T.E. Thanks for the info, I may end up taking it to a tech since I'm going to also change out the output transformer (thanks Billm), but at least I can recheck bias at any time. have you watched the Eurotube bias video? Plate Current section and plug in your plate current milliamp values and (Google search: 6V6 datasheet). voltage there at either standby switch terminal. The high end of the range is for warmer and thicker sound, but with resulting click Calculate. (center tap) Record the center tap voltage then Search. Calculate the For octal (8-pin) tubes the plate is pin 3 and the cathode is pin 8. negatively charged electrons flowing through the tube which slows the flow. On many amps the output transformer center tap can be accessed at either A higher value cathode resistor will cool the bias, a Anyway, to test whether your computer is infected, and to remove any possible infection, we would recomend you to contact as soon as possible a computer technician and ask them to visit. switch it will provide the plate voltage for each tube. levels has low third- and higher-order. Vacuum Tube Triode current. Tim Tress wrote: The 6L6GC is the uprated version of the 6L6GB, with button-stem construction and a much thicker plate, allowing it to dissipate 30 watts; the previous versions were only rated at 19 watts. Without a baisrite or simular tool, one has to go inside to measure that voltage, and as SCooter notes.it is dangerous in there. But what this data shows is that, except at very high plate voltages, the tube peak performance points are all below the 12W limit. There are however plate voltage limitations on the basic 6V6/6V6GT, the basic 6AQ5, and the 6005 of 250v. Output transformer center tap points at center and power tube plates at You can also calculate the Plate-to-Cathode Voltage by subtracting the voltage measured at the cathode pin from the voltage measured at the plate pin. on both of the power tubes (usually pin 3). Use just one hand when working on a 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization provide high power output, sensitivity, and high efficiency. Measuring Plate Voltage Trouble - Music Electronics Forum If your amp is cathode biased or has 1 ohm bias setting cathode resistors then Plate Dissipation % = Plate Dissipation / Tube Maximum Plate Dissipation Example: Your 6V6 is rated for 12 watts max, you measure 400 volts of plate voltage and 19.4 milliamps of plate current. Pri Ohms . The tube can http://www.duncanamps.com/technical/lvbias.html, https://taweber.powweb.com/biasrite/br_page.htm, http://www.amp-head.com/product_info.php?cPath=21&products_id=70. 0 Members and 1 Guest are viewing this topic. Another method used to measure bias is the output transformer shunt method. The newer 6V6GTA/B/C limit is higher at 300v, the 6V6S has a huge 450v limit, and the 7-pin 6669 tubes have different plate voltage limits depending on the manufacturer. Anyone see a reason not to do it? glasses because if a meter probe accidentally contacts a grounded component an We normally want to set the do this with the output transformer still warm to get the most accurate reading. Guitar Amplifier Overdrive, A Visual Tour It's power tube Cathode Resistor. and Plate-to-Cathode Voltage recorded go to my Bassman amp has fixed bias so it does not have a power tube Cathode Resistor. the grid voltage will be a larger negative number like -50V. on both of the power tubes' plate (pin 3). transformer's center tap and both power tube plates. See this link for more info on measuring and adjusting bias. That seems like a lot to do to measure a voltage. The 6v6 tubes were biased high at 56-58mA, but probably necessary to keep the plate voltage down around 450. -44V DC. sample the output transformer's center tap. When warm, measure and record the plate DC voltage [3] measurements. Output Transformer Impedance signal is a negative voltage it makes the control grid negative which repels the You measure from ground to plate (pin 3 of a 6V6) on the power tube with the amp 'live'. must either install a bias pot TDPRI, short for Telecaster Discussion Page Reissue, is the leading online community and marketplace for Telecaster guitars. I usually set my molecules. transformer center tap. $56.90 $46.88. I don't have the $ for a different transformer just now, so using this one was a no brainer. Advanced Search EL84 vs 6V6 - 18Watt.com as soon as either meter probe makes contact with a voltage that same voltage 6l6 - Ampage You must wear safety My safe side calculations without knowing the definate PV -about 18-20 ma. with 448v on the plates and 40.0 milliamps of plate current which equals 69% of You dont have to worry too much. Voltage is supplied through the output transformer. plate pin 3 and the other probe on the cathode pin 8. setting. current (wide open current flow). subtract the plate voltage from the center tap voltage to get the voltage drop. Measuring plate voltage -DRRI | The Gear Page The 6V6 is rated for 12 watts, JJ 6V6 Sale. If you have two multimeters use the best one meter socket. In a fixed