ruby el84's (jj's)

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scole90
Junior tube assistant
Posts: 10
(2/5/04 10:05 pm)
 ruby el84's (jj's)
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 i put a set of these in my spitfire brew, one tube lit up like a 1000 watt bulb, i shut down the amp, when i restarted the tube seemed ok but sounded weak, i just got a new set, one of the new ruby tubes comes on very brite then cools down, it seems like a standby problem, but my mesa el84's both start very slowly, what could be the problem? are the ruby (jj's) too weak for this amp?


 
eddiejg
Senior tube assistant
Posts: 214
(2/6/04 12:11 am)
 ruby el84's (jj's)
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 Short answer: Maybe. Of course, it could just be a bad tube.
Long answer: Matchless supposedly used EL84M's which can handle higher voltages. They set up the Spitfire to run 348 volts on the plates, 348 on the screens & -11.2 on the cathode with a 120 ohm resistor. That works out to a plate dissipation of 15+ watts per tube. I've built a few Spitfire based amps & I usually set my amps up with a 5Y3, a 15 volt zener to drop voltage, a 150 or 180 ohm cathode resistor or a combination thereof to get a plate dissipation of 12-13 watts per tube. I also built a couple set up to use the EL84M's specifically. If you brewed this, check the voltages on the power tubes & calculate the plate dissipation & adjust accordingly.
-Ed
 
scole90
Junior tube assistant
Posts: 11
(2/6/04 10:18 am)
 el84's
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 ive got 352 volts on the tubes, about 15 w dissipation
 
eddiejg
Senior tube assistant
Posts: 215
(2/6/04 10:26 am)
 el84's
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 I would make adjustments to bring that down.
Even if the tube is bad, you will go through good tubes pretty quickly at that rate.
Let me know some more details about the PT & I can give you some advice on the best way to proceed.
As a quick fix, try a 5Y3 if you have one & see if that at least brings down the #'s to something viable.
-Ed
 
scole90
Junior tube assistant
Posts: 11
(2/6/04 12:08 pm)
 Re: el84's
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 i already know how to fix the voltage to the tubes, i just wonder why these particular tubes start up so quick, even with a 5ar4 rectifier they seem to lite up instantly as i flip the power switch, other tubes wich are russian come on slow.
 
eddiejg
Senior tube assistant
Posts: 216
(2/6/04 12:34 pm)
 Re: el84's
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 Is there a standby switch on this amp?
 
scole90
Junior tube assistant
Posts: 11
(2/6/04 4:16 pm)
 Re: el84's
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 yes, there is a stanby switch, also a 5ar4 rectifier. could the rectifier be bad?

Edited by: scole90 at: 2/6/04 4:17 pm
 
eddiejg
Senior tube assistant
Posts: 217
(2/6/04 5:17 pm)
 Re: el84's
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 If the tube is lighting up like a 1000 watt light bulb when the standby switch is off, then it't probably not the rectifier- it should only be getting 6.3v heater current with the amp in standby.
 
Andy Poupart
Senior tube assistant
Posts: 113
(2/7/04 2:22 am)
 Re: el84's
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 I really don't like Ruby EL84s. I've had a bunch of problems with them redplating in amps. They can't handle high voltages.
 
GroundhogKen
Forum Moderator
Posts: 2242
(2/7/04 9:42 am)
 Re: el84's
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 Scole, this won't be much help for your situation but...

I've heard from decent sources that Ruby is a pretty good re-labeler of current production tubes.

JJ tubes have a reputation for being quite study.

I've never used JJ power tubes before, but yesterday I received a pair of JJ EL84s and a pair of their new 6V6.

I haven't tried the EL84 yet, but I'll give them a whirl this weekend. You may have unfortunately received a faulty set or two. My opinion is that due to the physical nature of EL84s they are especially susceptable to shipping damage, microphonics and stress from heating and cooling cycles.

I had about 2 hours last night to try out the JJ-6V6S in my BFDR. I compared them against a Fender-labeled pair of Philips 6V6-GTA. The Philips tubes have very low hours, so I believe it was a fair test. I was happy to see that the two brands biased the same. My initial impression is that the JJs sound great clean and have tigher bass when distorting. I intend to leave them in the amp.

Ken
 
jc
I only work on Fender's
Posts: 674
(2/7/04 9:53 am)
 Re: el84's
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 I have bought sovtek el84 and el84M. I have also gotten russian labelled el84M from ebay. All of these have held up to 350+ on the plates. I haven't had any issues with these tubes and have yet to get a bad one in the dozens of pairs that I have bought.  
 
scole90
Junior tube assistant
Posts: 12
(2/7/04 8:12 pm)
 Re: el84's
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 well my impression of the jj el84 is that they sound fantastic, very clear and lots of crunch, they are a dream come true, but this filiment flash situation is making me crazy, a guy on another board said he uses jj's exclusivly and they flash all the time, yet another guy says some ueropean manufacturers are making there tubes flash on purpose as kind of a signal that the tube is still good, has anyone heard of this bs?
 
PHATamps
I only work on tube amps
Posts: 416
(2/7/04 9:39 pm)
 Re: el84's
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 I don't think your filament flash is anything to worry about. I love the sound of JJs, but now that I read your post, I'm reminded that I've seen that flash myself.

You say the filament "lit up like a light bulb", but that's understandable, considering they're basically the same thing.

I've read that Thomas Edison tried 1000 different Tungsten alloys before he found one that would continue to glow brightly without dimming to a dull red after it got warm.

Apparently, with the alloy JJ is using, when the current hits the cold filament, its emission covers a relatively wide band in the EM spectrum (to include most of the visible light band), but once it warms up the emission band narrows to focus in on the IR band (overlapping into the red/orange part of the visible light spectrum).

Nothing to be concerned about. Crank it and JAM! (J M 2 $.02)
 
Jonas Gemini
Hey get your own solder
Posts: 294
(2/7/04 9:44 pm)
 Re: ruby el84's (jj's)
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 Hey,

I have a few amperex preamp tubes that flash brightly when turned on, I think amperex tubes are known for this feature, and I have even seen them advertised as with "flashing getters". I don't know if it was planned into production at all. I think it is just an peculiarity.

I plan on trying the solvtek EL84M's soon

Jonas
 
GroundhogKen
Forum Moderator
Posts: 2245
(2/7/04 10:11 pm)
 Re: ruby el84's (jj's)
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 I have a couple Ei 12AX7s which flash on startup. I think they are made on the same tooling that Amperex was made on--can't remember for sure.

I love the tone Ei 12AX7s, but the quality sucks--way too microphonic. I wish somebody with deep pockets would breath new life into that factory and improve the QC..


Ken
 
 
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