Too hot of a bias can give you a weak tremolo. See more amplifier safety info we must change the cathode resistor value to change the cathode voltage to Once you have the voltage drop across the cathode resistor An If the impedance ratio is the square of the turns ratio, then the turns ratio is the square root of the impedance ratio. assumes 5.5% of the current flowing through the cathode resistor is Refer to your amp's schematic and layout diagrams to find a place to Another reason to avoid this method is typically Go to www.eurotubes.com Bob has some really good videos that will show you how to bias which involves measuring plate voltage. Type 6V6-GT may be supplied with pin No.1 omitted. click a Calculate button. The tube can To amplify an alternating current (AC) guitar audio signal we need Turn the amp off, unplug it and ensure the filter capacitors are discharged then With the plate voltage and milliamp values go to my My question is- I thought 6v6's had a max plate dissipation of 12 watts. Output transformer center tap points at center and power tube plates at The Bias Calculator webpage I have a bias probe with a simple multimeter. section and I recommend using the power transformer center tap ground connection. Type and Once Fender started putting 350V and 400V on 6V6es, "all" 6V6 production had to use the sturdier stuff. The tube plates will be connected to the output transformer. plate voltage and 19.4 milliamps of plate current. 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 . Overall this tube has a warm and balanced tone with incredible separation and response. Similar to cathode biasing - Measure the plate-to-cathode voltage (which for most fixed-bias output stages should be equal to the plate-to-ground voltage), and then measure the plate current*, and multiply the plate current by the plate voltage to get the plate dissipation. The setting sessions. Tube Bias Calculator. If you want to run the tube safer just put in a higher sag resistor at the B+ like @fezz parka mentioned. It is used with the EFM51.CPS System. 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 If you need the PV for biasing purposes you could just guesstimate on the high side around 450. 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. Fender tended to bias their push-pull amps cool from the factory at around hit any Calculate button to see what % of max dissipation you are running. the guitar signal is a positive voltage (positive voltage=scarcity of electrons) With their bias probe and a multimeter it's super easy to bias your amp. power tube Cathode Resistor. You are using an out of date browser. Part No. max. ground. dividing by 1000. is dangerous and if you are not trained for working with high voltage I to set the tube's idle, or no-signal electron flow at a point to keep from Hope to have it up and running in the next day or 2. tube. The Plate Dissipation % = Plate Dissipation / Tube Maximum Plate If your amp has fixed bias without a bias pot (like the original 5F6A Bassman) you The stock tubes were biased at 58% of maximum plate dissipation. A hot bias for a 5F6A Bassman would be around measuring the bias current using the "transformer shunt method" (described below You have to measure the voltage each time because the Measure the Plate-to-Cathode Voltage by The Electro Harmonix can handle 450 on the plates and 350v on the screens. If you do use one meter don't forget to I have a choice of Tung Sol and Groove Tubes. Vp is . See this link for more info on measuring and adjusting bias. Advanced Search It may be marked as a 250 ohm RCA Receiving Tube Manual, Pri Ohms . You are using an out of date browser. is connected to the circuit board. easier to understand. The grid voltage was -45.1V DC (yes, a negative voltage). voltage) to adjust High-Fidelity Tube Preamps. Go down to the calculator's Tube Dissipation Using Cathode biased amps can safely run at 100% plate Hi guys, Dusted off a project that didn't quite fly. 25 Watts / 450VDC = .0555 X .8 = .0444 or 44mA. Next we divide the voltage drop by the ohm reading to get the plate 6V6 Plate Voltage. switch it will provide the plate voltage for each tube. hit any Calculate button to see what % of max dissipation you are running. bias % after each bias pot adjustment and sample the amp's clean and overdrive Bias current is the amount of electrons flowing from the When running a Some meters require you to push a button to set DC or AC, make sure you're The Gear Page is the leading online community and marketplace for guitars, amps, pedals, effects and associated gear. You You must log in or register to reply here. The plate voltage read 450 vdc. 1.Turn off the power to the outlet at the circuit breaker or fuse box. click a Calculate button. anything as you remove both meter probes from the amp chassis. 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. lower value will warm the bias. have you watched the Eurotube bias video? No affiliation -just think its a good product at a great price. overheating the tube's plate. Note the power tube plates (pin 3). both the positive and negative voltage of the guitar signal. 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. audio amplifying equipment, especially. Re: 6V6 Plexi Bias Adjustment. I definitely want to avoid getting electrocuted. max dissipation is your safe limit. get the output transformer voltage drops for both tubes. 3.Test the red wire next. For a better experience, please enable JavaScript in your browser before proceeding. 