So, this is what Tube Maintenance is all about

Weirdcuba · Jan 23, 2015

It's happened to me a second time. First, I had a tube go in my two month old C2500 (well chronicled: http://www.audiokarma.org/forums/showthread.php?t=617993&highlight=blew). Then, a couple of days ago, I sat down for my evening fix and I heard a loud pop (not the BOOM from the 2500) from my left 2301, then it was dead and the red sentry light was blinking on and off. Thank goodness for the Sentry Monitor - as it worked. I had a blown tube in one of my ~3 month old 2301s!!

Got the dealer over here with some spares and all is well now, but it still leaves me a little freaky that I'm going to blow another one and have something worse happen. There's been no extended loud listening sessions or anything of the sort - these things live the king's life as far as stereo components go, so I'm hopeful it's just bum luck with new tubes rather than anything else.

All that being said, the sound is just absolutely amazing and if I have to fiddle with tubes from here on out, I'm good with that. In fact, this has only accelerated my plan to roll the tubes in both the 2500 and the 2301s - really to have a set of back up tubes for these little unannounced surprises.

ahhh, the tubiness of it all.

Weirdcuba

twiiii · Jan 23, 2015

Now you know why I am all SS. I never had tubes blow up in my 275's, 240's and MC60's. But it seemed like more often than not something would go out of spec and I'd have to hall them down to either the radio station or the shop and put them on the HP test equipment and replace a tube here or there to bring them back to correct. That can be a hassle. And I bet 99% of you with tube gear don't have access to test gear you can use for free or get your tubes for distributor cost as I did in the 60's and early 70's. I got tired of the tube issue and went solid state. And over the next 30 years I never had a Mac go out of spec. That being said my Crowns seemed to need a tune-up every 10 years like clock-work. I'm back to being all Mac when I upgraded 5 years ago, make it six, and am very happy. The only severe issues I have had was the tube in the MPI-4 and the touch buttons on the MR-80. But I knew about the issue when I purchased the MR-80. I had a MVP861 have the hick-ups, but Frank Gow helped me out with that issue. Since then all has been well and emotionally enjoyable with out tube worries.

hunter00 · Jan 23, 2015

Tube worry's...really.Ive never worried about my tube amps,general maintenance/set bias/reset and forget,If your buying quality n.o.s tele,mullard.GE ,RCA tubes and running matched pairs very seldom have I ever even had redplateing issues..
All my vintage amps are recapped right from purchase tho
I wont be going back to SS in this lifetime

hunter

sKiZo · Jan 23, 2015

Tubes come, and yes, they glow, and then they blow ...

Seems a bit strange though to have both new and old going so close together. I'd invest in a Kill-A-Watt and check your AC line levels coming into the house. My "normal" is 124vac+ here, and that's HARD on tube gear. Built me a lil bucker to drop it down to around 117vac, which is more like the good old daze when tubes were king ...

x3workshop · Jan 23, 2015

sKiZo said:
Tubes come, and yes, they glow, and then they blow ...

Seems a bit strange though to have both new and old going so close together. I'd invest in a Kill-A-Watt and check your AC line levels coming into the house. My "normal" is 124vac+ here, and that's HARD on tube gear. Built me a lil bucker to drop it down to around 117vac, which is more like the good old daze when tubes were king ...

Mine hovers at 124v+ as well. Would love to know what you have to drop it down..

sKiZo · Jan 23, 2015

x3workshop said:
Mine hovers at 124v+ as well. Would love to know what you have to drop it down..

Built me a lil bucker using an old power strip ... nice shortcut, as those already have a switch and breaker built in.

That was actually a good day. Pretty straight forward ... one leg of the line is straight through, and the other (and ground) is tied in series through the secondary winding. The drop/gain is determined by the value of the secondary. Just gotta watch the amp rating - this one can handle 6 amps, and my tube amp tops out at 5 ... it barely warms up after a hard day of relaxing ...

I used a 6.3v heavy duty transformer from the parts pin. That met my target for a 114-120vac range where tubes tend to be happier. The lowest I've ever seen mine go is 115vac out of the bucker.

Here's a diagram that shows the hookup using a 30v secondary transformer.

About a zillion more ... just google "bucker transformer diagram" ...

gadget73 · Jan 23, 2015

Just make sure you check voltages first. If the secondary leads are reversed, you will get a boost transformer instead. There isn't a lot of way to tell, basically its a trial and error sort of situation.

Solid state amps blow up too. Nothing is indestructible.

smartin53 · Jan 23, 2015

Tube MX? Yea it certainly is fun...

