Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Searing on March 23, 2016, 06:18:53 pm
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so, I just added the 1ohm resistor to ground in a buddy's amp, so that I could bias it up with new 6V6's. It's a Fender Deluxe Reverb built by some private builder. Crash amp or something. Nice build. Anyways, pin 1 and 8 were tied together and sent to ground. I just left them tied together and put the 1 ohm resistor in series to ground. Biased the amp, and it sounds great! Should I worry about having it wired in this fashion? Thanks.
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No. Go look at a 6V6G or 6V6GT. Meaning; a GLASS 6V6 which is probably the only kind you'll encounter unless you rummage thru junk electronics (which I do at times) You'll see no pin #1. It isn't "missing" "just on the one I happen to have here". It's not there on purpose. It is a specification that there is no pin 1 connection within a 6V6. Thus the lug on the socket goes nowhere and can confidently be used as a tie point. In most Fenders pin 1 of the output tube socket is used to connect to and hold up one end of the 1500 ohm grid stopper resistors.
Back when 6V6 were metal, pin 1 connected to the shell. As opposed to 6V6"G" or 6V6"GT" or 6V6GT/G".
Prob true for 6L6 [metal] I have none at hand to check.
On a glass tube, "no pin 1 connection" can mean either pin 1 is missing OR, there IS a pin 1 but it goes nowhere. The JAN 6V6GT/G tubes I have seen DO have a pin 1, but they (the JAN ones) are very old, from the forties, so one could imagine the pin was left on so people wouldn't worry about a missing pin. If you go look at a 6V6G or GT from an old antique radio, meaning from the 40's or early 50's, they probably have a pin 1. Doesn't matter, doesn't go anywhere, use as tie point.
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Technically, Octal pin 1 should go to chassis ground. This keeps metal shell touch-safe.
Evidently the cathode (pin 8) was hard-grounded before. Adding 1 Ohm to it is a good idea.
If you just tucked a 1 Ohm resistor in there on *both* 1-and-8, don't worry. The maximum "deadly" voltage is a tenth of a volt or so, utterly safe. If some fool jams a beer can between chassis and a metal shell (which you are unlikely to find in 6V6), it just goes back to the no-1-Ohm connection, which worked before.