I had a 36LW6 run away once, but never the 6P 45s... I run them 320V or so with 120mA idle. Were your experiments SE or PP? Mine are all PP
And of course, I blew another MOSFET no idea why yet though. I had had a few drinks by the time it happened and rather than repair it, I just switched to the nearly impossible to destroy tube amp 🙂
The 6N50D2 seems fragile. They even come in a antistatic box full of antistatic foam. The 16N20D2 just comes in a antistatic bag.
And of course, I blew another MOSFET no idea why yet though. I had had a few drinks by the time it happened and rather than repair it, I just switched to the nearly impossible to destroy tube amp 🙂
The 6N50D2 seems fragile. They even come in a antistatic box full of antistatic foam. The 16N20D2 just comes in a antistatic bag.
The original death of 4 tubes happened in a SE amp and all tubes died when the amp was left on at idle. At first I was running 400 volts of B+, but the last two tubes were at 320 volts. The screen grid spec in 275 which is relatively high for a sweep tube.
The SE UNSET board has been running a pair of 36LW6's on a B+ varying from 450 to 550 volts and at dissipation levels far above the 40 watt spec for over a year. I usually run it at about 20 WPC, but it has been to 40 WPC for a few hours. There have been no issues with component death unless I'm messing with it, doing things like running it P-P and cranking stupid amounts of power through it.
Damn 🙂 I run my KT88 amp UL at 560V but the highest I went with sweep tubes was 380V since the screen spec is low. OTOH, the plate won't be a lower voltage than the screen so it should be ok, no? I usually use a 240R screen resistor anyway.
When the amp is sitting idle the tube has no idea if it's triode, UL or pentode, it just sees a constant screen voltage that it doesn't like.
The 4 dead 6LW6's all died at idle, The amp was connected between my PC and a pair of Yamaha NS10's. It replaced a SSE which was a cathode biased SE KT88 amp running in UL with about 450 volts on plate and screen. Idle current was usually 70 mA, but I had a switch to jump to 100 mA for loud stuff like Depeche Mode or Pink Floyd. The extra current raised the DF a bit helping in the bass department. That amp ran whenever the PC was on and most of the time it sat idle. It ran the same pair of EH tubes from the day it was built, till the day I packed it up to move, nearly 10 years later.
The 6LW6's were triode wired in a hacked up TSE which ran fixed bias with a mosfet CF driving G1. The first tube ran at 400 volts and sounded far better than the KT88 amp, but it developed a blue glow one day, and melted down the next day. I assumed a bad tube and popped in another. A few months later the tube in the other channel went into red plate meltdown, then developed a blue glow. After two dead tubes, I swapped the power transformer to get a lower voltage, around 320 volts I think. It took longer, but two more tubes died, so the SSE went back into the system and the TSE got converted back to 300B's.
Fast forward 10 years to about 2015. I am tinkering with 6W6's in triode, and another tube runs away. The 6W6 has a maximum plate (and screen) voltage of 300 volts in TV vertical sweep duty. I was running my tubes just under 300 volts, but I might have been a watt or two (really) over the 7.5 watt dissipation spec. They were crusty old tubes so I swapped in two brand new wafer based late production tubes. After several months of idle cooking one of them started to exhibit bias creep, but never went into runaway. A pair of 6W6's has been pushed to 40 watts in a push pull circuit on 350 volts using the mosfet in the cathode drive circuit with 135 volts on the screen. They have not blown up despite some serious abuse.
The 6W6 is the same tube as the 50L6 used in millions of old radios where they were left on for years without failure.....with 150 or less volts across them.
The only thing in common here, was that the dead tubes were all sitting idle for long periods of time. These are all tubes rated for, or intended for TV sweep duty......which NEVER idles, the sweep circuit runs at full power all of the time.
