Bare Knuckle Pickups Forum

Forum Ringside => Guitars, Amps and Effects => Topic started by: maliciousteve on June 13, 2006, 06:00:32 PM

Title: Power tubes failing?
Post by: maliciousteve on June 13, 2006, 06:00:32 PM
Hey. Just been playing through my set up and it just started to crackle and pop randomly. Turned off to stand by, turn back on again and it started popping and farting again within a couple of seconds. so i guess it's the power tubes.

As i'm going to need new ones. What are the advantages of EL34's? and what are the Advantages of 6L6's?

How easy are the tubes to change in a Peavey Classic poweramp?
Title: Power tubes failing?
Post by: CaffeineJunkie on June 13, 2006, 07:11:37 PM
depends on what tool you use, i personally like to use a hammer or brick...


no idea sorry, but you might wanna make sure that its the power amp valves before you change anything
Title: Power tubes failing?
Post by: Twinfan on June 13, 2006, 07:51:49 PM
You sure it's not a dodgy cable or jack socket?  I'd check the simple stuff first.  Try another cable, then another guitar.  If you get the same problems, it's the amp.  Try cranking it a bit too and see if it's obviously an output valve rather than a pre-amp valve...
Title: Power tubes failing?
Post by: maliciousteve on June 13, 2006, 08:19:25 PM
Yeah i've tried different cables, guitars, settings, cranking the damn thing and the popping etc still happens. Also output 2 of the power amp doesn't work either. Any one know of any amp repair guys near the london area?
Title: Power tubes failing?
Post by: _tom_ on June 13, 2006, 08:26:36 PM
Quote from: maliciousteve
Yeah i've tried different cables, guitars, settings, cranking the damn thing and the popping etc still happens. Also output 2 of the power amp doesn't work either. Any one know of any amp repair guys near the london area?


^Bainzy? Although I dont know where he lives...
Title: Power tubes failing?
Post by: HTH AMPS on June 13, 2006, 09:07:19 PM
Dennis Cornell is in the London area I do believe (do a google search on Cornell Amps)

 :twisted:
Title: Power tubes failing?
Post by: FELINEGUITARS on June 14, 2006, 12:49:48 AM
Peavey Classic 50/50 has EL84 valves (x8! 4 per side)

But it may be one of the driver/phase inverters giving  trouble - cheaper to try a spare 12AX7 in each position before shelling out on power tubes.

The Peavey amp is a case of taking the lid off for valve access

Be careful - lethal voltages inside!
Title: Power tubes failing?
Post by: maliciousteve on June 14, 2006, 03:54:02 PM
well i tried replacing the preamp valves and the problem still occurs. Looks like i'm going to have to replace the output valves.
Title: Power tubes failing?
Post by: downrodeo on June 14, 2006, 04:03:46 PM
I hope you're sure it's the tubes. It may be some other abnormality with the amplifier, your cords, guitar's input jack, pedals, etc.  :? Take it to a repair guy for a prognosis.
Title: Power tubes failing?
Post by: maliciousteve on June 14, 2006, 04:54:23 PM
It's deffinatly not my guitars, cables, pedals etc. It makes the crackling, popping sound even when i dont have anything plugged into it.
Title: Power tubes failing?
Post by: Searcher on June 14, 2006, 06:27:22 PM
Hey Steve, I was leaving the tubes question for people here who know more than me about it, but no one's come in to say anything yet, so I'll post my bit.

My amp happily takes either 6L6 or EL34 tubes without having to mess around with it.  So I've A/B-ed them before.  Now I have to try to remember my impressions!  ;)  I found the EL34s nicer overall--how's that for specific details: they're nice.  Heh.  Seriously, they had a slightly fatter sound to my ears.  A bit rounder and more mellow, but with a slightly mushier sound, especially when breaking up.  The 6L6 tubes seemed more even across the frequencies, but without quite as sweet a tone.  It was more even, but something was missing.  Damn, I wish I could remember it more clearly!  Supposedly, from what I've heard others say, 6L6 tubes are supposed to give you more bass than EL34s, but I certainly didn't notice it with my amp.
Title: Power tubes failing?
Post by: steve on June 14, 2006, 09:56:17 PM
Quote from: Searcher
Hey Steve, I was leaving the tubes question for people here who know more than me about it, but no one's come in to say anything yet, so I'll post my bit.

My amp happily takes either 6L6 or EL34 tubes without having to mess around with it.  So I've A/B-ed them before.  Now I have to try to remember my impressions!  ;)  I found the EL34s nicer overall--how's that for specific details: they're nice.  Heh.  Seriously, they had a slightly fatter sound to my ears.  A bit rounder and more mellow, but with a slightly mushier sound, especially when breaking up.  The 6L6 tubes seemed more even across the frequencies, but without quite as sweet a tone.  It was more even, but something was missing.  Damn, I wish I could remember it more clearly!  Supposedly, from what I've heard others say, 6L6 tubes are supposed to give you more bass than EL34s, but I certainly didn't notice it with my amp.


Did you set the bias each time you changed?
If i remember you have a speed twin like mine?
Title: Power tubes failing?
Post by: FELINEGUITARS on June 15, 2006, 12:04:05 AM
The Peavey is a fixed bias amp - no bias tweaking involved
Title: Power tubes failing?
Post by: Searcher on June 15, 2006, 01:56:45 AM
Quote from: steve
Did you set the bias each time you changed?


No.   :oops:

I didn't have a multimetre handy then, though I do now.  Maybe one day I'll do it again properly.
Title: Power tubes failing?
Post by: deg0ey on June 15, 2006, 09:16:27 AM
Can the Peavey take both? I know there's some that can do both, but i didn't think the peavey classic was one of them
Title: Power tubes failing?
Post by: FELINEGUITARS on June 15, 2006, 10:10:26 AM
Quote from: deg0ey
Can the Peavey take both? I know there's some that can do both, but i didn't think the peavey classic was one of them


The Peavey classic 50/50 takes 8 X  EL84 valves - small ones like in a Vox AC30

The older Peavey classic 60/60 used 4 x 6l6GC
Title: Power tubes failing?
Post by: maliciousteve on June 15, 2006, 01:12:01 PM
Will these do just fine?

http://www.watfordvalves.com/product_detail.asp?id=878
Title: Power tubes failing?
Post by: FELINEGUITARS on June 15, 2006, 06:23:39 PM
Yeah - they look just fine
Title: Power tubes failing?
Post by: HTH AMPS on June 15, 2006, 07:16:16 PM
check these out, MUCH cheaper & also my favourite EL84...

http://cgi.ebay.co.uk/EL84-7189A-6BQ5-Tubes-New-Set-of-4_W0QQitemZ7628944248QQcategoryZ14947QQrdZ1QQcmdZViewItem

 :twisted:
Title: Power tubes failing?
Post by: maliciousteve on June 21, 2006, 12:20:19 PM
Ok so i put in my new tubes. When i first started it all up, the sound was fine and i had a much more 'fuller' tone. I turned it off, put the poweramp back into the rack case and i get this hum. I can still get sound out of it, but i get an annoying amount of hum when i stop playing. Now there's nothing in the room or downstairs that can interfere with the signal so it must be something else. Any one help?
Title: Power tubes failing?
Post by: HTH AMPS on June 22, 2006, 06:28:22 PM
sounds like you have a ground loop in your rack case - try isolating the rack from the case with those plastic washers.

 :twisted: