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I have yet another amp here in the shop. Close to two years old, and the owner brought it to me thinking it was the EL34 Power Tubes causing the random noises...pops, clicks, sputters, etc that can occur with tube amps as they age, or perhaps produce in their infancy after manufacture.
I can't reveal the company nor model due to having signed Non-Disclosure Agreement with them. I can say it's produced east of the United States overseas. Nor can I attach the photos taken of the problem tube socket connections. Sigh..........
When the client brought it in, I moved it to the test bench, connected the 40W EL34-based amp to an 8 ohm speaker (it being 8 or 16 ohm), and was stuck having to use an awful sounding Hartke 15" bass cabinet instead of something decent. No matter. Powered it up. Had it also connected to my Amber 3501a Audio Analyzer, feeding my scope and headphone amp, so there was good monitoring on the unit. After it being on for a good five minutes, which gave me time to remove the cover (it being of a 'Lunchbox' type of construction), we began hearing random ticks and pops, and seeing those artifacts appear on the meter & scope.
Tapping lightly on the power tubes, I found to my surprise the behavior one sometimes hears on a Fender Deluxe or Twin Reverb that has been working for a good many years, and perhaps with somewhat weakened Bear-trap tube base clamps holding the power tubes in place. This one had very tight-fitting base clamps. Still, hearing this behavior being initiated by tapping on ANY of the five tubes...three preamp/driver tubes inside tube shields, and the two power tubes held firmly with their strong base clamps.... I'd have to say NO....this isn't a bad tube problem, but we'll look anyway.
Powered down to standby, swapped out the Driver Tube, which over time has often been the culprit, not so in this case. Restored the driver tube, leaving the shield off. Swapped out the middle preamp tube with no change. Swapped out the input stage tube, also with no change. I had stopped off at the Guitar Dept here at CenterStaging, LLC (Burbank, CA) to see if they had a fresh matched pair of J/J EL34 Power tubes, but no luck. All I had here in the shop were pulls, so I did power down, cool off the tubes and unplugged each one, then exercised it inserting/removing it from its tube socket, which was nice and tight-fitting as one would hope to find. Reseated each tube, and put the chassis cover on, while removing the handle so I could turn this upside down on the bench and then remove the bottom panel, exposing the insides of the amp. Nicely produced PCB assy, double-sided and somewhat tightly packed, though not with the density one finds in Mesa amplifiers. I was interested in looking at the PCB terminals of the five vacuum tube sockets. I set my eyeglasses aside and put on my surgical loupes and headlight, adjusted each eyepiece for max sharpness and went looking at the solder joints. Hand soldered at the factory, Lead-Free solder (presumed) though I was not impressed with the solder quality and was seeing evidence of circular fracture rings on several tube socket terminals, as well as open voids on their blades.
All of the power supply electrolytic caps were Radial Lead, so to get at those, extensive disassembly and fumbling about will be involved. Can't say I look forward to that.
I wrote up the invoice for the client, and having both lived thru this regrettable behavior of a like-new amp which lives in his home studio and has never taken it anywhere to play live with, he is at least covered by the manufacturer's 2-year warranty.
I sent an email to my contact at the factory advising of this latest find from their current production product, and also inquired about the power transformer I was waiting for on another repair of theirs that has substantial hum/RF buzz on the output.
I've since opened this amp back up and began de-soldering and re-soldering the first of two Power Tube sockets, and after getting horrible-looking frosty white results, I de-soldered again, removing all of the old solder on that terminal, and re-soldering again with fresh Kester Sn40-Pb60 0.032" solder, now yielding nice shiny results. I resoldered a few other joints on the tube sockets, but not all.... just those that looked questionable.
Powered the amp back up, and all seemed fine for the first ten minutes...no more snits and pops, could aggressively tap on the tubes without violent objection from them.
Then, the snits and pops began again, as did the nasty behavior when tapping on the tubes. RATS.
Now, getting a clearer picture of what's happening, perhaps. The symptoms require time and heat to begin the nasty behavior. I had a similar problem with another amp, which I did post about, forgetting I had also signed an NDA with that mfgr. No doubt lead-free solder there too, as I had trouble with re-soldering until I had fully removed all of the existing solder before re-soldering with the Kester 40-60 solder I normally use.
Anyone else having these problems? Today, after I post this, I'm back into that chassis and re-doing ALL of the solder joints, as well as the heater wires, as they use wires to route 6.3VAC heater voltage to all of the tubes on the PCB. I also have to extract the PCB from the chassis to get onto the bottom side to properly address those heater wires, as well as the Electrolytic Power Supply Caps.
