100w valve head cutting out

[pdf64]

It's looks like there's a chip out of it, but it can't have broken the vacuum, as the gettering still looks to be good (the silver grey flashing would have turned white).
So the functionality of the tube hasn't been affected by it.
Those retainers may be too much!

[Jazz P Bass]

If that tube lost it's vacuum, it would be white.

[Chuck H]

Yup. Or, if the tube is very old, the flashing can seem to just evaporate like the tube on the right appearing to have no flashing at all. Tubes are usually underperforming noticeably before all the flashing is gone though.

[RionZion]

Well it seems at least my tubes are serviceable... have a gig sunday so we'll see! Spare amp will be on standby... Opened my cab today, made an interesting discovery - very poor soldering on the input jack sockets, just dull lumps holding the wires on rather than actual bonded joints. Bought the cab originally 2nd hand off ebay... professionally made, very decent bit of cabinet-work, and the speakers are celestion vintage 30s. Shame about the soldering... Have re-soldered the joints now so that should help matters! Maybe, just maybe, that was my problem in the first place?? although i'm amazed i've gotten away with it for four years!!!
Anyway, this leads me on to a question about speaker/amp matching... currently the speakers are individually wired to two separate jack sockets and i use the two output jacks of my amp to drive these, speakers are 16 ohm and i have the amp set to 16 ohm although it can be switched to 8 ohm if desired. the v30s are rated 60w each. does this mean i'm effectively running 100w into 60w... or 120w? i cant seem to get my head around whether the speakers would be considered to be in parallel or not?!
the other option would be to wire them in series and change the amp setting to 8 ohm, which would be 100w into 120w if i'm not mistaken...
i know with hi-fi and sound reinforcement it's generally recommended to run slightly larger amps into smaller speakers to "drive" the speakers but i dont know if this applies to guitar amps? bearing in mind i run the master volume at 4 max for most gig stuations... occasionally crank it to 5 if i want a bit of madness toward the end of a set but thats the absolute limit!
I probably should have checked all this out 4 years ago when i first moved away from combo's (where it's all taken care of!) but to be honest was far too keen to get on and play... and everything seemed to work fine so off i went!
PS also may seem a dumb question but could amp/cab configuration have any effect on valve life or performance?

[g1]

If you are using both output jacks from the amp, each into a 16ohm speaker, then you should set the amp at 8ohms.
As far as the amp is concerned, you are running into an 8ohm load.
The full power of the amp will be divided between the 2 speakers, so 60W each.

[RionZion]

If you are using both output jacks from the amp, each into a 16ohm speaker, then you should set the amp at 8ohms.
As far as the amp is concerned, you are running into an 8ohm load.
The full power of the amp will be divided between the 2 speakers, so 60W each.

well you learn something new every day, thanks g1 !

[Chuck H]

If you are using both output jacks from the amp, each into a 16ohm speaker, then you should set the amp at 8ohms.
As far as the amp is concerned, you are running into an 8ohm load.
The full power of the amp will be divided between the 2 speakers, so 60W each.

We can bet the cab isn't wired for a series 32 ohm option So I'll bank on g1's assessment. One jack is for 8 ohms with the two speakers in parallel and using both is a 16 ohm speaker on each jack, switched when the right jack is used (Marshall did this with 4x12 cabs) and the right jack by itself would be one 16 ohm speaker. OR... The speakers are wired in parallel and so are the jacks. So it's 8 ohms from either jack. It would be best to get a firm grip on how the cabinet is wired. The way you are plugged in now raises another issue. Some amps have the output jacks wired to taps on the output transformer secondary to sort of auto correct for user unawareness So if you plug into one jack it's at the switch set impedance requirement but if you plug into both that requirement gets halved. This is at least a little important. You should get information about both the cabinet and the amp to be sure you are running at the desired impedance. The way you are plugging in now makes it a crap shoot depending on every variable I mentioned. Whether that is the spec'd impedance or not it would be good to know if it's what you want. I say that because a lot of guys like running their 100W Marshalls into a 16 ohm impedance when set for 8 ohms at the amp. It sounds and feels a little different. Since Marshalls run a fairly low OT primary impedance this is pretty safe as it doubles the primary impedance seen by the tubes and is only a little higher than what might be spec'd for a different sort of amp. So it's perfectly safe. I can't say about your amp.

