70s rickenbacker bass copy wiring

musicalstash · July 2023

Can anyone help me sort out the wiring on this Japanese 70s rickenbacker bass copy.

The bridge pickup cuts out and when it does work has a low output, there is also some hum which goes away when I touch the jack plate.

I am guessing that the back of the pots should be all connected in a "loop" to the wire coming from under the bridge? But is there anything else I should look at.

https://ibb.co/WKSWWgc

https://ibb.co/859r6NW

https://ibb.co/jw1fKd7

. Thankzs

ICBM · July 2023

Yes, that’s bad grounding. In theory the shielding foil on the pickguard is meant to provide the common ground - in practice, contact between the pots and the foil can be erratic. It’s best to connect all the pot casings together - and despite some popular belief, this does not cause a ground loop if the shielding is not isolated from them.

The tone pots should ideally be A500K not B250K - Rickenbacker did use mismatched volume and tone pot values, and A (audio/log) works best for tone controls. They do appear to be original though, so if you don’t use the tone controls much it’s best to leave alone.

prowla · July 2023

Image: https://i.ibb.co/j47vvgL/IMG-20230721-183136-edit-53372839367376.jpg

Image: https://i.ibb.co/k8X4Q5R/IMG-20230721-183126-edit-53348016947067.jpg

Image: https://i.ibb.co/4S5tycB/IMG-20230721-183135.jpg

prowla · July 2023

Here's a link to the RIC wiring schematic for a 4001 bass.
http://www.rickenbacker.com/pdfs/19507.pdf

prowla · July 2023

ICBM said:

Yes, that’s bad grounding. In theory the shielding foil on the pickguard is meant to provide the common ground - in practice, contact between the pots and the foil can be erratic. It’s best to connect all the pot casings together - and despite some popular belief, this does not cause a ground loop if the shielding is not isolated from them.

The tone pots should ideally be A500K not B250K - Rickenbacker did use mismatched volume and tone pot values, and A (audio/log) works best for tone controls. They do appear to be original though, so if you don’t use the tone controls much it’s best to leave alone.

I agree that it's a good idea to have Gnd wires to all pot bases rather than rely on the mechanical contact to the shielding; if any of the pots have become loose they could've worn it away to make a poor connection.

I also think that the could possibly be a contact between the legs/wires of green Treble pickup's cap and the Bass pickup's body, as it seems to be stretched across and pass very close; if that is the case, a bit of masking tape there would do the trick.

Regarding the posts, it's a moot point whether they should be 250k or 500k and A (audio/log) or B (linear); if you look at the above schematic, you'll see that Rickenbacker couldn't make their minds up and opted to go for 330k (ie. somewhere in the middle!).

ICBM · July 2023

prowla said:

Regarding the posts, it's a moot point whether they should be 250k or 500k and A (audio/log) or B (linear); if you look at the above schematic, you'll see that Rickenbacker couldn't make their minds up and opted to go for 330k (ie. somewhere in the middle!).

They do now - I don’t know the changeover date but I think it’s in the 1990s. Older ones used the 250K volume/500K tone setup, which I think works better - it’s slightly fuller but also clearer, if that makes sense.

Regardless of value, linear pots don’t work well as tone controls - all the sweep is at the bottom end of the turn. The exception is for very low values - 50K or possibly 100K - used for a deliberately ‘jazzy’ tone, eg in the rhythm circuit of a Fender Jazzmaster/Jaguar, where the whole pot turn is that low-end range by design.

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70s rickenbacker bass copy wiring

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