It sometimes takes a few minutes for them to get warmed up (see: stressed out.). EL84 - max. Total, each EL84 has 117 Ohms cathode resistance. You must log in or register to reply here. Still does bug me, as can be seen by my posting in the first place. by Gaz Thu Apr 21, 2011 9:39 pm, Post I"ve seen them with years of service on the original tubes. I'm running 300V B+ and a shared bypassed 110 Ohms cathode resistor. Lots of builders run them in the mid 300's. Psychonoodler once pointed out the the real criteria is is plate dissipation = 12W. It may not display this or other websites correctly. The words Fender, Telecaster, Stratocaster and the associated headstock designs are registered trademarks of the Fender Musical Instruments Corporation. It makes soundwise most probably a great difference if you run them at 140 % or at 70 % (like many amp gurus recommend). Amps with a single EL84 output tube are probably class A and will run normally at around 100% max. by Gaz Sat Apr 16, 2011 2:43 am, Post I'll try another resistor. EL84 Page 1 of 8 Telephone: +381 18 550 741 EL84 is A.F. I'm measuring plate voltage on a PP amp with EL84, and when turning on Vak jumps up to 380V before falling and hovering around 300V. EL34 triode mode connection. Plate Dissipation per Tube % = % If the tube is a triode (or dual triode with both triodes used): Plate Current = mA: Plate Dissipation: Watts: Plate Dissipation per Tube . I'm still left wondering why the "stock" values from the schematic weren't giving me something closer to the voltages on the schematic. Product Data Part Numbers You are using an out of date browser. Another volt is lost across each tube's separate current sense resistor (2 Ohms) and trimpot (10 Ohms). My Mesa Express 5:25 is at 360V plate & 300V screen in fixed bias mode. It's the average of all of these points that determines the total dissipation. Larger tubes such as 6550 and KT88 are happy with 30 ma. Joined: Tue Aug 25, 2009 6:27 am. I could be wrong, but I was under the impression that depending on whether a single coil fender type pickup (about 1/8 volt), a gibson type humbucker (about 1/4 volt) or p90 (about 1/2 volt) the pickups could produce from about 128mv'ish to say 500mV'ish in general. The other issue is the voltage. So, keep safely under that. Better to be aware of the dissipation each EL84 has. I'll try another resistor. The grid voltage was -45.1V DC (yes, a negative voltage). At idle, None of the aforementioned values dissipated over the 2W watt max. So all within range. Restaurants near Max-Joseph-Platz, Munich on Tripadvisor: Find traveler reviews and candid photos of dining near Max-Joseph-Platz in Munich, Bavaria. The maximum anode (plate) voltage is 550 volts as long as the valve is not drawing any current. By Rob Robinette https://www.bvwtm.org.uk/articles/Valves and Valve Testing.pdf, Music Reference RM-10 Vacuum Tube Amplifer, SYclotron Audio | The Red Light District, p4. $125.00 Details Add to cart All prices are per tube Westinghouse EL84 This is a suitable replacement for any 6BQ5 = EL84 = CV2975 = E84L = 7189 tube type. Maybe that's pushing it a bit (+13%). What's common for amps like Vox to run the EL84 plate voltage at in a cathode biased amp? Thank you for your feedback. When saturated the harmonics are rich and dynamic. The Russian 7189 tubes have been fine in it since then but not before we destroyed some other tubes in the learning process. between the plate and screen that you can measure. Going through the calculation I get about 17W @ about 48ma at the plate, which seems high to me. It is a Regarding screen grid resistor size, from 470R to 1K there is some local negative feedback happening with EL84 IME. Dissipation was at about 95% for both plate voltages. The PT looked close. The EL84 is assuredly different (but safe to use in the amp, as you . I haven't seen a circuit yet that isn't violating at lest one of "the mans" guidelines. Do you have a scope? On the Spitfire clone I have, a 120ohm cathode resistor yields plate voltage to about 365V using a GZ34 rectifier (JJ). Visseaux EL84 This is a suitable replacement for any 6BQ5 = EL84 = CV2975 = E84L = 7189 tube type. Turn off all the lights in the room, and allow your eyes to adapt to the dark. Each EL84 also has it's own 2 Ohm (unbypassed) cathode resistor to measure bias current, and I'm using a 10 Ohm potentiometer to