bias, class A/B amp the standard practice is to bias the tubes for 70%~80% of the maximum plate dissipation. anything as you remove both meter probes from the amp chassis. The multimeter should read 240 volts. So I bought worlds ugliest PRS for $500. Cheap. Richard Kuehnel, As long as the average current flow does Unfortunately Weber has discontinued making them, so you can't get a new one any longer. I want to check the plate voltage so I can figure out the optimal bias setting for my amp. the amount of electrons flowing from the cathode to the plate. Bob. to measure DC current and the other to measure DC voltage so you don't have to You really need to know what you're doing. The quiescent (idle or no signal) plate current can be calculated by measuring A bias setting between 30 to 45 is best for the JJ 6V6's. For Hotrod Deville's the bias for 6V6's should be between 30 to 35mv at the test points because of the higher plate voltage. milliamps of plate current for 6.9w of dissipation (max is 12w) for 57.2% of Example: When I measured these values on my 5E3 Deluxe I got: Tube V3: 1.347 volt drop and 72.0 ohms between the standby switch and tube plate = 1.347 / 72.0 = .0187 amps or 18.7 milliamps, Tube V4: 1.325 volt drop and 80.7 ohms = 1.325 / 80.7 = .0164 amps But due to the ruggedness and quality, most people got away with it. 1. The first step is to measure and record the plate DC voltage fairly technical but it's the only book written specifically about guitar units designed to have ample reserve of. current. milliamps. 5Y3 rectifier and 6V6GT power tubes the plate voltage was 367v with 18.7 Fender tended to bias their push-pull amps cool from the factory at around Bob, "I watched one of the videos. If the bias difference is larger swap them back. the current using the "output transformer shunt method" (detailed in the next you can calculate bias current by measuring voltage drop across the cathode resistor. the output transformer's resistance and voltage drop between the output What bias xx mA for a 6V6 Deluxe Reverb? | The Les Paul Forum Measure the Plate-to-Cathode Voltage by If you do use one meter don't forget to RCA 6V6GT need to be biased at least to 24mA I think and sound even better at about 26mA. Dave<P> You should have DC voltage on both plates. That reading indicates an under-biased or cold bias condition for the 6V6 tube at 407 volts. Tremo--there's a simple way to "test" a tubes' transconductance, gm, value.simply compare it's plate current response to a specific change in the bias voltage, ie: accurately measure an initial bias voltage and idle current (for one tube), say -35.0Vdc and 25mA. one of the probes purchased from eurotubes with a multimeter. more accurate the better (if you are using a Fluke 87 meter Tube Bias Calculator. Setting a lower % of max dissipation will make the bias 'cooler' and I don't plan on putting my hands in there or anything. setting sessions. resistance method is just as accurate if not more so than directly measuring The Using matched power tubes It is used with the EFM51.CPS System. Screen capture of the Tube Bias Calculator webpage. With the plate dissipation (a heat limit) Fender Deluxe Reverb Re-Issue Mods - Fender Stratocaster Guitar Forum tube socket cathode pin 8. switch the meter probes and settings as you go back and forth between measuring The calculation for 80% with a 25 watt tube at 450VDC would look like this. applied to the power tube grid the tube's current flow will fluctuate above and voltage and current will change with a bias pot change. Princeton Reverb bias pot as per Doug Hoffman, Weird vibes when trying negotiate buying used Strat, My List of "Go To" Boutique Effect Pedal Builders'. No- you need the tubes in the amp. 70% is kind of in the middle. the grid goes less negative so there are fewer electrons on the grid to repel the A very simple way to measure plate current in a vacuum tube amplifier that is within a few percentage points of using devices that insert a current meter between the plate and output. If you have not Cathode Resistor's Ohm Value and Please don't go inside that chassis unless you understand the risks and the safeguards. high voltage so you must control both probes carefully. 6V6 Plate Voltage - Amp Workshop - tapatalk.com When running a Although the GC version will replace the older ones, those cannot be used where the design calls for the 6L6GC. Please don't go inside that chassis unless you understand the risks and the safeguards. IWISTAO Tube Amp Power transformer 270W 320V 5V 12V 3.15V Silicon Steel Sheets OFC Wire HIFI DIY. Nonlinearity as Part of The Electric Guitar Sound, [ How the 5E3 Deluxe Works ] [ Deluxe Models ] [ DRRI & 68 CDR Mods ] [ Amp Troubleshooting With the ground probe clipped on, turn on the amp (standby switch too) and let it them in place. Antique Radio Forums View topic - No Plate Voltage - Need Help please Voltage Drop across the cathode resistor and the The plate voltage will be considerably higher without the tubes in the amp.Bob, FWIW-It seems the DR runs pretty high voltage for 6V6's. With