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Dialogue: 0,0:00:15.65,0:00:21.61,Default,,0000,0000,0000,,>> The purpose of this video is to dispel some myths about discharging a tube amplifier.
Dialogue: 0,0:00:21.61,0:00:25.30,Default,,0000,0000,0000,,I am using a vendor blues junior here as an example,
Dialogue: 0,0:00:25.30,0:00:28.58,Default,,0000,0000,0000,,but it applies to any other tube amplifier.
Dialogue: 0,0:00:28.58,0:00:31.12,Default,,0000,0000,0000,,As you can see, I've got a volt meter,
Dialogue: 0,0:00:31.12,0:00:35.14,Default,,0000,0000,0000,,hooked up to the main power supply filter capacitor,
Dialogue: 0,0:00:35.14,0:00:38.19,Default,,0000,0000,0000,,and it's measuring four volts right now,
Dialogue: 0,0:00:38.19,0:00:42.08,Default,,0000,0000,0000,,which is just a chemical residue in the electrolytic capacitor,
Dialogue: 0,0:00:42.08,0:00:43.55,Default,,0000,0000,0000,,it doesn't really mean anything,
Dialogue: 0,0:00:43.55,0:00:46.64,Default,,0000,0000,0000,,it's just a byproduct,
Dialogue: 0,0:00:46.64,0:00:48.46,Default,,0000,0000,0000,,not at all important.
Dialogue: 0,0:00:48.46,0:00:52.80,Default,,0000,0000,0000,,I'm going to turn the amplifier on and then turn it off quickly.
Dialogue: 0,0:00:53.66,0:00:57.80,Default,,0000,0000,0000,,Now, you see that it's going down and went up to
Dialogue: 0,0:00:57.80,0:01:01.85,Default,,0000,0000,0000,,about 330 volts and it slowly going down 266,
Dialogue: 0,0:01:01.85,0:01:07.58,Default,,0000,0000,0000,,265 and it's discharging slowly just leaking
Dialogue: 0,0:01:07.58,0:01:10.16,Default,,0000,0000,0000,,through various components inside the amp and
Dialogue: 0,0:01:10.16,0:01:13.88,Default,,0000,0000,0000,,natural leaked down that you get with electrolytic capacitors,
Dialogue: 0,0:01:13.88,0:01:17.39,Default,,0000,0000,0000,,but that's more than enough voltage to knock you on your tail,
Dialogue: 0,0:01:17.39,0:01:19.82,Default,,0000,0000,0000,,so you don't want to mess around with that.
Dialogue: 0,0:01:19.82,0:01:26.48,Default,,0000,0000,0000,,Now, one way to discharge a cold amplifier like this is with
Dialogue: 0,0:01:26.48,0:01:35.62,Default,,0000,0000,0000,,a simple jumper wire with a 10,000 ohm resistor 10K resistor held in one clip.
Dialogue: 0,0:01:35.62,0:01:40.57,Default,,0000,0000,0000,,If I touch that, actually anywhere around here,
Dialogue: 0,0:01:40.79,0:01:49.68,Default,,0000,0000,0000,,it'll take the voltage down rather quickly, 8460, 2216, 1812,
Dialogue: 0,0:01:49.68,0:01:53.87,Default,,0000,0000,0000,,anywhere in the power supply will take it down.
Dialogue: 0,0:01:53.87,0:01:56.61,Default,,0000,0000,0000,,Now we're down to two, one volt.
Dialogue: 0,0:01:57.64,0:02:04.98,Default,,0000,0000,0000,,So, that's a very safe and easy way to discharge any amplifier.
Dialogue: 0,0:02:04.98,0:02:07.70,Default,,0000,0000,0000,,The 10K resistor only prevents sparking,
Dialogue: 0,0:02:07.70,0:02:10.56,Default,,0000,0000,0000,,I could touch it directly but I would get an arc,
Dialogue: 0,0:02:10.56,0:02:14.92,Default,,0000,0000,0000,,the 10K resistor slows down the discharge and makes it easy.
Dialogue: 0,0:02:14.92,0:02:16.90,Default,,0000,0000,0000,,Now, let's do the same thing again,
Dialogue: 0,0:02:16.90,0:02:20.80,Default,,0000,0000,0000,,we'll bring the amp up to full operating voltage,
Dialogue: 0,0:02:20.80,0:02:22.100,Default,,0000,0000,0000,,which is in this case,
Dialogue: 0,0:02:22.100,0:02:27.40,Default,,0000,0000,0000,,we see 347 volts, 348,
Dialogue: 0,0:02:27.56,0:02:31.72,Default,,0000,0000,0000,,and as the two tubes warm up,
Dialogue: 0,0:02:32.45,0:02:35.84,Default,,0000,0000,0000,,you'll see that the amp will actually drop in
Dialogue: 0,0:02:35.84,0:02:39.48,Default,,0000,0000,0000,,voltage because the tubes will start conducting.
Dialogue: 0,0:02:39.55,0:02:46.22,Default,,0000,0000,0000,,Now it's down to 333, 334, 330.
Dialogue: 0,0:02:46.22,0:02:49.70,Default,,0000,0000,0000,,So this is a normal voltage that you would see in a blues
Dialogue: 0,0:02:49.70,0:02:53.98,Default,,0000,0000,0000,,junior with normal operating conditions.