[g1]

currently the speakers are individually wired to two separate jack sockets and i use the two output jacks of my amp to drive these, speakers are 16 ohm and i have the amp set to 16 ohm although it can be switched to 8 ohm if desired.

[RionZion]

oh shit.. after a bit of reading up, i'm starting to get worried.... i've been under-loading the amp which apparently does bad things to the transformers? i did notice a kind of resin substance on once of the transformers, but thought it was just something left over from manufacture. Not sure if its the power or output transformer at the moment... will have to look into this more but maybe i;ve fried one of the transformers? amp still works fine as far as i can tell, maybe only a problem at high temperature levels, which hopefully wont happen again if i have the amp head matched correctly to the cab.
Doh!

[Chuck H]

oh shit.. after a bit of reading up, i'm starting to get worried.... i've been under-loading the amp which apparently does bad things to the transformers? i did notice a kind of resin substance on once of the transformers, but thought it was just something left over from manufacture. Not sure if its the power or output transformer at the moment... will have to look into this more but maybe i;ve fried one of the transformers? amp still works fine as far as i can tell, maybe only a problem at high temperature levels, which hopefully wont happen again if i have the amp head matched correctly to the cab.
Doh!

Woah! Settle down Hoss! The worst mismatch in any scenario would be 100% low. That is, say, an 8 ohm load into a 16 ohm requirement. Not a big deal. In fact, Fender made all those classic amps with shorting jacks on the outputs just so the amp would see a dead short in the event that someone failed to plug in a speaker. They survive A LOT better than Marshalls where there is no shorting jack and a failure to plug in a speaker results in an open load. Your possibility of a lower than ideal load would actually be a little harder on the tubes and a little easier on the transformers. So it's all good. I can't say about your "goop" but it's almost certainly caused by something other than your speaker load. If the amp is working fine I'd say there is no chance that you've damaged the transformers by running a 16 ohm set secondary into an 8 ohm load. Take a deep breath.

[RionZion]

Phew... thanks Chuck for setting my mind at rest - brief attack of late night paranoia brought on by scare stories on the internet!

[RionZion]

Hi all, thought i'd resurrect this thread with an update...

Been using the amp average 2 gigs a week now past few months and no problems so original issue must have been to do with signal path. I fitted a 5751 at the input stage and am now using the correct 8ohm output for my speaker cab. This has improved my tone somewhat, seems clearer in the top end although i still cant seem to achieve a truly "clean" tone, there is a distorted sound "behind" the main signal if you know what i mean, and this can be heard on its own when the amp volume is turned all the way down. Also, the humming noise when i first turn on the amp has returned of late, the remedy for this seems to be a smart tap on the top of the head! The other night i forgot to do this before a gig and noticed that my sound was more distorted than it should have been ( i play with a mix of clean and gain channels so always a certain amount of overdrive in the sound - this is a fairly unique feature of the wharfedale/albion TCT100 i'm using).

So i'm back to wondering about the power tubes... i have a new set of Ruby EL34BHT's to fit, so i might as well give them a try. Am still waiting to hear back from Albion amps about bias procedure, but pdf64's post above seems a reasonable way to proceed - 60mv between pins, although i will check the readings for the existing tubes beforehand. Ruby tubes have this to say: "We have had a great response to our new RUBY EL34BHT tube. Many engineers have asked about what kind of power can be expected from the EL34BHT. In our tests, we used 600 V on the plates, 540 V on G2 and a bias setting of –54V. The tubes idled at 25ma each. The power output from a pair of EL34BHT tubes using these voltages was 70 watts at clipping." - which is a bit confusing to be honest!

My main question however is about burning-in... will i need to do this or are the tubes already burnt in? if i do need to burn them in, how long for?? does anyone have a fool-proof procedure for this???

Cheers, Rion