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Post by zenfly49 on Oct 14, 2020 5:43:00 GMT -7
I have read for days before asking stupid questions on my first post but here I am finally with greetings from Cape Canaveral...My beloved Maz 18 has been great since 2002 when it was made. The hum remains the same with nothing connected, same with all knobs set to zero and same with all 12ax7/at7 tubes swapped that leads me to think it's isolated to the power section.. I had one used pair of GT el84 I tried that made it worse so they were trashed. I have on order a pr of USSR 6n14n here in a few days. Does anyone have suggestions to try while I wait? Thanks
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Post by Jaguarguy (Mike) on Oct 14, 2020 6:11:14 GMT -7
Welcome to the Forum- a lot of good people and information here. I assume the hum is new, correct? Some things if you haven't already checked - make sure all chassis screws are tightened, make sure inputs are cleaned - Deoxit is your friend. Also, watch Doc's trouble shooting video below. Good luck!
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Post by KeithA on Oct 14, 2020 7:18:28 GMT -7
I'm not of something you could try, but if the new tubes don't solve things (along with the other trouble-shooting steps Mike highlighted above) there may be an issue with the caps in the power section, perhaps?
I'm not sure how a cap problem would manifest itself (but it should cause hum) but the amp is almost 20 years old so it could be the problem.
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Post by zenfly49 on Oct 14, 2020 8:34:51 GMT -7
Thanks for the video and Deoxit is indeed our friend..Some very good stuff to know in the video though I haven't blown a fuse in an amp in yrs. only a few since the 60s and never in my Z.. In the tube swapping I did get to clean up my reverb but the hum is still there.. edit: The hum isn't real bad, I don't hear it while I'm playing even at quiet condo volume but it is new to answer Jaguarguy.
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Post by easyed on Oct 14, 2020 11:45:12 GMT -7
I'll recommend checking all the grounds to chassis. The aluminum chassis won't receive solder (IFAIK), so the chassis grounds are bolted with star washer/lugs.
I had an amp that developed a serious AC hum and it turned out to be a loosened nut for the ground attached to the power transformer.
It was an easy fix, but my tech charged me a bench fee (only fair), he got the amp because I was too busy/lazy at the time to do it myself.
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Post by zenfly49 on Oct 14, 2020 12:42:28 GMT -7
I just went and pulled the chassis and checked the only 2 ground lugs I can see. One right next to the transformer with several heavy green wires attached and one other inside the face with a single small green wire. Both nuts seem tight. Are there others under the circuit board?
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Post by zpilot on Oct 14, 2020 15:05:30 GMT -7
Are you sure it is 60Hz hum and not 120Hz?
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Post by zenfly49 on Oct 14, 2020 17:45:53 GMT -7
Thanks zpilot.. this is the youtube I used..I'm pretty sure it's 60hz in mine... FF to 112 - 250..
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Post by zenfly49 on Oct 15, 2020 6:14:25 GMT -7
I recently read you can power up a tube amp with no tubes. All these yrs I never heard that but I always just got them repaired. Being retired it's a different story with the money.So now understanding a little more about tubes and what the PI tube does seems to me if that is removed the signal path to the power amp is broken so I removed it and the same hum is still there.. Might be a clue to someone here, thanks again for looking _____________________________________________________________________
In my short study of the PI I found this very interesting.
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Post by premiumplus (Dave) on Oct 15, 2020 6:55:55 GMT -7
My money's on the power tubes, and that it'll be fine with new ones. With the PI tube out it does isolate the hum to the power tubes or the power supply. It's 18 years old and the filter capacitors may be the problem but I'm betting that the new power tubes will solve the problem. Please let us know what you find out when you install them, and welcome to the forum!
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Post by DRZ on Oct 15, 2020 16:51:06 GMT -7
My money's on the power tubes, and that it'll be fine with new ones. With the PI tube out it does isolate the hum to the power tubes or the power supply. It's 18 years old and the filter capacitors may be the problem but I'm betting that the new power tubes will solve the problem. Please let us know what you find out when you install them, and welcome to the forum! +10000 DR.Z
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Post by zenfly49 on Oct 16, 2020 15:08:07 GMT -7
Thanks everyone for looking and comments so far.The NOS 6n14n tubes are in as well as a new 12ax7LPS(PI) and the sparkling in your face tone is back like crazy.I never heard it sound better. The hum seems a little less and it wouldn't be noticed in a club with people but something still isn't right.
Edit: I just had it on a half hr playing and it seems to be now even a little less hum after running. That might be a clue to someone but I can tell y'all after 18yrs I'm still in love with this little amp.
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Post by purpletele on Oct 16, 2020 19:24:46 GMT -7
good report!
