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From my Boogie owners manuals -
Originally Posted by rpjazzguitar
“Flip the POWER switch to the ON (up) position and wait at least 30 seconds for the power tube filaments to warm up with the STANDBY switch in the Standby (OFF/down) position. This cold start procedure prolongs tube life substantially if it is followed each time your amplifier is powered up. “
Old habits die hard. There’s no evidence to support this in audio amps. It is well accepted and proven for the high power tubes in RF equipment like transmitters, which may be where Leo got the idea. But he was such a cheapskate that it’s hard to believe he didn’t think a standby switch would somehow increase his profit margin. Who knows what nonsense lurks in the minds of men?
Nevertheless, when I’m using an amp with a SB switch, I do wait 30 seconds before switching it to “on”. Maybe it matters and maybe it doesn’t. But who doesn’t like to feel the snap of a good toggle switch?
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03-17-2024 09:09 PM
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For those that still need a reason to wait a bit after power on before hitting the SB switch, using the SB may promote quieter amp controls.
To the degree that guitarists set the controls on their amp similarly each time, it's likely some of the controls don't get rotated for long periods, especially an amp dedicated to home practice/study. The time it takes for control pots to become scratchy/noisy can be extended a lot by rotating each of them a full rotation both ways before each session... it takes a little while to do this; about the same time you might wait before hitting the SB.
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They're good in the winter if your amp's been sitting in a freezing car overnight. I use it to protect the cold tubes from the power surge.
I don't think it has any validity but that's what I tell myself.....
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Now there’s a great idea! I try to remember to give all pots on guitars & amps a few turns a few times a year. But there’s no reason not to turn each one through full rotation once or twice every time you use a guitar or an amp. I bet it actually prevents scratchiness until a pot starts to wear out, which should be many years. And you can do it before switching on even without a SB switch. Originally Posted by pauln
For those that still need a reason to wait a bit after power on before hitting the SB switch, using the SB may promote quieter amp controls.
To the degree that guitarists set the controls on their amp similarly each time, it's likely some of the controls don't get rotated for long periods, especially an amp dedicated to home practice/study. The time it takes for control pots to become scratchy/noisy can be extended a lot by rotating each of them a full rotation both ways before each session... it takes a little while to do this; about the same time you might wait before hitting the SB.
I’m going to start doing that today. Thanks for the thought.
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I've also read that one should set a pickup toggle switch on a 2xHB in the middle when not being used. I had a switch issue with a Tokai Firebird that I bought used. I think it had been cased for a long time set for a single pickup. It can mess up the springs. Originally Posted by nevershouldhavesoldit
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Originally Posted by garybaldy
I haven't had any problem with the springs. But I almost never use a bridge pickup, so the selector switches on the 2 PU guitars I've had remain set on neck for most of their lives with me. As a result, oxidation builds up on the contacts for the bridge PU and it doesn't work when switched on after many months of inaction. Because the contacts on most pickup selector switches are simply pressed against each other by the springs, switching back and forth does not remove the oxide coating as well as when rotating pots back and forth - so it's not easy to fix during a gig. Fortunately, the contacts are exposed on these switches and are easy to clean - so you should do this at least one or twice a year.
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Since we're discussing switches, here is another thing to consider if your amp uses a rectifier tube in the power supply.
These tubes are pretty tough, but they have an "Achilles heel"; after coming up to operating temperature they are susceptible to damage or failure if a certain event happens. That event is being powered off and then back on within a few seconds. I don't recall technically, but I think it might be connected to the power-on current in-rush into a circuit where the power supply caps are already holding residual charge. Not sure if that's quite right, but in any case they are more fragile with regard to a fast power-off-on cycle.
This can occur when a band is setting up and figuring out and adjusting the arrangement of who plugs in where... what's typical is there aren't enough service outlets and a multi-outlet power strip is inserted to provide additional connections, so your powered up amp connection may be unplugged from the wall and moved to the strip, then the strip plugged in and switched on... This can happen without you knowing about it, and it can even happen more than once until everyone is happy with their connections.
The only defense is to not turn your amp on until everyone has stopped adjusting the connections and routing for all the equipment - make sure you are the last one to power up. Also make sure you are the first to power off, as some folks in a hurry after the show may start pulling things from the wall (things you may be connected through).
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This might have been the case w/ me last month. we were working in an old building w/ ungrounded outlets and I plugged into a provided strip. Wasn't sure if the strip was plugged into an ungrounded outlet via an adapter plug or whether that outlet was grounded. Gig went fine [unless you count the lame PA they had w/ only 1 speaker working] Anyway the next gig I worked found my Vibrolux w/ a blown fuse as soon as I turned it on. I didn't know if it blew at the end of the last gig or right then and was expecting to find a fried rectifier or shorted power tube when I got home but a fresh fuse seemed to fix it, so maybe it was a surge on the previous gig, who knows. Originally Posted by pauln
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I’ve been a tech for almost 25 years for all manner of tube guitar and recording gear.
here’s a few facts to keep in mind so you can draw your own conclusion:
1) cathode stripping doesn’t occur until 5000v (see the rca tube manuals)
2) broadcast tube gear, studio tube gear never had a standby switch and was/is often left on for months/years at a time with no problem.
3) many amps have no standby switch and work just fine. I’ve seen many 50s ampeg amps for example with no sub switch and original tubes still kicking fine!
4) not all an switches work the same. So this is a more complicated question that it seems at first.
I’ll just say this, standby switches are definitely not required. And yes I think they can do harm in certain amps.
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That's called rectifier tube flash or flashover, and here's the story: Originally Posted by pauln
Discharged filter capacitor(s) is (are) a dead short to the rectifier when you first turn on the power. That short circuit (ie 0 Ohms) will drop as much current as the rectifier tube can put out. But the cap rapidly charges, so the voltage across it drops very quickly as the rectifier charges it. The other tubes are warming up so they take a few seconds to start conducting. This is a "soft" startup because the rectifier won't conduct immediately - it has to warm up, so there's a less abrupt output voltage rise. Once the rectifier tube is warmed up and there's a full charge in the filter cap(s), the voltages stabilize and everybody's happy.
If you turn the power off for a minute or two, the cap will bleed down some through various resistors and its resistance will drop. But the rectifier tube is still fairly hot and will not have to ramp up if the power is reapplied before it cools down - so it will immediately drop its maximum voltage across the load connected to it. If the output tubes are also still warm, they'll start conducting as soon as power is reapplied and add even more voltage draw on the rectifier than there was when all the tubes were cold.
This high voltage draw causes that "lightning" in the tube because it can't keep up with the voltage demand on it and is being driven beyond its spec limits (or is weak and is on its way to failure anyway). Once a tube flashes like this, it should be replaced. Some amps have fuse protection in that circuit, but many do not. The safest way to avoid this is to never repower until the tubes are all cold. That can be 15 or 20 minutes, so don't power up until you're sure you won't have to move your amp to a different outlet.
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Thanks for the inside explanation. Originally Posted by nevershouldhavesoldit
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