adjust the bias balance between the two tubes. For a better experience, please enable JavaScript in your browser before proceeding. The first dings in a new nitro guitar are painful, Tinnitus is ruining my life. This results in about 47mA bias current per tube, making the plate dissipation around 13.5 Watts. I have the impression that EL84s fall more strongly than most into the "they dont make em like they used to" category. The EL84M will run at up to 500 volts HT and also it is designed to withstand the vibrations that are experienced in military systems. You are using an out of date browser. by Gaz Thu Apr 14, 2011 9:51 pm, Post I measured 10.4 Volts across the shared 110 Ohm cathode resistor, which is 47mA per tube. You must log in or register to reply here. But do amp manufacturers generally run them higher than 300V? Thanks. { P = E x I } From this batch, tested at 400 volts, a tube with 18 ma idle current would be dissipating 7.2 watts {400 x .018 = 7.2}. ?--- and the guaranteed lifetime in hours ? Im not in favor of choosing to violate specs during a design phase, but much of the world did just that in the past with el84s. It's more like, "You can push the screens to 4 Watts during the chorus because you will fall into the next verse and give them a chance to cool down.". Gold Lion EL84 - All tubes in the EL84 family are tested in a cathode biased amp where they are really pushed and their harmonic content blooms. Screen current is small and ignored for the purpose of the above calculation. Output Pentode . 1 voltage Vg1-100 (V) Cathode current Ik 65 (mA . Dont some tubes have more of a tendency for the bias to run away on elevated plate supplies? The 70% figure refers to fixed bias amps. Problem is excessive gain and noise (hiss and hum) even when nothing is plugged in and the volume down. Vox worked that way for over 40 years yet. Apply New All Sellers All Sellers Star Sellers only . Before I blew it up, I had a bedrock that was pushing 428 across the plates. by Gaz Wed Apr 13, 2011 6:06 pm, Post If God had wanted us to keep playing upright basses. Hi guys, These questions relates to EL84/6bq5 pentode vacuum tubes. Plate Dissipation (max) 25. Max rating on the EL84 is 12 watts, but I suspect these amps must be measuring higher than that (?). dissipation. Post The EL84 is a vacuum tube of the power pentode type. Everything would be so much easier. When saturated the harmonics are rich and dynamic. p.p.s. RE: max plate voltage el84. But typical SE operation is 250V. screen grid resistors set the difference between the plate voltage and screen voltage. IME, however, doesn't mean the tube's gonna fail imminently, as long there are sizable screen R's and dissipation isn't through the roof. You are using an out of date browser. If you are getting higher current draws with a guitar than with a signal generator, that just suggests that you need to increase the output of your signal gen. a little to match the guitar level. the choke i'm using already has a 750R DC resistance, which I thought would be enough. Post . The JJ Electronic EL84 is a solidly built EL84 / 6BQ5 with excellent tonal qualities. I really would prefer to pop in a couple of power resistors for the filament and then just connect it to my 247v mains. by Gaz Wed Apr 13, 2011 1:29 am, Post For example, 25 ma at 360 volts is 9 watts, about the maximum for the EL84 whose maximum plate dissipation is 12 watts. RE scoping out the screens - yes, your screens are only conducting on half-cycles. Unlike 6v6 tubes, where you have JJ's and some others that exceeded the vintage robustness specifications, el84 is seemed to be a tube that suffers from modern production standards being less robust than the vintage tubes that survived in amps that sometimes abused the hell out of them. Carvin runs their EL84 amps at right around 400 volts in fixed bias, with no apparant reliability problems at all. But I still have no idea how much it would have to say for tube lifetime. It's got relatively low plate and screen voltages at about 310 and 304 with respect the cathode at about 10.5 volts. 