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Post by twilson on May 27, 2012 15:13:02 GMT -7
I'm the third proud ;D owner of a Maz Jr. I love this amp for several reasons, but before I bought the amp I noticed a hissing sound. After turning on the power switch and one minute later placing the standby switch to the "on" position, a volume swell/increase of hissing starts coming from the amp. Tapping on the controls of the front panel the hissing sound immediately stops or decreases in volume. If you persistently tap on the control knobs the sound will decrease or increase its erratic, sometimes it will and at other times it won't. Selecting the standby position again and back to the "on" position will also have the same affect on the amp. My corrective actions have been: Changed all the tubes, power and pre-amp Tightened all nuts, chassis screws and jam nuts Changed one potentiometer, ordered part from Dr. Z amps Checked all pedal cables and guitar. After changing the potentiometer, reverb position, I have had no problems for almost a year until recently. Could it be possible another Potty has gone south? I run two amps in stereo, play at in/outdoor venues with a Winfield and Maz Jr., but the Maz Jr periodically develops this hissing sound, but not all the time. Any ideas are welcomed.
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Post by lpetersenmusic on Jul 4, 2012 11:06:11 GMT -7
Yeah I'm having the same problem with my 18NR... It seems if I move the volume pot up and down several times it goes away. I know many forum guys suggest putting some DeOxit (no WD-40) in the pots, tube sockets, and connections to the reverb tank. With new production tubes these days I would definitely not rule them out as well. Best of luck!
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Post by GuitarZ on Jul 4, 2012 14:49:44 GMT -7
Did you check for a snake in there? I get one or two down in my basement. The hissing might be a dead giveaway. (You did say any ideas are welcomed. )
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Post by fritz2328 on Mar 27, 2013 8:35:45 GMT -7
I don't know what to do. I still have the problem of hissing (yes, I removed the damn snake from the basement) or static crackle upon powering up the amp. If I tap on the volume, treble, or mid rheostats the crackle/hissing either increases or decreases in volume. Although if I leave the amp alone, after tapping the volume knob several times to make the crackle/hissing sound go away, I have no problems afterwards. Only on occasion will the noise return. If I place the amp in standby mode the hissing comes back, sometimes.
I have replaced all the power, pre-amp tubes. I'm kinda lost, and yes I have GPS.
Hope everything goes your way today.
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gene
Full Member
Posts: 115
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Post by gene on Mar 28, 2013 7:20:15 GMT -7
Reading this (All about vacuum tube guitar amplifiers, Gerald Weber)made me thought of your thread. You might want to check it,just in case: "Sometimes a bypass capacitor can become very microphonic. On a bypass capacitor with axial leads, if the leads are tight, the capacitor can vibrate and resonate on certain notes and this resonance can come through the speaker. I've seen this occur where the amp would sound like a rattle in the speaker." p327 In the Maz 18, bypass capacitors are situated on the board, between the 12ax7 sockets and the volume pots and input jacks.(I believe...) Of course, high voltage might be present in this area.
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Post by muZician on Mar 28, 2013 12:29:14 GMT -7
I suggest you send your amp to a qualified repair shop. The Doc would be the best. What Gene says is a possibility. Or a cold solder dot somewhere. Who knows what the pre-owners have done with the amp...
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Post by Albert on Mar 28, 2013 14:22:03 GMT -7
My Maz had a cold solder joint from the reverb circuit if you are careful pull the chassis and tap with a wooden Dowell or wooden spoon/fork to see if you can find a noisy area on the board or if you're in NW Indiana area I would be happy t o look at it for ya...
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Post by LT on Mar 28, 2013 18:27:22 GMT -7
I suggest you send your amp to a qualified repair shop. The Doc would be the best. What Gene says is a possibility. Or a cold solder dot somewhere. Who knows what the pre-owners have done with the amp... Agree.....send to the good Doc for a thorough examination.
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Post by donnie on Apr 1, 2020 8:29:11 GMT -7
Haven't been on this board for a long time. I love my 2001 (L serial number means 2001, right?) Maz Jr. and haven't had a need to ask any questions about it in awhile, but over the last several years have noticed this problem recurring more frequently. My Maz Jr. (2x10" w/'verb) also has this hissing/popping problem when I fire it up,...sometimes. As the thread originator stated, mine also reacts when you tap on the control pots. I've decided the pots become slightly loose while the amp is in operation, vibrating, and it requires that I pull the knobs off and tighten each nut holding the pot to the chassis. It's really just a matter of applying slight pressure to snug the nut up to the chassis, making good ground contact, and it alleviates the problem. What I've found is the threaded shaft of the pots are a softer metal than the nut, so if applying too much pressure to the nut driver, it may cause the thread of the shaft to strip, not allowing the nut to grab any more. To remedy this problem, I removed the washer between the nut and chassis, revealing just enough thread to be able to once again capture the nut, but I have to be VERY careful to not overtighten again. Thing is, it's not like I really torqued the nut on there. I applied slight pressure and the nut feels like it's turning a little, then gives way, stripping the shaft. This has happened to 2 of my pots now - Volume and Master are secured, but without the washer. I'm wondering if something like Loctite would be useful in keeping these nuts tight and securing the pots against the chassis for good ground contact? I'm also wondering what to do if I end up stripping a pot such that the nut will no longer grab. Replacing one or more of those pots would be a nightmare with all the ground busses soldered to the backs of them.
