Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: J Rindt on August 01, 2010, 05:19:50 am
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I tried searching for this, but it became a herculean task. What is the purpose of the diode in parallel with the 1 ohm cathode resistor, on the power tubes do?
Thank You
http://www.schematicheaven.com/fenderamps/hotrod_deluxe.pdf
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I'm going to guess it's there if the 1ohm burns. The 1 ohm is there to check the bias of the two tubes.
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I'm going to be rude and say "It's stupid".
There is NO way that resistor is in-trouble in normal operation. It takes 1 Amp to cook it, the tubes will never get over 0.2A-0.3A RMS, 0.4A peak. So the diode never does anything in normal operation.
If the 1 ohm 1W resistor is endangered, the 6L6es and PT are already cooking. I'd rather have the 1 ohm burn than have the diodfe "save" it so the expensive stuff burns.
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I'm going to be rude and say "It's stupid".
There is NO way that resistor is in-trouble in normal operation. It takes 1 Amp to cook it, the tubes will never get over 0.2A-0.3A RMS, 0.4A peak. So the diode never does anything in normal operation.
If the 1 ohm 1W resistor is endangered, the 6L6es and PT are already cooking. I'd rather have the 1 ohm burn than have the diodfe "save" it so the expensive stuff burns.
Thank You
That is kind of what I thought, but do not have enough electronics knowledge to justify shooting my mouth off. I wonder if Fender had problems/foresaw problems in this part of the power supply. is this something that is common in modern day Fenders?
Thanks Again
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I'm guessing it's some kind of failsafe protection in conjunction with the diodes on the plates.