No sound on right channel (AKA: Apparently I must be a total newbie)

[bigfatpaulie]

Hello all,

I built my new Crack (this is my second one and 3rd BH amp) and it worked perfectly.  Now I added in the Speedball - all the voltage checks passed, all the LED's light up but there is no sound on the right channel.

I've checked continuity on all the paths.  I've flowed the solder on every connection on the SB boards and on the joints that I work on tonight.  I've switched L/R RCA cables, the side issue stays on the same side.  I've tested the headphones on a different amp and they work.

Added: I tested every transistor and diode.

Added: I've checked every resistor.

Added: I've rolled both tubes.

I should also not that the left channel sounds great.

Any thoughts?  Could it be a DOA part?  What am I missing?

Thanks for any advice.

-Paul

[fullheadofnothing]

Most likely a bad solder joint got jostled when you were changing out parts for the Speedball. Pictures of your build could be helpful, or just reflow every joint. If the voltages are correct, then the circuit is working, and therefore the parts cannot be "DOA."

[bigfatpaulie]

Yeah, I suspect so but this isn't my first build (I've also done three ANK kits, including a Level 5 DAC) and I've never been so stumped.  I've even tested the continuty from each post to the next one that the wire is connected too (IE, does the wire actually make a connection).

I've attached some photos.  Please let me know if there are others you would like to see.  I apologise for the mess, but at this point nearly everything has been re-flowed or re-solderd 3 times...

[fullheadofnothing]

The lock washers are missing from the standoffs — this won't cause the current problem, but it is a missed step.

Since the circuit is working, but not passing signal, the question is where is the signal getting lost. Several places that are somewhat common spots for this kind of thing are not shown in your images - the RCA jacks, the potentiometer (I see you've got an eBay special there, those are not always as reliable as the stock pot), and the headphone jack. Also the grid connections for the right channel: A7 is one of your sketchier looking joints and B1 is hard to see. A6 has too much solder on it, possibly concealing a joint that is not mechanically sound.

[bigfatpaulie]

Thanks.
Thanks for the input. 

As for the lock washers the manual says:

Insert a 4-40x¼" screw from the top side of the
chassis through the hole to the left of the 9-pin
socket. Slip a #6 lockwasher over the screw and
secure into a #4x1" nylon standoff.

For whatever reason I took that mean the washer went on the OTHER side of main plate. 

As for the RCA jacks there is continuity from them to the pot, resistance checks out on the pot and continuity from the end of the circuit to the headphone jack...  As well, keep in mind this did work before the Speedball and those areas are touched with the installation of it.

You're logic (Since the circuit is working, but not passing signal) however, is totally sound.  I will go over A7, B1 and A6 and report back.

[bigfatpaulie]

Okay, I cleaned them up a bit and nothing.  What is of note, however, is that if I unplug the left RCA cable and turn the volume way up on my source I can ever so slightly hear it on my right side (left is silent).

[fullheadofnothing]

Also meant to mention, most of your joints have too much solder already. When touching up, just hold the iron in place so the solder melts and flows evenly. No need to add more solder

That attenuator doesn't have lugs on it?!? That's just asking for poor joints. (The out end on the right channel is quite blobby...) If you have a pair of sacrificial headphones and a clip lead, you could try jumpering from the RCA hot to the red wire at the output of the attenuator. Note that this will be very loud - a source with a lowerable output is advised and definitely don't use the good headphones.

Also the HP jack looks a little under heated as well.

[bigfatpaulie]

Thank you so much for talking all the time to help me.  I really appreciate it.

RE; a lot fo solder.  Yeah...  Like I said, I've reflowed, and in come cases added solder so there is a lot.  The amp is a bit of a mess now. 

Okay, I completely bypassed the volume pot and RCA plugs - right from the inputs on the back of the RCA jacks right to A2 and A7 and the black to the ground.  Same.  Bloody.  Issue.

I swear, when I get this I will be screaming from the roof tops.

As for the volume pot being a piece; yeah.  I didn't know until it showed up.  Hey, at least it was cheap.  I don't use it so I could remove it entirely and just put in some resistors.

[fullheadofnothing]

Well if bypasssing it doesn't solve it, then that rules out its culpability.

I'm leaving the office for the night. You said your voltages were good, but could you please post them in case something stands out?

[bigfatpaulie]

Of course.  No problem:

OA : 77.4
IA : 196
B-A/B : 0.01MV
IB : 195.8
OB :70.4

OA : 104.3
OB : 123.7
G : 0.03 MV
B+ : 195.6

[bigfatpaulie]

FYI on HF a member asked me to test the tube voltages and they were:

A3: 1.53
A8: 1.53
B3: 137.6
B6: 103.7


Which prompted:

"somewhere in the circuit, from B3 to ground is not connected. so the tube is exhibiting the plate voltage (or near plate voltage) on the cathode, because its not conducting (fully). I would check the transistor's ground connection. R1 to ground of the constant current source board, and test the transistors (you don't have to pull them out in this circuit). Since its brand new, its not unheard of a 2n2222 to be bad brand new, thats why they are cheap (under a $1 each) and the tip50 is about half of that price."

Is that possible?  How would I test that?

[fullheadofnothing]

Permission is not granted to post any portion of our manuals on any forums.

That guy is very impressed with himself. I have asked the kit's designer to take a look at this thread and he should be helping you shortly.

[Paul Birkeland]

To bring down your B3/big board OB voltage, consider resoldering the joints on the TIP50 by OB.  The center leg can be difficult to properly solder as it is connected to the heatsink.  This iffy voltage could be causing the signal to drop.

To trace the signal, start by downloading a 60Hz tone onto your phone, then play that into the amp.  With the amp off, let us know the AC voltage you see with the volume control all the way up at A2 and A7.  Once you report those voltages, we can move along to the other parts of the amp.

The advice you got on HeadFi about the 2N2222 and TIP50 being cheap and unreliable is nonsense. 

[bigfatpaulie]

Yeah, it seemed he was trying to help but he couldn't help bashing every part.  When someone is that upset about something they lose perspective...  To each their own I suppose.

Thank you both for your help.

Okay, I have re-flowed the 6 solder joints on the 2 TIP50's.  I help the top of the iron on the underside of the board and used some very fine solder at on the top side letting is flow down though the board.

No change.

As for the 60Hz test I have a few questions.  So I did it ( from my MavBook) and right at the RCA input my multi-meter was read a fluctuating number between 0 and 0.09mV.  So I unplugged the RCA cable and measured it directly at the plug and I am getting the same result.  Is that correct or am I measuring something wrong?  What number (ish) should I be getting?  My 0 - 0.09 doesn't seem right.

[fullheadofnothing]

What does the left side measure? Is the volume cranked on the laptop?