be careful, alcohol is flamable. Dont ask me how i know.......
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Post by LuckyBlackCat on Jan 16, 2018 7:29:00 GMT -7
I'm not planning to attack the pots with alcohol. I'll wait for the deoxit for that. But I will do the jacks and plugs with alcohol. I just did that with my pedals the other day.
How much is too much alcohol? On my pedals, I dipped a Q-tip in alcohol, rubbed the plug all over, then inserted, twisted, and removed, the plug a couple times. I repeated this with every plug and jack.
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Post by BritInvasion on Jan 16, 2018 7:30:27 GMT -7
I'm not planning to attack the pots with alcohol. I'll wait for the deoxit for that. But I will do the jacks and plugs with alcohol. I just did that with my pedals the other day. How much is too much alcohol? On my pedals, I dipped a Q-tip in alcohol, rubbed the plug all over, then inserted, twisted, and removed, the plug a couple times. I repeated this with every plug and jack. Alcohol dries quickly , just don't soak the surrounding areas and you should be fine.
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Post by premiumplus (Dave) on Jan 16, 2018 14:01:01 GMT -7
If you're not going to use deoxit, naptha works very well for cleaning contacts, and it won't attack pots. I've been using it for years.
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Post by benttop (Steve) on Jan 16, 2018 16:16:16 GMT -7
The thing is, for your loop you really need a spray to get enough into the critical points. See the images below: Before you insert the plug, your signal flows through the loop via a contact on a leaf inside the jack. If this contact is not working, your signal may be interrupted or otherwise affected. When you plug the jack in, the contact is broken, sending the signal to the plug. If that leaf switch "dimple" is corroded, cleaning the jack by putting alcohol on the plug and inserting may not do anything for the dimple. Using DeOxit puts enough cleaner in the hole that some is bound to get on the location of the dimple and clean it. The alternative is to pull the chassis out so you can get to the switch in the jack. Do NOT do this if you don't know what you're doing. You can be killed by lethal voltages if you haven't the appropriate skills.
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Post by premiumplus (Dave) on Jan 17, 2018 6:32:19 GMT -7
Steve is absolutely right. In my mind, I was seeing the amp open on my bench and assuming I could physically get to the contact 'dimple'. A trick that I use is to cut a thin strip of printer paper, maybe 1/4" wide, and get it inbetween the dimple and the leafspring of the jack. Saturate with DeOxit and gently pull it between the dimple and it's connection. You'll see a black line on the paper which will be the corrosion being removed from the dimple. Q-tips work fine for cleaning the jack 'barrel'. You still have to be careful not to leave bits of cotton behind, because according to Murphy's Law they will find a way to cause a bad connection somewhere.
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Post by LuckyBlackCat on Jan 17, 2018 8:22:46 GMT -7
Thanks guys, will see what I can do.
When I do get some deoxit, I have a question about cleaning pots...
What's the best way? I assume spraying from the front panel is not sufficient and that I should pull the chassis and spray inside the pots from there, yes?
I am comfortable pulling a chassis and working very carefully on parts I can access easily if necessary.
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Post by BritInvasion on Jan 17, 2018 8:42:21 GMT -7
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