With the amp fully warmed up, can you see any hints of red color anywhere on the plates? 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). Gaz, I believe you know what you are talking about when you see screens glowing. El84 Max screen grid dissipation - Page 2 - The Amp Garage This tube can replace any EL84 or 6BQ5 tube. Did you compare with some off the shelf new tubes? I think you may be unpleasantly surprised by the results wth only a 560R shared resistor at those voltages. Plate Dissipation (max) 25. This tube has solid lows with warm bright mids and shimmery highs. Product Data Part Numbers by Structo Sat Apr 23, 2011 3:18 pm, Powered by phpBB Forum Software phpBB Limited. As an example, guitar amps abuse el84s, at least on paper, more than any of the other common output tube they use. 550Volts ? It'll be a little bit until I could post a picture, but there should be a little window in the plate structure (near the middle) where you can see the screen grid. By Rob Robinette If the electrolytic capacitors in the B+ are rated at 400V or more, you have nothing to worry about. When saturated the harmonics are rich and dynamic. Thanks DT7. Product Data Part Numbers The EL84 is a vacuum tube of the power pentode type. p.p.s. Bear in mind that amp has a cooling fan in it !! 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. W (*) These specifications are provided 'as-is', with no warranty of any kind. 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. 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). Mine has Sovteks in it. Use of these parameters shall be entirely at the user's own risk. Loadline calculator for power stages with reactive load Do you have a scope? It may not display this or other websites correctly. When saturated the harmonics are rich and dynamic. It may not display this or other websites correctly. Don't forget the fact that your 47 mA. by Alexo Wed Apr 13, 2011 2:27 pm, Post by Alexo Thu Apr 14, 2011 5:37 pm, Post Lots of builders run them in the mid 300's. Psychonoodler once pointed out the the real criteria is is plate dissipation = 12W. Various brands available. VHT 18 el84 dissipation | Telecaster Guitar Forum It may not display this or other websites correctly. Thank you for your feedback. The power P, is equal to the voltage E multiplied by the current I. main@funwithtubes.groups.io | EL84 Cathode or Plate voltage or current? 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. I measured 10.4 Volts across the shared 110 Ohm cathode resistor, which is 47mA per tube. 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 . 12ax7 el84 amp schematic - ltcgfz.microgreens-kiel.de Ready to ship in 1 business day. I have a few 5 watters kicking around. 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. 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. Enter maximum price Shipping Free shipping. You are using an out of date browser. The voltage is not what kills the tube,it's the current and the screen voltage.If you control those,the EL84's will live. Vacuum Tube - EL84, JJ Electronics | CE Distribution the choke i'm using already has a 750R DC resistance, which I thought would be enough. PDF EL84-TK Tube Data Sheet - TELEFUNKEN Elektroakustik $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. Amps with the cathode resistor you mentioned are cathode biased and generally run at a higher idle dissipation. Baah, what to do.. It's the average of all of these points that determines the total dissipation. Tube Matching, Bias and Breakup - How They Work Together So I bought worlds ugliest PRS for $500. Bavaria Royal Munich - Etsy I'll try another resistor. For my Tung-Sol 5881 power tubes rated at 26 watts of max dissipation in my 5F6A Bassman I ended up with 448v on the plates and 40.0 milliamps of plate current which equals 69% of max dissipation with 70% (40.6ma) being the max safe dissipation for fixed bias Class AB amps. Most amps for which the 100% dissapation rule has been used are running around 300 to 330VP and 300V on the screens. 1 voltage Vg1-100 (V) Cathode current Ik 65 (mA . @ 1 Volt peak input signal, with 16dB global negative feedback. I would turn it down a little. "Note that what most manufacturers pass off as "true Class A" or "pure Class A . That amp is rated at 30 watts from a quartet of EL84s. EL84 - Wikipedia If you can measure the plate voltage and plate current, then you can calculate the plate dissipation. So all within range. For a better experience, please enable JavaScript in your browser before proceeding. The Manual rates the EL84 at 300V MAX. So I expect when I bump the cathode resistor, my plate voltage will go somewhere north of 365V, but my current should reduce. I don't think they meant the peak of a waveform as we typically see "peak" used. The EL34 Tube - Audiomatica For cathode biased amps, 300v is about the norm, +/- 10 percent. Title: ECC82 is A . 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. At idle, None of the aforementioned values dissipated over the 2W watt max. Vacuum Tube - EL84, JJ Electronics | Antique Electronic Supply Total, each EL84 has 117 Ohms cathode resistance. The Gold Lion's just sound great at any volume level. Post . I'll try another resistor. 