Running up tube heads

[phmosele]

Hi
My son put his tube guitar amp into storage and someone has told him he should power it up now and again...but they didn't know particularly why.

I can't see that it makes any difference, so I thought I would ask you guys.

As he has no speaker to hook up to it, should he leave it in Standby mode please?
Thanks
Phil

 

[doozerdave]

The only reason I can think of would be to maintain the capacitors, but this is a topic of great debate. If you have no speaker then definitely leave it in standby mode, but depending on the amp circuit this may not power all of the high voltage capacitors, so it would be of little use...

 

[JMFahey]

Yes, once a year or so.
Or if it's stored in a very damp place, turning it on now and then will keep mold away.
Nothing too critical anyway.

 

[MarcelvdG]

If you don't use it for a very long time and then power it up, the electrolytic capacitors in the power supply may explode and/or ripple filter resistors may burn. That's quite common in old tube radio's that haven't been used since 1950 and suddenly get powered up. A workaround is to very slowly increase the voltage. That gives the isolation of the electrolytic capacitors time to get back in shape.

 

[doozerdave]

That's what I was driving at. If the caps are unpowered for a long time they need to be reformed in order to function properly. This is a point of debate in another thread right now...

 

[artosalo]

Hi
My son put his tube guitar amp into storage and someone has told him he should power it up now and again...but they didn't know particularly why...


Phil

If it will be stored more than 10 years at one sitting, then maybe...

 

[Robert Kesh]

carbon comp resistors suck up moisture. if it has them, warm them up to dry them out

 

[cyclecamper]

My solid state amps went 8 years without being used, and were fine. But you really should power up the filter caps at least once a year and preferably more often.

 

[cyclecamper]

I see a lot of old amps that look like crud from mold and rust. Too bad he has to store it.

 

[cyclecamper]

In standby it will form up the first set of caps, but not the ones lower down the filter ladder. It would definitely be best to plug in something and turn it all the way on. Also, on a very few tube guitar amps with solid-state rectifiers the standby switch is really a mute, and those require a speaker plugged in.

 

[phmosele]

Hi
All good stuff, thanks.
It won't be 10 years between power-ups, but it could be a while before he uses it again in anger. It's in a house in California, not a storage locker (which I might have implied) so I don't think damp will be a problem, but I will mention it.

Although he doesn't have his Marshall cab with him, I'll just hook up an old 8" 8-Ohm speaker to a 1/4-inch plug and send it to him so he can at least shut off the standby and have a load on the output. I know most SS amps have open circuit protection, but I wasn't sure about tube heads.
Thanks
Phil

 

[phmosele]

I'll send him a li'l old 8-Ohm 6.5-inch so heas something to plug in and turn off the standby
Thanks
Phil

 

[JRGuitarGuy]

very slowly induce lower voltages/current/power is a great idea variac is a great tool

 

[phmosele]

Hi
In principle a Variac is fine, but it's only been three months since it was being used regularly, so I don't think there is much worry turning it on.
Phil

 

[JRGuitarGuy]

probably not with only 3 months

 

[JRGuitarGuy]

I thought like he was talking about years lol

 

[ivan H]

Hi, yes it definitely needs a speaker or suitable dummy load hooked to the output to power it up, (not in standby). With regard to the filter caps, on another guitar amp forum they give the following instructions for forming new, or reforming electrolytics in amps. Disconnect the rectifier from the filters & hook it back up with a 100k, 2 watt resistor between the rectifier & filter caps, then power it up, periodically checking the voltage drop across the resistor. When the voltage drop across it is below a few volts the caps are formed. Drain the caps properly & remove the resistor, hook back up the way it was. This is current limiting the caps while forming them, whereas using a variac is only voltage limiting. Hope this helps. Cheers

 

[phmosele]

Ummmm...no. I am not putting my hands in a tube head for any reason. No sir. Besides, it's 3000 miles away, and I only really wanted to know about firing it up every few months. I'll be surprised if it's more than a year before he is back in a band again.
Thanks
Phil