Crack Build, Problems! (pics)

[dean0]

This is my first BH build, and I'm having some problems.
I only get one channel playing (left). Things I have tried:

-Checked all voltages/resistance readings are within 15%
-Re-soldered all joints
-Changed Tubes
-Tried different h/p's

Here are some pics;
Any ideas what to look for would be much appreciated

 

[dean0]

to view larger pics: http://s474.photobucket.com/albums/rr102/dean_8486/

 

[HF9]

A few quick questions that will help to narrow things down hopefully.

• Are all the LEDs lighting up?
• Did you verify all the measurements in the back of the assembly manual with a multimeter?
• Did you confirm that you wired the potentiometer correctly?
• Was the amp working before the Speedball upgrade?

 

[STURMJ]

Ive used this potentiometer many times, that was the first thing I looked at. (esp. since the white wire was not visable utill later pics).  I don't see any error, assuming there are no bad solder joints.

 

[Doc B]

Is the headphone plug making good contact with the headphone jack? A couple of folks have had issues with the jack and their headphone plug. We have one cable with a Neutrik plug that you have to twist just so to get it to work right in our house Crack, even though every other plug works just fine with it.

 

[dean0]

A few quick questions that will help to narrow things down hopefully.

• Are all the LEDs lighting up?
• Did you verify all the measurements in the back of the assembly manual with a multimeter?
• Did you confirm that you wired the potentiometer correctly?
• Was the amp working before the Speedball upgrade?

Yes all LED's light up.
Some resistance measurements are off, is this because of the speed-ball upgrade or large film caps?
The terminals below only have a reading in the 200M ohm scale on my DMM

7: no reading
9: no reading
13: no reading

B3: no reading
B6: no reading

 

[dean0]

Is the headphone plug making good contact with the headphone jack? A couple of folks have had issues with the jack and their headphone plug. We have one cable with a Neutrik plug that you have to twist just so to get it to work right in our house Crack, even though every other plug works just fine with it.

yes I read about this issue in other posts and replaced the jack, also if I short the tip/ring together I get sound in both channels, but I guess that is just mono right?

 

[Paul Joppa]

...
yes I read about this issue in other posts and replaced the jack, also if I short the tip/ring together I get sound in both channels, but I guess that is just mono right?

Since the plug must be in the jack when you do this (right? or have I misunderstood?) you must have done the shorting at the jack terminals. Therefor a) both jack terminals do connect to the plug, and b) one of them is not getting signal. The signal comes from the output capacitor, whose other end is connected to one of the cathodes of the 6080. If my logic is correct, then it must be one of those connections, or (unlikely!) a bad connection inside one of the output capacitors, or a bad tube section.

 

[Paul Birkeland]

To test the headphone jack, I would short the two outputs together at the jack (the tip and the ring fed by the big output caps) to see if that produces output on both channels into your headphones.

If it does, your jack is OK and we can point you in a few other directions to test the rest of the circuit.

If you still get no output from that channel, then the jack can be singled out as the cause.

If you get no output from either channel, then you have a short to ground in the output wiring (extremely unlikely). 

Give it a shot and let us know.  If you don't have a clip lead, I will often times use a cut lead from a resistor as a temporary jumper.

 

[dean0]

...
yes I read about this issue in other posts and replaced the jack, also if I short the tip/ring together I get sound in both channels, but I guess that is just mono right?

Since the plug must be in the jack when you do this (right? or have I misunderstood?) you must have done the shorting at the jack terminals. Therefor a) both jack terminals do connect to the plug, and b) one of them is not getting signal. The signal comes from the output capacitor, whose other end is connected to one of the cathodes of the 6080. If my logic is correct, then it must be one of those connections, or (unlikely!) a bad connection inside one of the output capacitors, or a bad tube section.

Yes I shorted the h/p jack. Done so more listening and there is sound in the right channel but very faint, I have swapped the 6080 for a 5998, but have not tried swapping the 12AU7, could a bad valve in this position cause a fault like this?
Also I have used my DMM to double check wiring around the output caps and all is okay.
Are these measurements in my previous post a problem?
The terminals below only have a reading in the 200M ohm scale on my DMM

7: no reading
9: no reading
13: no reading

B3: no reading
B6: no reading

 

[Laudanum]

A bit OT here but is it just me or are the pictures reversed?, or is the top of the plate actually the bottom of the plate or vice versa ... or something like that?

 

[dean0]

problem solved, bad 12AU7, I will update soon with more pics and listening impressions!

 

[Grainger49]

Dean,

Don't feel rained on.  I bought Seduction the day it came out.  During the build I had the tubes standing up in front of me.  I knocked them over more than once and the result was noise.  My bad fortune was self inflicted.  BUT...  I had already bought a hand full of NOS tubes to roll through.  I didn't mind.

Congratulations on a tidy, proper and successful first Botthehead build!