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Discussion in 'Glowing Bottle Tube Amp Forum' started by HotRodSteve, Jan 31, 2014.
Stand by your amp.....
Apparently tubes and circuitry are being made very brittle these days. When there was almost nothing but tube amps, and most anything with any transistors inside wore a tag that said "solid state", the answer was simple: use the power switch. Some amps had stand-by switches so they could stay warmed up but not amping, for things like plugging instruments in without making racket. But using them in some kind of technological ritual was unheard of. In the nine years I had my first amp (starting in '64) all I ever used was the power switch, and I never had to change one tube. Extreme power tubes like radio broadcast rectifiers, sure those had warm up and down cycles, but 6 or 12 volt thermionic valves for amplification, any such "procedures" would have been received as if the process included waving a dead chicken around.
Dad was an engineer, so he knew what not to do.
The really dangerous part of the older TV's is the picture tube. There's a vacuum inside and a fair amount of volume. A technician at Dad's plant was carrying one under his arm and accidently bumped a block wall. The tube exploded and the flying glass cut him fatally.
Radio shack had a tube tester when I was a kid. Big analog VU meter with a needle that seemed like it would either swung all the way or it wouldn't. Tubes had to be tested not only for TV's but Heathkit "hi-fi" amplifiers (before stereo, and yes I still have the late fifties pair of GE 6L6's that were in it with a couple of Mullard AX's). The store is still there, but they replaced the tube tester with a battery tester. Now it's all toys and cell phone accessories.
My recollection is that the tube tester that I mentioned above was about the size of a top loading washing machine. Is that what everyone else recalls?
Edit: searched images for tube tester, found this:
That's about what I remember.
...with the volume turned down.
Is there any manufacturer documented instructions on this topic? I've read all of the antidotes, from engineers and no nothings, but I don't recall anything in an instruction manual from a company which designs/sells amps.
Also, are there ANY tests comparing one method vs another? I keep reading about the effects of different methods on tube life, but I've never read any documented results of what the actual difference is. If it's +/- 10% I don't really care, I change tubes about every five years, or five times in my lifetime of playing. If one method saves a single tube change in twenty five years I would save ten times that skipping Starbucks once a week. YMMV
Main switch on, then after a few seconds, flip the Standby switch and play it.
To turn offg flip the Standby switch, wait a few seconds and Main switch off.
I've played Fender amps for years and I have never had a problem with this method.
Why would glass fly outward if the tube was under a vacuum? I'm just a dumb engineer, but that doesn't make sense.:neutral:
If a vacuum tube mechanically fails, the glass is accelerated towards the center of the tube, but any pieces that don't collide with pieces coming from the other direction (dissipating energy via glass breaking) will continue to travel until they collide with something.
Not a tube exploding, but it shows how violent a vacuum implosion can be:
Here is a method that is only guaranteed to work every time.
To turn the amp On...flip switch to On.
To turn amp Off...flip switch to Off.
Leave Stand-By in the off position
I have two 40 yo amps , a Fender Bandmaster and a Super Reverb , both imported through the joint importer Hagström in Sweden for all of Scandinavia.
These amp were modded right from the start , the "Death Capacitor " was never legal over here , and off course the PT was changed for the 230 volts we use. The amps were also without standby switches right from the very start.........Never heard about anyone harming any of these amps through all these years
My Super from 74 had been used as the primary amp for 20 years by the previous owner , and he had retubed it exactly once in 20 years , studio work , countless gigs etc.......Some might not like any or all of Hartley Peaveys amps , but he doesnt look or sound like a stupid man to me....
Often wondered, no idea really, it's not in the operating manual.
I'm willing to go with what MuchXS says.
My amp came with some instructions about using the standby function.
Vacuum tube amps require a warm up period of up to 1 minute before they become 100% operational,and usually sound best as they"burn in". Your Regal amp will get hot during operation;this is normal.Your Regal amp is equipped with a standby switch,which aside from muting the amplifier,removes the B+ voltage from the circuit while allowing the heaters to remain energized.
I followed Merlin's suggestion of putting a resistor across the Standby Switch terminals. It completely eliminated my Standby Switch 'pop' by allowing a small current to flow around the Standby Switch to charge the Filter Capacitors. This prevents a current surge when you close the Standby Switch. I like to have the Standby Switch in the standby position before powering up the amp. Turn on the Power Switch then wait 15 to 30 seconds for the tube heaters to come up to temp and for the pop resistor to charge the filter caps enough to prevent a current inrush which is what causes the pop.
Preventing the current inrush may also make your filter caps last longer. Merlin (The Valve Wizard) recommends a resistor between 47k (2watt) and 150k (1watt). I had a 100k 2watt on hand so I used that.
Can anyone share a specific negative result, either their own or from someone they know, which was the caused by turning on/off the "wrong" way, whatever that is?
Here's an interesting explanation in understandable language.
The last 3 paragraphs sum it all up.
Index Home About Blog
From: "Barry Ornitz" <firstname.lastname@example.org>
Subject: Re: Discussion topic - full wave rectifiers
Date: Sat, 6 Jan 2001 19:28:25 -0500
"John Byrns" <email@example.com> wrote in message
> In article <3A5772BC.60FC@xs4all.nl>, firstname.lastname@example.org wrote:
> > When you replace such a rectifier with semiconductor diodes, at the
> > moment of switch-on there is (a) a potentially damaging H.T. inrush
> > current into the reservoir / filter capacitors, followed by (b) these
> > capacitors, since there is yet no 'load', are operating at well above
> > their design voltage, and (c) H.T. is applied to the other stages
> > before they are properly warmed up, with possible side-effects
> > depending up the set's design.
> > Silicon diodes can be substituted, but my recommendation is to include
> > (a) series resistors as appropriate and (b) some form of time delay
> > (e.g. a diode, resistor, electrolytic and a relay) before the H.T. is
> > applied.
> I agree that a series resistor should be used, but is a time delay really
> necessary? Look at all the sets, both American and European that were
> built with selinum rectifiers instead of vacuum rectifiers, and they seem
> to suffer no ill effects even though their design is otherwise identical
> to sets using vacuum rectifiers.
One common argument used by tube rectifier aficionados is the so-called
cathode stripping effect where high voltage applied to the plate of a tube
before the cathode has warmed up can strip the cathode of emitting
Unfortunately, this effect only occurs at high voltage, typically above 10
kilovolts. It is not a factor in small receiving or transmitting tubes.
If it really were a problem, it would destroy the tube rectifiers which
have plate voltage applied immediately at turn-on.
The only purpose a time-delay on turning on the high voltage can provide is
for the remaining tubes to be warmed up so they draw some current
immediately from the power supply. This slightly reduces the stress on the
high voltage capacitors. It is actually far superior to use properly rated
capacitors and forget about the time delay. Besides most electrolytic
capacitors have surge voltage ratings well above their normal operating
voltages. This is typically 50 volts or more.
Dr. Barry L. Ornitz WA4VZQ email@example.com
What Wally QUOTES above ^^^^^^^ THAT is what I have always heard was the reason "Leo" used an SB Switch.....to protect the caps of the day.
It never did have anything to do with "Cathode Stripping", which, as everyone knows, doe not happen at anywhere near guitar amp B+ numbers.
To My Knowledge...there has never been one, single, case of cathode stripping in a guitar amp.
But after years of misrepresentation, the SB Switch is firmly entrenched as a solution for a problem that never existed.