Worn Tubes

[Jimbo]

What signs should I look for to indicate that a valve is either on its way out or should be replaced in a valve amp.

[Magna Audio]

Could be

1. Crackles or pops or humming
2. Odd illuminations indicating the heater elements are on the way out or the heater element fails - no heat, no boiling off of electrons, no sound.
3. Output tube developed an internal short, can be that it burns out the screen grid resistor
4. Losing gain
5. Hum level increasing. Can be slow so creeps up on you
6. Loss of or odd tone

Despite all of these they are generally pretty reliable and picking up and fixing issues, keeping pins clean, bias adjusted helps prevent melt downs.
New tubes are usually the cure. I've had input stage tubes go and also 1 power tube got noisy, so 4 new power tubes needed.
On a phono stage I had loss of SQ but that was just the pins needing cleaning. I now do that job about once a year and never had the problem again.

What signs should I look for to indicate that a valve is either on its way out or should be replaced in a valve amp.

[Jimbo]

Could be

1. Crackles or pops or humming
2. Odd illuminations indicating the heater elements are on the way out or the heater element fails - no heat, no boiling off of electrons, no sound.
3. Output tube developed an internal short, can be that it burns out the screen grid resistor
4. Losing gain
5. Hum level increasing. Can be slow so creeps up on you
6. Loss of or odd tone

Despite all of these they are generally pretty reliable and picking up and fixing issues, keeping pins clean, bias adjusted helps prevent melt downs.
New tubes are usually the cure. I've had input stage tubes go and also 1 power tube got noisy, so 4 new power tubes needed.
On a phono stage I had loss of SQ but that was just the pins needing cleaning. I now do that job about once a year and never had the problem again.

Hi Steve, thanks very much for that info. What do you clean your tube pins with?