The horizontal sweep (line output) tube is used to switch a nearly constant current through an inductor (the "flyback" transformer) generating a ramp voltage which "sweeps" the electron beam across the face of the CRT, once near saturation is reached, the current is halted and the beam "flies back" to the starting point on the CRT screen. The abrupt cessation of current through the transformer creates a huge voltage spike generating the high voltage for running the CRT, in a manner similar to the ignition coil on a car.
The vertical sweep circuit is a class A audio amp that is optimized for a single frequency, 60 Hz in North America, and 50 Hz in much of the world. I made many guitar amps as a kid just by ripping the vertical sweep circuit out of a dead TV and sticking it in a box with a speaker.
Maybe these tubes just don't like doing nothing, they get bored and eat themselves🙂
The 4 dead 6LW6's all died at idle, The amp was connected between my PC and a pair of Yamaha NS10's. It replaced a SSE which was a cathode biased SE KT88 amp running in UL with about 450 volts on plate and screen. Idle current was usually 70 mA, but I had a switch to jump to 100 mA for loud stuff like Depeche Mode or Pink Floyd. The extra current raised the DF a bit helping in the bass department. That amp ran whenever the PC was on and most of the time it sat idle. It ran the same pair of EH tubes from the day it was built, till the day I packed it up to move, nearly 10 years later.
The 6LW6's were triode wired in a hacked up TSE which ran fixed bias with a mosfet CF driving G1. The first tube ran at 400 volts and sounded far better than the KT88 amp, but it developed a blue glow one day, and melted down the next day. I assumed a bad tube and popped in another. A few months later the tube in the other channel went into red plate meltdown, then developed a blue glow. After two dead tubes, I swapped the power transformer to get a lower voltage, around 320 volts I think. It took longer, but two more tubes died, so the SSE went back into the system and the TSE got converted back to 300B's.
Fast forward 10 years to about 2015. I am tinkering with 6W6's in triode, and another tube runs away. The 6W6 has a maximum plate (and screen) voltage of 300 volts in TV vertical sweep duty. I was running my tubes just under 300 volts, but I might have been a watt or two (really) over the 7.5 watt dissipation spec. They were crusty old tubes so I swapped in two brand new wafer based late production tubes. After several months of idle cooking one of them started to exhibit bias creep, but never went into runaway. A pair of 6W6's has been pushed to 40 watts in a push pull circuit on 350 volts using the mosfet in the cathode drive circuit with 135 volts on the screen. They have not blown up despite some serious abuse.
The 6W6 is the same tube as the 50L6 used in millions of old radios where they were left on for years without failure.....with 150 or less volts across them.
The only thing in common here, was that the dead tubes were all sitting idle for long periods of time. These are all tubes rated for, or intended for TV sweep duty......which NEVER idles, the sweep circuit runs at full power all of the time.
The horizontal sweep (line output) tube is used to switch a nearly constant current through an inductor (the "flyback" transformer) generating a ramp voltage which "sweeps" the electron beam across the face of the CRT, once near saturation is reached, the current is halted and the beam "flies back" to the starting point on the CRT screen. The abrupt cessation of current through the transformer creates a huge voltage spike generating the high voltage for running the CRT, in a manner similar to the ignition coil on a car.
The vertical sweep circuit is a class A audio amp that is optimized for a single frequency, 60 Hz in North America, and 50 Hz in much of the world. I made many guitar amps as a kid just by ripping the vertical sweep circuit out of a dead TV and sticking it in a box with a speaker.
Maybe these tubes just don't like doing nothing, they get bored and eat themselves🙂
I destroyed a 47uF capacitor today. Apparently they don't like being heated up to ~350deg C 🙄
It was close to an smd chip I had just replaced, which I had managed to get some solder bridges on, and was trying to remove them, and well it went bang! scared the crap out of me. No idea where the shell ended up!
Tony.
It was close to an smd chip I had just replaced, which I had managed to get some solder bridges on, and was trying to remove them, and well it went bang! scared the crap out of me. No idea where the shell ended up!
Tony.
