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Post by hikari on Oct 6, 2021 8:37:03 GMT -7
Hi guys,
I just picked up a 2014 maz jr, sounds great so far with the exception of the reverb. If the reverb pot is above about 75% the reverb section slowly feeds back. Below 75% on the dial it is fine.
I have changed the tubes in the reverb section. I removed the tank and reinstalled it. The feedback stops if I shake the amp or hold the tank.
What do you think? Bad tank?
Also, this thing seems to run real hot. I put two old Mullard el84s in and Iam not sure if they were red plating but they were definitely cooking. I could smell it. So I put the EH tubes back in which seems to run cooler.
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Post by headshrinker (Marc) on Oct 6, 2021 9:09:02 GMT -7
Need to know how far up the volume and master are when this happens and if it's a combo or head. If it's a combo,or the head is directly on the cab, and the volume and master are up a good bit, I would guess, since it stops when you hold the tank or shake the amp, that it is the tank picking up vibration from the cab, and that causes it to go into oscillation. You might want to try pulling up on the whole tank bag to loosen it from the cab. You might even loosen the screws that hold it down a little. You can also try some foam under the bag once it is loosened up. Those are old tricks that I have used when Fender amps did that back in the day. If it's a head on a cab, see if it does it with the head off of the cab. You have a newer Maz. If it's a Mark II, in my opinion, that's a whole lot of reverb if you are up 75%.
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Post by hikari on Oct 6, 2021 9:46:09 GMT -7
Its a 2x10 combo. I believe it's a mkI. Master is all the way up. Volume about 9 o'clock. It will do this regardless of volume and will even do it when a guitar is not plugged in so likely not vibration but could be. I have other reverb tanks...guess I should try a different one to rule out the tank. Kind of pain to get to the tank in the Z though. I don't find the reverb strong or fendery. The reverb all the way up on the man jr is about the same as a blackface amp on 3.
This is my first Z. I have built blackface fenders and Tweeds and have Vox's too. The build quality on the Z is really nice. It's exactly what I try to do with my own amps. The sound is pretty unique I think. I am still trying to figure it out...its kind of fendery but not exactly the same. Not as glassy and far more predictable. Its not really Vox but can get close. It's interesting.
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Post by premiumplus (Dave) on Oct 6, 2021 11:55:16 GMT -7
Since the amp isn't all that old and you've already changed the reverb tubes (driver and recovery), I'd be suspecting the tank. I have a Maz 8 1x12 combo and just checked the tank bag on mine. It's mounted so that the bag hangs in a way that it stays loose from the side of the cab. Check to make sure yours has some freedom of movement; it should have some suspension. If it's not tightly bound to the cab I'd try another tank.
PS...welcome to the forum!
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kcash
New Member
Posts: 28
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Post by kcash on Oct 6, 2021 12:14:56 GMT -7
I had an older Maz 38 with the same issue. I attempted many different fixes, nothing worked. I sent it to Dr Z and Don did the MK II updates. This not only fixed the reverb feeding back, but the amp was much sweeter sounding and the master volume (PPI-MV) worked like it never did prior to the updates. Well worth getting the updates done.
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Post by hikari on Oct 6, 2021 12:27:29 GMT -7
I hooked up a Princeton reverb tank and got no feedback...didin't sound good because the ohms are wrong though. So I removed the maz jr reverb pan and bag and placed it on top of the amp. Reverb feedback is gone. It's definitely a position/mounting thing. Seems like Z has had this problem before as there are two pieces of cut up aluminum faceplate on my reverb bag. Probably trying to shield it. Not sure if just getting a new tank will fix it. I think the reverb circuit is probably built to be on the edge of oscillation...might need a mod to the circuit. My reverb pan is already one of the newer MOD units.
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Post by hikari on Oct 6, 2021 20:03:06 GMT -7
I had an older Maz 38 with the same issue. I attempted many different fixes, nothing worked. I sent it to Dr Z and Don did the MK II updates. This not only fixed the reverb feeding back, but the amp was much sweeter sounding and the master volume (PPI-MV) worked like it never did prior to the updates. Well worth getting the updates done. What does the mk2 update involve? Do we know? I have built my own amps for years and could probably do it myself.
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Post by dcarver on Oct 7, 2021 0:33:50 GMT -7
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Post by hikari on Oct 8, 2021 19:50:39 GMT -7
Solved:
Had a nice talk w/don at dr z. He solved the issue and it cost nothing except a little bubble wrap around the tank. Seemed to be a bit of mechanical vibration causing the tank to go into a feedback loop.
Great customer service. He reached out and was great to talk to.
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