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. Re: El84 Max screen grid dissipation. The EL84 is designed for a max plate dissipation of 12 Watts, referring to old tube data books. Tube specs say max voltage is 300. Screen current is small and ignored for the purpose of the above calculation. EL34 triode mode connection. JJ's rugged construction of this tube offers high reliability without any compromise to the sound. biasing el84's - Amp Workshop For a better experience, please enable JavaScript in your browser before proceeding. This tube has solid lows with warm bright mids and shimmery highs. You are using an out of date browser. Need Info on El84 Tubes and Biasingplease Help! I'll give it a try to see if the plate is glowing. Dont some tubes have more of a tendency for the bias to run away on elevated plate supplies? EL84 / 6BQ5 higher than specified plate voltage? Another volt is lost across each tube's separate current sense resistor (2 Ohms) and trimpot (10 Ohms). The TELEFUNKEN EL84-TK is a perfect replacement for any EL84 / 6BQ5 tube offering a reliable and great sound. I have completed the build, double checked the connections and the amp works. Some of the add-ons on this site are powered by, Amps/Cabs Tech Corner: Amplifier, Cab & Speakers. Any chance you could post a pic of the glowing screens in question? Carvin runs their EL84 amps at right around 400 volts in fixed bias, with no apparant reliability problems at all. El84 Max screen grid dissipation - The Amp Garage You have not told us which amplifier it is. Grid No. You must log in or register to reply here. Life is a tale told by an idiot -- full of sound and fury, signifying nothing. by Gaz Wed Apr 13, 2011 5:16 am, Post by Gaz Thu Apr 21, 2011 9:39 pm, Post I think it's happy now. Visseaux EL84 This is a suitable replacement for any 6BQ5 = EL84 = CV2975 = E84L = 7189 tube type. I just finished an EL84 push-pull amplifier using Electro-Harmonix (EL84EH) tubes. 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. Turn off all the lights in the room, and allow your eyes to adapt to the dark. EL84 safe plate voltages | diyAudio 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. It's got relatively low plate and screen voltages at about 310 and 304 with respect the cathode at about 10.5 volts. Sovtek EL84M lifetime is estimated to be 5000 hours versus 3000 hours for a standard Sovtek EL84. I looked at some original manufacturers EL84 data sheets, and some modern EL84 data sheets. Problem is excessive gain and noise (hiss and hum) even when nothing is plugged in and the volume down. W: Screen Voltage (max) 425. WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. I'll build an autotransformer and play it safe. You must enter Tube Type and Plate-to-Cathode Voltage above before calculating Tube Dissipation. The JJ Electronic EL84 is a solidly built EL84 / 6BQ5 with excellent tonal qualities. EL84 Page 1 of 8 Telephone: +381 18 550 741 EL84 is A.F. Where did you get it? My amp tech states that Peavey's Classic 50 actually does an honest 50 watts. The PT looked close. 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.". by Ian444 Thu Apr 14, 2011 10:41 am, Post between the plate and screen that you can measure. Alexo, you're totally right about the output level of my scope! 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. It's a 1967 Harmony H415. 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. Joined: Tue Aug 25, 2009 6:27 am. That put me at about 388Vdc plate, about 33ma per EL84 (at the cathode) and a little over 12W dissipation at the plate. So I expect when I bump the cathode resistor, my plate voltage will go somewhere north of 365V, but my current should reduce. Yes, unfortunately I've seen them glow too many times. Thats what I would be afraid of - the IQ being in dissipation spec initially and going red plate after several hours (when youre not looking, of course). Tube Bias Calc - Rob Robinette The Russian 7189 tubes have been fine in it since then but not before we destroyed some other tubes in the learning process. For example, 25 ma at 360 volts is 9 watts, about the maximum for the EL84 whose maximum plate dissipation is 12 watts. And sanded it down and refinished it! I just put a pair in an el84 driven train wreckinspired build and they sound spectacular. 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. You are using an out of date browser. $50.00 Details Add to cart You are using an out of date browser. { 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}. The words Fender, Telecaster, Stratocaster and the associated headstock designs are registered trademarks of the Fender Musical Instruments Corporation. by jjman Wed Apr 13, 2011 2:43 am, Post You must log in or register to reply here. I get about 12.5V on the cathode. This results in about 47mA bias current per tube, making the plate dissipation around 13.5 Watts. You want to make sure that idle dissipation is not more than 50-75% of the rated plate wattage. 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. You do not have the required permissions to view the files attached to this post. If God had wanted us to keep playing upright basses. Posted by garymuffley (D) on August 23, 2013 at 08:40:13 . by Gaz Wed Apr 13, 2011 1:29 am, Post My Traynor Bassmate ran them in PP at 410V! mbratch Member Messages 2,379 Feb 8, 2010 #7 TopBooster said: 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. Various brands available. So, keep safely under that. But do amp manufacturers generally run them higher than 300V? I'm curious to see what you come up with, as I've never seen blue screens myself. If a tube/valve is run above its DESIGNED operating conditions (maximum ) of course it shortens its life . I haven't seen a circuit yet that isn't violating at lest one of "the mans" guidelines. RE: max plate voltage el84 - garymuffley - Tube DIY Asylum Power Stage: 2x 2 EL84 power vacuum tubes in Push-Pull Ultra-Linear configurat 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. Fixed bias. FWIW, I serviced an EL84 amp that was running them at 400 and many tubes weren't up to the task. It's also common for cathode biased EL84 amps to run at 100% plate dissipation.Dr Z amps idle happily at 14 watts. It's the average of all of these points that determines the total dissipation. 