Not sure what to hope for....

[fender3x]

This is the primitive wiring diagram that I made for an ESB-4 type bass. It has developed a problem with the bridge pickup. Not sure how clear the diagram is. This bass has push-pull switches on the Volume pots. In the normal (down) position, the bridge pickup is humbucking. In the up position only the Red/White coil is activated.

That's the way it always worked. But a few days ago the pup stopped working with the switch in the down position. With the switch in the up position, single coil mode was still working. With the switch down, humbucking position made no sound at all.

So, I disconnected the green and white wires from the switch, and connected them to each other. That should have bypassed the switch and put the pickup in humbucking mode. Still no sound. I checked the to see that the black wire was well grounded (earthed) and it had a good connection.

What that makes me think is that there is a break either in the green lead or the black lead somewhere between the switch and the pickup (unlikely) or that one of the wires inside the green/black coil has broken (likely).

So can anyone think of another possible problem I can test, or am I dealing with a busted pickup?

These pickups are Bill Lawrence EB-50's. I just put a review of them on the aftermarket parts forum, because I really like them and there were a few available on Reverb/eBay. Since I hadn't seen any since about 2018, I thought I'd share my joy. When I checked a few minutes ago there was only one left. So I bought it. These pickups sound great, and are dead quiet when you are not playing. In spite of that neither of the companies that make BL pups make this particular model anymore.

I will feel a bit stupid, and about $60 lighter, if my current pickup is fine. Nevertheless, I am hoping that the last known replacement in existence arrives safely. The bobbins are the wrong color...but you can't hear the color of the bobbins....

[fender3x]

I'd still like to see if anyone comes up with a different diagnosis. I ordered a couple of new push-pull pots, and plan to replace the one that's currently in place rather than re-solder the old one. I don't think the pot's the problem, but might as well eliminate the possibility.

[WeirdBits]

Disconnect the Green and White from the push/pull (in case it is shorting/broken internally), and connect the Green to the Red on the pot lug. That should tell you if the Green/Black coil is working (assuming the Black is still connected to ground).

A Multimeter is still the best test option. Disconnect the pickup and check the resistance across the coil pairs, that will show what’s working and that all the colours are correct. Just in case. Test the push/pul too.

[fender3x]

Disconnect the Green and White from the push/pull (in case it is shorting/broken internally), and connect the Green to the Red on the pot lug. That should tell you if the Green/Black coil is working (assuming the Black is still connected to ground).

When I connected the green lead to the red on the pot lug, the pickup sounded fine.

So I completely disconnected the pot/switch and tried three combos: 1) red to output jack; white to ground; 2) green to output, black to ground; 3) red to output, white to green, black to ground. All three sounded fine.

A Multimeter is still the best test option. Disconnect the pickup and check the resistance across the coil pairs, that will show what’s working and that all the colours are correct. Just in case. Test the push/pul too.

With the pot/switch out, I measure the coils individually. Both read at 3.4K Ohms. I connected the white and green wires, and tested from red to black. This was about 6.8 ohms, so it looks to me like the pickup is fine.

So I tested the switch...and it seems OK too. I am guessing that this means a solder connection was bad. I have already ordered some new push/pull pots, so will be replacing the pot/switch when it comes. Hopefully this will take care of the problem.

Thanks, Weirdbits! Looks like I'll have a backup pickup (already on its way here) if the pickup ever really does go bad again ;-)

[McCreed]

Looks like I'll have a backup pickup (already on its way here) if the pickup ever really does go bad again ;-)

Or, you're half way to the next bass!

[fender3x]

That thought had occurred to me...

[fender3x]

I am guessing there was nothing wrong with either pickup or pot/switch, but I replaced the pot anyway. It's working fine now. Thanks again! Managed to do the replacement pulling just the volume pot and switch through the F-hole, so I did not even have to take the wiring harness out. Whew!