Dialogue: 0,0:02:53.98,0:02:58.62,Default,,0000,0000,0000,,Now, you can play through the amp, it's live.
Dialogue: 0,0:03:00.08,0:03:02.68,Default,,0000,0000,0000,,Now, if we just turn it off,
Dialogue: 0,0:03:02.68,0:03:06.95,Default,,0000,0000,0000,,remember we turned it off before when the amp was cold and nothing happened.
Dialogue: 0,0:03:06.95,0:03:12.59,Default,,0000,0000,0000,,Now, I'm going to turn it off and watch how quickly the voltage goes down, 50, 42,
Dialogue: 0,0:03:12.59,0:03:16.88,Default,,0000,0000,0000,,26, 16, faster than it did through the 10K resistor,
Dialogue: 0,0:03:16.88,0:03:19.34,Default,,0000,0000,0000,,three volts, two volts.
Dialogue: 0,0:03:19.34,0:03:24.53,Default,,0000,0000,0000,,Why? Because it's conducting through the ELAD force primarily and the other tubes,
Dialogue: 0,0:03:24.53,0:03:29.34,Default,,0000,0000,0000,,but these guys are always using a lot of current all the time.
Dialogue: 0,0:03:29.34,0:03:35.64,Default,,0000,0000,0000,,So, simply turning off a warm amplifier is all you have to do to discharge it.
Dialogue: 0,0:03:35.64,0:03:38.01,Default,,0000,0000,0000,,So, now we can strum it,
Dialogue: 0,0:03:38.01,0:03:39.80,Default,,0000,0000,0000,,nothing is coming through the amp,
Dialogue: 0,0:03:39.80,0:03:41.85,Default,,0000,0000,0000,,and this is ice cold,
Dialogue: 0,0:03:41.85,0:03:44.00,Default,,0000,0000,0000,,I can touch it with confidence,
Dialogue: 0,0:03:44.00,0:03:47.88,Default,,0000,0000,0000,,know that I'm not going to get knocked on my tail or anything like that.
Dialogue: 0,0:03:47.88,0:03:55.78,Default,,0000,0000,0000,,So, what about the old myth of having to strum the guitar while you're discharging?
Dialogue: 0,0:03:55.78,0:04:00.42,Default,,0000,0000,0000,,Let's take a look at that, we'll bring it back up to operating voltage again.
Dialogue: 0,0:04:05.45,0:04:09.97,Default,,0000,0000,0000,,So, we're stable at around 334 volts,
Dialogue: 0,0:04:11.75,0:04:14.12,Default,,0000,0000,0000,,and we have a normal sound,
Dialogue: 0,0:04:14.12,0:04:17.14,Default,,0000,0000,0000,,and now we'll strum while we're discharging,
Dialogue: 0,0:04:19.55,0:04:22.87,Default,,0000,0000,0000,,the powerful E chord there,
Dialogue: 0,0:04:24.41,0:04:31.40,Default,,0000,0000,0000,,and you notice that it discharged in exactly the same way as it did when we didn't strum.
Dialogue: 0,0:04:31.40,0:04:34.45,Default,,0000,0000,0000,,There is no reason to actually strum the guitar,
Dialogue: 0,0:04:34.45,0:04:38.04,Default,,0000,0000,0000,,that's just one of those internet myths that gets perpetuated.
Dialogue: 0,0:04:38.04,0:04:41.84,Default,,0000,0000,0000,,The only thing that the strumming does is
Dialogue: 0,0:04:41.84,0:04:46.91,Default,,0000,0000,0000,,confirm that all of the current is gone from the tubes,
Dialogue: 0,0:04:46.91,0:04:48.00,Default,,0000,0000,0000,,but it can be deceptive,
Dialogue: 0,0:04:48.00,0:04:53.64,Default,,0000,0000,0000,,if you had turned the amplifier on and off quickly and these were cold tubes,
Dialogue: 0,0:04:53.64,0:04:58.12,Default,,0000,0000,0000,,it would hold a charge and it wouldn't play when you strummed it.
Dialogue: 0,0:04:58.12,0:05:04.02,Default,,0000,0000,0000,,So, the safest thing to do is always to bring the amp up to full operating temperature,
Dialogue: 0,0:05:04.02,0:05:07.19,Default,,0000,0000,0000,,so you can play through it and simply turn it off,
Dialogue: 0,0:05:07.19,0:05:09.64,Default,,0000,0000,0000,,that will always discharge it all the way down.
Dialogue: 0,0:05:09.64,0:05:10.97,Default,,0000,0000,0000,,Don't put it in standby,
Dialogue: 0,0:05:10.97,0:05:12.78,Default,,0000,0000,0000,,don't do anything else with it,
Dialogue: 0,0:05:12.78,0:05:15.27,Default,,0000,0000,0000,,and you can play if you want to confirm,
Dialogue: 0,0:05:15.27,0:05:16.85,Default,,0000,0000,0000,,as the sound fades out,
Dialogue: 0,0:05:16.85,0:05:22.05,Default,,0000,0000,0000,,you know that it's being discharged and that's all there is to it.