#1
I am currently building P1x form Ax84. I had finished my build, put the tubes in and put in on standby. The indicator light came on, the preamp tube started to warm up, but the power tube did not. It was an EL34. I put a 6L6 in there and it started to warm up.
When it is on, I get silence, unless I poke at the star ground (using a chop stick). Then I get hum. I looked at the EL34 and realized that pin 6 is missing. I don't know if they just don't have a 6th pin or what, but according to the bias circuit option the bias is set between pin 6 and pin 4. At least that is how I understood it.

Simpler version- Do EL34s not have a pin 6?
Do I have the bias pot option set up right?

EDIT: I'm a moron. I just realized where the bias mod is supposed to be done.
Last edited by end_citizen at Oct 19, 2008,
#2
Okay, I have the bias set up right. (Now I'm actually getting readings that make sense...) Also, it seems a little more functional. It buzzes constantly, but no guitar signal comes out. Also, the tone controls/ volume/ gain controls have no effect.
Last edited by end_citizen at Oct 19, 2008,
#3
El34 does not have pin 6 and an EL34 and 6L6 are not directly interchangable. It sounds to me like the tube is bad. They both share the same heater pins, so if the 6l6 heats up then it sounds like the el34 heaters are bad. Get a new one to check.
#4
I kinda thought it was the tube. I've never had an amp that used EL34s, but their site said you could bias it over to a 6L6. I had no such luck. If it is the tube, I'm gonna be kinda disgruntled. It is a brand new tube. Oh well, I need to retube my Traynor anyways.
Question-If the tube has gone bad, would it just kinda feel like it is vibrating when it is supposed to be warming up?
#5
Use the electrical schematic to do your circuit check and not the build drawing. I have found during several builds the drawings are not always complete. I make a copy and use a highliter as I check the schematic to the build.
#6
Quote by end_citizen
I kinda thought it was the tube. I've never had an amp that used EL34s, but their site said you could bias it over to a 6L6. I had no such luck. If it is the tube, I'm gonna be kinda disgruntled. It is a brand new tube. Oh well, I need to retube my Traynor anyways.
Question-If the tube has gone bad, would it just kinda feel like it is vibrating when it is supposed to be warming up?


I'd look for an orange glow from the tube. If you are not getting one the tube is more than likely bad especially if the 6l6 does warm up. Try it in another amp if you can. If it still doesn't work then its a bad tube.
#7
Okay, I got a new tube. It does warm up. I get the traditional "it's on" light buzz when I turn the amp on, but there is no sound. I found something that is troubling me in the tone circuit. There is about 65v before the capacitors, but 0v after the capacitors (with respect to ground). There is 65v across the capactiors. Should this voltage not just go into the potentiometers? Everywhere else seems to be functioning fine. I get close to the same voltage everywhere that I am supposed to.