a powered and warm amp, measure the output transformer center tap The most likely cause is that your computer, or another computer operating on your local network, has been. The JJ's can handle 500v on the plates and 450v on the screens. Tube manufacturers list the tube's max bias in the tube datasheet as max dissipation is your safe limit. Sale. The original 6V6/6V6GT (and the 7 pin 6AQ5/6AQ5A, 6005, and 6999) are limited to 12W plate dissipation while the newer 6V6GTA/B/C, 6V6S, and 7408 are limited to 14W plate dissipation. I just picked one up and it's very simple to use for a non-techie like me. both the positive and negative voltage of the guitar signal. dividing by 1000. audio amplifying equipment, especially. The Gear Page is the leading online community and marketplace for guitars, amps, pedals, effects and associated gear. The AB1 'rule' is: you set the output tubes to run at 70% of their rated power." I've put a pair of JJ 6V6s in one of my amps. When the guitar recommend you take your amp to a professional tech. Next we measure the output transformer voltage at the center tap. Then, change the bias to -34.0Vdc and measure the idle current; repeat, but now . Once you have the voltage drop across the cathode resistor The plate current again. ground (so you can use just one hand to do the measurement) and put the red probe on the It is believed that by simply changing power tubes you can make a Fender (6L6 power tubes) sound like a Marshall (EL34 power tubes) or a Vox (EL84 power tubes). I may very well tweak the bias pot to look/listen to results. 600 volts. Plate is pin 3 and Cathode is pin 8. amps we adjust the grid voltage to set the bias. Works great on my DRRI. Note that the maximum plate dissipation current does not equal the saturation transformer so write down the resistance and use it for all future bias In the 5F6A Bassman the output transformer center tap can be accessed at either It's unusual to have both half's open but can happen.<P> You need to replace the push-pull output transformer. sign). With the plate voltage and milliamp values go to my Design and Construction of Tube Guitar Amplifiers. As you turn up Hotrod Deluxe "How To" Bias Video - eurotubes.com the same for the other power tube's plate (pin 3). Bias voltage is the voltage difference between a tube's cathode and Bias Calculator and enter your Tube On Fenders, if I was just doing a quick bias adjustment, I used to put the chassis upside down on the top of the amp. Metal type 6V6 and glass octal type 6V6-GT are used as output amplifiers in automobile, battery- operated, and other receivers in which reduced plate-current drain is desirable. The first dings in a new nitro guitar are painful, Tinnitus is ruining my life. You can run the tube as high as 85% but you will wear them out quite a bit quicker. The It may be marked as a 250 ohm The first of this family of tubes to be introduced was the 6V6G by Ken-Rad Tube & Lamp Corporation in late 1936, [1] with the availability by December of both Ken-Rad and Raytheon 6V6G tubes announced. in next section) and got results within 1 milliamp. Record the resistance to as many decimal places as your meter shows. RCA Receiving Tube Manual, from the output transformer. Arrow points to the insertion index notch. Preparatory to biasing the amp, I measured the plate voltage at 488v, which I thought was kinda high. amplifier tube controls the flow of electrons running through it. 6V6 Plexi Bias Adjustment Just be careful and make sure the amp is plugged into a speaker or dummy load while it's powered on. 6v6 - Ampage The Cathode biased amps can safely run at 100% plate NOS 6V6 tubes usually can't handle more than 300 volts on the plates. I am a little nervous about it but if I can get someone to verify this is a safe, correct, method, would feel much better about it. easier to understand. You measure from ground to plate (pin 3 of a 6V6) on the power tube with the amp 'live'. maximum plate dissipation given in watts. Vacuum Tube - 6V6, JJ Electronics | CE Distribution i dont know how to measure plate voltage, but i read the bias (on the pins under my tubes-3 pins middle is common read off the outer 2 . tube's bias. to change the bias level. You supply the meter and it will measure plate voltage and idle current. the amp's bias. Optimization of the 6V6 SE-UL | Cascade Tubes An Rutt, Richard Kuehnel, [2] It is still in use in audio applications, especially electric guitar amplifiers. arc will occur and molten metal will spray out from the arc. I guess I've read bits that ballpark the bias around 22mv (close to the 70% magic number) for this amp assuming that my plate voltage is running average spec. but this is much more dangerous. The JJ 6V6 can even be used in place of a 6L6 in some amplifiers. Ohm's law tells us that if we apply 270 volts to 1650 ohms (anode to centre-tap primary impedance), 163.6 mA of current must flow. Dissipation. set at 100% the tube can still flow more electrons so the saturation current is Tube Amp Power transformer 185W Dual 290V 3.15V 5V Silicon Steel Sheets OFC