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Post by bryan0418 on Nov 13, 2012 20:12:23 GMT -7
I have a Z Wreck which all of a sudden the sound was cutting in and out. It almost sounded like my guitar cable was bad (it wasn't). I would play and the sound would cut out for a microsecond and then back. Finally it gave one loud hum and blew the fuse. Any ideas what could have happened? The rectifier, Pre-amp (2) and phase inverter tubes are all original stock and the 7189's are a replacement Russian quad from the Tube Store.
I can replace the fuse but my fear is that this will happen again. I was planning to use this amp Friday night at a show. I have extra tubes on hand which I could switch out.
Any ideas? Is my amp fried/damaged?
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Post by doctorice on Nov 14, 2012 4:46:08 GMT -7
Most likely a power tube. Before you replace the tubes, though, I'd recommend pulling the amp from the chassis and checking to make sure that there are no "fried out" components inside. I had an EZG-50 fail and one of the resistors blew up/melted. I think it took a power tube with it and the fuse blew before further damage ensued. Took it to a local tech for repair.
I also had a power tube fail on the Z Wreck. It sounded like the amp was imploding as the tube died. Fortunately, that was an easy fix.
Good luck, and let us know what you find.
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Post by bryan0418 on Nov 14, 2012 6:57:59 GMT -7
Thanks for the response, Doctorice. So far, no charred components that I can see on either of the circuit boards. I will try a new quad of tubes and fuse later today. Can I just use any automotive fuse as long as the amp specs match?
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Post by doctorice on Nov 14, 2012 7:41:50 GMT -7
Yes, standard size fuse. It may be that it is a "slo blo" version. Take the blown one with you and you should be able to match it up without a problem.
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Post by bryan0418 on Nov 14, 2012 14:40:32 GMT -7
Ok, replaced the fuse in the Z Wreck and swapped a new quad of 7189's. it seems to be working again.
I decided to test the old quad to see if I could isolate the bad 7189. I used my Ghia and did 2 tubes at a time. What is weird is that all the tubes are good. I was expecting to see 1 or more bad tubes. I did not see the sputtering in the Ghia as I saw in the Wreck. I am afraid to put the quad back into the Wreck.
My power souce here is good and clean. I wouldn't think a fuse would just die, would it? I am kinda scratching my head here cause besides the fuse, I expected to see some component bad. I am glad it just cost me a fuse and not an expensive 7189 but my fear is this may happen during a show. Any ideas?
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Post by headshrinker (Marc) on Nov 14, 2012 17:22:07 GMT -7
Not on the problem, but I would bring the ghia to the gig and have it set up and on standby so I could quickly change to it if the problem comes back during the gig.
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Post by "Z" Steve on Nov 14, 2012 17:34:45 GMT -7
Wonder if the rectifier is on it's way out? Is that stock as well? Usually they just quit but they do cause the fuse to blow as well.
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Post by bryan0418 on Nov 14, 2012 18:02:52 GMT -7
The rectifier is stock. I have very low hours on the Z Wreck cause I do have the Ghia and now a Remedy and MAZ18. Wonder if I should just toss the rectifier and buy myself a new one as insurance? I always thought rectifiers just died and never went marginal. But yes, I always bring a backup. As good as the Zs are, tubes are not so i don't want to get stuck at a show. I do plan to play the snot out of it before Friday just to see if it will die!
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Post by Albert on Nov 14, 2012 18:26:25 GMT -7
Wonder if the rectifier is on it's way out? Is that stock as well? Usually they just quit but they do cause the fuse to blow as well. My thought as well it may have arced over inside ....toss that tube and get a NOS tube or NOS JAN tube it will be the last one you ever buy ... ;D ;D
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Post by bryan0418 on Nov 14, 2012 18:43:39 GMT -7
I just played a good 30 min with the spare set of 7189's and the original 5AR4 Rectifier and am happy to say that it ran well. I had the Z Wreck volume about 2:30 and used my AirBrake to keep the neighbors happy. Do you still think it could be the rectifier? Tomorrow I will get daring and try the old set of 7189's to see if I can get it to fail.
