captain38
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I followed you big river...
Posts: 198
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Post by captain38 on Aug 25, 2019 12:48:41 GMT -7
Hello all,
I've got a Maz 38 NR that was recently overhauled to a mkII (February 2019).
The amp worked fine last night. I tried to play this morning and I got nothing but static and crackle (that increases when you turn up the volume). Luckily there was a trusty Hot Rod Deluxe...not the same.
When I got home, I did a bit of testing. I tried hi and lo channel as well as 38w and 18w. I tried replacing the 12ax7s (and tapping on the existing ones with an eraser). I noticed that it went silent when I plugged into only the return of the effects loop. If I was in the send and return, the static and crackle was back. I then noticed that I was able to plug my guitar into the return of the effects loop and it worked...but only the master volume (since I thing the effects loop is after the pre amp?) - This makes me think it is a preamp issue, not sure though. Any thoughts?
Thanks.
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Post by purpletele on Aug 25, 2019 13:05:37 GMT -7
Hello all, I've got a Maz 38 NR that was recently overhauled to a mkII (February 2019). The amp worked fine last night. I tried to play this morning and I got nothing but static and crackle (that increases when you turn up the volume). Luckily there was a trusty Hot Rod Deluxe...not the same. When I got home, I did a bit of testing. I tried hi and lo channel as well as 38w and 18w. I tried replacing the 12ax7s (and tapping on the existing ones with an eraser). I noticed that it went silent when I plugged into only the return of the effects loop. If I was in the send and return, the static and crackle was back. I then noticed that I was able to plug my guitar into the return of the effects loop and it worked...but only the master volume (since I thing the effects loop is after the pre amp?) - This makes me think it is a preamp issue, not sure though. Any thoughts? Thanks. C38, If it was fine last night then you most likely have a tube issue, that is as long as you didn't notice an Event. If you replaced the Pre-amp tubes then the next logical thing is to roll the power tubes. If you need to order power tubes then you should grab a rectifier as well. I'm not sure what can be discerned from plugging into the FX loop, but that may be an indicator to someone. My money is on the Quad, and it does seem a little early if they are the good Russian 6n14p or whatever the title is.
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captain38
Full Member
I followed you big river...
Posts: 198
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Post by captain38 on Aug 25, 2019 13:13:00 GMT -7
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Post by DeanG on Aug 25, 2019 14:08:40 GMT -7
MAZ 38 NR Effects Return is back at V2 Tone Stack circuit, which V1 is bypassed. Turning up the volume increases the V1 drive.
You can pull V1, V2 & V3 one at a time to isolate a preamp issue.
I just had a MAZ 38 NR up dated to MK II. One of the power tubes was arching. Replaced with a spare set 6n14n power tubes then had crackle in 18w mode.
When fresh 6n14n tubes came in, sprayed each socket with DeoxIT and installed tubes.
Problem solved. Recommend the DeoxIT.
Return shipping handling was the instigator.
Also, now with the half power Mod, a matched quad power tubes are most important, no longer can one get away with two matched pairs.
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Post by doctorice on Aug 25, 2019 14:08:52 GMT -7
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Post by DRZ on Aug 26, 2019 0:46:56 GMT -7
Hello all, I've got a Maz 38 NR that was recently overhauled to a mkII (February 2019). The amp worked fine last night. I tried to play this morning and I got nothing but static and crackle (that increases when you turn up the volume). Luckily there was a trusty Hot Rod Deluxe...not the same. When I got home, I did a bit of testing. I tried hi and lo channel as well as 38w and 18w. I tried replacing the 12ax7s (and tapping on the existing ones with an eraser). I noticed that it went silent when I plugged into only the return of the effects loop. If I was in the send and return, the static and crackle was back. I then noticed that I was able to plug my guitar into the return of the effects loop and it worked...but only the master volume (since I thing the effects loop is after the pre amp?) - This makes me think it is a preamp issue, not sure though. Any thoughts? Thanks. Alway tough to guess troubleshoot, easier if I have the amp on my bench. But I'll give it a try. From what you state I would say the Return Jack isn't shorting properly. Try to Detox the jack with spray, or just replace the Return Jack. The Return Jack is a three connector Shorting Jack, I think the Shorting leg isn't operating due to Oxidation , or a trip on the Return Cord bent the shorting alignment. Thats were I would start. Z
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captain38
Full Member
I followed you big river...
Posts: 198
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Post by captain38 on Aug 27, 2019 13:23:21 GMT -7
Thanks for the replies everyone - below is some follow up.
I followed the trouble shooting. No issues with fuses blowing. The noise only happens when there is a tube in V2. A few things to note: 1) I deox'd all of the tube sockets and the send and return jack (also the Volume pot) 2) I tried several different tubes in V2 (including tubes that worked in other preamp tube spots) 3) When a guitar is plugged into the Send, the Volume occasionally works - however, it seems to operate as on or off. Whereas the Master will fluctuate volume across its entire sweep...both with a guitar in the Send and the Return. 4) I've been searching for a Shorting Jack - I'm not having much luck. I'm not sure where to find the same style that is currently in my amp.
Lastly, here is a video that shows what is going on.
Thoughts?
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captain38
Full Member
I followed you big river...
Posts: 198
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Post by captain38 on Sept 6, 2019 10:52:26 GMT -7
Another little update. 1) All of the grey cable/wire (which has a very different feel from the rest of the cables used) seems to be pretty noisy. (hard to capture on video, but prevalent in real life) 2) I wonder about the V2 socket. Seems loose. Thoughts? 3) Tried about 5 different quads of 84's and about 12 different 12ax7's. This makes me think that it might now be a tube. 4) Tried messing around with the shorting jack (return of effects loop) seems to be shorting like you would expect it to...that said, I'm not that informed on these. 5) Seems to be some rust colored happenings at some of the solder areas.
Couple other thoughts. I read online of people having similar sounding issues and it ended up being bad pots or bleeding caps. Also, I use quick drying electronics cleaner (supposed to be safe) but then read that you need to use a cleaner w/ lubrication in it for all pots. Any chance volume pot is shot?
Anybody have a trusted amp tech in St Louis?
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Post by DeanG on Sept 7, 2019 5:49:03 GMT -7
C38, One thought you can plug a 6" patch cord in Send/Return, this to will disengage the Return leaf shunt, and the connections are made through the patch cord. If static cleans up then you localized the trouble to the Return 1/4 jack shunt. One of the Z-Bro's posted this suggestion. The MOP seems to be a good idea. I normally spray DeoxIT on a 1/4" Plug, Insert in the Jack. Then push/pull the plug to cause a wiping action on the contacts. ztalk.proboards.com/post/911721/thread22-25 Calibre
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captain38
Full Member
I followed you big river...
Posts: 198
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Post by captain38 on Sept 7, 2019 14:05:44 GMT -7
Thanks for the reply!
I should have mentioned that I have tried running a patch cable in the effects loop. Unfortunately, the problem persists. I am going to try cleaning the jacks. What a great test that was done in that other thread!
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Post by thatstatuemoved on Sept 20, 2019 13:22:15 GMT -7
Send the chassis to the doc--will come back good as new.
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