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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Does anybody have a copy of the VTL Book ? posted by beetlezipp on September 20, 2004 at 16:48:23:
That Master Bias Resistor will be in series after the bridge rectifiers in the bias supply before all the splitting mixer resistors and bias adjust pots located in the middle of the big PCB on the old Manley 350'sLook on the rear of the main big board just near the power transformer... you'll see the MBR near the first PI filter cap for the bias supply, the axial cap (might be 47uf or 100uf) with (+) going to the ground tracks. He probably is a grey bodied 3W puppy.
So first find him... then...
The value of the Master Bias Resistor was indeed different on different amps depending on tubes used of the day, and maybe a power transformer change here or there. I think I have seen 100 ohms up to 750 ohms used as the MBR in those amps.
Lower the value of it to get more negative volts to be able to hold the tubes down more.
Raise the value of the Master Bias Resistor if you need to have less negative volts and need to make the tubes draw MORE current.
Goto the service page on my website to hit me with an email form thing to request a schematic...
Cheers, EveAnna Manley
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Follow Ups
- Master Bias Resistor... - Vanimal Manley 21:19:14 09/20/04 (0)
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