Crack - Speedball Voltages - no sound left channel (resolved)

[ostoich]

I know the manual says that being off by a few % isn't a big deal. I just want to make sure before I turn this puppy loose.

All voltages were within suggested range for the small board. The big board was a bit higher:

OA - 135v
OB - 120v
G - 0v
B+ - 206v

Everything look good?

Thanks for all the support.

[ostoich]

Well it sounds great in the right channel...

Nothing in left channel. Bummer. Back to work tomorrow I suppose.

[calmiswar]

DO NOT connect your good headphones into the amp right now.

I destroyed my HD700s doing that, don't make the same mistake.

[ostoich]

Right. I unplugged them right away. Tried taking some cheapies to find a loose connection with chopsticks. Couldn't find anything last night.

[Paul Birkeland]

What are the small board voltages?

[ostoich]

What are the small board voltages?

Small board:

OA - 78V
IA  - 202V
B-A/B - 0V
IB - 202V
OB - 78V

[ostoich]

The most noticeable thing is that the TIP50 on O2B runs hot and O2A stays cool. I suppose I'll focus on that side of the board. Any other thoughts about what might be wrong?

[Paul Birkeland]

Yes, I would agree that focusing on that side of the big PCB is a good idea.  It could be as simple as a bad solder joint that isn't allowing adequate current draw.  Since you have Speedball 1.1, the R1 resistors are where they should be, and the PN2907 and 2N2222 are impossible to mix up (your small board is also working, which excludes these possibilities).

I would bet on the center leg of the TIP50 on the offending side not being soldered well enough.

-PB

[ostoich]

Resoldered all leads of the TIP50. The soldering iron caused a spark on the lead closest to the center of the board. Now the LEDs on the A side of the board won't light. Thoughts?

Now I'm running:

OA: 196V
B+: 202V
OB: 120 V
G: 0V

What did I break? I'm​ a total novice but I thought the instructions were so clear that there was no way I could mess this thing up.

[Paul Birkeland]

How are your voltages at 6 and 10?

[ostoich]

How are your voltages at 6 and 10?

Both terminals 0V.

[Paul Birkeland]

I would suggest replacement of the TIP50 and the 2N2222 on that side of the big PCB.  A spring-loaded solder sucker makes this work much easier. 

[ostoich]

Ordered these from Mouser. Will they work or should I email replacement parts?

TIP50: http://www.mouser.com/Search/m_ProductDetail.aspx?r=512-TIP50

2N2222A: http://www.mouser.com/Search/m_ProductDetail.aspx?r=494-2N2222A

Sadly, I'm feeling a little impatient because of how close I am to finishing.

[Paul Birkeland]

You don't need to spend $6 on a 2N2222 transistor, Mouser # 610-2N2222  will do the job nicely.  The TIP50 selection you made is a good choice.

-PB

[ostoich]

So, I replaced the TIP50 and the 2N2222. LEDs still don't light on the A side of the big board. B side LEDs lights up fine after about 10 seconds. The 270ohm resistor from T15 to T21 also gets really hot... Really fast. Voltages are now:

Large Board:
OA - 55V
OB - 79V
B+ - 89V
G - 0V

Small Board:
OA - 77V
IA - 88V
B-A/B - 0V
IB - 88V
OB - 51V

I just removed the entire big board and will resolder every joint. Then try reinstalling it. Wish me luck.