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Post by Chilly Gibbons (Todd T.) on Apr 1, 2020 9:16:39 GMT -7
I’m going to take a guess on this one and say Docs tried it and doesn’t do it as a matter of practice due to what you described. The pots are soft metal and when you need to loosen them to service the amp you wind up destroying them in the process. Could also be that Loctite could interfere with grounding required with the pots and the chassis. Just my guess, hopefully we’ll see what Doc says.
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Post by purpletele on Apr 1, 2020 9:17:34 GMT -7
Haven't been on this board for a long time. I love my 2001 (L serial number means 2001, right?) Maz Jr. and haven't had a need to ask any questions about it in awhile, but over the last several years have noticed this problem recurring more frequently. My Maz Jr. (2x10" w/'verb) also has this hissing/popping problem when I fire it up,...sometimes. As the thread originator stated, mine also reacts when you tap on the control pots. I've decided the pots become slightly loose while the amp is in operation, vibrating, and it requires that I pull the knobs off and tighten each nut holding the pot to the chassis. It's really just a matter of applying slight pressure to snug the nut up to the chassis, making good ground contact, and it alleviates the problem. What I've found is the threaded shaft of the pots are a softer metal than the nut, so if applying too much pressure to the nut driver, it may cause the thread of the shaft to strip, not allowing the nut to grab any more. To remedy this problem, I removed the washer between the nut and chassis, revealing just enough thread to be able to once again capture the nut, but I have to be VERY careful to not overtighten again. Thing is, it's not like I really torqued the nut on there. I applied slight pressure and the nut feels like it's turning a little, then gives way, stripping the shaft. This has happened to 2 of my pots now - Volume and Master are secured, but without the washer. I'm wondering if something like Loctite would be useful in keeping these nuts tight and securing the pots against the chassis for good ground contact? I'm also wondering what to do if I end up stripping a pot such that the nut will no longer grab. Replacing one or more of those pots would be a nightmare with all the ground busses soldered to the backs of them. I have never heard of anyone using Locktite to help with a ground connection, that is only a statistic, I don't know if it will work. If you strip the threads on a POT then you can certainly replace it with a new one like a CTS. I don't recall Z amps having a Buss bar soldered to the backs of the pots. That is not his style of pre amp grounding. It is certainly possible that it was done that way, but I'm betting it is not. I suspect the ground wires from the Pots are wired to a ground post somewhere near the middle of the controls. If that is the case then the replacement is much easier. Let us know if it indeed has a buss bar across the back of the POTs.
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Post by donnie on Apr 1, 2020 17:27:33 GMT -7
This photo is from several years ago when I had the chassis out of the cab for some reason. Not a clear shot of the subject, but if you look closely, you can see the ground buss that is soldered to the back of the pots. If my memory serves, there are 3 buss bar wires soldered to the backs of all the pots, straight across. Replacing a pot (or 2, in my case) would be tedious. The idea of Loctite was simply to perhaps 'glue' the nuts in place such that they would not vibrate ever so slightly loose, causing the aforementioned problem of hissing and popping.
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Post by easyed on Apr 2, 2020 21:38:51 GMT -7
Z-tube has a session with Mike Z discussind annual amp maintenance.
He recommends loosening the nuts on the pots and squirting in a little DeOxit between the body of the pot and the chassis, then retightening the nut. I've never done it and I don't know if it will solve your problem, but it couldn't hurt.
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Post by donnie on Apr 3, 2020 9:06:25 GMT -7
Z-tube has a session with Mike Z discussind annual amp maintenance. He recommends loosening the nuts on the pots and squirting in a little DeOxit between the body of the pot and the chassis, then retightening the nut. I've never done it and I don't know if it will solve your problem, but it couldn't hurt. That would certainly help the problem, and as he states right around the 4:30-4:35 mark, tightening the nuts gives you a good ground connection. Unfortunately, the threads on the pots strip out too easily when you're trying to snug them up. That's the real problem. I'll give the Deoxit solution a try. Perhaps that will keep me from tightening those nuts too often, decreasing the chances that I'll strip the threads. Thanks for posting that.
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Post by daddyelmis (Greg) on Apr 3, 2020 12:12:18 GMT -7
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