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Hi all, I'm embarrased and a bit lost.
my SEX amp only produces sound when the speakers are connected to the red speaker outputs. The sound is very scratchy and of poor quality. Sound is only produced if the red rca input jack is connected (no sound when just the black RCA input is connected). I've switched the tubes and then problem persists.
I didn't bleed the power from the amp after unplugging it and poking around to figure this problem out. I got a nasty shock and I know that I am very lucky. I need to know how to safely dishcharge/bleed the power from the amp before working on it. I've got a piece of wire with an alligator clip on either end; where should I put it?
Thanks for your help.
Follow Ups:
If you waited more than about 30 seconds and still got shocked, your amp certainly has at least a bad joint, if not a miswire. You generally bleed the amp through a resistor, not a wire. Did you do the voltage/resistance checks in the manual? I would imagine your voltage checks in the offending channel will be way, way off and lead to the solution if you post them...
Oh, I should mention that the speaker posts/wires might be only one of possibly many things that could go wrong. When I first wired my SEX amp, I screwed something up at the headphone jack and plugging in my speakers resulted in a weird, scratchy, out of phase signal that sounded like the difference between the two channels. Turns out I had misread something in the manual, and my red (positive connections) ended up really being the two outside/opposite posts, nearest the power plug and inputs, and the black (ground) ended up being the two inner posts between them. Needless to say, I figured that one out pretty quickly, since the headphones worked fine....
In terms of the speaker issue, are you sure that a) your speakers are connected to the posts properly (i.e., positive to red, negative/ground to the black post right NEXT to it)? If so, are your solder joints good on the solder cups at the end of the pins? If so, I would trace backwards and rule out the obvious. Are the lines going to each pin in the right place (i.e., did you cross over anything accidentally after the headphone jack?). Also, check your headphone jack connections for mix-ups - make sure the ground and signal wires are connected in the right places, and that the 120ohm resistors are in the right place (in series with the signal). If that still doesn't help, trace things back from the headphone jack to the transformer and terminal strip preceding it. Troubleshooting a circuit comes down to methodically working down the line and ruling out various possibilities. We've all been there at some point or another.
I'm surprised you got shocked by your SEX amp - I've never used a bleeder and always show 0V across the caps when I've worked on it. Of course, I let music keep playing through it after I've turned it off to keep the tubes conducting while they're still hot, which seems to bleed the B+ dry. You would want to use a big resistor on your alligator clips, not a wire! A wire will just short out whatever you're trying to bleed - you want to dissipate energy. Maybe somebody else will chime in on exactly where to place the bleeder, since I've never used one with the SEX. I've always bled big capacitors individually, but I'm sure there's a quicker way....
Still stumped. Rewired the project again. Still no sound from the left channel. Sound from the right is scratchy, bass is nearly absent. Here are the voltages for the connections, clearly there is something going on with the input jacks...
Center pin - input jacks: Black 96 when vol set to min, 96 when vol set to max, Red 96 when vol set to min, 96 when vol set to max
1,21 *
2,22 *
4,24 *
5,25 0
6,26 *
9,29 650
10,30 10 !!
12,32 600
14,34 *
15,35 0
16,36 *
17,37 0
18,38 0
19,39 vol min 0, vol max 95
20,40 250
A1,B1 *
A2,B2 *
A3,B3 0
A4,B4 vol min 0,vol max 95
A5,B5 *
A6,B6 1.3K
A7,B7 2
A8,B8 (A8, 4), (B8, 2)
C1,C2,C3,C4,C5 0
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