Zig zag pick up wiring

[Oliver Sheen]

I have just removed 19 dead pickups from my 1969 Rhodes which (reading other posts here) probably isn't too bad. I noticed the wiring of the bottom 10 pickups were in a zig zag pattern and not in there parallel 6's as the rest of the harp is.
Why is this? Many thanks O

[David Aubke]

The KMC 1 I recently worked on had all its pickups wired to alternating poles.


I think it's for hum-cancellation but I can't explain why they stopped doing it or why it was only done to a subset of your pickups.
http://www.seymourduncan.com/blog/the-tone-garage/how-hum-cancelling-works-part-1

[Ben Bove]

This concerns me - rarely are there that many pickups dead on your vintage of your piano.

On top of that, the zig-zag wiring is factory, and is done across the entire harp from top to bottom.  In your case, someone may have mistakenly rewired the pickups according to the newer pickup wiring chart in the service manual.

Here's a 1967 or 1968 harp where you can see zig zag all the way up to the top.


Your pickups may not be dead, its just they weren't matching the rest of the piano's wiring.  It should be wired the old way or the new way, one or the other... so don't toss those pickups!

[Oliver Sheen]

Hi Ben I tested every pickup with a screened cable, jack on one end and croc clips on the screen and core so could listen to each individual pickup. Admittedly when I got to the criss cross wired ones there were an alarming amount that were gone (10 out of 13 I think) and only another 9 across the whole keyboard...

On the strength of your doubts I will test again tomorrow. Maybe with them all being separate I will get a different result.

Also the criss crossed wired pickups are orientated with the terminals facing down as opposed to up as on all the other pickups.

[Oliver Sheen]

...in any event I'm a shocking hoarder and would never throw away something with such historical significance

[adcbicycle]

I bet Ben is right that someone wired it wrong, the pattern should continue all the way through, either all x-crossed, or crossed every X pickups. Probably worth removing the wire on the bottom ones, and while it's off checking the resistance to see if they're dead. 19 does seem high, not impossible though, I had a 1980 stage with 9 dead.

[Oliver Sheen]

Does the fact that the terminals for the criss crossed pickups are facing the other way from all the other pickups mean anything?

[sean]

Yes.  It means that the pickups are mounted upside down.

So happy to help.

Sean

(I was joking here.  My "apology" is three posts down below.  I just typed it too slow.)

[David Aubke]

Does the fact that the terminals for the criss crossed pickups are facing the other way from all the other pickups mean anything?

Does this suggest the group of cross-wired pickups came from an earlier Sparkle Top?
http://ep-forum.com/smf/index.php?topic=9126.msg49629#msg49629

[Ben Bove]

My guess is that the upside down pickups (which is factory) were not rewired because the previous owner didn't see them.  He probably only wired the pickups he could see, turned right-side up, according to the modern pickup wiring diagram.  That's the only way I can conceive someone combining 2 different wiring schemes.

[sean]

Sorry.

I believe that the pickups on the lowest notes might have their terminals mounted underneath to avoid collisions with the very long tonebars.

I would love to see a photo of the pickups mounted with the terminals down.  It is not just a regular pickup flipped over (with the aluminum tab at the tail end of the pickup clipped off), right?  I hope it is a pickup with the bobbin mounted just like a normal pickup (so that the coil and bobbin hang below the aluminum mounting tail), but with the metal terminals inserted from the bottom side of the bobbin.

Sean

[Ben Bove]

Hey I thought it was funny Sean

You are correct, the pickups are flipped because of the tonebars - but specifically because the lowest notes have weights on them, so if tone was adjusted in a certain way, the weights would short out the terminals.

The pics aren't specifically highlighting this issue, but you can make it out:

[Oliver Sheen]

Hi Sean Sorry wasn't being cool about your joke (I thought it was funny too) been paying the bills with crappy gigs...

I have attached a photo with the remaining (i.e. ones that still work and haven't been taken out for rewinding) pickups. As you can see the bass pickups are mounted, as you rightly pointed out, upside down 

[Oliver Sheen]

Just to be clear my Rhodes has the transitional single twist tone bars.

You can also see the original position of the front rail pins