I love the colors during operation in one of those massive high-power recitfier tubes...
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AMPEG SVT 2 PRO Warm up/Cool down time?
- Thread starter slapstick13
- Start date
I love the colors during operation in one of those massive high-power recitfier tubes...
okcrum
in your chest
Yeah those mercury-vapor rectifiers were awesome, and the glow would modulate to the audio in big old AM transmitters.
Anyway, Bob's spot on. Once the amp's at room temp, turn it on, and it'll be ready to use within a minute. We're talking about receiving tubes here, in the old vernacular. They have quick heating, small, and generally quite rugged filaments, and indirectly heated cathodes.
Big Big transmitting and industrial tubes take longer to warm up because they are almost always directly heated (the tube's operating current comes directly off the filament, instead of indirectly from a heated cathode) and that filament is so physically large it needs to be heated gradually so it doesn't warp or fracture from mechanical expansion as it comes up to operating temperature.
Now, an 8974 takes about 5 min to come all the way up, but that's an extreme case. Filament on that is 16.3 volts at 625 amps. You connect it using 1/4" x 4" copper bus bar.
really? that's crazy. i'll take your word for it, but it seems it would have to be shockmounted somehow in order to keep working day after day.
Got to tell you a little story about those Mercury rectifier tubes. I built a couple big power amps using those when I was a kid. Built a 1KW out four 813 RF power amp for about $50 bucks using all surplus parts. Those same four tubes would make an easy 500W of real audio too.
The power supply was all mil surplus parts, including a tall pair of mercury vapor rectifiers. They glow a real nice purple at resting current and a very bright blue at full smoke.
Well when you power them down the MERCURY solidifys all over inside the tube. If you throw HV at them they will arc and destroy the tubes. You need to turn them on and wait about 4-6 hours the first time after flipping around one of these tubes; or installing for the first time. Once installed the mercury will all flow to the bottom and not short when turned off.
Well I needed to do some work on this home brew POS power supply I whipped up. SO I thought I'd outsmart the tubes and keep their filaments running even though the HV was off and the power supply was unplugged. I had a Heathkit mutli-voltage service power supply that had the 5V (2.5V a tube center tapped) necessary to light the filaments, I jumpered them in to the pins and turned the supply on, then flipped it over.
I reached in and started working... I didn't think this all the way through...
Filament supply hooked to tubes, they were lit and able to rectify. 5V onone side of the filament transformer made 220V on the primary side of that same transformer. With all the switches turned on, the primary of the filament transformer was connected to the primary of the HV transformer.... THat made voltage on the secondary which put at low current a lot of high voltage on the rectifier plates and made about 2000V of DC at the HV output of the power supply.
I managed to get my hand across that... At 15 years old BUZZZZZAP. Woke me up pretty good. Took me a few minutes to figure out what happened. Been in 100's of huge amps since and never caught B+ again after that.
Have caught AC in panels working as an electrician every once in a while, but I'm a pretty cautious guy around power after those first few lessions.
BOB
The power supply was all mil surplus parts, including a tall pair of mercury vapor rectifiers. They glow a real nice purple at resting current and a very bright blue at full smoke.
Well when you power them down the MERCURY solidifys all over inside the tube. If you throw HV at them they will arc and destroy the tubes. You need to turn them on and wait about 4-6 hours the first time after flipping around one of these tubes; or installing for the first time. Once installed the mercury will all flow to the bottom and not short when turned off.
Well I needed to do some work on this home brew POS power supply I whipped up. SO I thought I'd outsmart the tubes and keep their filaments running even though the HV was off and the power supply was unplugged. I had a Heathkit mutli-voltage service power supply that had the 5V (2.5V a tube center tapped) necessary to light the filaments, I jumpered them in to the pins and turned the supply on, then flipped it over.
I reached in and started working... I didn't think this all the way through...
Filament supply hooked to tubes, they were lit and able to rectify. 5V onone side of the filament transformer made 220V on the primary side of that same transformer. With all the switches turned on, the primary of the filament transformer was connected to the primary of the HV transformer.... THat made voltage on the secondary which put at low current a lot of high voltage on the rectifier plates and made about 2000V of DC at the HV output of the power supply.
I managed to get my hand across that... At 15 years old BUZZZZZAP. Woke me up pretty good. Took me a few minutes to figure out what happened. Been in 100's of huge amps since and never caught B+ again after that.
Have caught AC in panels working as an electrician every once in a while, but I'm a pretty cautious guy around power after those first few lessions.
BOB
i understood none of that but the last sentence, but it sounds like the message is "be careful."
Yeah, that's what I got, too. Something involving Bob getting zapped in a pretty attention-getting fashion. Seems like an ordeal to avoid.
okcrum
in your chest
i understood none of that but the last sentence, but it sounds like the message is "be careful."
...or it will take your soul away to the heavens at a touch!
I hear ya. On my 70's v4 and vt40, the chassis' are suspended on flexible mounts. I was always impressed by that. I wonder if the 70's svt are the same way?
But as far as my svt 2 pro, everything's rigidly mounted to the chassis, and the feet are hard plastic.
The thing is really microphonic if you tap the chassis, especially with the gain and drive turned up.
