tube saving power up tweaks?

[daz]

What are some of your options to save tube life when you power up a lot? It a 50 watt EL34 amp with SS rectifier. I often play it for minutes at a time many times a day, so now with my fav tube going the way of the dinosaur I'm wondering what options i have to create a soft power up to my SED's. I really don't want any SS circuits as i've seen mentioned before, so if you guys know of some simpler way I'd like to hear it. Thanks.

[nickb]

What are some of your options to save tube life when you power up a lot? It a 50 watt EL34 amp with SS rectifier. I often play it for minutes at a time many times a day, so now with my fav tube going the way of the dinosaur I'm wondering what options i have to create a soft power up to my SED's. I really don't want any SS circuits as i've seen mentioned before, so if you guys know of some simpler way I'd like to hear it. Thanks.

The cheapest thing that springs to mind is a negative temp coef thermistor designed for inrush limiting in series with the heater supply. You'l have to do some checking to pick the right one but this may well be in the ballpark SL32 0R230 Ametherm | Mouser

[daz]

The cheapest thing that springs to mind is a positive temp coef thermistor designed for inrush limiting in series with the heater supply. You'l have to do some checking to pick the right one but this may well be in the ballpark SL32 0R230 Ametherm | Mouser

Thanks. But i'm not sure what specs to use or how to determine. But assuming i did, could this have any tonal effects when playing?

[trobbins]

Why did you think that there was a way to 'save' the tube? Do you mean to try and minimise the wear-out of the tube over a long time? Or are you concerned about the tube being more stressed by your mode of using the amp, compared to just leaving it on all day, or ?

[nickb]

If chosen properly it would have no effect on tone. In order to select one (if a suitable one even exists) I would need to know what the heater load is (or what amp model it is).

Also, the basic premise is that it's the thermal stress of the heaters that contributes to the ultimate demise. I think that would apply primarily to preamp and lightly used power tubes. It's certainly up for debate. Anyway, that wasn't the point of your original post so best to avoid digression.

How about you consider a small practice amp or solid state instead?

[daz]

How about you consider a small practice amp or solid state instead?

There would be no point since i don't gig. If i was to do that there would be no reason for my tube amp. The entire reason I have it is for the tone and feel it has.

[Enzo]

For a thermistor, if you don't know how to spec on for yourself, just look at something similar that already uses one. For example the Fender Hot Rod DeVille or HR Deluxe. 50 watt amp. Uses a C60-11 thermistor. 10 ohm 5 amp, Fender part 028503 if you can;t find it at Mouser.


Having said that, just how much tube life do you think you are losing as it is? Not much, I;d say.

[daz]

Having said that, just how much tube life do you think you are losing as it is? Not much, I;d say.

I don't know Enzo. You'd know better than me, but like i said i generally play for 1-10 minutes at a time and sometimes turn the amp on and off 10 times a day. Consider than and also the fact the SED el34's are going out of production and i designed this thing around those and while other tubes can sound good, they just don't give me the perfection i find in those. Possibly because it was designed around them, maybe i just like them, maybe a bit of both. But whatever it is i really don't want to wear these out faster, and if this is truly a non issue then i'm confused because i have seen so much said about it that would seem to contradict that.

[Enzo]

It is like anything else, you are going to find different opinions. Of course I think my own opinions are the correct ones, as do we all. I mean we all think our own ones are right.

There are some people who decide that a standby switch is absolutely necessary on everything and prooceed to add them to a Champ. They offer arguments about cathode stripping or cathode poisoning and whatever. But in a Champ? That is just silly. The problem is context. Yes, cathode stripping is a real thing. Does it happen at 300v in a EL84? No.

But helpful or not, a standby switch will reduce any turn on stress to the tube. YOu have a standby? Is turning it off not enough of a stress reliever?

I think the thing to do in this project is to identify the threats to the amp and address them. I'm not poo-pooing your plan, if you want to protect the tubes, then identify against what. What failure mode or modes do you think will occur? Hell, you might want to worry about wearing out your switch. But what will happen to the tubes if left unprotected? My mom used to obsess over turning light bulbs off and on. Said that would burn them out faster. There was always a story about someone who had the same bulb burning on the porch for 20 years. But the heater burning out on a EL34? No way. I can count on my fingers the number of tubes that have had a burnt out (open) heater in my last 25 years on the bench.

