Issues with voltage, 12AU7, and A8 LED [resolved]

[JL23]

Hi there, I am having some issues with my amp and I would greatly appreciate any feedback. Below are the voltages and the problems, thanks in advance!

1 - 144 (90)
2 - 160 (170)
3 - 0 (0)
4 - 161 (170)
5 - 76 (90)
6 - 0 (0)
7 - 144 (100)
8 - 0 (0)
9 - 100 (100)
10 - 0 (0)
11 - 0 (0)
12 - 0 (0)
13 - 160 (170)
14 - 0 (0)
15 - 183 (185)
20 - 0 (0)
21 - 207 (206)

A1 - 76 (90)
A2 - 0 (0)
A3 – 1.5 (1.5)
A4 - 0 (0)
A5 - 0 (0)
A6 - 145 (90)
A7 - 0 (0)
A8 - 12 (1.5)
A9 - 0 (0)

B1 - 144 (90)
B2 - 160 (170)
B3 - 144 (100)
B4 - 76 (90)
B5 - 161 (170)
B6 - 100 (100)
B7 - 0 (0)
B8 - 0 (0)

Issues:
1. Terminals: 1, 7, A6, A8, B1 and B3 are not within the 10% voltage range outlined in the assembly manual.
2. The 12AU7 tube does not glow when plugged in and turned on.
3. The LED connected to A8 does not light up -- I would mention that it previously did light up, however, after fixing a mistake (I had to rotate the octal tube socket, note the burnt insulation on many of those wires) the LED no longer turned on.
4. The 6080 tube does not fully sit inside the octal tube socket, however, both sides of it glow when turned on. Im pretty sure the reason it does not fit is because of solder that dripped down into the bottom of the B1 and B2 sockets. I have tried using solder wick to extract the solder, as well as scraping it with a small screw driver. Neither work.

Edit: Uploaded Photos

 

[i luvmusic 2]

Double check the orientation of those 2 LED's the silver band should be facing each other towards the centre pin.

 

[JL23]

Double check the orientation of those 2 LED's the silver band should be facing each other towards the centre pin.

The LED's stripes are both facing the middle pin.

 

[fullheadofnothing]

Nothing will work (including the LEDs) unless the tube is conducting, which requires a functional heater circuit. Check your solder joints at 4&5 on the transformer, A4/A5, and B7/B8.

 

[JL23]

Nothing will work (including the LEDs) unless the tube is conducting, which requires a functional heater circuit. Check your solder joints at 4&5 on the transformer, A4/A5, and B7/B8.

I resoldered all of the connections you mentioned. The A4/A5 connection looked pretty terrible so I cut off the end, and routed the wire first through A5 and then A4, it is now more tidy.
All of the issues still persist though.

 

[Paul Birkeland]

So one half of the 12AU7 glows but not the other? That is the place to start, and Josh is correct that the A4/5 connection is what you'll want to look over to get both halves of the tube to glow, and thusly the LED to glow.

 

[JL23]

So one half of the 12AU7 glows but not the other? That is the place to start, and Josh is correct that the A4/5 connection is what you'll want to look over to get both halves of the tube to glow, and thusly the LED to glow.

Hi there, neither side of the 12au7 tube glows. Also, I have resoldered the a4 a5 connection with no changes.
Thank you for the input, is there anything else I could try?

 

[Paul Birkeland]

Hi there, neither side of the 12au7 tube glows.

If one of the LED's on the 9 pin socket is glowing, then at least one half of the 12AU7 is being heated (look carefully in a dark room), or there is a grievous wiring error (we haven't seen one produce these symptoms before).

 

[JL23]

If one of the LED's on the 9 pin socket is glowing, then at least one half of the 12AU7 is being heated (look carefully in a dark room), or there is a grievous wiring error (we haven't seen one produce these symptoms before).

I was completely wrong, the 12au7 does glow, my apologies. Im not sure why I was expecting the the 12au7 to glow as brightly as the larger tube! Just to double check, there are two glowing points on the 12AU7 tube. Does this mean that both sides are actually turning on, or is it just one side?

 

[Rocketman248]

Sounds like your tube is working properly.  You are correct, though, the 12AU7 won't glow as brightly as the 6080. 

 

[JL23]

Great! Im not sure why the LED wouldnt be working then.. Also, if both tubes are working properly, what would be causing the voltage issues?

 

[Paul Birkeland]

there are two glowing points on the 12AU7 tube. Does this mean that both sides are actually turning on, or is it just one side?

If you look at the insides of the tube itself, you will see two distinct structures.  If you have a glowing point in both structures, then both halves are being heated.  If you have a glowing point at the top and bottom of one side, then you still have one side that isn't glowing.

If both halves are glowing, you can add a jumper wire between A3 and A8 and that may get you back in business (if you have a damaged LED).

-PB

 

[JL23]

After adding the jumper cable, all voltages read very close to the values listed in the manual, except A1, A6, and B1, which read as 79, rather than 90. This is right at the edge of the +/- 15% recommendation, is this okay?

Thank you for your help!

 

[Paul Birkeland]

79 is actually a better voltage than 90, so no concerns there.

-PB

 

[JL23]

Perfect! I set it all up and it is working fairly well. The aforementioned solder in the octal tube socket is making the 6080 tube not sit perfectly, which is noticeable sometimes through a humming in the left channel.

This currently isn't a problem as I firmly pushed the tube in place and it seems to be working okay, but I was wondering if there was any tip to remove the solder from the socket in order to avoid future complications?

After listening to my 650s directly connect to my computer for the last year, this is fabulous.

 

[Rocketman248]

Try heating up that pin while the amp is upright.  Gravity should help pull the excess solder out.

 

[Grainger49]

It might take a blow of air from the top too.  The solder "Wicks" up into the tube socket by capillary action.

 

[JL23]

I tried turning it over and blowing in it while it was being heated--it helped a bit but not completely. Additionally, i made a loop of solder wick, stuck it inside the socket and put the iron in on top of it... this removed a bit more solder but not all of it. This did yellow the plastic but I don't think it did any further damage than that.

The tube still  is clearly not fully seated, however, it is better than before. Concurrently, there is less background noise. Now there is just a quiet static that occasionally appears. I have ordered a new socket from bottlehead, as I already needed to replace the LED that has previously been found to not work! Hopefully this ameliorates all of the issues! I feel like it is a good idea to get everything perfect before carrying on with the speedball upgrade.