Hi All,
Apologies for the long post, but I was wondering anyone's thoughts:
I have a TSE-II with 300b tubes that I recently completed (or so I thought). It has about 40 hours of use on the bench, and maybe 10 since being finished up in its case, with no issues.
Last night, I had it on the bench as I was trying to troubleshoot some hum in my phono preamp (and DIY PH14 from tubes4hifi). I had the preamp outputs plugged into the SE, either nothing on the preamp inputs, or just RCA cables connected to nothing, and the speakers hooked up to the SE.
I was trying shortening and moving cables in the preamp, and was repeatedly turning everything on and off. Probably like a minute or so in-between on and off. Doing stuff like turning on the SE, then turning on the Preamp, waiting for the hum / tube hiss to come up, turning everything off, adjusting, and then repeat.
After a while I blew a fuse in the SE, which has never happened before. This happened during startup the SE had been on for maybe 5 seconds and as I hit the preamp on it blew. The rectifier glowed at the same time, so it took me a while to figure out it was the fuse and not the 5AR4.
With fuse #2, I started up, and after about 5 seconds a hum/buzz came out of the speakers, crackling sound, and then fuse blown. At this point I thought maybe it was the 5AR4 after all, so I switched it out.
With fuse #3, I started up, after maybe 2-3 seconds a bit of lightning in *all* the tubes at the same time, no sound from the speakers, and dead.
I have found the other threads about fuses blowing so I will get started on troubleshooting, but my two questions for now are:
1) Does it sound like I destroyed anything serious?
2) Is it a coincidence that this happened when it did? Or did I stress the amp by turning it on and off repeatedly?
Apologies for the long post, but I was wondering anyone's thoughts:
I have a TSE-II with 300b tubes that I recently completed (or so I thought). It has about 40 hours of use on the bench, and maybe 10 since being finished up in its case, with no issues.
Last night, I had it on the bench as I was trying to troubleshoot some hum in my phono preamp (and DIY PH14 from tubes4hifi). I had the preamp outputs plugged into the SE, either nothing on the preamp inputs, or just RCA cables connected to nothing, and the speakers hooked up to the SE.
I was trying shortening and moving cables in the preamp, and was repeatedly turning everything on and off. Probably like a minute or so in-between on and off. Doing stuff like turning on the SE, then turning on the Preamp, waiting for the hum / tube hiss to come up, turning everything off, adjusting, and then repeat.
After a while I blew a fuse in the SE, which has never happened before. This happened during startup the SE had been on for maybe 5 seconds and as I hit the preamp on it blew. The rectifier glowed at the same time, so it took me a while to figure out it was the fuse and not the 5AR4.
With fuse #2, I started up, and after about 5 seconds a hum/buzz came out of the speakers, crackling sound, and then fuse blown. At this point I thought maybe it was the 5AR4 after all, so I switched it out.
With fuse #3, I started up, after maybe 2-3 seconds a bit of lightning in *all* the tubes at the same time, no sound from the speakers, and dead.
I have found the other threads about fuses blowing so I will get started on troubleshooting, but my two questions for now are:
1) Does it sound like I destroyed anything serious?
2) Is it a coincidence that this happened when it did? Or did I stress the amp by turning it on and off repeatedly?
Start by unplugging the amp.
Check for bulging capacitors or arc/burn marks anywhere on the board.
A flash in all the tubes doesn't sound good.
Short cycling tube amps can cause voltage spikes which can over volt component parts that run near there limits.
Check for bulging capacitors or arc/burn marks anywhere on the board.
A flash in all the tubes doesn't sound good.
Short cycling tube amps can cause voltage spikes which can over volt component parts that run near there limits.
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Thanks! Yes I should have mentioned I did check it out and saw no obvious damage, but I will take all the tubes and check out D2/D3 and the capacitors near the power supply as other threads have suggested.
Jerkbag-- you've probably found why it's not good to turn the amp off and on because there's a big surge of voltage/current blasting the tubes when you switch on/off.
You're on the right track checking D2/D3 and the power supply caps. Check D2/D3 first and remember to wait maybe five minutes before switching the amp off/on.
You're on the right track checking D2/D3 and the power supply caps. Check D2/D3 first and remember to wait maybe five minutes before switching the amp off/on.