The Mark II Upgrade is fantastic if you are curious
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Post by zenfly49 on Oct 17, 2020 3:17:18 GMT -7
good report! The Mark II Upgrade is fantastic if you are curious Thanks for the kind "good report!". I wasn't sure I was doing OK here. I just want to find the hum that seems loudest when I switch it off standby then in a minute mysteriously fades to about 1/2 the hum but still there. In my searches there doesn't seem to be any reports of anything like this. If I have to use an amp tech I'll be sure to finish this thread with the answer.
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Post by premiumplus (Dave) on Oct 18, 2020 1:53:43 GMT -7
+ 1000 on the Mark II upgrade. The Master Volume is greatly improved plus the amp gets more 'open' while simultaneously getting better overdrive. Highly recommended, and they'll go through the amp while it's there. Mine's been upgraded and I loved the amp before but it's incredible now. The improved Master Volume alone is worth the price of admission! You can get very, very quiet and still maintain great drive tone.
It sounds like you've got power supply issues with that hum. It wouldn't hurt to try a different rectifier tube but I suspect your filter capacitors are a more likely culprit. It's easy to replace filter caps and Z amps are built to allow easy servicing.
You're in the right place, so don't be a stranger around here...it's the best corner on the internet.
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Post by zenfly49 on Oct 18, 2020 9:15:10 GMT -7
I tried a GE-5y3, Sylvania 5v4, Tried a Blackburn Mullard GZ34 then put it back in my JTM45, nothing works better than the Sovtek 5ar4 that is in there and I have a spare one I tried.. I wish it was that easy. "It sounds like I've got power supply/filter cap issues with that hum."that I don't doubt and there's a good amp tech about an hour from me that did work on my 67 Super Rev and Vibroking when I had them.This amp has been so bullet proof I've really taken it for granted and haven't seen him in years.
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Post by KeithA on Oct 18, 2020 20:34:20 GMT -7
I tried a GE-5y3, Sylvania 5v4, Tried a Blackburn Mullard GZ34 then put it back in my JTM45, nothing works better than the Sovtek 5ar4 that is in there and I have a spare one I tried.. I wish it was that easy. "It sounds like I've got power supply/filter cap issues with that hum."that I don't doubt and there's a good amp tech about an hour from me that did work on my 67 Super Rev and Vibroking when I had them.This amp has been so bullet proof I've really taken it for granted and haven't seen him in years. If you are in the US I'd consider sending it back to the Z shop for a full checkup.
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Post by zenfly49 on Oct 18, 2020 21:37:09 GMT -7
Thanks, I had considered that and I appreciate the thought but these should be easy to work on for any decent tech. Since 1965 I've never sent an amp back to Fender or Marshall and this is for a hum that is about the same as the reverb hums at 12 o'clock.
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Post by j4gitr (John) on Oct 18, 2020 23:01:32 GMT -7
If you haven’t seen this video, this may be worth a view. Just a thought.
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Post by zenfly49 on Oct 19, 2020 3:34:03 GMT -7
Thanks j4. I already did all that but didn't spray the ground lugs to the chassis like he did but I did check they were tight. I mentioned above I only found 2 ground lugs, one near the transformer with multiple wires grounded and one between the switches and jacks with a single green wire. These amps notoriously don't have this problem because the only "hum" I have found in searches is related to the reverb and the transformer proximity in heads.
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Post by zenfly49 on Oct 26, 2020 12:11:03 GMT -7
My money's on the power tubes, and that it'll be fine with new ones. With the PI tube out it does isolate the hum to the power tubes or the power supply. It's 18 years old and the filter capacitors may be the problem but I'm betting that the new power tubes will solve the problem. Please let us know what you find out when you install them, and welcome to the forum! +10000 It's not the power tubes unless I just bought two matched pair of 6n14n that are not matched and I doubt that because they sound amazing. I will let you know what's up when I get it to an amp tech. Thanks
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Post by jlc on Nov 1, 2020 9:44:32 GMT -7
Great troubling shooting and maintenance video's Doc, watching the process makes it easier to understand and perform, thanks.
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Post by zenfly49 on Nov 3, 2020 3:23:25 GMT -7
If you are in the US I'd consider sending it back to the Z shop for a full checkup. A local amp tech just fixed my little hum for $25 while I went for a coffee and donut.
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Post by daddyelmis (Greg) on Nov 3, 2020 4:39:39 GMT -7
What was the issue?
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Post by Chilly Gibbons (Todd T.) on Nov 3, 2020 5:47:42 GMT -7
If you are in the US I'd consider sending it back to the Z shop for a full checkup. A local amp tech just fixed my little hum for $25 while I went for a coffee and donut. Already this morning?
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Post by zenfly49 on Nov 4, 2020 3:42:56 GMT -7
"Already this morning?" No, it was a few days ago and to answer daddy it was just a filter cap.
Thanks all here for your time and advice.
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