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Post by Russell B on May 23, 2020 10:56:17 GMT -7
I have a "rumble" going on under certain higher notes. For instance, Eb on the 4th fret, 2nd string causes an underlining low rumble while the note is ringing. My first thought was that a bad preamp tube is probably causing that. Any opinions on this before I pull the chassis out and start changing tubes?
Thanks.
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Post by Deleted on May 23, 2020 11:04:09 GMT -7
Probably a microphonic preamp tube, yeah. The chassis undermount, or whatever you might call it, would complicate the tube-tapping process some, I'd imagine. Might be easiest to just reach in and swap out V1 with a known good tube first, if you can--might save you the trouble of pulling the whole chassis. You might also check around your playing environment and just see if there's anything nearby that might be rattling due to sympathetic vibrations. My guitar room's in part of the house (built in 1901) that still has plaster and lath instead of drywall, and if I crank up an amp a bit there are certain frequencies that can cause audible vibrations/rattles inside the walls. It was kind of unsettling until I figured it out.
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Post by Russell B on May 23, 2020 11:16:16 GMT -7
Thanks Jon. The amp is sitting on scored concrete floors. There's nothing around it vibrating. I can tell that it's coming out of the speaker. I'll see if I can reach in there to tap the tubes. I really do think I'll have take the chassis out. I'll never the get tube lined up
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Post by purpletele on May 23, 2020 11:51:20 GMT -7
Earlier this year I performed a MOD on one of my AB763 amps, it was a upgraded tremolo mod. When I completed the mod I had distortion on the lower register.
I had assumed that I caused collateral damage during the mod.
I replaced a number of components, I replaced all of the tubes at one point or another. I had all of the guys at Hoffman pitching in with advice. I thought I had resolved the issue and then one night it came back, and then stopped when I put my arm on the handle.
I had checked for rattle, etc. I was certain that the distortion was coming through the speaker.
It was the cover of the side of a Marshall type handle. I was embarrassed, but I finally resolved the issue.
I must have spent three weeks troubleshooting.
The rattle was sounding like a resistor frying at a certain frequency.
The moral of the story, don't rule out a physical connection rumble, but I would certainly look at pre-amp tubes.
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Post by Russell B on May 23, 2020 12:07:12 GMT -7
I pulled the chassis out. There was a broken retainer on one of the 6N14Ns. I replaced it. I tapped all the tubes. Nothing. I fired the amp back up with the chassis out, and what do you know, NO rumble. So, I put the chassis back in and the rumble is back. It must have a tube rattling. I'll start over. Alas!
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Post by DRZ on May 23, 2020 14:12:11 GMT -7
Sorry to hear the about the problem Russ. If it didn't rattle out of the cab then I would say it is a tube , not some other part. It will be hard to swap out tubes due to the chassis mount on the Wreck combo. I would start with replacing both 6n14n's , just try any good pair of EL 84's for the test . If not that try the 5Y3 again any rectifier will work temporarily for the troubleshooting test. If not those them my next guess would be V1 it is a Tung-Sol 12AX7 again any good 12AX7 will work for the test. Call or PM me let me know how it worked out.
Z
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Post by Russell B on May 23, 2020 14:32:36 GMT -7
Sorry to hear the about the problem Russ. If it didn't rattle out of the cab then I would say it is a tube , not some other part. It will be hard to swap out tubes due to the chassis mount on the Wreck combo. I would start with replacing both 6n14n's , just try any good pair of EL 84's for the test . If not that try the 5Y3 again any rectifier will work temporarily for the troubleshooting test. If not those them my next guess would be V1 it is a Tung-Sol 12AX7 again any good 12AX7 will work for the test. Call or PM me let me know how it worked out. Z Thanks Doc! It was at least one of the power tubes. I had some that I’d bought from Perry. Popped them in and all is well now. I also put in a NOS 5Y3 that I got just for this amp! It’s back to its stellar self!
