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Need some help with DC wired preamp heaters. I have Traynor YCV80Q which I installed an additional preamp tube socket into, to use one of the triodes for a cathode follower before the TS, using a 12AT7. So, I've been playing and it sounds really, really good....but I want to see is, if someone could look at the schematic and see if I hooked the heater up correctly. I'm a bit lost on DC heaters...but the specs of the two voltage regulars (MC7915 & 7815) indicate they can handle the extra heater connection. One question is, why does the -15v have 18 ohm resistors (R143 & R144) between the voltage source and tube ......and the +15v has the 18 ohm resistor (R142) between the tube and ground. At any rate, I ran a wire from pin 4 of V3:C to pin 4 of the newly installed tube and put an 18 ohm resistor between pin 9 of new tube and ground. All measurements are good and nothing seems to be out of whack...is there more than one way to do this ? or better way ?
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Don't use pin9 ! I hope that's a typo, the heaters in each tube here are run in series, 12V heaters instead of the usual 6V. With pin9 connected you are running 12V to a 6V heater and only lighting up half the tube.
The resistors are in series with each tube, so it doesn't matter if they are in the ground side or "hot" side.
Hook it up out of phase like the 2 shown at the bottom, aside from the resistors.
So new tube pin5 to V3C pin4. New tube pin4 to resistor to ground. The out of phase heaters is probably done to help with hum.Originally posted by Enzo
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Wow, glad I posted, thanks g1 !! Yes, I was using pin 9 to resistor to ground. Thanks for clearing this up. My thought was that I was only using one triode...so heater connect one side. I see now, will definitely change it ! Thanks again !Originally posted by g1 View PostComment
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