Oil City Pickups: fixing an old DiMarzio

OilCityPickups

Yet another dead pickup to resurrect ... this one is interesting ... late 70s/early80s and 14k DCR, so of the 'Super Distortion' family ... four conductor wired, but with the old square mounting feet and definitely unpotted.

The 'pigtails' and output lead is in a bit of a 'two and eight', so the first thing was to separate the coils from the baseplate, un-solder the leads, and check the DCR of each coil to find the dead one.

Old (and I think new) DiMarzios don't have keeper bars ... the coils sort of hang precariously in mid air with tons of real estate on either side, and rely on the pole grub screws resting in some sort of yellow 'gumph' like bath sealant to keep the bobbins from drooping. Many go wonky with age ... this one hasn't, but once the sealant is broken it should be replaced to keep the bobbins stable.

 Here you see the slightly unusual sight of the narrower than modern standard ceramic magnet butted up to the pole screws on one side by a mild steel shim ... another interesting design 'feature'. 

The knackered and very short old four conductor cable cable is replaced with some of our new higher spec stuff ... and the dead bobbin is identified as the 'north' coil ... a loop of wire had come out of the top of the tape, been caught by something and snapped. Luckily this break was less than 100 turns in, so I simply stripped wire to the break and made good with a new pigtail and a properly shrink insulated solder joint. No loss of output will be noticed for being missing so few turns. As you can see ... very clearly unpotted.

The coil was re taped and the bobbins re installed ... using shrink tube to make a neat job of the connections (I used DiMarzio's colour code)

Hot melt glue is used here to give the bobbin ends a bit more support

And she's done ... with a smart new tape wrap ... ready to rock out for another 30 years :-)

Sarge

Yet another excellent post giving some valuable insight, thanks.

Btw this looks awfully like my Westbury Standard's dead sd which you worked wonders on, could it be?

OilCityPickups

Actually no ... but very similar

DefaultM

I bought one of these from eBay years ago that arrived dead. Must be quite common.

OilCityPickups

As they are not potted, it's fairly easy for the wire to creep out from under the tape (it's rather soft and gooey tape) ... if that happens on the top of an uncovered pickup ... a disaster may well happen.