A3 LED doesn't light up and half of 12AU7 doesn't glow

[ritchiepurple]

After installing the speedball upgrade I cant seem to get the amp to work. The A3 LED no longer lights up and the back half of the 12AU7 doesn't seem to light up. I have tried re-soldering points A1-A5 and I have re-soldered my way through the other points in the channel but voltage readings haven't changed (see readings below, my readings in the brackets).
Terminal
1 75 (85)
2 170 (185)
3 0 (0)
4 170 (184)
5 75 (170)
6 0 (0)
7 100 (95)
8 0 (0)
9 100 (176)
10 0 (0)
11 0 (0)
12 0 (0)
13 170 (185)
14 0 (0)
15 185 (203)

19 0 (84)
20 206 (0)

A1 75 (175)
A2 0 (0)
A3 1.56 (14)
A4 0 (0)
A5 0 (0)
A6 75 (85)
A7 0 (0)
A8 1.56 (1)
A9 0 (0)

B1 5 (84)
B2 170 (184)
B3 100 (95)
B4 75 (176)
B5 170 (182)
B6 100 (175)
B7 0 (0)
B8 0 (0)

I hadn't used the amp in a while before i did the upgrade so there may be more than one issue. Any ideas?
Thanks in advance!

 

[Paul Birkeland]

If the 12AU7 doesn't light up, this is indicative of a bad solder joint on A4/5.
-PB

 

[ritchiepurple]

I've tried re-soldering that joint a couple of times and still nothing. Half the 12AU7 lights up but still nothing from the LED or the other half of the 12AU7.

 

[Paul Birkeland]

I would double check in a dark room, just to be sure that both halves aren't lighting.

 

[ritchiepurple]

You were right! both are lit but the back one is just a lot dimmer but can be seen in a dark room. A3 LED still not lit though.

 

[Paul Birkeland]

Now that we have that sorted, the center leg on the MJE-350 is generally very resistant to soldering.  You might want to try reheating that joint.

Also, it's a fairly common error to swap the 2N2222 and 2N2907 transistors, as they look very similar.

-PB

 

[ritchiepurple]

Ok transistors were in the right places and i tried reheating the middle leg on the MJE-350 and a few of the other suspect looking joints on both of the small PC boards but for my efforts the two LED on the right PC board are also no now not lighting up. A3 LED not lighting still either.

 

[Paul Birkeland]

Are the MJE350's oriented properly themselves?

 

[ritchiepurple]

Yes they are!

 

[ritchiepurple]

Anything else you think I should try? I haven't try changing the tubes yet as I'm out of spares but have some on order. Did the voltages suggest it could be a bad tube?

 

[Paul Birkeland]

You could try installing a temporary jumper between A3 and A8, on the off chance that an LED on the 9 pin socket got damaged when installing the Speedball. 

The voltages suggest either an issue on the small board feeding T5 (usually that pesky MJE-350 center leg), half the tube not being heated, or an issue with the LED on the tube socket.  Generally speaking, since the Speedball is installed into working Cracks, this narrows down the troubleshooting considerably.

I would also note that one LED on the 9 pin socket glowing much brighter than the other, along with a high voltage at T1 or T5 indicates that the R1 resistors are not the correct value, this might also be something to triple check.

-PB