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Post by doctorice on May 24, 2020 9:48:56 GMT -7
Glad you got it sorted out. I've had the same issue several times. Often it is a tube, but not always. I had an instance when something was going on with the tube covers. Took them off and all was well. Go figure...
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Post by felixw on Sept 15, 2020 2:30:07 GMT -7
It will be hard to swap out tubes due to the chassis mount on the Wreck combo. I have a Z-Wreck Jr. Combo on order which should arrive in a few days (looking forward ...!!). I noticed from product shots that on the combo the chassis is mounted in a way that seems to make tube access somewhat difficult ... and now I read the Doc's confirmation of this point in this thread (quoted above). My question: What is the best/easiest/recommended method to change tubes on the Wreck Combo? Do you pull the chassis to swap a tube? Any tips or tricks? Thanks!
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Post by KeithA on Sept 15, 2020 2:47:51 GMT -7
It will be hard to swap out tubes due to the chassis mount on the Wreck combo. I have a Z-Wreck Jr. Combo on order which should arrive in a few days (looking forward ...!!). I noticed from product shots that on the combo the chassis is mounted in a way that seems to make tube access somewhat difficult ... and now I read the Doc's confirmation of this point in this thread (quoted above). My question: What is the best/easiest/recommended method to change tubes on the Wreck Combo? Do you pull the chassis to swap a tube? Any tips or tricks? Thanks! I would imagine to get access to all tubes it’s just easy to remove the back panel with the chassis still attached to it. It looks like only six screws. It would be similar to working on the head Version as you would have to remove the rear screened panel.
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Post by Russell B on Sept 15, 2020 3:21:30 GMT -7
I have a Z-Wreck Jr. Combo on order which should arrive in a few days (looking forward ...!!). I noticed from product shots that on the combo the chassis is mounted in a way that seems to make tube access somewhat difficult ... and now I read the Doc's confirmation of this point in this thread (quoted above). My question: What is the best/easiest/recommended method to change tubes on the Wreck Combo? Do you pull the chassis to swap a tube? Any tips or tricks? Thanks! I would imagine to get access to all tubes it’s just easy to remove the back panel with the chassis still attached to it. It looks like only six screws. It would be similar to working on the head Version as you would have to remove the rear screened panel. I 2nd this. The back panel that holds the chassis is just four screws/bolts. It's not too bad.
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Post by felixw on Sept 16, 2020 5:07:35 GMT -7
Keith, Russell - thanks for your reply. Makes sense - will try this when the time comes ...
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Post by Russell B on Sept 16, 2020 7:33:21 GMT -7
I've had the chassis out several times. It's not too bad.
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Post by shonsolo on Dec 28, 2020 13:54:39 GMT -7
Sorry to hear the about the problem Russ. If it didn't rattle out of the cab then I would say it is a tube , not some other part. It will be hard to swap out tubes due to the chassis mount on the Wreck combo. I would start with replacing both 6n14n's , just try any good pair of EL 84's for the test . If not that try the 5Y3 again any rectifier will work temporarily for the troubleshooting test. If not those them my next guess would be V1 it is a Tung-Sol 12AX7 again any good 12AX7 will work for the test. Call or PM me let me know how it worked out. Z I appreciate this thread! I unexpectedly(another story) acquired a Wreck JR in a trade. I’m typically in the EL84 camp so...why not.?! Called out to work, have to wait,...finally some time to crank it up! Notice after short time same problem described by Russ, very discreet and could have easily gone undetected. Called back out,.. wait,.. Read up on this thread,.. Treasure hunt at home to find two 20 year old sovtek EL84s still in the box. I pulled the back off, sat the chassis on the bench and admired the craftsmanship for a full 5 minutes. Replaced the power tubes and that’s all she needed to roar back to life. 😁 Thanks for taking the time to lay out a simple troubleshooting path,. I’m going to order a replacement set now that I’m sure of the issue. It’s easy to see why this model is so popular,. Thanks again.
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