New-to-me 1979 Series 1 pre-amp wire not connected

[el8ed]

Hello,

Series 1 SSB named “Honey” on account of her glowing Koa top just arrived, and since she is such a lovely girl I am going to restore her to all her shiny like-new glory.


When I took off the electronics cavity cover to polish it I found one wire from the pre-amp board not connected to the rest of the bass—see photo.


That does not look right to me, but what do I know of the mysteries of Series electronics. The bass seems to play just fine and sounds great safe for some slight RF noise.


I would appreciate it if someone knowledgable could have a look at the photo below and tell me if I should connect the open wire.


Thank you much!

[adriaan]

If the two loose ends reconnect easily, they make up the middle connection, which might be for the dummy humcanceller, which might help with hum. RF interference might require the proper upgrade, which is often (though not always) needed for older Series instruments (which this one clearly is).

[jazzyvee]

I think it is the hum canceller. The board looks like mine and the connectors for the two pickups are the coax to computer type connectors that alembic made for me. Like mine the middle one is still uses the original connector. It is possible that bass has replacement pickups which may also be a sign that it has the humcancelling upgrade as sometimes the pickups need changing for that process. But like mine it may just have new pickups.

here is my card for reference

[el8ed]

Thanks for the help guys!


I was getting brave and connected the “open” wire and voila—no more EF noise or hum. Yeah!


Hope all the refurbishing tasks are going to be that easy and successful.


Cheers,
Oliver

[adriaan]

Fortune favours the brave.

[gtrguy]

Yes, the middle wire is for the hum pickup. It usually takes a good tug to disconnect those wires, which makes me wonder if something else might be going on.

[gtrguy]

Oh OK, I see the pickup wires were updated for use with newer pickups that have the square wire ends. maybe they didn't have 3 of those connectors and only bothered to do two instead and leave the middle PUP unconnected.

[JimmyJ]

More likely the two pickups are replacements which needed the adaptors - but the hum canceller is original.  Why they left it unplugged is a mystery but we're glad you figured it out.

Jimmy J

[el8ed]

Thanks again for the collective hand-holding. I’ll be back with more questions as I did deeper into the restore.


The previous owner had the pre-amp card recently refurbished at the mothership. I assume that the guitar tech who did the re-assembly “missed" the third wire.


It’s all good now  .

[rv_bass]

The hum cancel wire looks frayed on the other end and wrapped with electrical tape, you might want to check that if it acts up again.  Lots of metal tape placed in there as well.

[el8ed]

Good eye Rob, thank you. I might look what’s beneath that electrical tape and maybe do some cleanup.
The whole electronics cavity does not look quite as clean as one might have hoped for…but, if it’s not broken...

[gtrguy]

Be sure to do a hum canceling procedure with the pots after finished. The ones that you can access from the outside of the big control cover. There are good instructions on this site for the procedure involved.

[el8ed]

I’ll do that once all the immediate updates are finished: clean-up, brass polish, new strings, set-up, intonation, etc.
Thank you for the advise!