300V is not so bad. Bear in mind that amp has a cooling fan in it !! I would turn it down a little. by pdf64 Thu Apr 21, 2011 8:38 pm, Post If EL84's are supposed to withstand this, then maybe my tube(s) is (are) weak. Tube specs say max voltage is 300. by Alexo Wed Apr 13, 2011 2:27 pm, Post I think you may be unpleasantly surprised by the results wth only a 560R shared resistor at those voltages. I'll give it a try to see if the plate is glowing. Alexo, you're totally right about the output level of my scope! Thanks DT7. I looked at some original manufacturers EL84 data sheets, and some modern EL84 data sheets. Fixed bias. Baah, what to do.. V: Screen Current (max) 50. mA: Screen Dissipation (max) 8. I don't think they meant the peak of a waveform as we typically see "peak" used. FWIW, I serviced an EL84 amp that was running them at 400 and many tubes weren't up to the task. I have a Seymour Duncan 84-40 amp that runs the plates at 550 v, however the screens are half that at 275 v. Well, I tried a 250ohm cathode resistor. Tube Max Design Dissipation = Watts 100% Pa: Class A Fixed Bias: 70% Cool = mA . Re: El84 Max screen grid dissipation. For a better experience, please enable JavaScript in your browser before proceeding. Been losing sleep over screen R values in an AC30 type build. JavaScript is disabled. values of Va and Vg2 are 250V and that of Wa is 9W. plate dissipation: 12W, anode voltage: 300V, screen voltage: 300V As you can see from the data, only the EL83 has different power and anode voltage ratings, which backs up my hunch that the EL83 is not quite the same in character when compared to the 6P15P and SV83. If it glows, it should do so when more signal is applied, usually past clipping. That is 25% higher than the stated max values. JavaScript is disabled. W (*) These specifications are provided 'as-is', with no warranty of any kind. The Gold Lion's just sound great at any volume level. You have not told us which amplifier it is. I was under the impression that JJ EL84 can easily survive 340V B+ and 340V on the screens up to max power without glow, but have not tried it myself. The new JJ EL844 is an entirely new tube that dissipates 9 watts and is a drop in replacement for EL84's in most all amps. by Ian444 Fri Apr 15, 2011 9:28 am, Post It's a 1967 Harmony H415. by Andy Le Blanc Sat Apr 23, 2011 11:58 am, Post TDPRI, short for Telecaster Discussion Page Reissue, is the leading online community and marketplace for Telecaster guitars. Many amp designers run these tubes at 400V to 430V on the plate. If I were you I'd check the dissipation at max signal by checking the voltage across the resistor, divide by the resistance as usual, and multiply that times the voltage from cathode to screen with at max signal (not idle signal). OK. Sovtek EL84M lifetime is estimated to be 5000 hours versus 3000 hours for a standard Sovtek EL84. WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. @ 1 Volt peak input signal, with 16dB global negative feedback. In a properly biased amp, the plate current x plate voltage should be in the neighborhood of 70% of the max plate dissipation for an EL84, or 12W. Never heard of 'local NFB' being the cause for lower output and less desirable tone. Multiply the plate-to-cathode voltage by the plate current to get the plate dissipation. I have it on my bench and never considered the screens which are fed by a shared 560ohm resistor off the B+1. I have a few 5 watters kicking around. You must enter Tube Type and Plate-to-Cathode Voltage above before calculating Tube Dissipation. The PT is nominally 275-0-275, although I was measuring 308-0-308. I'll build an autotransformer and play it safe. Vox AC30's are up at 350v on the plates.It's common for guitar amps to go beyond design centers. Both amps are SS rectified, have two 12ax7s and 2 EL84s, and an 8 ohm 12" speaker. Sorry if I was unclear in my post, but those measurements were taken with max signal, not at idle. This tube can replace any EL84 or 6BQ5 tube. of. If a tube/valve is run above its DESIGNED operating conditions (maximum ) of course it shortens its life . I have 1k resistors on the screens (this was a mistake, I will be changing to 150 Ohms), so the screens aren't contributing much power dissipation. I just did a traynor that had only one common resistor for the screens . I just put a pair in an el84 driven train wreckinspired build and they sound spectacular. This calculator allows you to compute and tune loadline and operating point of tube amplifiers' power stages. As an example, guitar amps abuse el84s, at least on paper, more than any of the other common output tube they use. Matched versions of this