Standby or Not

[gearhead]

Interesting thread on the use and effects of standby (or not):

http://www.thegearpage.net/board/showth ... p?t=594870

Anyone have different exprerience on cathode stripping wrt Billm's experience/observations?

Will still use standby switch, cause I'm stupid enough to connect an amp with no load. Always reminds me to check.

[Bob-I]

Interesting thread on the use and effects of standby (or not):

http://www.thegearpage.net/board/showth ... p?t=594870

Anyone have different exprerience on cathode stripping wrt Billm's experience/observations?

Will still use standby switch, cause I'm stupid enough to connect an amp with no load. Always reminds me to check.

In the 70's a friend of mine played bass in a club band using a SF Bassman. He'd go through power tubes like candy. One day I watched him power it up, he hit both switches at the same time. I suggested he use the standby as it's supposted to be used, power first, wait 2 minutes, standby on. His power tubes never failed again.

Cathode stripping? I don't know, I only knew what the manual said.

[Structo]

I like them.

It's just old school electronics for me.
I guess in an indirectly heated cathode rectifier they are not needed but I still like the idea of getting that cathode hot before hitting it with high voltage.

[sliberty]

I've always thought that the conventional wisdom is that if your amp has a SS rectifier, you really should use the standby. But if the amp has a tube rectifier, since they take some time to fire up anyway, a standby is less critical.

Steve

[Structo]

But that depends on what type of tube rectifier it is.

With directly heated cathodes (where the heater is the cathode) you will get high voltage rather quickly where as an indirectly heated cathode will take longer and will delay the high voltage to the tubes until it has warmed up sufficiently.

[sliberty]

So which is which?

[Structo]

Well I would say that a directly heated cathode rectifier amp would benefit from a standby switch.

[Darkbluemurder]

So which is which?

GZ34, 5Y3 = indirectly heated, slow turn-on, standby switch optional
5U4, 5U4B = directly heated, fast turn-on, standby switch beneficial

EZ81?

[Phil_S]

5Y3 is directly heated.

[ampdan]

5Y3 is directly heated.

Yep. And yet the tweed Deluxe amps never had a standby..

[tweedeluxe]

Yep. And yet the tweed Deluxe amps never had a standby..

I use the 5Y3WGT/6106 in 5Y3-rectified Fenders with no standby switch. It is indirectly heated with a sloooow warm-up period.

[benoit]

Hmm... I have an old fender combo (Bassman 20, runs a pair of 6v6s in fixed bias) that has no standby. Should I put one in?

[Chappy]

But that depends on what type of tube rectifier it is.

With directly heated cathodes (where the heater is the cathode) you will get high voltage rather quickly where as an indirectly heated cathode will take longer and will delay the high voltage to the tubes until it has warmed up sufficiently.

I have an old Bogen Challenger PA amp that I converted into a guitar amp. It did not have a standby switch and it used a 5U4 rectifier and 6LGG tubes in the output (6L6G's are rated at 400V max). I put my digital voltmeter on it to check the voltages. When I flipped it on the B+ shot up to 530V. OUCH. After about 10sec the rectifier tube would warm up and the voltage would settle back down to about 420V.

The amp now has a standby switch to warm up the filaments prior to putting B+ on my power tubes. Regardless of cathode stripping, I don't think that it is a great idea to put 530V on the plates of my vintage Tungsol 5881's every time I start up the amp.

Chappy

[aclempoppi]

Yep the 5U4 is a directly heated cathode design and would present an initial voltage surge in the B+. But it will also provide a higher resistance causing a larger voltage drop, once it's warmed up. A standby switch would definitely be a good idea. The cathode in the indirectly heated design would afford a little time for tube heater warmup. Apparently, some tubes need more time to form the electron cloud around the cathode. This is usually stated on the tube specs. Some military tubes state 0 seconds for warm up. ART

[jjman]

I read a post one time requesting that anyone post a link to any documentation that any guitar amp has ever experienced any cathode stripping from not having a standby. He mentioned that the voltages probably are not high enough. I haven't seen such a link yet.

Still, I use my standby in my amps that have it.