Author Topic: Pickup ohm reading when connected in piano  (Read 1695 times)

Offline goldphinga

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Pickup ohm reading when connected in piano
« on: January 13, 2015, 01:29:24 PM »
On a stage 73 how much should a pickup read on the multimeter when connected in situe as normal? I know when out of the piano they read between 160-190 ohms...

Thanks

Offline David Aubke

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Re: Pickup ohm reading when connected in piano
« Reply #1 on: January 13, 2015, 01:46:58 PM »
~60 ohms? 180 / 3.
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Offline goldphinga

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Re: Pickup ohm reading when connected in piano
« Reply #2 on: January 13, 2015, 01:58:00 PM »
I knew you'd know David! Many thanks, just checked my piano now and they read 62.5 each. Seems I have some bad ones reading only 27.5 from notes 8-14. White tape if course!

Offline David Aubke

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Re: Pickup ohm reading when connected in piano
« Reply #3 on: January 13, 2015, 02:08:19 PM »
I don't know how to interpret a reading of 27.5 ohms. If one pickup in a set of parallel-wired three suffers a break, you'd see 90 ohms when reading across any one of the three pickups. The one broken pickup would eliminate an available path for the signal leaving it only the other two to fight its way across so your overall reading would increase. If two of three are bad, you'd see a full 180 across the set. All three bad: no sound from the entire piano.

The only way to lower the resistance would be if there's an internal short inside a coil thereby shortening the signal path and making it easier for the current to flow.
« Last Edit: January 13, 2015, 02:09:59 PM by David Aubke »
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Offline goldphinga

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Re: Pickup ohm reading when connected in piano
« Reply #4 on: January 13, 2015, 03:19:30 PM »
I should go into more detail...

Basically all the pickups are passing audio in the piano, but from pickup 14 down to pickup 8 (the first 6 pickups on the piano) the volume output gradually decreases. They are all set close to the tines like the other pickups.

All the pickups on the piano read 62.5 from the top note down to pickup 14, then from 14 down to 8 they all read 27.5 (these are all the ones where the volume is getting lower and lower).

So I'm thinking either all 6 must be bad or one is knocking them all out perhaps?

Any ideas gratefully received! I'm normally good with this sort of thing but its stumped me currently!

Offline drpepper

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Re: Pickup ohm reading when connected in piano
« Reply #5 on: January 14, 2015, 01:20:24 PM »
if the pickups are wired in sets of 3, that would leave 1 left over (73/3=24 remainder 1)
how is that last pick up wired? or does it work out somehow?
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Offline David Aubke

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Re: Pickup ohm reading when connected in piano
« Reply #6 on: January 14, 2015, 01:26:51 PM »
The first set on the bass end of the circuit is a set of four in parallel.

« Last Edit: January 14, 2015, 01:28:49 PM by David Aubke »
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Offline drpepper

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Re: Pickup ohm reading when connected in piano
« Reply #7 on: January 14, 2015, 02:04:40 PM »
thank you!
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Offline goldphinga

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Re: Pickup ohm reading when connected in piano
« Reply #8 on: January 14, 2015, 04:28:04 PM »
Great info guys- but can this explain the low readings on my last 6 pickups? Any ideas whats causing the gradual drop in volume? Do you think i should just replace the low reading pickups?

Cheers!

Offline drpepper

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Re: Pickup ohm reading when connected in piano
« Reply #9 on: January 14, 2015, 04:59:54 PM »
i am no expert, but you know there is a porblem in that region. If you are confident with a solder iron i would cut the first pickup free an measuing the resistance across it.
if it is ok, move to the next one, with one 6 beong of interest.
hopefully one will stick out.
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Offline David Aubke

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Re: Pickup ohm reading when connected in piano
« Reply #10 on: January 15, 2015, 08:04:22 AM »
I agree with drpepper. It will be difficult to diagnose any further without isolating the pickups. When you test across the terminals of a connected pickup, you're actually testing across all of the pickups in the parallel set. Testing from North of the first pickup to South of the last is the exact same thing as testing across a single pickup.
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