Hi all, the bridge p90 in my '67 Firebird has died.
Putting it on the multimeter it reads 23k ohms. With it producing no output I expected it to register nil, so I'm a little confused.
The multimeter is brand new and the other pickups read correct at around 8k.
Do I have an open coil or partially open coil?
Any help/advice greatly appreciated. Thanks!
P90 Issues
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jvin248
- PAT. # 2.972.923
- Posts: 660
- Joined: Mon Apr 11, 2016 5:34 pm
Re: P90 Issues
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Any other visible damage?
Are you measuring the free ends of the pickup wires? or still in the guitar circuit? Unsolder the hot lead from the switch and test so you know the pots/caps are not influencing your reading or they could be damaged. Could be bad solder joint from the pickup leads to ground and/or switch. Re-flow the solder and recheck.
If still a problem in the unconnected pickup, I'd suspect the solder junction where the lead wires are attached to the very thin bobbin wires to have corroded or even have been a poor factory solder job. So before you order replacement pickup(s), carefully dismantle the pickup and using a soldering iron heat up and add a little more solder (not a lot) to the junctions. Measure the kohms again after. If that does not fix then unwind ten percent of the outer wraps on a bobbin to discard, scrape the coating off the new free end of the bobbin wire with a knife, wrap that around the pickup lead several times, and resolder. Check kohms.
Be extremely cautious with the 'start' bobbin lead wire as those break off and to get the end of them you have to unwind the whole bobbin. You can buy a sewing machine motor for about $15 on ebay to rewind ....
A side note: you could be a victim of steel wool chips if anyone used steel wool on the frets/fretboard... those wool chips get drawn into the coils by the magnets and slice up the bobbin wire coating over time. Look for any such build up -- if that's the cause then removing the outer wraps of wire may fix you up.
.
Any other visible damage?
Are you measuring the free ends of the pickup wires? or still in the guitar circuit? Unsolder the hot lead from the switch and test so you know the pots/caps are not influencing your reading or they could be damaged. Could be bad solder joint from the pickup leads to ground and/or switch. Re-flow the solder and recheck.
If still a problem in the unconnected pickup, I'd suspect the solder junction where the lead wires are attached to the very thin bobbin wires to have corroded or even have been a poor factory solder job. So before you order replacement pickup(s), carefully dismantle the pickup and using a soldering iron heat up and add a little more solder (not a lot) to the junctions. Measure the kohms again after. If that does not fix then unwind ten percent of the outer wraps on a bobbin to discard, scrape the coating off the new free end of the bobbin wire with a knife, wrap that around the pickup lead several times, and resolder. Check kohms.
Be extremely cautious with the 'start' bobbin lead wire as those break off and to get the end of them you have to unwind the whole bobbin. You can buy a sewing machine motor for about $15 on ebay to rewind ....
A side note: you could be a victim of steel wool chips if anyone used steel wool on the frets/fretboard... those wool chips get drawn into the coils by the magnets and slice up the bobbin wire coating over time. Look for any such build up -- if that's the cause then removing the outer wraps of wire may fix you up.
.
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mijmog
- PAT. # 2.972.923
- Posts: 1041
- Joined: Tue Sep 09, 2008 7:03 am
Re: P90 Issues
Thanks for the reply, really appreciate it.
Anyone wound their own pickups, I'd like to get a cheap winder as I'm fairly mechanically minded and it doesn't look hard at all?
Yes, I've took the pickup out of the guitar to double check there's nothing odd going on, and to isolate it. Still reads the same.
I'm going to check these again and reflow the join, there must be something on to make it read over 20k ohms. Surely it should say 0? I did notice it going very thin over time and suddenly one day it stopped.
Anyone wound their own pickups, I'd like to get a cheap winder as I'm fairly mechanically minded and it doesn't look hard at all?