Bad Channel [resolved]

[Nixalot]

I was so excited when I completed building the Crack headphone kit and it worked and it sounded wonderful. It played beautifully all day yesterday,  Today, I installed the Speedball upgrade. It played great for about 20 minutes when their was a loud crack in the headphones. Now it sounds like mono with one channel playing at normal volume and the other channel playing at one quarter volume. All of the tiny LEDs on the small board and the bigger board were on when it was working, now the tiny LEDs on the Speedball's small and large boards  are off.  I have no idea what went wrong. This is my first time ever using a forum.  I hope someone can help me.

[Paul Birkeland]

Can you post the voltages on terminals 1-10?

[Nixalot]

I can't believe I went from a fully functional Crack to this.  It seemed like the more I tried to figure out what was wrong, the worse things got.  It started with things going on and of as I raised and lowered the top panel   Now this, really pathetic:
Terminal 1 = 0vdc
             2 =109vdc
             3 = 0vdc
             4 = 0vdc
             5 - 69vdc
             6 = 0vdc
             7= 21vdc
             8 = 0vdc
             9 = 77 vdc
            10 = 0vdc

[Nixalot]

And the transformer was too hot to touch.

[Paul Birkeland]

Can you post some build photos? 

Terminals 2 and 4 are wired together, so one can't be 109 and the other 0V.

Frequently we used to see a problem like this when the insulators on the TIP50 transistors were not properly installed, but the warnings in the manual have so far been pretty effective at preventing that for the most part. 

[Nixalot]

I have attached a couple build photos.  Terminal 2 goes on and off as I move wires around but I cannot seem to find the loose connection.  I guarantee that all of the components are in the right place and right orientation.  I am 71 and I have successfully built many electronic kits over the years.  After all, my Crack played beautifully before I installed the upgrade.  The more I work on it, the worse it seems to get.  I am frustrated with this and nervous about my upcoming surgery.  I ask a favor.  Could I please send my Crack to you for evaluation and repair?  If I shipped it to you priority tomorrow, 08/12, you should get it next Monday, 08/15.  If you were able to finish by 08/25 and shipped it back to me priority, I should have it by 08/29, right before my surgery.  That would give you 10 days to work on it and get it back to me before surgery.  I hope that you can help me here, or I am going to need to quickly order a different headphone amp for myself.  Thanks, Gary

[Paul Birkeland]

If you pull the 6080 and run the amp with just the 12AU7, what happens to the voltages on terminals 1-5?

[AB2KH]

Gary,
From your photos it looks as though you have some level of short going on evidenced by the first and possibly second 270 ohm resistor in the power supply. Are the diodes on the left side of the terminal strip oriented and installed correctly? It's hard to tell from the photo.
I would revert the amp back to non speedball and use it that way until after your surgery at which point it might make a good project during your recovery period.
Take Pauls advice pull the tubes and measure the power supply voltages and make sure it has not been over heated to the point of non repair. somewhere between standard circuit and speedball you have a miss wire or faulty components.
How long did you listen to the standard build before adding the speedball? the problem may have been there all along but did not have enough time to present it self before you shut it off to add the new circuit.

Chris/AB2KH

[Nixalot]

Only one terminal shows voltage, terminal 5, 70vdc.  Terminal 2 goes up and down as I push on it, but I cannot find where the loose connection is.  I have resoldered the terminal strips and everything around it.  I swear that I listened to the Crack without the Speedball for 6 hours.  And I have been a good kit builder all my life.  And it just goes from bad to worse.  I used my $4,000 headphones to test Crack.  After getting nowhere  yesterday, when I took the headphones to my other system, one channel is blown.  I know it is the headphones because my other headphones work.  Something must have shorted.  If I need a new transformer, then so be it.  I will pay for my mistakes.  I am afraid to work on this anymore and I need to concentrate on my health.  I guess I will ask one more time.  Can I please pay you to fix it, whatever it costs?

[Paul Birkeland]

Damaged headphones will happen from backwards 100uF caps, which you probably don't have, and loose black wires at the headphone jack (which is extremely common).

You can contact queen(at)bottlehead(dot)com to request the repair service if you'd like and I can sort it out for you.

[Paul Birkeland]

It's important to mention here that we do not accept repairs in packaging we haven't provided specifically for that purpose.  The box used to send this kit to me was absolutely tiny and the amount of packaging used to protect the kit was insufficient.  Your power transformer is dented and damaged, your top plate is smashed in, and there's enough broken glass rattling around in there that I will be taping this one back up and returning it as-is and we will refund the repair order.