Series I neck pickup problem.

[tdukes]

This morning I was getting a loud hum from the neck pickup of my '77 Series I guitar with the 5 pin cable and no sound at all with a regular 1/4 jack. (I had previously wired the 1/4 jack for mono and used it successfully) The bridge pickup seems to be working fine. I used the guitar this weekend with no issues.
 
What should be my first step in resolving this?
 
Todd.

[lbpesq]

Todd:
 
You might want to unplug the pickups inside the electronics cavity and swap them.  Then see if the problem switches to the bridge pickup or stays with the neck pickup.  If it stays with the neck, then the problem is with the pickup, if it moves to the bridge, then the problem is somewhere down the line in the circuit.
 
Bill, tgo

[tdukes]

Thanks Bill. I'll try that.
 
Todd.

[tdukes]

I took the back panel off. There are three coaxial cables marked red, blue, and black. I swapped the red and blue and replaced the panel.
 
The hum still occurs when the selector is in the neck position. I infer this means the problem is not with the pickup itself.
 
Todd.

[LMiwa]

I would look at the points where the neck pickup lead connects to the circuit board.
 
Can you post a closeup of the circuit boards? Someone may be able to spot something or mark places to check.

[David Houck]

Todd; when you say that you had previously wired the 1/4 jack, are you saying that you yourself did the work?  If this part of the circuit has been modified by someone other than Alembic, I would be inclined to check the modification; perhaps a bad solder joint, or a short between the lead for the neck side and the ground where they attach to the quarter inch jack.  Also, if done by someone other than Alembic, were the recommended resisters used, and do the resisters look good?

[tdukes]

I did the work myself. There is a picture in this thread.
 
When I say there is hum on the neck pickup, that is all there is, hum. No signal. The bright switch, volumn, and filter change the character of the hum (60 Hz maybe), but no (or very little, inaudible) signal from the strings.
 
Todd.

[David Houck]

Oh yes, I remember that thread now!  Did you move the resister leads away from the shielding and back plate?
 
Another quick check; is the pickup selector switch loose?  Could it have moved and have developed a grounding problem with the shielding?

[tdukes]

I did now (before I posted my last message). It did not help. The pickup selector seems very secure. I do not believe it has moved.
 
Todd.

[tdukes]

I have talked with Tony at Alembic. I am removing the PF-6 card and sending it to them for testing.
 
Thanks for all the help.
 
Todd.

[tdukes]

I found an old thread where Mica said a PF-6 card was $350. Does anyone think that is not a good amount to insure one for when shipping it back?
 
Thanks,
Todd.

[David Houck]

Let us know how it turns out.  I can't recall how much shipping companies charge for that amount of insurance, but I'm thinking the charge for $350 can't be too much, and it's certainly a good idea.  I have no idea what the current cost of a PF-6 would be.

[mica]

Darn, Todd. The card tests out OK. Maybe you can email a few clear photos of the output jack wiring, and the electronics cavity in general.

[tdukes]

I feared as much. I have taken some pictures of the electronics, trying to show the connections. I took pictures of the control knob as well, but they were all too fuzzy to be of any use. Let me know if they would help. The connections there looked good to me. If there are points I can check with a multimeter, I have one.  Let me know if you need additional pictures.  Thanks, Todd.  

 

 

 

 

 

 

 

 

 

[mica]

Thanks for posting these pics. My dad is going to take a look over them tonight. I'll let you know if he's got any theories after that.