First build, sound problems

[Krmikeb]

So, I just finished building my crack.

I plugged my computer into a Modi 2 uber then to the crack.  Hooked up my HD600s and....

SO much interference....and very flat sound and a lot of buzzing, especially in the left ear.  Then.... POP, and it sounds amazing.  A little while later, POP, and its back to bad sound.  And this keeps happening.  Sometimes quickly, other times it will be fine for 10 minutes before back to bad sound.

During the testing process, everything looked good, except when I did a voltage check.  Anything that was supposed to be at 170, consistently was 155. 185 was 175. 90 was 80. 

I am pretty new to this stuff, but I fear I must have done something really wrong to be getting this popping. 

Help?

[Doc B.]

You probably have a missed or bad solder joint.

[Krmikeb]

So, i have gone back through it and checked every joint and connection.  No cold solders, and everything seems to be connected well.  But, i still get that popping sound....

[Doc B.]

If you have a pair of cheap, expendable headphones, plug those in to the amp. Turn it over in the wood base and carefully lift the chassis to plug in the power cord. Turn the power switch on and then plug the power cord into the wall outlet. Now take a non-conductive object - a wood or plastic chopstick is a favorite - and try carefully tapping and/or pushing gently on all the various wires and components to see if you can force the sound to occur in the headphone when you press on a particular connection. Be careful, cheap headphones can be very sensitive and you may not even need to be wearing them to hear the pop. They can just sit next to the amp while you test the connections if the noise is too loud for your ears. Also keep in mind at all times that the circuit will be live and you can get a shock reaching into the components with your hand rather than the stick. You can also shut the amp down, wait about a minute, turn it over to its normal operating position, turn it back on and try rocking the tubes a little in their sockets and tapping on them lightly to see if you can induce the pop.

[Krmikeb]

Ok, i can induce the pop by messing with the smaller tube.  It seems to be the issue.  Everything else I mess with doesnt cause any change, but when i move around the tube i get the pop as well as the static.

[Krmikeb]

By messing with that tube, i seem to have it in a position where it works consistently.  So, i guess my question is, what is most likely the problem?  Loose pin connectors?

[Doc B.]

Yes, the tube socket is a likely culprit. Closely inspect all of the connections on the socket pins and to try reflowing all of the solder connections on the tube pins even if you don't see an obvious bad connection. You might also plug and unplug the tube a few times to burnish off any oxidation that might be on the pins.

[Krmikeb]

Doc, thanks so much. Seems to be consistently working now!

I take it that my lower than normal voltages pose no problem?

Anyways, thanks! When i get up the courage, I'll move onto the speedball