Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: richierick on May 07, 2022, 07:45:50 am

Title: A Quick Question (to clear the fog in my mind)
Post by: richierick on May 07, 2022, 07:45:50 am

Hi There, I have been a lurker for many years and I have benefited from the collective wisdom of the Forum admins and many contributors, and I have sourced enough information to build myself an amplifier. I built a Fender AB763 Deluxe based power amp, with the reverb, no vibrato, using the AX84 project's P1x pre-amp with the switch/resistor option on the 2nd gain stage cathode and it worked the first time it was fired up, except for the dreaded Blue/Brown OT wire swap. So a big thank you to the Whole Forum for the education.So to the question, I have wanted to try Cathode Biasing. Going through Sluckey's Amp Scrapbook I found the Fixed/Cathode Bias Switching schematics on page 10. Thinking of using the bottom diagram, as I got the Bias supply from one of the PT HT winding, and I did use a high value resistor between the PT and the bias rectifier/filter circuit. But isn't the orientation of the capacitor backwards? Meaning, shouldn't the -ve lead be to ground, and the +ve lead be to the common terminal (away from ground). Thanks in advance for the replies and I hope the question is not too silly.
Blessings & Love to Everyone Always!!

Title: Re: A Quick Question (to clear the fog in my mind)
Post by: sluckey on May 07, 2022, 07:55:51 am

Quote from: richierick on May 07, 2022, 07:45:50 am

But isn't the orientation of the capacitor backwards?

Yes. The negative cap lead should go to ground. I'll fix that to clear the fog.   :icon_biggrin:

Title: Re: A Quick Question (to clear the fog in my mind)
Post by: richierick on May 07, 2022, 08:04:01 am

Thanks a million for the quick reply, and no less than from the guru himself. :worthy1: