Sibob Posted January 9, 2011 Share Posted January 9, 2011 A sequel to my last pickup output thread basically . Got my multimeter working right and took readings from all my 4 Jazz basses. It does turn out that the bridge pickup on my '83 is 'open circuit'?! (a reading of 124 as opposed to in the 6.5-7.5 ranges), so therefore damaged and in need it replacing/rewinding. Now my question is, how might these readings differ whilst actually fitted to the bass, as opposed to just the pickup on a work bench?. Why I ask is I've been recommended Wizard 84's which apparently have a dc output of around 11kohms. Now my readings across all basses seem to be between 6.70 and 7.6. Baring in mind that i'm more than happy with those, the Wizard 64's seem to be more like it at outputs of around 8kohms?! Enlighten me? Lol Si Quote Link to comment Share on other sites More sharing options...
BOD2 Posted January 9, 2011 Share Posted January 9, 2011 If the pickup winding has broken somewhere then you would get an "open circuit" reading and no signal from the pickup. It's worth checking that the wire hasn't broken where it leaves the bobbin. If you examine the pickup there will be two blobs of solder where the hookup wires join the bobbin. The pickup winding should also be attached to these blobs of solder and should be visible (just) as two very fine wires coming from the pickup. Sometimes the pickup winding breaks here, disconnecting it from the hookup wires. If you can see a stray "hair" of pickup winding here that's not soldered to the blob then you could repair it simply by resoldering at this point. The DC resistance is a measure of the number of windings on the pickup. More windings = higher DC resistance. Higher output pickups will often have more windings, although it's not quite as simple as that. The Wizard 84s (at 11kOhms) are probably heavily overwound, as opposed to the Wizard 64s which are a more vintage style of pickup. These two pickups probably sound quite different. Quote Link to comment Share on other sites More sharing options...
LawrenceH Posted January 9, 2011 Share Posted January 9, 2011 If you're planning on mixing pickup types then you might find the overwound pickup is lost when the pickups are both on full (despite being hotter output on its own), unless you used a buffering pre-amp. Best to check with Wizard if that's the route you're going down, I'd guess a single 64 would be a better match both tonally and resistance-wise than the 84 but I've not used them myself. Quote Link to comment Share on other sites More sharing options...
Sibob Posted January 9, 2011 Author Share Posted January 9, 2011 If I was to replace the erroneous pickup, I would do so with a matched pair. But would a set of 64's be a better match to the rest of my collection than the 84's?....I don't want a bass that is considerably louder than my others. So I'm trying to assatain whether the ratings of pickups unattached would be similar to their equivalent ratings whilst fitted in the bass. 11kohms unattached might equate to 9kohms fitted because of pots/caps/wiring etc?? I don't know these things lol If not, I'm thinking the 64's would better match the '83 Jazz with my other basses Si Quote Link to comment Share on other sites More sharing options...
flyfisher Posted January 9, 2011 Share Posted January 9, 2011 [quote name='Sibob' post='1083162' date='Jan 9 2011, 02:27 PM']Now my question is, how might these readings differ whilst actually fitted to the bass, as opposed to just the pickup on a work bench?.[/quote] The meter will only measure the resistance between the its two probes (obvious, yes, but bear with me). Thus when you measure the dc resistance on the work bench, the only thing connected between the probes is the pickup, so you are only measuring the pickup itself. Which is what you want. When you measure the dc resistance fully fitted into the bass, there are also other things connected across the pickup, and thus between the probes, notably pots but possibly a whole host of active circuitry in some cases. Thus, without a circuit diagram, it's difficult to know exactly what you're measuring - except the dc resistance between the meter probes. Quote Link to comment Share on other sites More sharing options...
icastle Posted January 9, 2011 Share Posted January 9, 2011 [quote name='Sibob' post='1083397' date='Jan 9 2011, 06:28 PM']If I was to replace the erroneous pickup, I would do so with a matched pair. But would a set of 64's be a better match to the rest of my collection than the 84's?....I don't want a bass that is considerably louder than my others. So I'm trying to assatain whether the ratings of pickups unattached would be similar to their equivalent ratings whilst fitted in the bass. 11kohms unattached might equate to 9kohms fitted because of pots/caps/wiring etc?? I don't know these things lol If not, I'm thinking the 64's would better match the '83 Jazz with my other basses Si[/quote] As you've already surmised, measuring a component in circuit has the potential to be incorrect. If you haven't got a circuit diagram or the ability to translate metered resistance readings into 'real values', the best thing to do is to disconnect one end of the component you are testing. That way there's no chance of any items paralleled with said component affecting the reading - 30 seconds spent desoldering and then resoldering the connection after metering could save you a lot of stress... Quote Link to comment Share on other sites More sharing options...
Sibob Posted January 9, 2011 Author Share Posted January 9, 2011 Ok cool, that's what I thought might be the case. All my basses are standard wired Fender Jazz Basses, so nothing too complicated. I wonder what the added resistance of the other components would bring the readings down to?!.....I don't know what the standard cap is in a Jazz?.....plus Volume/Volume/Tone pots.....although I was only measuring one pickup at a time, so only it's relevant volume pot would affect each pickup!? I guess I'm not too fussed about bang-on accurate readings, all I'm trying to assatain is whether the 84's or 64's will be better suited to the rest of my collection based on the readings I can easily get I don't have a soldering iron to hand, but could source one I'm sure Cheers Si Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted January 9, 2011 Share Posted January 9, 2011 Don't forget that the impedance and DC resistance are not the same. As well as the resistance of the wire itself there is the inductance of the coil to add on. Inductance is frequency dependent and so the impedance of the coil is a 'nominal' figure anyway. Quote Link to comment Share on other sites More sharing options...
icastle Posted January 9, 2011 Share Posted January 9, 2011 [quote name='Phil Starr' post='1083555' date='Jan 9 2011, 08:31 PM']Don't forget that the impedance and DC resistance are not the same. As well as the resistance of the wire itself there is the inductance of the coil to add on. Inductance is frequency dependent and so the impedance of the coil is a 'nominal' figure anyway.[/quote] Makes little difference in this scenario. The OP is just taking readings on 'cold' pups for comparative purposes. Quote Link to comment Share on other sites More sharing options...
flyfisher Posted January 10, 2011 Share Posted January 10, 2011 [quote name='Sibob' post='1083461' date='Jan 9 2011, 07:21 PM']I wonder what the added resistance of the other components would bring the readings down to?!.....I don't know what the standard cap is in a Jazz?.....plus Volume/Volume/Tone pots.....although I was only measuring one pickup at a time, so only it's relevant volume pot would affect each pickup!?[/quote] Caps should have no effect as they block dc (unless they are failing). Tone pots will also probably have no effect if they are wired in series with a cap - but you can easily test this by turning the pot during measurements and seeing if the resistance changes. But, all in all, I agree with the other comments. Desolder the pickups (one end anyway) to be absolutely sure of what you're measuring, but also be aware that simple dc resistance may be of limited use anyway. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.