Problem was either the notorious JJ KT77s (sound great, terrible pins) or aged sockets...replaced both at the same time so not sure for sure which was the ultimate issue...but no problems since.

jayvis · Jan 26, 2015

Tubes....seems like you either love or hate 'em. I never had any desire to own tube gear after doing a number of listening comparison tests 15 years ago. Tubes are nothing but expensive mascara in my opinion.

TheDoctor · Jan 26, 2015

smartin53 said:
Tube MX? Yea it certainly is fun...

Problem was either the notorious JJ KT77s (sound great, terrible pins) or aged sockets...replaced both at the same time so not sure for sure which was the ultimate issue...but no problems since.

Is that KT77 in the back right red-plating? If it is, that is a MAJOR problem...

Sam Cogley · Jan 26, 2015

I tend to just adjust my power supplies on rebuilds to get the right output voltages. Considering that voltages are high everywhere these days, it seems easier that messing with bucking transformers.

smartin53 · Jan 26, 2015

TheDoctor said:
Is that KT77 in the back right red-plating? If it is, that is a MAJOR problem...

That was why I posted it. One of the many joys of tube maintenance

drknstrmyknight · Jan 26, 2015

I've had Scott, Sherwood, Stromberg Carlson, Eico and McIntosh, among other brands and I can't say tube's are more of an issue than any other maintenance item.

gadget73 · Jan 26, 2015

Sam Cogley said:
I tend to just adjust my power supplies on rebuilds to get the right output voltages. Considering that voltages are high everywhere these days, it seems easier that messing with bucking transformers.

If only one part of the supply is out, I'll modify the circuit. If both HV and heater supply is off by the same percentage, it doesn't really make huge sense to me to fool with modding the power supply by adding dropping resistors and such. Lately I've been using thermistors in things to help with power-on surge and they have the added bonus of dropping just a smidge of line voltage. I get dead-on voltages now with the couple amps I've added them to. Heater specs at 6.3 volts and all of the B+ is well within factory tolerances.

Sam Cogley · Jan 26, 2015

gadget73 said:
If only one part of the supply is out, I'll modify the circuit. If both HV and heater supply is off by the same percentage, it doesn't really make huge sense to me to fool with modding the power supply by adding dropping resistors and such. Lately I've been using thermistors in things to help with power-on surge and they have the added bonus of dropping just a smidge of line voltage. I get dead-on voltages now with the couple amps I've added them to. Heater specs at 6.3 volts and all of the B+ is well within factory tolerances.

That's something I've considered, and probably should start doing.

CountD · Jan 26, 2015

smartin53 said:
Tube MX? Yea it certainly is fun...

Problem was either the notorious JJ KT77s (sound great, terrible pins) or aged sockets...replaced both at the same time so not sure for sure which was the ultimate issue...but no problems since.

Sweet ST70. Best sounding tube amplifier besides a Mc225. I love ST70s - design is clean and genius. The sound is incredible, not to mention they sound way beyond the rated output. Best deal in the world. Sound amazing with a Mx110.

I used vintage Westinghouse tubes circa 1964 in my C22 that was on for 24/7 for almost two years - and finally had one go bad in the right channel. I was bummed, but then again it had been on for thousands of hours. The old stuff rules.

sKiZo · Jan 26, 2015

smartin53 said:
That was why I posted it. One of the many joys of tube maintenance

I'll see your red plate, and raise you one ...

For those who don't think tubes are worth the effort ... you'll never understand if you've never stuck your tongue in a light socket ... :yikes:

jayvis · Jan 28, 2015

sKiZo said:
I'll see your red plate, and raise you one ...

For those who don't think tubes are worth the effort ... you'll never understand if you've never stuck your tongue in a light socket ...

Thank you Joe Walsh. :beer:

sKiZo · Jan 28, 2015

Ack ack ack ... sorry, hairball ... Actually ... not far off from what I was seeing with a Chinese 5AR4 in my ST120 trying to drive a quad of KT120's. That had a scary bright glow to it, even on idle. Dang near read by it I could. Not an issue since changing out to a Mullard GZ37 ... those are the sh!t for heavy duty rectifier action ... and a direct swap with no mods ... at least in my amp. Be forewarned - it does take some heavy iron to keep this setup happy.

Beowulf62 · Jan 29, 2015

So...here's what tube maintenance looks like for a diehard tube lover:

Tube list:

Power supply (x2): 6336A/6528A, 6AU6A, 5651WA

Amplifiers (x2): 6B4G/5881/6L6GC/6CA7/EL34/6550/KT90 (x2), 5814A/12AU7A (x2), 5751/12AX7A/7025A, OA2WA

A complete retube requires 18 tubes... :banana:

So, this is what Tube Maintenance is all about

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