How hot should a valve get?

[Pow_22]

Im a valve newbie and have read a lot of conflicting stuff online about how much glow is normal from an EL34 valve. The main thing im concerned about is the so called 'Red Plating' where the valve glows where it shouldnt.

I have 6 EL34's in my amp and they all seem to glow pretty full on. Not as bad as some of the pictures ive seen online but also ive seen some that glow less. I will try and get a picture tonight of the amp just on standby then after a bit of playing. In the meantime anybody have pictures of a 'healthy' EL34 at idle or after playing?

I do want to book it in for a service soon and i know this will sort any biasing issues but i need to save up as i think its gonna be quite expensive. The cheapest ive seen 6 x EL34's was about £80 on the HotRox website

[chris_b]

A service and bias shouldn't be more than hour's labour, £30 - £40? Replacing valves should only add the cost of the parts to that.

If the amp sounds good then you probably don't have a problem.

[Pow_22]

Cheers mate. The amp sounds brill but as its an old vintage effort there is no fan on it so its gets fairly hot (which is perfectly fine and understandable) its just the amount of glow that concerns me. Ive read it should be a few pin-prick like dots at the base of the valve that glows where as mine glow much more than that.

[Slipperydick]

If all 6 glow about the same, and it sounds alright, then it probably is.

[Pow_22]

Thanks SD. Maybe im just being an over cautious valve newbie . So basically if it sounds right and the valves are all similar then its ok? Ill still get it booked in for a service soon, either David Pye in Preston or Dave Lunt in Manchester.

Will try and get some pics tonight just to make sure

[Mr. Foxen]

The grey metal part that is the bulk of the insides of an EL34 shouldn't glow, there should be a glowy bit inside that which shines out the top some. Really hot valves do sound good, doesn't mean it isn't about to explode though. Distorting valve amps sound great, often, they aren't supposed to be distorting.

[Slipperydick]

[quote name='Mr. Foxen' post='1307817' date='Jul 18 2011, 01:39 PM']The grey metal part that is the bulk of the insides of an EL34 shouldn't glow, there should be a glowy bit inside that which shines out the top some. Really hot valves do sound good, doesn't mean it isn't about to explode though. Distorting valve amps sound great, often, they aren't supposed to be distorting.[/quote]

[size=2]If its distorted, it dont sound alright - it sounds distorted.

A [i]little bit[/i] of a red hot glow on EL34s, not talking about the valve heaters here but as said - the grey plate, is not uncommon, if the bias is [i]miles out[/i] it will sound crap.[/size]

[Pow_22]

A couple of 'idle' shots after being on stand by for 10-15 mins. It does sound absolutely fine with no major distortion (usual slight valve 'crank' but only when driven REALLY hard) Crappy camera so not sure how easy it is to tell if this is normal or not....

[Doctor J]

A mate called down at the weekend with a THD univalve and we had some fun trying different valves in the thing. I took this image of a KT77 which was visually almost as spectacular as it sounded.

[Pow_22]

Also, for cleaning purposes, can i just remove the power valves, clean inside then replace the tubes without having to re-bias etc (assuming i put each valve back in its original place?

[umph]

[quote name='Pow_22' post='1308292' date='Jul 18 2011, 07:31 PM']Also, for cleaning purposes, can i just remove the power valves, clean inside then replace the tubes without having to re-bias etc (assuming i put each valve back in its original place?[/quote]

Aye you should have no problem doing that.

The valves look fine, the pictures are a bit blury but it doesn't look like the plates are glowing. The only thing that should be glowing is the heater (the thin wire that runs through the middle)

[Pow_22]

D'OH. Took the valves out, gave the amp a good clean aaannnnnndddd......only 5 now glow

EDIT. I swapped the valves around to see if it was the valve or the socket......now all 6 glow again . Does it matter that 2 are no longer in their original position?

Sorry for all the questions. I will learn/research valve amps i promise

Edited July 18, 2011 by Pow_22

[Ancient Mariner]

Is there any possibility that you didn't put them back quite right? An EL34 should have a peg with a key in the middle of the base to ensure correct fitting, but these can get snapped off sometimes and allow the valve to be plugged in 'wrong'. Another possibility is that a heater wire has just come off that valve socket, although that's a not very common.

[Slipperydick]

The heaters do look a bit bright, but it could be the photographs. It is on the correct mains tapping (ie set for the corect mains voltage)isnt it ?

Oh yeah, and if you pull em out, grip them by the bakelite bases, not by the glass, otherwise you might pull the wires that connect the pins.

[Pow_22]

Ive checked closely and it is down to the crappy camera. It is just the inside of the valves glowing and not the plates. The is a hole in the middle inside the valve that is why the top is glowing. It does seem to be purely the inside wire so im much happier now. Thanks for everyones help on this. Will be phoning the tech tommorow to get it booked in for a services and once over.

I assume the two valves that i have switched places dont matter? Ive had it on standby for 30 mins since swappin and they all seem fine now

[Mr. Foxen]

[quote name='Slipperydick' post='1307986' date='Jul 18 2011, 03:41 PM'][size=2]If its distorted, it dont sound alright - it sounds distorted.[/quote]

I think you might need to listen to some more records.

[4 Strings]

[quote name='Pow_22' post='1308418' date='Jul 18 2011, 08:53 PM']Ive checked closely and it is down to the crappy camera. It is just the inside of the valves glowing and not the plates. The is a hole in the middle inside the valve that is why the top is glowing. It does seem to be purely the inside wire so im much happier now. Thanks for everyones help on this. Will be phoning the tech tommorow to get it booked in for a services and once over.

I assume the two valves that i have switched places dont matter? Ive had it on standby for 30 mins since swappin and they all seem fine now[/quote]


As far as I understand bias is applied to each valve individually and so they should go back in their original sockets - anyone know more than me?

Valves are suppose to get hot, if they don't the heater element in them is not adequate.

[umph]

[quote name='4 Strings' post='1308593' date='Jul 18 2011, 11:08 PM']As far as I understand bias is applied to each valve individually and so they should go back in their original sockets - anyone know more than me?

Valves are suppose to get hot, if they don't the heater element in them is not adequate.[/quote]

in the soundcities theres a bias pot for each side, so aslong as it goes back with the same trio it'll be fine