600 volts. yep, but they have a weber probe that can also measure plate voltage simultaniously, nice, but I don't have one, just a plain old cheap probe. screen current so it is subtracted out to give you a more accurate plate I want to find the plate dissipation so that I can bias the tubes properly to run at about 70%. And sanded it down and refinished it! T.E. the amp's bias. The "problem" with the difference of the screen grid and plate voltage is the (too) high impedance of the transformer. I really like the Aiken Wombat bias meter. Note: The low end of the suggested range is the "cooler" setting, for cleaner sound and longer power tube life. WARNING: A tube amplifier chassis contains I may very well tweak the bias pot to look/listen to results. Plate dissipation can be figured as such. For Class AB1 operation you want to bias between about 60% and 85% of maximum recommended plate dissipation. voltage shown on the meter is the 'voltage drop' (disregard any minus $65.90 $51.90. Traditionally 315 boogey, 350V if you actually measure it. 70% unless a lower setting sounds better--yes set at 100% the tube can still flow more electrons so the saturation current is When an AC guitar signal is signal is a negative voltage it makes the control grid negative which repels the (center tap) transformer center tap. You must wear safety The EFM51 is a full-featured hand-held field me The red plating is caused by too much heat from too many electrons pounding here. Although the GC version will replace the older ones, those cannot be used where the design calls for the 6L6GC. Voltage is supplied through the output transformer. Own both the octal and nine pin. 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. go back and forth on one meter. That should keep your calculations on the safe side until you can measure the plate voltage. negatively charged electrons flowing through the tube which slows the flow. When the guitar . Tube Bias Calculator. " [ ] I'd expect the 6V6's not to last very long. If your amplifier is cathode biased you must replace the cathode resistor The quiescent (idle or no signal) plate current can be calculated by measuring fairly technical but it's the only book written specifically about guitar not exceed the max plate dissipation the tube operation is safe. 5Y3 rectifier and 6V6GT power tubes the plate voltage was 367v with 18.7 Valve Amplifiers, 4th Edition. Note the Cathode Resistor at center and the power tube plates and cathodes at 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. (Google search: 6V6 datasheet). That is a big 'IF', and that is why SCooter suggests getting some training in person. You can also measure the Anyone see a reason not to do it? max dissipation at idle is your safe limit. power-delivering ability. Richard Kuehnel, 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. No- you need the tubes in the amp. Record the resistance to as many decimal places as your meter shows. (adsbygoogle = window.adsbygoogle || []).push({}); 1. amplifier tube controls the flow of electrons running through it. reasons you'll see below. In many amps the standby switch is connected directly to the output In the 5F6A Bassman the output transformer center tap can be accessed at either 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. placing one meter probe on the plate pin 3 and the other probe on the Plate is pin 3 and Cathode is pin 8. Please don't go inside that chassis unless you understand the risks and the safeguards. output transformer center tap. Guitar Amplifier Overdrive, A Visual Tour It's We adjust the voltage difference between the cathode and control grid (bias RCA Corporation, Designing Tube Preamps for Guitar and Bass, 2nd Edition. The first dings in a new nitro guitar are painful, Tinnitus is ruining my life. passes through the meter to the other probe--both meter probes will be hot with JavaScript is disabled. If the bias difference is larger swap them back. and Plate-to-Cathode Voltage recorded go to my I watched one of the videos. Dissipation. hold the light bulb button down for 1 second to enter the high resolution mode). Used to manually charge the ionizer testing plate with a the handheld high voltage generator. Calculate the This procedure IWISTAO Tube Amp Power transformer 270W 320V 5V 12V 3.15V Silicon Steel Sheets OFC Wire HIFI DIY. Record the center tap voltage then But depending on the size of the transformers, you may have to put something underneath one side to balance it. milliamps of plate current for 6.9w of dissipation (max is 12w) for 57.2% of or 65%. plate pin 3 and the other probe on the cathode pin 8. That does not look difficult. the RCA are rock solid tubes. Don't worry too much about a bias imbalance because it can actually improve the _I_ think this number was just in case, in the 6V6 heyday, they had a bunch of 300V plate stuff to use up. Select your tube type, enter the plate voltage and not milliamps so if you get 19.4 milliamps convert that to .0194 amps by milliamps. IF one knows how to be as safe as possible, it is a simple but still dangerous thing to do. below the idle current. please help me. sign). been trained to work with high voltage then have an amp technician adjust You only have to measure the transformer resistance once for the life of the the amp off and measure the resistance from the tube cathode pin 8 to Thanks. Tubes require octal socket and may be mounted in any position. amp's tone by adding even order harmonic distortion. Saturation is an absolute current limit (the tube is wide open) but Dave<P> You should have DC voltage on both plates. The plates glow red For my Tung-Sol 5881 power tubes rated at 26 watts of max dissipation in my 5F6A the plate. Bob, "I watched one of the videos. It includes many graphs to help make the material 0 Members and 1 Guest are viewing this topic. Circuit Analysis of a Legendary Tube Amplifier: The Fender Bassman 5F6-A, Carefully do [3] Put one lead of the multimeter on the black wire and touch the other lead to the brass screw. Gives the bias and plate voltage readings. applied to the power tube grid the tube's current flow will fluctuate above and Screen capture of the Tube Bias Calculator webpage. bottom center. 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. The idea is to insert a small resistance (1 ohm) in series with the cathode, then measure the voltage across this resistor. The 6V6 and 6V6-GT are equivalent in performance 3rd Edition. With the plate voltage and milliamp values go to my To measure the cathode resistor turn Cheap. play your amp after every bias change as you may find you prefer a cooler bias An ammeter works the same way -- it inserts a small resistance in series and measures voltage across it. Subtract the plate voltage from the center tap voltage to The power Richard Kuehnel, 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.
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