Acousticaster hum issue

[Nad259]

I have a Godin Acousticaster with the 18v (2 battery) pre amp. It has a hum that goes away if I touch the output jack plate.

It did have some crackling noise, but this has gone after I re-soldered the battery connections, the 3connections to the output jack as well as where the out put wires attach to the board. However the hum persists. Any ideas how to fix the hum?

[Caleb_Elling]

Have you examined the pickup to see if it's become damaged at all?

Sometimes the brass portion of the pickup can delaminate from the saddle itself, which can cause a hum.

[Nad259]

Thanks Caleb. The pickup look solid the brass portion seems well attached to the saddle. no damage or gaps visible. Touching the brass section of the pickup stops the hum. I haven't unsoldered the pick up from the pre amp to check it independently. Are there visible signs of delamination?

I did find that many of the wire/solder joints [battery connectors and attachments to the output jack) had deteriorated and were very brittle. The battery connectors broke off when changing the batteries and the the shield wire broke when removing the output jack from the body. Once resoldered the crackling noise was eliminated. The pickup/preamp sounds wonderful, except for the hum.

[Caleb_Elling]

OK,
It should be fairly easy to tell if the pickup was coming apart. It sounds like it's not.

If all of the ground contacts going to the PCB are connected, you shouldn't be getting shielding hum. It might be worth trying a shielded output jack or shielding the existing jack.

Have you tried this guitar in different rooms, locations, or amps/PA's with the same issue?

[Nad259]

Thanks Caleb - I've tried the guitar using different amps and different rooms all have the same hum.

I'll try shielding the output jack.

My other thought was to put a metal /foil strip under the bridge to ground the strings and attach this too the output shield - as in an electric guitar. Its dealing with the symptom rather than the cause but may be a work around.

[Caleb_Elling]

Thanks Caleb - I've tried the guitar using different amps and different rooms all have the same hum.

I'll try shielding the output jack.

My other thought was to put a metal /foil strip under the bridge to ground the strings and attach this too the output shield - as in an electric guitar. Its dealing with the symptom rather than the cause but may be a work around.

That should be a doable workaround. Obviously, it's not ideal, but short of shielding the whole preamp cavity, it's probably the easier option.

[Nad259]

Hum eliminated!
I placed some shielding metal tape under the bridge to ground the strings. I soldered a wire to the tape and connected the other end to the shield on the output jack. Hum gone!

Before grounding the strings I shielded the pre amp cavity, but the Hum persisted.

The images are of the underside of the bridge after shielding. With and without strings. Getting the tape under the tines was a challenge.

320318565_548284603914813_9193805993302732342_n.jpg
324652402_484768643865287_2983386808099190949_n.jpg

[Caleb_Elling]

That's great news and excellent work!

Thanks for sharing pictures of it too. I'm sure this will be helpful for other users in the future.