DRRI power valves: 5-6 years a decent innings?

noisepolluter

Should qualify that amp was used pretty much daily but at flat-friendly volume, and probably a couple of dozen times at gig volume. Valves were EHX 6v6GTs.  
V7 went pop today - to be fair, noise leveks and finally crackles had been increasing for a while. 
I suppose I've done well out of them?

ICBM

Valves aren't made as well as they used to be… that's not a bad life expectancy for modern ones.

penguinpaul

Sounds good to me. Power tubes in my PR (68 not the 65 RI) had to be changed after 1 year. That was the original groove tubes, one went mechanically rattly.
Oddly I've had better luck with power valves than preamp. I often find 12AX7s going noisy in my amp. Trouble is, I use that as an excuse to change brand/model, and end up on tube changing spiral!

noisepolluter

Sounds like I should plan to replace every couple of years in any case.

Hope it's not taken anything else out along with it - there was a flash and a horrible noise before I switched off, but no smoke or smell and the fuse is intact.

It's a bit unsettling, all the same! I did wonder if it's worth getting a bias probe and multimeter at some point and learning how to bias it myself, but if it's (hopefully) only every couple of years it's probably not worth it, plus it's probably best to have everything checked over after any electrical trauma!

ICBM

If you want to confirm there's no other damage, put the surviving valve in the socket the dead one came out of, and try the amp. If it works - it will be a bit lower volume, and oddly distorted if you turn it up beyond quiet - then the amp should be fine. If it doesn't, the dead valve has taken out the screen resistor which can sometimes happen. If the valve starts to glow very hot, the grid stopper resistor is blown - but that's very unusual.

JD50

I've never had a valve blow on me.... I do have an awful microphonic noise coming out of my amp as i type.... Presume its a pre amp valve.

MattFGBI

Valves can last 10 minutes or 10 years. Always carry spares!

JD50

A friend of mine has an old sound city head which he has been using regularly since the early 90's, still has the same valves.

ICBM

JD50 said:

A friend of mine has an old sound city head which he has been using regularly since the early 90's, still has the same valves.

I have a 1964 Centurion amp which still has its original valves . Given that it's clearly been used quite a lot and the circuit runs the power valve quite hot, that may be surprising… but they're Mullards.

Old-production valves like this can literally last decades, if they're run within the design spec. An old Sound City may well have old-production RFT valves, or similar - even if they were replaced in the early 90s, it's quite likely they will be the same, modern-production valves were just coming through around then but a lot of suppliers had old stock. 'Zaerex' was a very common brand for example - old-stock RFT EL34s from East Germany.

Modern valves tend to last nowhere near as long, they wear out quicker even if they don't fail.

james

MattFGBI said:

Valves can last 10 minutes or 10 years. Always carry spares!

What valves do you carry spares for? A full set, or just specific ones?

I also have a DRRI, and we are doing another short tour later in the year and I'd like to be prepared.

ICBM

james said:

MattFGBI said:

Valves can last 10 minutes or 10 years. Always carry spares!

What valves do you carry spares for? A full set, or just specific ones?

I also have a DRRI, and we are doing another short tour later in the year and I'd like to be prepared.

A set of power valves, a rectifier (a solid-state plug-in is ideal) if the amp has a valve one, and one each of the preamp valve types. And the correct fuses - this is important since a power valve or rectifier failure will very often blow the fuse - both types if the amp has separate mains and HT fuses.

So for a DR - 2x 6V6, GZ34 or solid-state rectifier, 12AX7, 12AT7. The DR doesn't have a separate HT fuse so just F1A fuses - you don't need many, one or two is actually enough.

If the fuse blows, replace the power valves and the rectifier, and try again. If it blows again, give up - it's not a valve problem.

Preamp valve failures don't blow fuses, they either stop working or go noisy or microphonic, and only one will be faulty - so you only need to swap one valve at a time for the spare to find it.

If all this sounds like too much trouble, take a spare amp or some other backup solution.

ecc83

I know of a couple of 'Wimbledon' PA amps that sat in a cupboard in WMCs for over three decades and ran twice a week for bingo and then party bashes at Christmas time plus the odd wedding/21st.

GEC KT66, last forever.

My mate's TV shop have the contract with the local gen hospital to do the yearly service on the 50W Pamphonic amps that drove the headphone system. All the valves were replaced including 4X KT66 so I had a never ending supply of used but perfectly good valves! The fact that the amps ran 24/7 did not seem to faze them.

Dave.

Danny1969

I have a friend with a Boogie Mk1V from around 92 that's still on the same valves, I only recently changed the valves in the JMP1 pre amp I use which were 20 odd years old but they are only 12AX7 rather than power valves 

ICBM

Danny1969 said:

I have a friend with a Boogie Mk1V from around 92 that's still on the same valves

That quite likely has the special-order Mesa STR415 Philips/Sylvania 6L6GCs in it - probably the best 6L6s ever made, basically the same as the 7581A military-grade equivalent. Mesa bought a lot and were still supplying them until about 2000 on request I think, although they stopped using them in new amps earlier than that.

richardhomer

ICBM said:

Danny1969 said:

I have a friend with a Boogie Mk1V from around 92 that's still on the same valves

That quite likely has the special-order Mesa STR415 Philips/Sylvania 6L6GCs in it - probably the best 6L6s ever made, basically the same as the 7581A military-grade equivalent. Mesa bought a lot and were still supplying them until about 2000 on request I think, although they stopped using them in new amps earlier than that.

My MkIII had those - once I replaced them, it never recaptured the magic, which is one of the reasons I no longer own it....

ICBM

Sounds familiar. I fitted a NOS (not Mesa branded) pair to my DC-5, and it just about doubled in perceived power - a huge increase in depth, clarity and presence. One eventually went rattly after about seven years use, and the replacement standard 6L6s never sounded as good, so I don't have it any more either.

thermionic

I should probably consider changing the EL84s in my 1996 AC15 at some point. Home use only though, and they are JAN Phillips.

ICBM

thermionic said:

I should probably consider changing the EL84s in my 1996 AC15 at some point. Home use only though, and they are JAN Phillips.

They're probably fine then .

noisepolluter

Wonder if it's worth getting some NOS  6v6's then. Looks like Phillips and GE ones can be had for £50-60 a pair... maybe next time round...

MartinB

Fender Deluxes and Princeton Reverbs run their 6v6s at some pretty high voltages.  JJ 6v6s seem to have a reputation for coping with this OK, and the datasheet rates them for up to 500V plate and 450V screen voltage.  In my own Princeton copy I've had an EH 6v6 fail dramatically with visible arcing inside, and haven't had a problem running a set of JJ for several years, though maybe that's a small sample from which to make any generalisation about them.