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Topic: Grounding problem with a pre-war Rickenbacker |
Gary Meixner
From:
New York, USA
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Posted 21 Feb 2011 1:53 pm |
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My six string Rickenbacker bakelite has developed a nasty hum. If I keep my hand in contact with the magnets it is just your everyday single coil annoyance but when I take my hand off it gets quite loud. I can't see any obvious culprets and I am reluctant to mess with the wireing too much without knowing what I am looking for. Does anyone have an idea of the cause.
Thank you,
Gary |
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Andrea Tazzini
From:
Massa, Italy
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Posted 22 Feb 2011 2:45 am
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| Did you try to unplug lamps and computer near your guitar and amp ? |
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Jason Hull
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Posted 22 Feb 2011 2:56 am
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| Does it quiet only when you touch the magnets, or will it quiet when touching other metal parts? I suspect that you need a bridge/string ground wire. |
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Gary Meixner
From:
New York, USA
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Posted 22 Feb 2011 5:55 pm
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Guys,
Thanks for the replies. The hum is not caused by any outside factors, its source seems to be in the pickup circuit. Touching the magnets is the only way to stop it. I will take more of the guitar a part and see what I can find. Thanks again.
Gary |
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Rick Aiello
From:
Berryville, VA USA
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Posted 22 Feb 2011 6:22 pm
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If this just recently occured ...
Sounds like the ground end of the winding ... which exits through the bottom of the pickup via a bare solid copper wire ... and is soldered to the grounding loop interfacing with the aluminum mounting plate by way of the bobbin mounting screw (#6-32) ...
Has torn loose from it's # 38 winding ... inside the deepest layers of the winding ...
You need to send it to Jason Lollar ...info@lollarguitars.com ... for a rewind !
Hope that helps ... |
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Kelvin Monaghan
From:
Victoria, Australia
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Posted 22 Feb 2011 7:42 pm
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| Hi Gary,check no dry solder joints on the grounds,also check the cap connections those old caps can give out and hum.By the way there is no string grounding on the Bakelites because the strings dont touch any metal parts only the Pickup assembly and bottom control plate are grounded assuming it has metal plates and not the plastic ones.Under normal conditions Bakelites are pretty quiet. |
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Gary Meixner
From:
New York, USA
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Posted 28 Feb 2011 6:20 pm
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Rick,
I contacted Jason Lollar and have sent my pickup off to him for repair and rewinding. The body of the guitar is in very good shape but the bridge has had grooves cut for the three lower strings which don't look like they were done at the factory. Does anyone know if this would have been done by Rickenbacker? I may decide to fill these. I may also fill and recut the nut slots. Thanks for the help.
Gary |
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Rick Aiello
From:
Berryville, VA USA
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Posted 28 Feb 2011 6:38 pm
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For poor slotting jobs ... which are numerous ???
Get Devcon's Plastic Steel ... fill in all the slots ... let it cure for 7 days ... then sand flush ...
Don't cut bridge slots !!!
Just slide the strings over the pole pieces ... and bring to pitch ...
Adjust height with knurl nuts ...
Folks have adjusted height and/or compensated for string gauge ... by taking V shaped files to bakelight bridges ... big mistake
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David Matzenik
From:
Cairns, on the Coral Sea
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Posted 1 Mar 2011 4:44 am
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My Pre-war Ric had a hum that was reduced by touching the horseshoes or the metal jackplug. I lined the control cavety with copper tape which grounded to the jack socket. The metal cover plate completed the Faraday cage and reduced the hum to almost nothing.
_________________
Don't go in the water after lunch. You'll get a cramp and drown. - Mother. |
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Gary Meixner
From:
New York, USA
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Posted 1 Mar 2011 6:15 am
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Rick,
Thanks for the tip on using Devcon Plastic Steel. I work for an epoxy formulator and we make a wide variety filled epoxy products, some that are very close to items in the Devcon line up. I will look at the tech data and compare. Have you ever tried using Resorcinol or one of it variants, Aerodux, Aerolite etc. They are essential the same resin as Bakelite. Ground nut shells may have been used as a filler. This is what I was planning to use prior to hearing your suggestion for Devcon Plastic Steel.
Dave, I will get a roll of copper adhesive foil to line the control cavities with.
Thanks,
Gary |
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Rick Aiello
From:
Berryville, VA USA
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Posted 1 Mar 2011 6:48 am
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Devcon's Plastic Steel is just the hardest epoxy I've found at my local hardware store ... so thats what I have used ...
But whatever you use, let it cure longer than the the product recommends ... alot of pressure will be exerted when bringing the strings to pitch ... and you don't want too much settling ...
As far as bridge slotting ... in some Bakelites ... lining the strings directly over the poles is difficult because of the poor pickup seating, drilled string thru holes, etc ... so cutting TINY slots to help you position the string may be needed ... but very shallow cuts will do ... nothing like the nut's depth ... just a scratch line.
Also, as mentioned above ... prewars are always going to have some hum that will dissipate some when your hand touches the magnets ... mine are worse in low humity conditions (ie winter) ... so any extra shielding as David has mentioned ... can't hurt.
But from your original description of the hum ... I think things will be much improved after Jason's fix.
Hope that helps ... |
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