5E3 Clone Build Trouble- Hum w/ Standby on

[Wittgenstein]

Hello,

I just fired up my 5E3 for the first time (Triode Kit) and as soon as the tubes warm up there is a loud hum coming from the speaker. If I switch the standby off the hum dissipates, but no signal from the guitar can be heard. Any suggestions?

Thanks in advance.

[Wittgenstein]

Some more info...

-Link to Tridoe 5E3 layout diagram here

-Here is what happens when I turn the amp on with standby on. After about 30 seconds when the rectifier has warmed up, a buzz or hum starts really faintly and builds to a very loud noise and remains constant. If I then switch the standby off, the noise makes a weird dissipating noise (like turning off an old CRT TV) and the hum drops to almost nothing.

-The hum is not present when I have the 2 6V6's removed and just the rectifier in. It was still present but less severe with the 6V6's in and the 12ax7 and 12ay7 out.

-I also was poking around on the inside with the amp on using chopsticks (I was taking great care to avoid getting blasted by the caps) and I did find that pin #8 on the 6V6 closest to the rectifier affected the hum when the standby is off slightly (I could move the wire slightly to cause no hum while standby is off) but there is still no sound that comes out.

-Whether in standby or not, it seems to make no difference at all turning the tone and gain from 0-12. The same is true for having the guitar plugged into any of the 4 channels.

-One question I have. There are 2 black wires coming from the power transformer. One runs to the power switch and one connects to the neutral (white wire) on the power cord. Does it matter which is connected to which? The wire diagram I followed from Triode does not distinguish the two.

Please please help me!!!! I was so hoping to rock out on my first amp build =(

[JHow]

Since this is a scratch-build, go over every connection (there aren't too many) and look for a mistake. I would start with the input jacks (they somehow cause a lot of trouble), and follow the circuit path throughout the amp. This is just looking at each connection, amp unplugged, caps discharged.

[Chuck H]

Since the problem persists with no preamp tubes in and the amp on standby I'm going to guess the hum problem isn't the input jacks. The same thing still applies, you need to go through the build until you find the error. A couple of tips where to look, there should be no hum in standby because there should be no voltage on the tube plates. That is an indication that the power supply is wired incorrectly somehow. The amps behavior is incorrect. If it was only the standby switch that was incorrect the amp should still function but the switch would be backwards, so something else is wrong with how the power supply is wired. The fact that you can poke pin 8 on one of the power tubes and stop the hum seems to me to mean two things. That pin 8 connection is intermittant for some reason, could be bad solder, broken wire or a short (I don't think this is the primary problem though) and taking one of the power tubes out of the circuit stops the hum. By interrupting pin 8 you stop conduction in that tube. This is somehow stopping the hum. This is also not the primary problem, because that tube should conduct (off standby) but it may be an indicor of where to look.

It seems to me that there must be a few things cattywhompus in there. If you can't redily find one thing wrong with the wiring that is a problem, because that's where the problem is.

It is dangerous to you, your transformers, your filter caps and your tubes to operate the amp as it is. You should not plug it in again until you have found and corrected any errors in wiring.

Once you have found and corrected any incorrect wiring you should take voltage readings to be sure the amp is functioning properly.

It does not matter which PT primary lead goes to the power switch.

Chuck

[Wittgenstein]

Thanks for the suggestions! I was a bonehead and had accidentally reversed the wiring on my 9 pin sockets (pin 1 was pin 9 and so on). I thought I had triple checked everything, but I kept making the same assumption about which pin was #1 (neither socket nor tube was marked like it is on the octal tubes). So I redid the work wiring the 12AX7 & 12AY7 up the correct way and now I have sound, but I'm still running into some trouble.

-It seems like I have to turn the pot to at least a volume of 2 or 3 before I can hear sound.... 1-2 does not produce sound. More importantly however, when I turn the amp up to half volume or louder and then strum all the strings the amp breaks up and makes a strange popping / electric sound and cuts out. If I play lightly it does not happen, and it seems to be especially worse when pushing out bass notes.

-There was a decent amount of hum that I reduced by moving the ground wire off the speaker output with chopsticks. That cut the hum in half but there is still a small amount I can hear.

-I did not have time last weekend after rewiring to check the voltages of all the pin-outs, but I will post them here as soon as I get a chance. I'm wondering if perhaps I burned something out when I had the wires mixed up. I plan on going back through every part with my Fluke meter to see if I can find any culprits. Any suggestions would be appreciated! I am so close and it felt good to play a guitar through it and hear that tube sound, however brief.