Tube failure mystery: Solved, I think!

[wproffitt]

Hello all,
My family and I moved a few months ago and I haven’t had as much time to play through my amps as I’d like. Here’s the mystery I’d like to solve: why have tubes in positions 1 and 3 in my 5e9 failed (one in November and the other today) when I only have an hour playing time on this amp since we moved? Is it:
1) my children are turning it on when I’m not in the room and it’s running for days without my knowledge?
2) we’ve had power surges and, even though I leave the thing plugged into the wall via a surge protector, it’s killing my tubes.

Thoughts?

[Squirrel]

The fact that you recently moved house probably has something to do with it. Those older style valves really don't like being shaken.

[sookwinder]

Why would you say "the older style valves" don't like being shaken?

Given the "older style valves" are from the 50s, 60s, 70s when they were the main type of design component for amps rather than what are used in modern (cheaper more common) amps, they would have been designed and validated for normal use (even military use) where bumps and shaking are accounted for. If anything I would put my money on modern valves not liking being shaken, rather than "older style" valves.

[Embenny]

Valves 1 and 3 are the 5Y3 rectifier and one of the 6V6's, right?

The fact that both tubes are on the power side of the equation makes me suspect your hypothesis #2 might be the closest to the truth.

It's a new house. Have you tested that the outlet(s) in question are actually properly grounded? If the ground is broken/improperly connected, your surge protector simply won't do anything.

Also, what kind of surge protector are you using? If it's cheap or old, it might not be doing its job even if the ground of the outlet is connected properly. Cheap ones might not do the job right, old ones might have stopped working right. If the ground wire anywhere in the prong/cord/unit itself has broken from wear or damage (including during the move), it won't be doing anything. You can test for continuity easily enough with a multimeter.

Working our way inward from house to surge protector to amp, has your tremolux been converted to a proper 3-prong cord? When were the filter caps last changed? The filter caps smooth the voltage coming from the rectifier through to the rest of the amp. If the filter caps are old/not working properly, maybe the scenario was that your rectifier was on its way out, and as it was kicking the bucket, some wonky voltage variations were getting through those caps which stressed your power tubes. That's one of the ways in which I could envision a rectifier failure and power tube failure coinciding so closely.

I'm not an amp tech, but those are some of my thoughts based on my limited "amp geek" level of understanding.

[wproffitt]

Thanks for your thoughts. Sorry I wasn’t more clear and maybe I’ve been thinking or this the wrong way, but reading the tube chart from right to left, V1 would be the 12AY7 on preamp duties and V3 would be the 12Ax7 that governs trem functions. The 12AY7 in V1 was a NOS Sylvannia and I was bummed to see it go. The 12AX7 was a Tung Sol that I got for not too much, so I’m only so bummed. All I can say is that I started trying to figure things out the other day after I turned the amp on it sounded like a bad distortion pedal (low volume, ratty, fizzy sound when played).
As I checked each of the smaller tubes to the right, they were all sitting proud of their sockets by about 1/8 of an inch when I KNOW they were tight a few months ago. Bear in mind, these are new tube sockets and are pretty snug when you try to move tubes in or out, so I’m a bit confused. What’s up with that? Maybe the kids have been rocking it back and forth on its stand?
-as for the power supply, maybe I should just buy a newer, nicer surge protector? This one is older.

[Embenny]

Ah, I don't have a 5E3 and when I looked it up quickly online, I thought V1 was the rectifier and V3 was the second power tube.

Did you check the sockets right after you moved? Maybe the got jostled by the move? And how old are those filter caps?

Honestly, having preamp tubes blowing but power and rectifier tubes doing fine makes me less worried about the seriousness of the issue. Since it's isolated to preamp tubes (for now), that makes me wonder a bit if it could be transformer-related?

[wproffitt]

The 5e9 is like the 5e3, only with a trem (fender’s first) and a paraphase phase inverter. The trem ads a 6th tube to the compliment. I’m hoping it’s just that the tubes got jostled somehow. That would certainly explain why they were sitting a bit proud of their sockets. This is one that i built a couple of summers ago (thanks again for all of your help, David and Racing!) so I’m not so worried about the big electrolytic caps yet.

[Embenny]

Oh sorry for the typo - and I didn't realize this was a recent build. I can forget about the two prong cord and ancient caps then, but that's a bummer that two preamp tubes but the dust after such a short period of time.

[wproffitt]

Is it time to bust out the multimeter and check some voltages to be sure?

[sookwinder]

also check whether the contacts in the valve sockets are spread too far apart... i.e. not enough froce on the vlave pins to keep them fast in the socket

[wproffitt]

also check whether the contacts in the valve sockets are spread too far apart... i.e. not enough froce on the vlave pins to keep them fast in the socket

So, uh, how do I check that? Not trying to be dense here, but not sure how to do this. The tubes certainly require quite a bit of force to wiggle in or out!
-I’ll pick up the multimeter from work tomorrow.

[jthomas]

Following up on Sookwinder: New manufacture tubes that have not been tested by the seller (such as Tube Amp Doctor, Ruby Tubes, etc.) prior to sale can have pretty significant reliability problems. One guy on another amp forum who re-sells tubes has reported really high failure rates (I believe that he's had somewhere around a 50% failure rates with some preamp tubes) when he pre-tests non-vintage tubes. If you did not get the tubes from a re-seller who pre-tests it could just be a run of bad tubes.

[wproffitt]

Following up on Sookwinder: New manufacture tubes that have not been tested by the seller (such as Tube Amp Doctor, Ruby Tubes, etc.) prior to sale can have pretty significant reliability problems. One guy on another amp forum who re-sells tubes has reported really high failure rates (I believe that he's had somewhere around a 50% failure rates with some preamp tubes) when he pre-tests non-vintage tubes. If you did not get the tubes from a re-seller who pre-tests it could just be a run of bad tubes.

That’s good to know. I have to admit that I mostly feel like I’m buying new production stuff blind. Are there reputable resellers for new production tubes that anyone can recommend? So far, the only tubes that this amp hasn’t eaten are NOS, with the exception of the Sylvannia 12AY7 I had in V1. Still, I’m hesitant to put old glass in positions 1 and 3 if they could be dead in a couple of months. Am I thinking about this in the wrong way? Testing voltages at work today, btw.

[wproffitt]

See wiring diagram below for reference. I did some voltage measurements at work today and found that the lead coming off of the big capacitor feeding onto pin 6 of V3 (the one governing the trem) was only reading 167 when it should have been reading 225. All of the voltages on the circuit up to this point were spot on, so I wasn’t sure where to go. Sooooo...I yanked V3 and swapped it for the 12ax7 in V2 and, voila!, that lead heading to pin 6 of V3 now read at 225 on the nose. So, bad tube, right? I came home and replaced the offending tube and everything sounds glorious, and LOUD. I forgot how loud this amp is.
-Also, there was some oscillation between 1.9V and 3.5V on the lead coming off the 25 MGD capacitor going to pin 8 of V2. Thoughts?

[jthomas]

You can buy Ruby Tubes at a lot of online tube shops (e.g., AmplifiedParts.com - they have always been good to deal with). I believe that the Ruby Tubes are primarily Chinese tubes but they are tested before being resold. Tube amp Doctor does the same. There's also https://www.kcanostubes.com/. I am pretty sure that he tests his new manufacture tubes. There probably are many others, also.

You pay a little more for pre-tested tubes but usually get a no-questions kind of warranty (or should).