Heat & Age (years from date of MFGR), plus, perhaps...just HOW WELL were they produced at the factory before this sort of behavior begins? This is racking up a lot of hours, and I know I won't get fully compensated for the labor hours to achieve a solution.
I can't reveal the company nor model due to having signed Non-Disclosure Agreement with them. I can say it's produced east of the United States overseas. Nor can I attach the photos taken of the problem tube socket connections. Sigh..........
When the client brought it in, I moved it to the test bench, connected the 40W EL34-based amp to an 8 ohm speaker (it being 8 or 16 ohm), and was stuck having to use an awful sounding Hartke 15" bass cabinet instead of something decent. No matter. Powered it up. Had it also connected to my Amber 3501a Audio Analyzer, feeding my scope and headphone amp, so there was good monitoring on the unit. After it being on for a good five minutes, which gave me time to remove the cover (it being of a 'Lunchbox' type of construction), we began hearing random ticks and pops, and seeing those artifacts appear on the meter & scope.
Tapping lightly on the power tubes, I found to my surprise the behavior one sometimes hears on a Fender Deluxe or Twin Reverb that has been working for a good many years, and perhaps with somewhat weakened Bear-trap tube base clamps holding the power tubes in place. This one had very tight-fitting base clamps. Still, hearing this behavior being initiated by tapping on ANY of the five tubes...three preamp/driver tubes inside tube shields, and the two power tubes held firmly with their strong base clamps.... I'd have to say NO....this isn't a bad tube problem, but we'll look anyway.
Powered down to standby, swapped out the Driver Tube, which over time has often been the culprit, not so in this case. Restored the driver tube, leaving the shield off. Swapped out the middle preamp tube with no change. Swapped out the input stage tube, also with no change. I had stopped off at the Guitar Dept here at CenterStaging, LLC (Burbank, CA) to see if they had a fresh matched pair of J/J EL34 Power tubes, but no luck. All I had here in the shop were pulls, so I did power down, cool off the tubes and unplugged each one, then exercised it inserting/removing it from its tube socket, which was nice and tight-fitting as one would hope to find. Reseated each tube, and put the chassis cover on, while removing the handle so I could turn this upside down on the bench and then remove the bottom panel, exposing the insides of the amp. Nicely produced PCB assy, double-sided and somewhat tightly packed, though not with the density one finds in Mesa amplifiers. I was interested in looking at the PCB terminals of the five vacuum tube sockets. I set my eyeglasses aside and put on my surgical loupes and headlight, adjusted each eyepiece for max sharpness and went looking at the solder joints. Hand soldered at the factory, Lead-Free solder (presumed) though I was not impressed with the solder quality and was seeing evidence of circular fracture rings on several tube socket terminals, as well as open voids on their blades.
All of the power supply electrolytic caps were Radial Lead, so to get at those, extensive disassembly and fumbling about will be involved. Can't say I look forward to that.
I wrote up the invoice for the client, and having both lived thru this regrettable behavior of a like-new amp which lives in his home studio and has never taken it anywhere to play live with, he is at least covered by the manufacturer's 2-year warranty.
I sent an email to my contact at the factory advising of this latest find from their current production product, and also inquired about the power transformer I was waiting for on another repair of theirs that has substantial hum/RF buzz on the output.
I've since opened this amp back up and began de-soldering and re-soldering the first of two Power Tube sockets, and after getting horrible-looking frosty white results, I de-soldered again, removing all of the old solder on that terminal, and re-soldering again with fresh Kester Sn40-Pb60 0.032" solder, now yielding nice shiny results. I resoldered a few other joints on the tube sockets, but not all.... just those that looked questionable.
Powered the amp back up, and all seemed fine for the first ten minutes...no more snits and pops, could aggressively tap on the tubes without violent objection from them.
Then, the snits and pops began again, as did the nasty behavior when tapping on the tubes. RATS.
Now, getting a clearer picture of what's happening, perhaps. The symptoms require time and heat to begin the nasty behavior. I had a similar problem with another amp, which I did post about, forgetting I had also signed an NDA with that mfgr. No doubt lead-free solder there too, as I had trouble with re-soldering until I had fully removed all of the existing solder before re-soldering with the Kester 40-60 solder I normally use.
Anyone else having these problems? Today, after I post this, I'm back into that chassis and re-doing ALL of the solder joints, as well as the heater wires, as they use wires to route 6.3VAC heater voltage to all of the tubes on the PCB. I also have to extract the PCB from the chassis to get onto the bottom side to properly address those heater wires, as well as the Electrolytic Power Supply Caps.
Heat & Age (years from date of MFGR), plus, perhaps...just HOW WELL were they produced at the factory before this sort of behavior begins? This is racking up a lot of hours, and I know I won't get fully compensated for the labor hours to achieve a solution.
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