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Post by cdhenson on Feb 26, 2018 17:36:01 GMT -7
Hey guys, I’ve got this crazy oscillation happening on my EZG. Anyone had this issue and thoughts on the fix? Is this tube related or something deeper?
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Post by Maddog on Feb 26, 2018 18:05:47 GMT -7
I've not seen/heard that particular problem, but I would venture to say that more than 95% of these type issues we see in our Z amps are tube failures.....
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Post by zpilot on Feb 27, 2018 3:16:04 GMT -7
It's called motorboating. Here's one explanation:
I've usually found it caused by a bad coupling cap but that amp is too new for that to likely be the case. Still, it happens.
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Post by pitcheramps on Feb 28, 2018 10:56:55 GMT -7
Coincidentally, I have CDHenson's EZG in my shop. I will share what I did to repair the amp to benefit others. He did indeed have low end motor boating, but also high frequency squealing, or oscillation. This occurred if you turned the pre and post levels up past about 12 oclock. In the video zpilot posted, the narrator mentioned a bad ground may cause this issue and that is exactly what I found. On these amps there is a ground bus wire soldered across the back of the pots. With this design, a good ground depends on the pots being securely fastened to the chassis. To fix it, I removed the knobs, loosened each pot, wiggled them a bit and re-tightened them. Problem solved. One other thing to keep in mind is the fact that the chassis is aluminum, but the pots are steel, so there is the added chance of corrosion caused by mating dissimilar metals. This is the first Z amp I have seen with this issue, so it is rare.
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Post by zpilot on Mar 12, 2018 23:25:52 GMT -7
But easy and cheap to fix.
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Post by Chilly Gibbons (Todd T.) on Mar 13, 2018 14:26:56 GMT -7
Thanks for sharing, good info!
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Post by M Fowler on Apr 14, 2018 8:19:44 GMT -7
Also, I've found that the pot holes are 3/8" and the pot shafts are the smaller shaft Alpha so you need to make sure ground contact is good. I maintain a gigging musician's EZG50 and after 1 year I have to go through the amp and tighten things up plus spray the jacks, tube sockets and pots. The reverb cuts in and out or goes out completely after replacing reverb pan that had broken transducer lead. Spray the RCA reverb jacks.
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onegreatnote
Full Member
Let me hear your balalaikas ringing out!
Posts: 102
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Post by onegreatnote on Sept 18, 2019 23:54:58 GMT -7
Hi, all. I have a '13 EZG50 that was exhibiting the exact same symptoms as the OP's amp. M Fowler's advice ended up being excellent, but I actually found Doc's AMA video on yearly maintenance which solved the problem for me. Essentially the same process described by MF with a few extra steps thrown in. So if you find yourself with an EZG that has a motorboating issue, just giver her a good cleaning as shown and chances are better than not you'll be good.
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Post by DeanG on Sept 19, 2019 5:46:30 GMT -7
DeoxIT between Pots and chassis once loosen.
Also reduces idle noise.
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