5yr Old Crack+SB Suddenly No Left Channel...PLEASE HELP [resolved]

[Timoteo]

Hey All!

Ok so I recently got back into the headphone game & got out my Crack+SB to power my HD600s.
Such a BEAUTIFUL combo I cannot speak highly enough of my Bottlehead Crack. LOVE LOVE LOVE this setup.
Been using it strong for a few months again.

However, just a day ago I plugged my 600s into the Crack...no left channel audio!! Oh no.

This is the troubleshooting I have done so far with no results.

Checked LEDs under amp - all light up (I counted 9)
Tested different input & output tubes (I have a handful of each for rolling) - still no left
Tested another 1/4" adapter - still no left
Tested with my Beyerdynamic DT177X - no left audio
Different RCA cables - still no left
Swapped L & R RCA cables - still no left
Visually inspected all joints - look good & feel solid (I know that doesn't tell me much)
Tested my Schiit Modi2 DAC with a different amp - all works normal (so its not the DAC)
Smashed it with a hammer - STILL no left audio (hahaha jk)

Now here is a weird issue. When I unplug the right RCA from the Crack & I turn up the volume I can hear the music very faint in the right channel.
So there is some obvious crosstalk of some sort going on. The left channel is bleeding into the right channel with only the left channel plugged into the Crack.
It may have always happened & I would never have known but thought I'd mention that.

I do have a mutimeter but have not checked any of the readings because I cannot find my manual (of course).
Plus I cant remember what I ate for lunch yesterday let alone how to check my Crack hahaha (no pun intended lol)

I am really bummed at this setback & I am looking for any/all help with where to go from here.
I've ready many forum threads where you guys help people diagnose so I know I'm at the right place.
I'll keep reading around here for other people who have experienced something similar but some direct help here would be greatly appreciated!!

Thank you guys in advance,
Tim

[Paul Birkeland]

You would really want to measure the DC voltages and post some build photos. 

Terminals 1 and 5 should measure about 80V, 2 and 4 about 170V, 7 and 9 about 100V.

-PB

[diynewbie]

Aren't there suppose to be 10 LEDs? Did you have to use a jumper for one of the two LEDs on the 9 pin socket in the original build?

[Timoteo]

@diynewbie

Thank you for pointing out that there should be 10 LEDs!
This got me looking closer near the 9 pin socket & sure enough there is an LED out. I don't know if this is the cause of my left audio being out so maybe you can help?
The LED that is out is connected from terminal A3 to the Center terminal for the 12AU7 socket. I am going to try & post a pic of it. Last time I tried I could not get any pics to post.

[Timoteo]

Here are some pictures of my Crack build. I built my Crack at the very end of 2016 & into the beginning of 2017.
My wife was pregnant with our now almost 5yr old. So while she was laid up on the couch not wanting to do a whole lot I setup my work station in the living room with her & worked on my amp.
I sanded down & buffed out the top plate to a mirror finish. I really should buff the top plate out again & maybe clear coat it so I don't have to keep on top of it. Right now the top plate looks ehh not so shiny. Its just that the amp sounds so good I don't want to mess with it.

Anyways, here are a few build pics as PB requested

[Paul Birkeland]

Build pics would be what the amp looks like now, not what things looked like as you assembled them.

You really need to check your DC voltages to get specific recommendations.  "An LED doesn't glow" will not suffice.

[Timoteo]

I see, my bad I misunderstood when you requested build pics. Ok I will make some time later today to get readings & post current pics. Just grabbed a new 9v battery for my meter, it was all over the place with readings. Its more stable now. Ill keep you guys posted. Thx again for your patience & help.

[Timoteo]

Ok got a few quick minutes to check the recommended terminal voltages. Here is what I got:

B1 = 81v
B5 = 171v (connected to A2 with wire)
B2 = 171v
B4 = 166v
A9 = 0

Looking closer I see one joint of the LED between A9 & the center connection of the 12AU7 socket has broken.
The LED looks to not be connected.
Even with my glasses on its difficult to see but from what I can tell the LED wire snapped (I probably overheated it during install)

Thoughts?

[Paul Birkeland]

You can install a jumper between A3 and A8 to get the amp back up and running.

[Timoteo]

Ugh I'm SO sorry...I mistyped.

The LED between A3 & the center terminal of the 12au7 socket is disconnected. Looks like the wire snapped between the LED itself & the center terminal of the socket.

[Deluk]

If you have to fit a new LED, make sure there is a service bend in the lead. They are very prone to break if you straight line the connections.

[Paul Birkeland]

You can still install the jumper between A3 and A8.

[Timoteo]

Thank you Paul & Deluk for the advise.

Paul, I am assuming the jumper is recommended as a temporary fix until I am able to replace the LED?

Do the LEDs act as a fuse in any way or do they just light up to let you know the connection is good between the two points of contact?

[Paul Birkeland]

The LEDs provide 1.57V of bias for each half of the 12AU7.  They are not fuses, nor are they intended to be indicators or used for visual diagnosis of whether the circuit is working properly.

The jumper isn't quite as good as two separate LEDs, but it will function until you can obtain replacements.

[Timoteo]

OK so I ordered & received a 5 pack of LEDs from Doc.
It took a couple weeks to find a few minutes to remove & resoldered the new LED in but to my glee it was all that was needed to get my Crack up to speed!

Long story short, I work from home on Wednesdays. While I am in the office I use my Beyerdynamic DT177X-GO with my Schiit Modi & Magni. A really fun combination. However, when at home working on Wednesdays I look forward to settling into my fully modded HD600s with non other than my Crack + Speedball. My home setup is such a beautiful setup & doesn't compare to any of my other combos.

So thank you all for helping me troubleshoot & get my home setup back up!!!

I really appreciate all your help.