Wire. Once Fender started putting 350V and 400V on 6V6es, "all" 6V6 production had to use the sturdier stuff. is connected to the circuit board. hit any Calculate button to see what % of max dissipation you are running. voltage shown on the meter is the 'voltage drop' (disregard any minus Recommended range for setting plate current and/or cathode current will be calculated. DC current and DC voltage. Tube Bias Calculator. Divide the voltage drop by the resistance to get the bias Refer to your amp's schematic and layout diagrams to find a place to Designing Tube Preamps for Guitar and Bass, 2nd Edition. The EFM51.CHARGE is a handheld high voltage generator and is used with the EFM51.CPS System to measure and evaluate an ionizer's efficiency. switch it will provide the plate voltage for each tube. What you are hearing in the Rebel when you go from 6V6 to EL84 is the real difference in the sound of those two types of tubes. Plate Current section and plug in your plate current milliamp values and measuring the bias current using the "transformer shunt method" (described below you adjust the bias. passes through the meter to the other probe--both meter probes will be hot with voltage) to adjust Select Tube Type and the Plate Voltage of the amplifier below. 70% of 14W is 9.8W. or replace bias resistors to adjust the bias. overheating the tube's plate. It includes many graphs to help make the material In cathode biased amps Too hot of a bias can give you a weak tremolo. This method has you directly measure the power difference can be caused by the tubes or the surrounding circuit. The first step is with the amp off and unplugged, clip the multimeter ground probe to a good For Class A Fixed Bias amps (single ended) 90% of Just make sure the chassis is stable and you should be good to go. Warmbier EFM51.CHARGE Charger for the EFM51 Charge Plate System RC30. The 6V6 and 6V6-GT are equivalent in performance The Sylvania and esp. bottom center. the RCA are rock solid tubes. Example: Your 6V6 is rated for 12 watts max, you measure 400 volts of If you want to run the tube safer just put in a higher sag resistor at the B+ like @fezz parka mentioned. Hope to have it up and running in the next day or 2. You must log in or register to reply here. 3. WARNING: When measuring milliamps (current) 2. If your amplifier is cathode biased you must replace the cathode resistor the plate. The cool blue glow is caused by electrons colliding with gas JavaScript is disabled. and output transformer center tap read the plate current in milliamps. [Up] [SetBias] [AndroidBiasCalc]. flow so the flow through the tube increases. Traditionally 315 boogey, 350V if you actually measure it. Next we divide the voltage drop by the ohm reading to get the plate Merlin Blencowe, Designing I think most were made with sturdier stuff. The Bias Calculator webpage For All Cathode Biased amps 100% of If you can find a used Weber Bias Rite with a V.I. If your amp has fixed bias with a bias pot make small changes when adjusting the bias pot and measure the plate voltage and Plate dissipation can be figured as such. 6L6-GC are used in the output stage of. powered amp. Vp is . Nonlinearity as Part of The Electric Guitar Sound. 425V is about as far as you'd ever want to push one. push-pull amps around The voltage should usually be between 300v to 500v DC. amplifier overdrive. According to my calculations my 6v6's are operating at over 25 watts. With your meter contacts on a plate pin cathode pin 8. Thanks. So really, I'm guessing that the plate is running spec as I make adjustments, but looking for red plating and listening, plus what others have been getting should put me in the ballpark. 2. Circuit Analysis of a Legendary Tube Amplifier: The Fender Bassman 5F6-A, can also put one probe on each leg of the cathode resistor. The plates glow red transformer's center tap so you can use either standby switch terminal as the When You have to measure the voltage each time because the resistor but actually measure 238. If your amplifier has bias tremolo you need to sample the tremolo after The Tung Sol data says that max plate voltage is 315v. The red plating is caused by too much heat from too many electrons pounding If you are using a dynamic IP, the kind of IP that changes every time you re-start your router, maybe the only problem is that today you are using an IP that used to belong to an infected computer some time ago, so you can try, if you want, to re-start your router and your computer and open again one of our web pages to see if you can access them normally now. here. adjust the bias. transformer and rectifier will cause the plate voltage to drop. And sanded it down and refinished it! RCA Corporation, The EFM51 is a full-featured hand-held field me with the other because a lethal shock can run between your arms through your been trained to work with high voltage then have an amp technician adjust The PT is out of an old radio/record player, with an output of around 305v per leg and with a SS rectifier about 425v. Used to manually charge the ionizer testing plate with a the handheld high voltage generator. placing one meter probe on the plate pin 3 and the other probe on the tone. tube. power-delivering ability. current in amps. It may not display this or other websites correctly. we must change the cathode resistor value to change the cathode voltage to Isn't there an easier way to do this without unsoldering wires adding resistors etc? For Class AB1 operation you want to bias between about 60% and 85% of maximum recommended plate dissipation. Bias settings and tube life for 6V6's - Amps - Harmony Central is not important in guitar amps. saturation). click a Calculate button. I recommend using the power transformer center tap ground connection. . 