Attachments
Such a clean "pop"... No sprayed electrolyte goo all over 🙂 That's a nice thing. David Attenborough could be reading like "And here we see a circuit board in it's natural habitat. Oh dear! It seems one of the electrolytic capacitors have expired and flowered into a paper fuzz". LMAO
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hehe yes I was very surprised at the lack of electrolyte. I guess it vapourised! It clearly hadn't leaked as it wouldn't have exploded if it had. I'm just lucky I didn't get hit by flying metal!
Tony.
Tony.
I sent 12V into the output of a dac chip and it didn't appreciate it. Oops.
CS4397 is obsolete, hard to find except from China (if it's even real) and 28 pin SMD so I replaced the board.
CS4397 is obsolete, hard to find except from China (if it's even real) and 28 pin SMD so I replaced the board.
I've seen a horizontal oscillator tube (6LF6, I think) with a little funnel-shaped hole in its side.
I had a 6P45S run away for long enough the glass cracked... I didn't notice until I heard it pop. Forget "redplate" it was full Orange like when you turn on the electric stove to max without a pot or pan.
Today, I broke a IN13... It looks like it should work, but it doesn't. Must have a hairline crack. Grr.
Ordered a replacement pair from Ukraine... Maybe it'll be here before July but I doubt it.
Ordered a replacement pair from Ukraine... Maybe it'll be here before July but I doubt it.
Hey, thanks for reviving the thread!
Destroyed a few things during the pandemic, mostly physically due to own impulsivity. Some died on their own.
-AlieExpress sinewave generator that stopped working, then got finished by hammer blows.
-Experimental NaOH enamel wire stripper that killed herself in her own-microspits of corrosive NaOH into the electronics. Sloppy of me not to have covered them enough.
-Had to scrap 300g of 0.5 copper yesterday, due to a sharp piece of metal scratching the surface of the content.
-Raging over a clamp (destroyed the clamp's handle) due to self-loosening while gluing the airgap of a C-core choke. The inductance value was of course unacceptable and the choke had to be stored for "who knows when" use.
Destroyed a few things during the pandemic, mostly physically due to own impulsivity. Some died on their own.
-AlieExpress sinewave generator that stopped working, then got finished by hammer blows.
-Experimental NaOH enamel wire stripper that killed herself in her own-microspits of corrosive NaOH into the electronics. Sloppy of me not to have covered them enough.
-Had to scrap 300g of 0.5 copper yesterday, due to a sharp piece of metal scratching the surface of the content.
-Raging over a clamp (destroyed the clamp's handle) due to self-loosening while gluing the airgap of a C-core choke. The inductance value was of course unacceptable and the choke had to be stored for "who knows when" use.
“Hammer blows” - hmmmmm. Seems like I’ve done that a few times recently.
One of the Toyota keys
The Dish remote
A stubborn Cub Cadet weedwhacker ( well, used as it’s own hammer)
The wife’s IPhone is next on the chopping block, as soon as I finish getting all the critical data off of it and onto other non-Apple media (And get us signed up for Consumer Cellular or similar). My IPhone will follow soon thereafter. They will both die horrible deaths - I’m open to suggestions on how this might be achieved for maximum satisfaction. Axe, drill press, .380 round, C4, 13.8 kV?
One of the Toyota keys
The Dish remote
A stubborn Cub Cadet weedwhacker ( well, used as it’s own hammer)
The wife’s IPhone is next on the chopping block, as soon as I finish getting all the critical data off of it and onto other non-Apple media (And get us signed up for Consumer Cellular or similar). My IPhone will follow soon thereafter. They will both die horrible deaths - I’m open to suggestions on how this might be achieved for maximum satisfaction. Axe, drill press, .380 round, C4, 13.8 kV?
I had trouble getting AD9201 from UK. They are about £15.00 each.
So had a look on Ali Express and found some there £0.90 each!
So bought a few and they work ! amazing.