Thanks Duke. I just powered without any tubes and new fuse, and R5 started to smoke. It's this (ohmite 270 2W wirewound):
42J270E Ohmite | Mouser Canada
I have another ohmite (just 1) but should I be checking that something else is causing this -- will it just smoke out again -- or do you think it's fair to assume, since the amp had been working fine for while, that I stressed / wrecked R5 and that's the end of the story?
I can't get the ohmite locally so I'd like to be as sure as I can be that it's not something else.
42J270E Ohmite | Mouser Canada
I have another ohmite (just 1) but should I be checking that something else is causing this -- will it just smoke out again -- or do you think it's fair to assume, since the amp had been working fine for while, that I stressed / wrecked R5 and that's the end of the story?
I can't get the ohmite locally so I'd like to be as sure as I can be that it's not something else.
It looks like R5 is right near D2/D3? Part of your -150V bias supply if I'm looking at the correct schematic. (I'll dig out my schematic, can't seem to find the TSE-II on the Tubelab website.)
Are you using a preamp because you want to listen to vinyl? You can connect most other source devices directly to the amp and use it like a integrated amp otherwise.
Are you using a preamp because you want to listen to vinyl? You can connect most other source devices directly to the amp and use it like a integrated amp otherwise.
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Yup they are near D2/D3 and part of the negative bias supply. I found this post from the main thread so I suspect what happened is that R5 failed and losing neg bias caused too much current to flow to the output tubes? The weird thing is I still got neg bias when I was powering up to test -- even while it was smoking. D2 and D3 are common parts so maybe i will replace those anyway while I am replacing R5.
Can't seem to find the edit button but I should add yes it's a phono preamp I am using for vinyl. I am going to try replacing R5, D2 & D3 and will report back later tonight or tomorrow.
So I replaced R5 (5 watt ceramic for good measure) D2 and D3. Powered up fine and B- steady with no tubes. Then i put the original 5AR4 back in, and it came up slowly before arcing and blowing a fuse. I chalked this up to it being damaged from the first fuse blowing mess, and swapped for another 5AR4.
At this point the rest of the checkout went smoothly, and I can listen to music. BUT: everything needed to be 'turned up' a little bit -- the 5842s needed adjustment to get back to 175, and the 300b needed turning up as well. My B+ with the old rectifier was ~360V, now it's ~330V. And, my power transformer is buzzing. Is this a symptom of another shitty rectifier tube? I'm disorganized right now so am not sure if this 5AR4 is new or not -- I just have a few in a pile.
At this point the rest of the checkout went smoothly, and I can listen to music. BUT: everything needed to be 'turned up' a little bit -- the 5842s needed adjustment to get back to 175, and the 300b needed turning up as well. My B+ with the old rectifier was ~360V, now it's ~330V. And, my power transformer is buzzing. Is this a symptom of another shitty rectifier tube? I'm disorganized right now so am not sure if this 5AR4 is new or not -- I just have a few in a pile.
You're within ~10% of your original voltage with the tube, so I don't think it's a big deal if your voltage went from 360V to 330V. It's a different tube and you say you have a few. Just the variation in the tubes you have.
Is the power transformer buzzing so loud that you can hear it over the music? Other people might be able to tell you how to reduce buzzing, only way I know is to replace it. But if you can't hear it while playing music from your listening chair, why worry.
Lesson here is not to turn the power off/on without waiting 5 or more minutes between cycling power.
Enjoy some music now! You solved the problem.
Is the power transformer buzzing so loud that you can hear it over the music? Other people might be able to tell you how to reduce buzzing, only way I know is to replace it. But if you can't hear it while playing music from your listening chair, why worry.
Lesson here is not to turn the power off/on without waiting 5 or more minutes between cycling power.
Enjoy some music now! You solved the problem.
No I couldn't hear the buzzing over the music. In any case, I swapped out the 5AR4 again with another I had lying around and now my B+ came up as expected (and I had to dial the 5842s and 300b back down), the PT quieted down, and I'm back in business.
Definitely learned my lesson re: quick power cycles. Thanks so much for the help!
Definitely learned my lesson re: quick power cycles. Thanks so much for the help!