Author Topic: Pickup Wiring  (Read 534 times)

Offline groovemonkey73

  • Fiesta Red
  • **
  • Posts: 19
    • View Profile
Pickup Wiring
« on: June 08, 2019, 12:21:15 PM »
Hey folks,
I'm a newbie here, and a newbie to the Rhodes, so I apologise in advance if the question I'm about to ask are obvious, and/or been covered before!
Quick back story:
I'm servicing/repairing/modding a 77' MK1 73 for a good friend if mine. Ive already done the bump mod, and replaced the hammer tips, and about to replace the tone bar screws and grommits in preparation for voicing and tuning.

Angwho, Ive wanted one of my own for so long, and having his to work on was unbearable knowing I'd have to give it back, so I bought one for myself!! Found a 79' Mk1 73 being sold by someone else I knew, and he was 100% with its state and condition, which isn't very good. With it being a 79' it has the factory bumps on the key pedestals which is great. Ive replaced the damper felts as they were shot, and Ive got a tone bar screw and grommit kit ready for this one too. The only thing with this one is, is there are more dead pickups than good ones. I can't see any visible breaks in the pickup wiring, but I'm going to re-wire it anyway.

My question is related to the red wire at the top end of the harp and where it connects, as there is a difference in the 77 Im doing for my mate, and my 79, and I'm not sure which one is right, or if they both are. Here are the pics:

His 77' mk1:


My 79' mk1:


My other question is, when measuring the resistance of each pickup, (probe of meter on each side of one pickup) what number should I expect to see?

There are differences all over the place on mine, consistant on my mates (which I'd expect as his pickups are sounding fine). His read on average avout 0.50.

Ive done the screwdriver test on both pianos (his all pop) - although not very very loudly. Some of mine do, most don't, and the ones that do, some don't actually play when its plugged into an amp.

Help! (And many many thanks in advance)

Newbie Glen
1979 Mk1 Rhodes 73
Nord Stage 2 Compact
Hammond XK3c
1915 John Broadwood & Sons Upright

Offline sean

  • Mark II
  • *****
  • Posts: 811
    • View Profile
Re: Pickup Wiring
« Reply #1 on: June 08, 2019, 08:22:14 PM »


The wiring on both pianos is fine.  The top pickup is grounded, well, tied to the tape on each rail, and then connected to the squiggly black wire that runs over to the ground tab of the RCA jack.
__________


A single good pickup will measure about 180Ω when not connected to anything else.

In the piano, the parallel nature of the pickup wiring shows up on the ohm-meter.

I would expect you to put your meter between the front and back terminals on the same pickup.

In a group-of-three, you should get about 60Ω if all three pickups are working,
In a group-of-three, you should get about 90Ω if two pickups are working,
In a group-of-three, you should get about 180Ω if only one pickup is working.
If your meter says OL, infinity, or just blinks at you, then all three pickups are dead.

Use the alligator clip and screwdriver method to determine exactly which pickups in the group are working.  Basically, you bridge across the dead pickups with an alligator clip, so that you can hear the remaining good pickups work.  See https://ep-forum.com/smf/index.php?topic=7116.msg36655#msg36655 or https://ep-forum.com/smf/index.php?topic=3839.msg17262#msg17262, and, of course, see http://www.fenderrhodes.com/service/pickups.html.

Text above copied from https://ep-forum.com/smf/index.php?topic=9989.msg55589#msg55589

Sean

Offline sean

  • Mark II
  • *****
  • Posts: 811
    • View Profile
Re: Pickup Wiring
« Reply #2 on: June 08, 2019, 08:31:16 PM »


This little diagram clearly shows the pickups wired in groups-of-threes:



(On a 73-key piano, the leftmost group is a group-of-four, the rest are groups-of-threes.)

Sean


Offline groovemonkey73

  • Fiesta Red
  • **
  • Posts: 19
    • View Profile
Re: Pickup Wiring
« Reply #3 on: June 10, 2019, 04:54:10 AM »
Hi Sean,

Thank you so much for both of your replies, that info is invaluable, and I shall certainly be following it to diagnose my pickup issues.

Good to know the top end harp wiring is fine for both, I'll leave alone!

I shall report back when I've got them both singing again!
1979 Mk1 Rhodes 73
Nord Stage 2 Compact
Hammond XK3c
1915 John Broadwood & Sons Upright

Offline groovemonkey73

  • Fiesta Red
  • **
  • Posts: 19
    • View Profile
Re: Pickup Wiring
« Reply #4 on: June 11, 2019, 02:29:18 AM »
So,

19 pickups dead in total, which isn't as bad as I first thought.

I can get them £12 each from a guy in the UK, which makes quite a sum of £228, or do I rewind and repair the dead ones?

Whats the general consensus on this topic?
1979 Mk1 Rhodes 73
Nord Stage 2 Compact
Hammond XK3c
1915 John Broadwood & Sons Upright

Offline goldphinga

  • Mark I
  • ****
  • Posts: 271
    • View Profile
Re: Pickup Wiring
« Reply #5 on: June 11, 2019, 10:40:38 AM »
Depending on where the corrosion is you can sometimes repair them. If you want to send them to me (PM me for details/price, Im based in Leeds UK) I can try repair them for you, though the disclaimer is it's not always possible depending on where the corrosion resides. If it's on the exposed bit of wire that comes out of the coil then we are good, if not then its a case of rewinding, or replacing them with new ones from Electric Keys. Currently I'm not in a position to offer rewinding yet, (but will be soon).  8) Cheers!
« Last Edit: June 11, 2019, 10:42:14 AM by goldphinga »

Offline groovemonkey73

  • Fiesta Red
  • **
  • Posts: 19
    • View Profile
Re: Pickup Wiring
« Reply #6 on: June 12, 2019, 02:15:06 AM »
Hey Dan! (Don't worry, I already follow your FB page, and a mutual friend Dan Burnett let me know about you recently!

I have read that you can sometimes bring them back, and this is going to be my first port of call. I'm quite handy, and as I've done all the other bits so far, I'm going to give this a go. There is definitely corrosion on the pickup terminals, but the rest of the coils looks OK on all of the dead ones so far, unless any corrosion is lurking under the top layer. If I get stuck, I'll give you a shout. Hope that's OK. I love learning to do and doing new things, so I'm quite looking forward to the challenge. (As I've enjoyed the challenge so far with both of these 73s, as they are my first EPs to service/repair).

All of the tape is peeling and although I know this isn't at all necessary at all to replace, I'm thinking of doing that too anyway. Whats your take on that?

I met Christian from EK on Friday funnily enough, as amazingly he is local to me, and he's currently waiting on a shipment from VV containing pickups as he currently doesn't have any in stock, so I've got him on backup to give me a shout as soon as they are! 

1979 Mk1 Rhodes 73
Nord Stage 2 Compact
Hammond XK3c
1915 John Broadwood & Sons Upright