Buzz/jingle in left channel. goes away when tilted

[Grainger49]

This is one of the slight drawbacks of the Crack.  Most often in stereo amps we will say swap tubes.  Of course, you can't do this.  For the Crack you have to have a spare set.  It is inconvenient bu you should always have spare tubes that can be used for troubleshooting.

As long as you hang in with the forum you will get your amp fixed.  You, too, will say, "Got It!  My amp is dead silent now and I'm enjoying the beautiful music." 

So have faith.  We know that a shrink and a Latin teacher can do this.  So can you.

[fullheadofnothing]

I was taking some measurements before I get the new tube installed.  I dont understand the measurement between 12 and 13.  my measurements start at like 4Mohms and come down.  slowly..  sup?

also, where is the center pin measurement?  is it the center pin of the 12au7a socket?

12 should be zero, because it is ground, something is not connected properly at that terminal or at a terminal connected on the ground buss (black wires).

13 is connected to a large capacitor, which is trying to charge itself from the battery of your meter. Exactly what this means will vary from meter to meter.

Center pin is the center pin of the RCA.

[keithpgdrb]

ok, I double checked my results.  I think pin 13 is fine.  its not the 270, but its not zero either.

I've got the new tube from bottlehead installed.  when I first powered it up, there was a VERY loud POP in the right channel of my headphones.  so much so, that I was worried they may have been damaged.  They seem to be ok though.  I read in the instructions that sometimes this happens, so I'm choosing not to worry about it too much.

the new tube has solved the tube issues I was having, but I wouldnt call this new tube "dead silent" as many do.  there is a very faint white noise sound coming from the left, and the tube rings a little off and on in the right channel.  I'm going to let it cook for a while to see if that irons out these issues.

found out from guy I got the amp from that he had sent it in to bottle head to check his work, so Im assuming everything should be good to go on that end.

[adamct]

Some tubes are louder than others. Your new tube may be a loud one. Thus far, I have found the quietest tubes to be a Bedix 6080 with graphite plates, and a G.E.C. 6AS7G. I like my G.E.C. 6AS7G best not because it magically sounds better than other tubes I have tried (and I've tried a fair number, including 5998s), but because it is so quiet. That may just be a function of the luck of the draw, however.

Best regards,
Adam

[adamct]

Also, I don't know if you have the Speedball installed, but I found that made the amp significantly quieter, too. I would install the Speedball before doing anything else (including rolling tubes).

[keithpgdrb]

Thanks Adam,

yes, speedball is on my list.  I just wanted to make sure everything is working as it should before I add more variables.  I am probably more sensitive to the noises because I generally listen at pretty low volumes.

as far as tubes, I'll be reading the tube rolling thread extensively.  I'll make special note of those you mentioned.

[adamct]

I definitely applaud the idea of getting the stock Crack nailed down before moving on to any changes. And as you said, your tube might clear up after you let it cook a while. You can also rub the tube pins with a little steel wool or sandpaper, or apply some DeOxit, in case the pins are slightly corroded/oxidized.

[Grainger49]

Ok, if you have a grounding problem you should use a good meter and check all the resistances to ground.  Clip one meter lead to the chassis plate.  The other meter lead goes to the terminals or pins called out.  Check every point as called out.

If you have painted both sides or powder coated it, you must scratch off to get to metal to clip on.

This is a post I have made before:

The start of the grounding points is terminal 3.  This jumps to the 2 left lugs of the volume pot and back from there to the RCA jacks.  From the top left lug of the volume pot there is a grounding jumper to the two bottom lugs of the headphone jack.  This jack may be different than what is being delivered today.

Also from terminal 3 you go to the center lug of the 9 pin tube socket.  This is the ground route for the LEDs in the cathode circuits.

The power supply ground comes from those bottom headphone jack terminals to terminal 12.  From there it jumps to terminal 14 and ends at terminal 20.

The heater (AC) supply is a ground wire from transformer terminal 4 to terminal 22.

You should read zero to T3, Volume 2 left lugs, both RCA outer conductors, headphone jack bottom terminals, T12, T14, T20, center pin of the 9 pin socket, and to T22.

Other grounds that should be solid are pin 8 of the large tube, pin 4 and 5 of the small tube, T8, T11, T14, T16, T17, T20, T21 & T22.