tube use Apex Matching Choose burned-in tubes for maximum stability and performance. You see 380 volts when the valves are not drawing current at first switch on. Plate Dissipation % = % = Plate Dissipation / Tube Maximum Rated Dissipation. mbratch Member Messages 2,379 Feb 8, 2010 #7 TopBooster said: JJ's rugged construction of this tube offers high reliability without any compromise to the sound. So I expect when I bump the cathode resistor, my plate voltage will go somewhere north of 365V, but my current should reduce. W: Screen Voltage (max) 425. Gaz, I believe you know what you are talking about when you see screens glowing. Ready to ship in 1-3 business days. I totally overlooked that while in testing frenzy. This tube has solid lows with warm bright mids and shimmery highs. by Ian444 Thu Apr 14, 2011 10:41 am, Post Matched versions of this tube use Apex Matching Choose burned-in tubes for maximum stability and performance. Total, each EL84 has 117 Ohms cathode resistance. Enter maximum price Shipping Free shipping. If the plate voltage is too high, it will be hard to impossible to cathode bias. Unlike 6v6 tubes, where you have JJ's and some others that exceeded the vintage robustness specifications, el84 is seemed to be a tube that suffers from modern production standards being less robust than the vintage tubes that survived in amps that sometimes abused the hell out of them. Thanks DT7. That amp is rated at 30 watts from a quartet of EL84s. *When the heater and positive voltages are obtained from a storage battery by means of vibrator, the max. 1 el84 power pentode p e n t a l a b o r a t o r i e s 9740 cozycroft avenue * chatsworth * california 91311 (800) 421-4219 * (818) 882-3872 * fax: (818) 882-3968 Hmm. Max Output Power 2x ~12W. And sanded it down and refinished it! Life is a tale told by an idiot -- full of sound and fury, signifying nothing. Sodo we know who were the ones that Dumble refused to build amp for ? Unlike 6v6 tubes, where you have JJ's and some others that exceeded the vintage robustness specifications, el84 is seemed to be a tube that suffers from modern production standards. Enter Plate Current: DC milliamps Plate Dissipation = watts = Plate Voltage * Plate Current. Each EL84 also has it's own 2 Ohm (unbypassed) cathode resistor to measure bias current, and I'm using a 10 Ohm potentiometer to adjust the bias balance between the two tubes. It has a very smooth sweet breakup just like the JJ EL84 and it will breakup a couple decibels earlier. This tube has solid lows with warm bright mids and shimmery highs. My amp tech states that Peavey's Classic 50 actually does an honest 50 watts. The EL84 is designed for a max plate dissipation of 12 Watts, referring to old tube data books. I think I have a quad or so of those Rooskies 360v on the plates, 338v on the screens, fixed bias at about 62%. The specs on the EL84 say 250V operating, 300V max. Infrared basics for digital photographers, http://s69.photobucket.com/albums/i43/Ty_Bower/Tubes/P1070379.jpg, http://s69.photobucket.com/albums/i43/Ty_Bower/Tubes/P1070380.jpg. All the data sheets for EL84 tubes give a max plate voltage of 300V and a plate dissipation of 12 watts. It may not display this or other websites correctly. So at 350 to 400V on the plate, what kind of plate dissipation (at idle) is common or to be expected? For cathode bias, you can run the plate dissipation anywhere between as high as 90-100%, or as low as say 60% - but the higher you run it, the better it will sound. It's also common for cathode biased EL84 amps to run at 100% plate dissipation.Dr Z amps idle happily at 14 watts. Did you compare with some off the shelf new tubes? It may not display this or other websites correctly. $50.00 Details Add to cart The JJ EL84 nails the classic sound of this tube. Cabinet Plate with Lily of the Valley Flowers and Violets, Royal Munich, Bavaria, Vintage Plate, 9.75 Inches JavaScript is disabled. Just like when factoring plate dissipation in a push-pull amp, it's okay to cross the line because it's only for a small portion of one half of the signal. But when you get above a certain voltage, pushing the current in an el84 can get dangerous. As they heat up and draw current then that pulls your HT (B+) down to 300 volts. It's the average of all of these points that determines the total dissipation. I'm getting about 340V on a Spitfire clone