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| | #1 |
| Gear interested Joined: Dec 2009
Posts: 26
Thread Starter | Bias measuring unit -which one?
Hi there, ust wondering if any of you have had experience with e Weber Bias Rite https://taweber.powweb.com/biasrite/br_page.htm or the Tad Bias Master Mojotone Replacing and Biasing Tubes Any other good ones? Acuracey? Quality? Cheers. |
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| | #2 |
| Gear nut Joined: May 2009
Posts: 91
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Hi there I find the best way to bias an amp is to install 1 ohm resistors from the cathodes to ground. that way you can measure the voltage across the resistor. this reading will be in mV but translates to mA because of ohms law. |
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| | #3 |
| Gear interested Joined: Dec 2009
Posts: 26
Thread Starter |
Yeah,but I gotta screw around and spend time doing that ...then hope I haven't messed it up and blow the amp |
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| | #4 |
| Gear addict Joined: Jan 2010 Location: Rhode Island
Posts: 439
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Those Webers look nice, but I would be afraid the adapters are too tall and you wont be able to fit a tube in it while in a head like a marshall, there might not be enough clearance. I use this Welcome to the Home of The Bias King™ It has worked great and setting bias now is easy. VP |
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| | #5 |
| Gear interested Joined: Dec 2009
Posts: 26
Thread Starter |
I understnad they do fit into Marshalls. YouTube - Strange meter reading while biasing a Marshall 50 watt Super Lead I like the fact you can have current & dc reading. The bias king looks good too. |
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| | #6 | |
| Gear addict Joined: Jan 2010 Location: Rhode Island
Posts: 439
| Quote:
VP | |
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| | #7 |
| Lives for gear Joined: Apr 2007
Posts: 1,673
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| | #8 |
| Gear addict Joined: Jan 2010 Location: Rhode Island
Posts: 439
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| | #9 | |
| Gear addict | Quote:
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| | #10 |
| Gear addict Joined: Jan 2010 Location: Rhode Island
Posts: 439
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| | #11 |
| Lives for gear Joined: Aug 2006 Location: Rapid City, SD
Posts: 602
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one mod you can do is a couple of 1 ohm 5 watt resistors and put them between ground and cathode or cathode resistors (depending on output amp tube) and permanently mount some panel meters on your chassis. then another between cathodes. alot of people forget to look at differential current. this is caused by either the phase splitter tube getting weak, or associated circuit, or the bias feed grid resistors drifting out of tolerance from each other ( bias voltage screening resistors after voltage adjust trim pot like in JCM800's)
__________________ In live sound, we make the band one with the environment, In recording, we define the environment in which the vision of the song is recorded. |
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| | #12 |
| Gear interested Joined: Dec 2009
Posts: 26
Thread Starter |
Can someone show me on the schematic where pin 3 plate voltage is measured?
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| | #13 |
| Lives for gear Joined: Apr 2007
Posts: 1,673
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| | #14 |
| Gear addict Joined: Mar 2008
Posts: 359
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I have a weber BiasRite and it works great. Makes doing bias adjustments very easy. The other recommended methods (1ohhm resistor off the cathode then measure the voltage drop across the resistor to get the Cathode Current) work great as well but for a quick, pull tubes, get the readings, adjust the knob and lock it.. cant beat it.
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| | #15 |
| Lives for gear Joined: Apr 2007
Posts: 1,673
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I just picked up a Compu-Bias, which is a dual octal bias tool. It displays plate voltage, plate current, and wattage. Similar to the Bias-Right, but calculates dissipation as wattage, so no need for a separate plate reading and calculator.
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