And be wary of rationalization. It is common and simple to see something in a circuit and then rationalize its purpose. "This amp has inrush limiting...that must be to protect the tubes." When the inrush might in fact be protecting the things around the tubes. For instance an inrush limiter will reduce nuisance fuse blows, and let them use a smaller fuse than they might otherwise. It will reduce the stress to rectifiers trying to service empty filter caps. That sort of thing.

SO if you want one, I'd just grab the sort Fender used in their similar sized amp, and use that. Peavey also used the C60 in some of their amps.

[daz]

I'll take your word. If it weren't for the winged C tubes being dropped i would never have even asked this. And yes, i have a standby on it.

It is like anything else, you are going to find different opinions. Of course I think my own opinions are the correct ones, as do we all. I mean we all think our own ones are right.

There are some people who decide that a standby switch is absolutely necessary on everything and prooceed to add them to a Champ. They offer arguments about cathode stripping or cathode poisoning and whatever. But in a Champ? That is just silly. The problem is context. Yes, cathode stripping is a real thing. Does it happen at 300v in a EL84? No.

But helpful or not, a standby switch will reduce any turn on stress to the tube. YOu have a standby? Is turning it off not enough of a stress reliever?

I think the thing to do in this project is to identify the threats to the amp and address them. I'm not poo-pooing your plan, if you want to protect the tubes, then identify against what. What failure mode or modes do you think will occur? Hell, you might want to worry about wearing out your switch. But what will happen to the tubes if left unprotected? My mom used to obsess over turning light bulbs off and on. Said that would burn them out faster. There was always a story about someone who had the same bulb burning on the porch for 20 years. But the heater burning out on a EL34? No way. I can count on my fingers the number of tubes that have had a burnt out (open) heater in my last 25 years on the bench.

And be wary of rationalization. It is common and simple to see something in a circuit and then rationalize its purpose. "This amp has inrush limiting...that must be to protect the tubes." When the inrush might in fact be protecting the things around the tubes. For instance an inrush limiter will reduce nuisance fuse blows, and let them use a smaller fuse than they might otherwise. It will reduce the stress to rectifiers trying to service empty filter caps. That sort of thing.

SO if you want one, I'd just grab the sort Fender used in their similar sized amp, and use that. Peavey also used the C60 in some of their amps.

[Enzo]

Daz, don't just accept it from me, do the exercise - identify what failure modes you are uncomfortable about. You may have a point I am overlooking.


To me, probably the biggest threat to those power tubes would be a bias failure, or shorted coupling cap overcoming bias, and the excess tube current melting a screen grid, and the tube is destroyed.

[daz]

Well Enzo, you know worlds more about electronics than I and you seem to think theres no real worry about tube wear so I tend to trust you a heck of a lot more than myself. All i have to go on is what i've read, and there is conflicting info out there. To clarify, i'm simply worried that when i flip the standby on the inrush is wearing to the tubes. But again, you'd know more than I about how likely that is so i'd rather take your word.

[soundmasterg]

Well Enzo, you know worlds more about electronics than I and you seem to think theres no real worry about tube wear so I tend to trust you a heck of a lot more than myself. All i have to go on is what i've read, and there is conflicting info out there. To clarify, i'm simply worried that when i flip the standby on the inrush is wearing to the tubes. But again, you'd know more than I about how likely that is so i'd rather take your word.

With large tubes like what might be used in a transmitter, the tubes can be bothered by sudden application of voltage before the tube is warmed up....this is known as cathode stripping.....but with receiving tubes (the type of tubes that we use in our guitar amps) it is not a concern. It says so right in the RCA tube manual. Want more examples?? Take a look at the Fender 5E3 Tweed Deluxe....there is no standby switch on that amp and there never has been. My 1956 Fender Tweed Deluxe still has the original tubes in it and it works just fine. (I bought it from the original owner who told me he had never changed any tubes in the amp.) Another example would be the Silvertone 1484 and 1485...they do have a standby switch but all it does is to short the signal on the power tube grids together. The B+ voltage is on the tubes as soon as the amp is turned on.

Standby is more of a performance thing....when you are stage and you need to quiet the amp but you don't want to shut it off....a switch is easier than rolling the volume down on the amp or your guitar....and standbys can be applied in many ways besides interrupting the B+ too as I noted above with the Silvertone example. In fact a mute condition is all you need so this can be done and has been done in multiple ways, but there is no need to worry about harming the tubes with the sudden application of voltage when the amp is turned on.

Greg

[frus]

There was always a story about someone who had the same bulb burning on the porch for 20 years.

well...

Mythbusters visit the Livermore Centennial Light Bulb! - YouTube