I have. Kashmire - Neat circuit board, by the way. Curious what screen voltage, screen stopper value, and screen filter supply/bypass capacitance your build has? I've been wondering about my screen current too. Amps with the cathode resistor you mentioned are cathode biased and generally run at a higher idle dissipation. amplifier. I just hadnt run into a data sheet that gave 2 maximums, one for continuous (2W) like you described and then one for peak (4W). This tube can replace any EL84 or 6BQ5 tube. So I expect when I bump the cathode resistor, my plate voltage will go somewhere north of 365V, but my current should reduce. Various brands available. Where did you get it? Maximum Ratings Plate Voltage Plate Dissipation Grid #2 Voltage Grid #2 Dissipation Grid #1 Voltage Cathode Current Grid #1 Resistor (automatic bias) Grid #1 Resistor (fixed bias) Cathode to Heater Voltage . Marshall did something like this on the early amps. Great idea on the digital camera. Hey, this company claims to be running 6BQ5's at 700 volts for 35 watts per channel, although I can't find any info mentioning that number today. An interchangeable North American type is the 6BQ5 (the RETMA tube designation name for the EL84). Various brands available. If the electrolytic capacitors in the B+ are rated at 400V or more, you have nothing to worry about. You do not have the required permissions to view the files attached to this post. WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. So I bought worlds ugliest PRS for $500. It is used in the power-output-stages of audio-amplifiers, most commonly now in guitar amplifiers, but originally in radios.The EL84 is smaller and more sensitive than the octal 6V6 that was widely used around the world until the 1960s. Oh nice! The B+ is actually (301 - 12) = 289, so the power is 289 * 0.047 = 13.6W per tube (measured at the cathode). Grid No. Don't forget the fact that your 47 mA. You must log in or register to reply here. I suspect that this really makes a meter-based RMS reading inaccurate, since that non-conducting half-cycle while bring the average power way down. What do you mean by "bypassing to ground?". With the amp fully warmed up, can you see any hints of red color anywhere on the plates? The Gear Page is the leading online community and marketplace for guitars, amps, pedals, effects and associated gear. Subtract the cathode voltage from the plate voltage, to get the plate-to-cathode voltage. 550Volts ? I'm curious to see what you come up with, as I've never seen blue screens myself. I have a few 5 watters kicking around. With the amp fully warmed up, can you see any hints of red color anywhere on the plates? For cathode biased amps, 300v is about the norm, +/- 10 percent. In Reply to: max plate voltage el84 posted by altecboy on August 22, 2013 at 10:20:03: Roger Modjeski's RM-10 amp uses El 84 tubes with 6oo volts on the plate and 300 volts on the screen grid--with a low idle current to keep it within the dissipation limits of the tube. Power Stage: 2x 2 EL84 power vacuum tubes in Push-Pull Ultra-Linear configurat The majority of the time it's below max dissipation and at the opposite edge of the signal it'll be completely cutoff. My Peavey amp's schematic shows a plate supply of 332V. by Philoffline Thu Apr 14, 2011 8:57 pm, Post Are you subtracting the cathode voltage from the plate voltage to get the 340V calculation? You must log in or register to reply here. ! 2 dissipation Wg2p 4 (W) Grid No. by jjman Wed Apr 13, 2011 2:43 am, Post I think it's happy now. When saturated the harmonics are rich and dynamic. please help me. 1.5k screen grid resistors and a 40uf filter cap on the screen node, with a 3k dropping resistor between the plate and screen supply nodes. I've been contemplating the screens on my 2xel84 amp the last few days. Yes, unfortunately I've seen them glow too many times. My Traynor Bassmate ran them in PP at 410V! Think'n this could be my new "Forever" Tele -An Am Pro II. Guitar amps routinly run EL84s up near 350V. El84 Max screen grid dissipation by Gaz Wed Apr 13, 2011 1:29 am Been losing sleep over screen R values in an AC30 type build. Another way to tell before your eyes can is to use a digital camera - their CCD's are quite sensitive to shortwave infrared. Posted by garymuffley (D) on August 23, 2013 at 08:40:13 .
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