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Post by tjstrat on Jan 24, 2007 5:24:09 GMT -7
My late '90s Maz 38 Studio Lead head has developed an intermittant but BIG problem. Every so often the amp will suddenly begin humming VERY loudly, This humming is not related to any of the controls, as it does not change or drop in volume when the controls are all dialed off, and it completely masks any guitar signal coming through. It stops but returns when the standby is toggled off and back on, and often (but not always) when powered completely down and restarted. This happens several times a night. So far it has stopped as capriciously as it's started, without too much harm...
I run a fan to cool the tubes, so I don't think it's a heat issue, and retubed when I bought the amp in April. All cables test as good on my board and going to the cabinet. Any thoughts on what I might try?
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Post by BW on Jan 24, 2007 8:53:49 GMT -7
I was waitin' fer Doc to come to your aid before I spew forth with my font of hard knocks knowledge... I have an early Studio Deluxe 1X12 that I had an intermittent lead on one of the big power supply electrolytics. (can't remember what voltage rating or mfd without lookin', but it's at the very end of the board.) It finally broke all the way off and I replaced it (observe polarity or become a fried ham!) Do you notice it when you move the amp around, or rock it back and forth? Is it a 'shock' related problem? That might not be it, but that's what happened on this end. Also, is it blowing fuses? Just for grins, make sure you don't have a tube retaining clip (if indeed that amp has 'em at all) bent under the output tubes intermittently shorting pins together. Are the plates glowing? Not the filaments, but the PLATES? Guess it could be a bad 84 too. Tap 'em w/ a chopstick while she's runnin' and see if it starts hummin'.
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Post by DRZ on Jan 24, 2007 15:04:08 GMT -7
Thanks Bud. Your old MAZ is about the same circa's as this one. Good point about the filter cap and tube clip. I did e-mail TJ with some other hints as well.
DR.Z
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Post by tjstrat on Jan 25, 2007 3:29:13 GMT -7
Thanks Buddy and Doc... Rather than fiddle with the innards I'm bringing it to a Chicago area tech who comes highly recommended by the folks at Ax in Hand here in town. He tossed in the broken or compromised solder joint somewhere theory as well. An honor to get advice from not just one but BOTH of you. We'll get her figured out.
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Post by dizeased on Jan 25, 2007 12:35:02 GMT -7
Hi tjstrat -
I'm looking for a good, reliable tech who is experienced with Z-amps in the Chicago area. Can you tell me or e-mail the name/address/phone number of the tech you used if you thought he did good work?
I'd appreciate it. Thanks.
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Post by tjstrat on Jan 25, 2007 17:26:39 GMT -7
His name's Matt at Hix Brothers in Aurora. The guy at Ax in Hand goes to him when he can't figure something out. $95.00/hr bench charges, though. The guy camped next to MakenMusic downtown is supposed to be good too.
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Post by dizeased on Jan 25, 2007 20:48:53 GMT -7
Tjstrat -
Thanks for the info. I'll keep HIX Brothers in mind. I think I'll try the guy next door to Make 'n Music first, that way I can stare at all the stuff I can't afford next door.
Thanks again.
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Post by tjstrat on Jan 26, 2007 5:34:52 GMT -7
Going to MNM always makes me feel like a guy looking to buy a new keychain at a Porsche dealership. Just like I TOTALLY shouldn't be there.
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Post by billyguitar on Jan 26, 2007 9:21:58 GMT -7
I have a Lexus but I always feel out of place when I go in there for service wearing Dickies work jeans, Dickies blue chambray shirt and distressed Ararat work cowboy boots, carhart jacket and company logoed ball cap. I always feel that I shouldn't be rubbing elbows with all the high income customers. That doesn't stop me from enjoying their complimentary snacks, coffee and pop though! Actually those are some of the best dealerships in the world and they are always friendly, polite and respectful.
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Post by tjstrat on Jan 28, 2007 10:10:49 GMT -7
Just for information... The tech told me that my and V5 preamp tubes were the cause. Cleaned the amp, checked the power stage out, and expressed admiration for the Z's construction. Since she's on eBay now, a new JJ 12AX and a balanced AT7 will hopefully do the trick.
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