Help! Voltage check after Crack built

[beriault]

Hi guys,

Need some help figuring out what is wrong with my newly completed Crack amp.  Both tubes are glowing.  2 LEDs are light but the LED at A8 sometimes flicker during first minute or so (I have not let the amp run for too long since some voltages are off).

I've re-checked and re-flow all connectors and still getting high voltages on terminal #1, #7, A6, B1 & B3. 

 I get the following voltage values with both tubes inserted:

1 - 131 (90)
2 - 161 (170)
3 - 0 (0)
4 - 161 (170)
5 - 82 (90)
6 - 0 (0)
7 - 133 (100)
8 - 0 (0)
9 - 98 (100)
10 - 0 (0)
11 - 0 (0)
12 - 0 (0)
13 - 160 (170)
14 - 0 (0)
15 - 185 (185)
20 - 0 (0)
21 - 210 (206)

A1 - 82 (90)
A2 - 0 (0)
A4 - 0 (0)
A5 - 0 (0)
A6 - 133 (90)
A7 - 0 (0)
A9 - 0 (0)

B1 - 134 (90)
B2 - 159 (170)
B3 - 135 (100)
B4 - 82 (90)
B5 - 159 (170)
B6 - 98 (100)
B7 - 0 (0)
B8 - 0 (0)

I've included a pic of the board.

Thanks!

----------------
Alexis B.

[Paul Birkeland]

The flickering LED and high voltage on one side of the 12AU7 suggests and issue with the red wire passing through A4/A5, mainly that it isn't really connecting all that well to A5. 

Also, the black wire leaving the RCA jacks and heading to the pot looks like it has some funkiness around the pot, is it connected? 

[beriault]

The black wire from the pot to the RCA was a tad short during assembly so I soldered a lead from the end of the wire to the two terminals on the pot. 

I will check the wire through A4/A5 again tonight but I remember re-flowing this joint yesterday.

[beriault]

I resoldered a couple of connections and now the voltages are where they should be...   However there seems to be a lot of static,  scratching and buzzing on the right channel..  I find that the slightest vibration affects the buzzing (worsens or becomes quieter) .  The volume of the noise is constant no matter the position of the pot.  I am wondering if this is a bad solder joint or something wrong with a tube..

[Doc B.]

If you found that redoing some solder joints fixed the first problem it would be logical to see if this problem is solved by resoldering any more questionable looking connections.

[Grainger49]

Also, look in Grainger's Corner, at the FAQ thread.  The tube pins or socket might have some dirt on them.  There are suggestions there for cleaning them.

[beriault]

Hey guys,

It's been a while and I thought I should share news about this.  Turns out the problem was with the 6080 tube.  After resoldering and rechecking all connections I was still finding nothing so decided to take a break while I waited for my spare tubes.  As soon as I put the "new" 6080 in the socket the weird microphonics and buzz disappeared!  I'm actually surprised with how quiet it is right now.... very nice.

Thanks for the support,
Alexis