What the???

[flying snake]

Woe is me! I've been working on a Hiwatt DR103 clone from Tilo Zotolla's book on building tube amps. I had some biasing problems but I worked those out with help from Amp Kat on this here forum. Well...None of the tone pots were working at all and the bright volume pot was all messed up as well. I was taking some voltage readings on each tube tonight and I had higher than normal DC readings on the 3rd and 4th 12ax7s. The 3.15 AC pins measured right on. I could hear a pop each time I took a measurement. However, then all of a sudden I started getting zeros on all of the DC pins of each 12ax7. No voltage whatsoever...and no popping sound when the probe of my multimeter hit the pins. Now the amp will make no sound at all. Does anyone know what might be causing this?

[Satamax]

http://www.geofex.com/ampdbug/ampdebug.htm

[Amp Kat]

If you can follow or conceive what RG's page gives it is an excellent tool for finding your problem snake but I'm not sure you have the tools or gear to do many of those test and procedures neccesary to get the job done. Snake I would think it is posible that you blew that HT fuse which I'm showing is a 3.15amp fuse on the HT circuit. There are 3 nodes on the power supply that feed your high voltage to the tubes. If that fuse is blown you will get nothing and hear nothing. The 1st node is the Highest voltage of the 3 that goes to the center tap on the power tube transformer and is the plate voltage for the power tubes. The 2 node is the screen voltage that goes to the 100 ohm 5 watt resistors going to pin 4 of the power tubes. The 3rd node is the preamp voltage that powers the preamp section and is the lowest voltage of the 3 so this is the one you want to check. Pins 1 & 6 of the 12AX7's are where this voltage are and if you don't get around 140 volts there than you most likely blew that fuse. On the tone stack problem it is possible that you may have a pot reversed like pin 1 used instead of pin3. Make sure the bass pot is grounded as this tone stack is quite different than many others like the fender. Did you get a pinout exactly where each pot should go and in what order. Something not right with that tone stack somehow is my guess or a supply problem mainly with node 3.