Dimarzio Chopper Wiring Query

Adzy

Hi

New member here

I am new to doing mods / upgrades and as a first step bought a Dimarzio Chopper Rail Humbucker to replace the single coil in my Bridge. Initially no intention to coil split etc, just straightforward series wiring initially to see if I like it. Aware I’ll lose hum canceling at position 2 but this is a first step only.

I checked the pickup with my Multimeter prior to installation as per the Dimarzio schematic:-

RED (North Start) - Hot

BLACK (North Finish) + WHITE (South Finish) Taped together

GREEN (South Start) to Ground

BARE to Ground

RED to GREEN (Both Coils in Series) = 8.80 Kohm

RED to BLACK+WHITE (North Coil) = 3.80 Kohm

GREEN to BLACK+WHITE (South Coil) = 5.00 Kohm

However when I tie GREEN + BARE together as is (I assume?) normally required to ground to the Volume Pot, this reduces both coils in series output to 3.80 Kohm. I assume this is because it is effectively sending the South Coil to Ground?

Dimarzio does state that “...when connecting the BARE wire to ground, make sure it does not come in contact with any other connections”. How would this be practically achieved? Even if grounded separately on the Volume pot, it would still be effectively in contact with the GREEN (South Start) 

As a test I switched the wiring around as follows:-

BLACK (North Finish) - Hot

RED (North Start) + GREEN (South Start) Taped together

WHITE (South Finish) to Ground

BARE to Ground

This gave me the same outputs as follows:-

BLACK to WHITE (Both Coils in Series) = 8.80 Kohm

BLACK to RED+GREEN (North Coil) = 3.80 Kohm

WHITE to RED+GREEN (South Coil) = 5.00 Kohm

But….In this instance, when I tie WHITE + BARE together, both coils in series output remains at 8.80 Kohm…?

I purchased the pickup direct from Dimarzio so I’m confident it’s genuine.

As a new modder I’m probably missing something obvious, but if not and the pickup is faulty I need to return it within 30 days, so any help would be greatly appreciated.

Cheers

ICBM

The pickup - or more likely the hookup cable - is faulty. There's a short, I think between black and ground. Measure from the bare wire to all the other wires and see what you get. (The red-black resistance seems too low too.)

The two individual coils (black to red, and green to white) should give the same reading, and the bare wire shouldn't be connected to any of the other wires or make any difference to the coil readings when it's connected to one of them.

Funkfingers

Where are you taking the meter readings? At the end of the output conductors or on the solder joints on the pickup's PCB?

If the output cable has been abused, it is possible for the insulation on the output conductors to be damaged. (Usually near the hole where the 4-con + shield cable passes through the pickup baseplate.)

DiMarzio "track" pickups with a chrome finished cover have an additional solid wire connection to ground the cover. This could be touching the solder joint for one of the coil ends. (In this instance, the black one.)

•

My comments assume that your pickup has the traditional hard-wired output cable rather than the Solderless™ block and pins system. 

The Solderless cabling is not infallible.

Funkfingers

Adzy said:

Dimarzio does state that “...when connecting the BARE wire to ground, make sure it does not come in contact with any other connections”.

By this, DiMarzio means do not run the bare grounding cable strands such that they could make physical contact with the metal terminals of the selector switch, the input and output terminals of the pots and the switch contacts beneath a push-pull pot.

If you have no option but to run things close together, add insulation around the bare grounding wires.

Common sense really.

Adzy

ICBM said:

The pickup - or more likely the hookup cable - is faulty. There's a short, I think between black and ground. Measure from the bare wire to all the other wires and see what you get. (The red-black resistance seems too low too.)

The two individual coils (black to red, and green to white) should give the same reading, and the bare wire shouldn't be connected to any of the other wires or make any difference to the coil readings when it's connected to one of them.

Thanks ICBM,
I did a Continuity test between the bare wire and the other wires and got a positive for the White and Bare. All other wires returned nothing. As this is a quick connect model I disconnected the cable and this outcome was repeated when testing the connector pins on the pickup directly.

It appears then there is an internal short between the Bare and White. Would this explain why using a "BLACK (North Finish) = Hot" configuration as detailed in my initial post returns a full power Series output, as this requires the White & Bare to be sent together to ground, and as such they are connected together anyway?

Thanks

ICBM

Adzy said:

Thanks ICBM,

I did a Continuity test between the bare wire and the other wires and got a positive for the White and Bare. All other wires returned nothing. As this is a quick connect model I disconnected the cable and this outcome was repeated when testing the connector pins on the pickup directly.

It appears then there is an internal short between the Bare and White. Would this explain why using a "BLACK (North Finish) = Hot" configuration as detailed in my initial post returns a full power Series output, as this requires the White & Bare to be sent together to ground, and as such they are connected together anyway?

Yes.

I thought it was a white-to-ground short initially, but changed my mind for some reason! Anyway, that's the problem - the pickup is faulty if there's conductivity from white to ground at the pins on the pickup. It will work if you want to use it in the white to ground configuration - but the different coil readings still seem off to me. I would return it.