Could the root cause just be a one time power surge or bad fuse?
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Post by bryan0418 on Nov 15, 2012 9:07:54 GMT -7
So I tested the amp again today. Original rectifier, power and pre amp tubes. Basically just a new fuse. Same sputtering issue but this time I shut the amp down before the fuse blew. Replaced the rectifier, same issue. Replaced the rectifier and put in my backup set of 7189s. No issues anymore. So as Doctorice originally said, it is the power tube(s) going bad.
What kinda irritates me is these 7189s are pretty new. I bought them from the Tube Store. I had 2 failures of them since I received them and Jon has been very good about providing me replacements under the warranty. Is there just a bad batch of 7189s or is there another source I can get them from? I appreaciate the customer service but I need reliable tubes during a show.
Thank you for everyones help with this issue.
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Post by "Z" Steve on Nov 15, 2012 11:07:16 GMT -7
I don't own a Z Wreck so I'm not too familiar with the 7189's, but as far as the vendor goes are the tubes being tested before they are being shipped? Is this vendor recommended by the Doc or Brent? I understand tubes can be finicky but there are other vendors who test all their tubes before shipping (and yes, they can have failures too) but that seems odd to have two failures that close. As you said , it is good customer service but.......just trying to rule out every possibility.
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Post by bryan0418 on Nov 15, 2012 11:12:59 GMT -7
Yes, the Tube Store is the Dr Z preferred vendor for 7189's which are industrial strength EL84's. I do believe they test them but everything I have ever read is that these 7189's are supposed to be tough tubes so it is kinda strange that I see failures with them and none with my regular EL84 based amps. I am going to send an email to see what's up. I don't mind paying for quality but when it doesn't deliver is when I want to find an alternative.
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Post by bryan0418 on Nov 17, 2012 9:12:34 GMT -7
Update - I used the Z Wreck last night for 2-90 min sets and it did NOT fail! Woo Hoo! So it wasn't the rectifier tube, it was a bad set of 7189's. I hate to spend a hundred bucks on a new quad but that is what I gotta do. Thanks everyone for your help.
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Post by heynewguy (Ol’ Bill) on Nov 17, 2012 9:36:22 GMT -7
Glad it was only tubes. ;D
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Post by doctorice on Nov 17, 2012 10:06:46 GMT -7
Update - I used the Z Wreck last night for 2-90 min sets and it did NOT fail! Woo Hoo! So it wasn't the rectifier tube, it was a bad set of 7189's. I hate to spend a hundred bucks on a new quad but that is what I gotta do. Thanks everyone for your help. That's (relatively) great news. Replacing power tubes is part of the price of tone, isn't it? Even though Dr Z carefully selects tubes for the Wreck, I had one fail within hours on a brand-new amp. (Got the Doc's usual great customer service to fix the problem.)
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Post by bryan0418 on Nov 17, 2012 11:34:27 GMT -7
I agree Doctorice, good tubes=good tone but I am a little concerned about the Preferred Series 7189's that I had. I really didn't have a lot of hours on them to have had now 3 failures. I do run my Z's hot with the Airbrake but they should stand up to it. My original set of 7189's work great from the Doc.
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Post by deaconblues on Nov 22, 2012 16:44:58 GMT -7
So, who makes the Preferred Series 7189's?
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Post by mpa93 on Nov 22, 2012 17:11:56 GMT -7
Yes, the Tube Store is the Dr Z preferred vendor for 7189's which are industrial strength EL84's. I do believe they test them but everything I have ever read is that these 7189's are supposed to be tough tubes so it is kinda strange that I see failures with them and none with my regular EL84 based amps. I am going to send an email to see what's up. I don't mind paying for quality but when it doesn't deliver is when I want to find an alternative. I ordered a set of 4 as well...just to have for back up...I'm a little concerned now
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