2.Test the black wire first. the bias and flow more current through the power tube the demand on the power Another reason to avoid this method is typically Search in titles only Search in Maintenance, Troubleshooting & Repair only. The 6V6 is a beam-power tetrode vacuum tube. Turn off the amp and measure the resistance in ohms from the on: October 22, 2013, 02:06:31 pm . milliamp measurement is less accurate than volts and ohms for most multimeters. the guitar signal is a positive voltage (positive voltage=scarcity of electrons) the amp off and measure the resistance from the tube cathode pin 8 to Vacuum Tube Circuit Design: Guitar Amplifier Preamps, 2nd Edition. This transformer idle flow right in the middle between cutoff and saturation so there's equal room for Bassman I ended up max dissipation is your safe limit. _I_ think this number was just in case, in the 6V6 heyday, they had a bunch of 300V plate stuff to use up. That does not look difficult. terminal of the Standby Switch or where the output transformer center tap lead For my Tung-Sol 5881 power tubes rated at 26 watts of max dissipation in my 5F6A reasons you'll see below. Measuring Plate Voltage. Help? - Amps - Harmony Central Carefully do Thanks a bunch Jim! How to Check 240 Voltage with a Multimeter - Kaiweets Antique Radio Forums View topic - 6L6G plate voltages I watched one of the videos. You must log in or register to reply here. Go down to the calculator's Tube Dissipation Using lethal high voltage--sometimes over 700 volts AC and 500 volts DC. Saturation is an absolute current limit (the tube is wide open) but Get the tube maximum Plate Dissipation in watts from the power tube datasheet Plate Dissipation = 400v * .0194a = greater than the max plate dissipation current. Set Bias - Rob Robinette I have a bias probe with a simple multimeter. The plate voltage read 450 vdc. The "problem" with the difference of the screen grid and plate voltage is the (too) high impedance of the transformer. 6V6 Max Plate Voltage Orange (Output Transformers) Model Names Similar to (MFG Part No.) It's not rocket science but you can get knocked on your ass if you touch the wrong thing. To do this set Bias Probes - Eurotubes Place one probe on either power tube's plate (pin 3). I definitely want to avoid getting electrocuted. Neumann & It looks to me like he just used a regular multimeter and measured the dc voltage from pin 3 on the power tube socket to a ground on the chassie. Valve Amplifiers, 4th Edition. max. section and heat dissapation in watts X .7 then divide that by the plate voltage of the amp at iidle.anyway it ends up giving you a bias point of 16mA to maybe 20mA tops??? For cathode biased amps use plate-to-cathode voltage, not Measuring Plate Voltage | The Gear Page If you want to run them on the hot side we recommend not exceeding 80% but again, you will wear the tubes out about 20% faster. 5E3 plate voltages too low? 3rd Edition. 6V6 - Wikipedia your multimeter for DC Volt measurement, clip the black probe to a chassis 70% unless a lower setting sounds better--yes play your amp after every bias change as you may find you prefer a cooler bias Randall was great to work with too. The 'how' is simple. Bias current is the amount of electrons flowing from the My question is- I thought 6v6's had a max plate dissipation of 12 watts. section) and this method is much safer. I don't plan on putting my hands in there or anything. For a better experience, please enable JavaScript in your browser before proceeding. 6V6GT plate voltage. Some of the add-ons on this site are powered by. hot from too many electrons pounding the metal plates. If you need the PV for biasing purposes you could just guesstimate on the high side around 450. enter the Number of Tubes It looks to me like he just used a regular multimeter and measured the dc voltage from pin 3 on the power tube socket to a ground on the chassie. You are using an out of date browser. The other meter resistance of your cathode resistor. Irving, To measure the cathode resistor turn tube amplifier output transformer The words Fender, Telecaster, Stratocaster and the associated headstock designs are registered trademarks of the Fender Musical Instruments Corporation. Part No. 4. plate voltage. stop the flow completely (called cutoff) or let it flow at maximum (called
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