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. Sorry if I was unclear in my post, but those measurements were taken with max signal, not at idle. Been losing sleep over screen R values in an AC30 type build. Plate voltage issues and it's effect in vacuum tubes - Page 1 6BQ5 = EL84 = CV2975 = E84L = 7189 - NOS Vacuum Tubes for Sale I think I have a quad or so of those Rooskies 360v on the plates, 338v on the screens, fixed bias at about 62%. RE scoping out the screens - yes, your screens are only conducting on half-cycles. Output Pentode . Sodo we know who were the ones that Dumble refused to build amp for ? Another way to tell before your eyes can is to use a digital camera - their CCD's are quite sensitive to shortwave infrared. The grid voltage was -45.1V DC (yes, a negative voltage). by Gaz Sat Apr 16, 2011 2:43 am, Post 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. The first dings in a new nitro guitar are painful, Tinnitus is ruining my life. el84 biasHow hot? - Music Electronics Forum According to the datasheet, 300V is the maximum value. The PT is nominally 275-0-275, although I was measuring 308-0-308. 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. Great idea on the digital camera. PDF EL84 Page 1 of 8 - PoC-Net I'll see where it goes overall for wattage. JavaScript is disabled. I really would prefer to pop in a couple of power resistors for the filament and then just connect it to my 247v mains. It is a 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. What's common for amps like Vox to run the EL84 plate voltage at in a cathode biased amp? EL84 Plate Dissipation | diyAudio You must log in or register to reply here. That is 25% higher than the stated max values. Tube Bias Calculator Cabinet Plate with Lily of the Valley Flowers and Violets, Royal Munich, Bavaria, Vintage Plate, 9.75 Inches Maybe that's pushing it a bit (+13%). Matched versions of this tube use Apex Matching Choose burned-in tubes for maximum stability and performance. I've found some old Brimar datasheets that suggest 2W max at idle, and 4W at max signal. It's got relatively low plate and screen voltages at about 310 and 304 with respect the cathode at about 10.5 volts. Plate Dissipation % = % = Plate Dissipation / Tube Maximum Rated Dissipation. Think'n this could be my new "Forever" Tele -An Am Pro II. WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES. Turn off all the lights in the room, and allow your eyes to adapt to the dark. Tube Max Design Dissipation = Watts 100% Pa: Class A Fixed Bias: 70% Cool = mA . EL84 6BQ5 Screen Grid Peak Dissipation Question The specs on the EL84 say 250V operating, 300V max. Multiply the plate-to-cathode voltage by the plate current to get the plate dissipation. The majority of the time it's below max dissipation and at the opposite edge of the signal it'll be completely cutoff. 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. The EL84 is assuredly different (but safe to use in the amp, as you . JavaScript is disabled. RE: max plate voltage el84. So at 350 to 400V on the plate, what kind of plate dissipation (at idle) is common or to be expected? Curious what screen voltage, screen stopper value, and screen filter supply/bypass capacitance your build has? Thanks DT7. EL84 - max. The B+ is actually (301 - 12) = 289, so the power is 289 * 0.047 = 13.6W per tube (measured at the cathode). ?--- and the guaranteed lifetime in hours ? I've been contemplating the screens on my 2xel84 amp the last few days. Still does bug me, as can be seen by my posting in the first place. So, dont worry too much about the plate dissipation. Everything would be so much easier. You see 380 volts when the valves are not drawing current at first switch on. I'm running 300V B+ and a shared bypassed 110 Ohms cathode resistor. Better to be aware of the dissipation each EL84 has. Guitar amps routinly run EL84s up near 350V. But when you get above a certain voltage, pushing the current in an el84 can get dangerous. by Ian444 Fri Apr 15, 2011 9:28 am, Post An interchangeable North American type is the 6BQ5 (the RETMA tube designation name for the EL84). The JJ EL84 nails the classic sound of this tube. The JJ EL84 nails the classic sound of this tube. 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 If the plate voltage is too high, it will be hard to impossible to cathode bias. 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 Gear Page is the leading online community and marketplace for guitars, amps, pedals, effects and associated gear. 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. This tube can replace any EL84 or 6BQ5 tube. Decware Zen Rectifier Tubes Power Tube Descriptions - Eurotubes They don't last as long, sure, but they generally give a few thousand hours all the same. amplifier. The voltage rating of electrolytic capacitors that are employed for B+ filtering, has nothing to do with the life of an output tube. Radio stations used to replace the high power RF and High Power modulator tubes, after a specific number of hours. Going through the calculation I get about 17W @ about 48ma at the plate, which seems high to me. Regarding screen grid resistor size, from 470R to 1K there is some local negative feedback happening with EL84 IME. As they heat up and draw current then that pulls your HT (B+) down to 300 volts. of. What's the most plate voltage you have ever seen on an el84? The 70% figure refers to fixed bias amps. This is my 4th amp build. How do I determine plate dissapation in a cathode biased amp?? Hi guys, These questions relates to EL84/6bq5 pentode vacuum tubes. Vacuum Tube - EL84, JJ Electronics | Amplified Parts OK. Never heard of 'local NFB' being the cause for lower output and less desirable tone. I have it on my bench and never considered the screens which are fed by a shared 560ohm resistor off the B+1.
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