@jjasniew Now this is a plan, I like it. I was at the point of simply installing all the tubes and firing it up to see what blows up....rather crude I realize, but frustration leads (me anyway) to push to destruction. LOL
I like this approach, I'll give it a whirl just as soon as I have things re-soldered and checked out.
I like this approach, I'll give it a whirl just as soon as I have things re-soldered and checked out.
I read on another forum that the 3.3mohm R in the LNFB (see the schematic at the top of the post) is the wrong value they recommended 33mohm. My experience with negative feedback is limited to NFB coming off the speaker jack. My understanding of this NFB circuit isn't good. So, I don't know if a change in value here would have anything to do with my ground fault issue.
Can someone enlighten me on LNFB or refer me to somewhere I can study up on the subject?
Can someone enlighten me on LNFB or refer me to somewhere I can study up on the subject?
There is nothing associated with the 12AX7 circuitry that could draw much current since all B+ voltage into them comes through 100K resistors. Unless there is a serious wiring error the problem is likely in the output stage or the power supply.
If I had this thing on my bench the first thing I would do is discharge all of the caps, then take resistance readings from each of the B+ supplies to ground, the plate pins of the 6V6 tubes and every pin on the rectifier tube to ground. One thought that just popped into my mind, does your power transformer have a center tap on the heater windings? If so the CT on the 5 volt winding MUST not be grounded or connected to anything.
Thank you Tubelab and rayma! I will do the recommended.
Prior to sitting down to the computer tonight, I pulled the first 33uf filter cap and it checks out close at 37uf and just to be certain I tack soldered in a fresh one. Then I plugged into the variac without the current limiter and fired it up with a full tube compliment. Bringing voltage up slowly (time elapsed taking the variac from 0 - 50 might have been about 30 seconds not more than a minute) and watching the B+1 it blew the 2A fuse at 50.8 volts on the variac. The B+ was over 300vDC but in my excitement I didn't get the exact B+ voltage.
...but I did notice that the cap had discharged immediately down to 246mv the rest of the caps checked the same. I'm assuming that whatever event happened to cause a short to ground it is discharging the caps.
Tomorrow if I can get out of some "honey-do's" I'll do as suggested by Tubelab and rayma.
Prior to sitting down to the computer tonight, I pulled the first 33uf filter cap and it checks out close at 37uf and just to be certain I tack soldered in a fresh one. Then I plugged into the variac without the current limiter and fired it up with a full tube compliment. Bringing voltage up slowly (time elapsed taking the variac from 0 - 50 might have been about 30 seconds not more than a minute) and watching the B+1 it blew the 2A fuse at 50.8 volts on the variac. The B+ was over 300vDC but in my excitement I didn't get the exact B+ voltage.
...but I did notice that the cap had discharged immediately down to 246mv the rest of the caps checked the same. I'm assuming that whatever event happened to cause a short to ground it is discharging the caps.
Tomorrow if I can get out of some "honey-do's" I'll do as suggested by Tubelab and rayma.