What does one or two dead strings mean for my pickup?

[Jon Flynn]

I just bought an old supro lap steel with the string-through pickup. Unfortunately, I had buy it long distance and was unable to inspect it before hand.

Upon plugging it in, I found that the 4th and 5th strings have remarkably less volume than the others. It is very obvious. I tested it in two amps and the results were the same.

Does anyone know what this means or how easy (or not) a potential fix might be?

Thanks a million..

[Bob Tuttle]

Have you tried a new set of strings?

[Clyde Mattocks]

I have an old Supro with the same issue on the second string. The pole pice screws were frozen in place, so I super-glued a little piece of solid wire onto the pole to get it closer and it worked.

[Jon Flynn]

I hope my word choice wasn't confusing. I don't think older strings could account for this kind of drastic differnce between the strings. There must be some malfunction in the pickup. I just don't know enough to figure out whether it's worthwhile to hold on to this thing and fix it or return it.

I posted here after getting a not-helpful response from the shop I bought it from, but since then, they've written again and provided a more helpful response.

He suggests that the magnets might have been re-installed incorrectly (upside down or on the wrong side or something) after cleaning. Does this jive with anyone's knowledge about these pickups?

[Michael Brebes]

The pickup has to be one of two different designs:
1. Separate magnetic pole pieces for each string, like a Fender pickup.
2. One magnet in contact with steel slugs or screws, like Gibson, Gretsch, etc.

If they are separate magnetic pole pieces, either those two pole pieces are too low, lost some of their magnetism, or possible inverted field (but very unlikely.

If they are a magnet with screws or slugs, then the screw or slug needs to be adjusted closer to the string. From Clyde's reply, this might be the case. If the screw is frozen, you can always use one of the commercially available compounds to free it up, which might include having to open the pickup.

Hope that helps.

[Paul Sutherland]

I had the exact same problem with a 1947 Supro that was given to me. It has the string through pickup, probably exactly the same as your Supro. The final outcome was that one half of the pickup was dead. I had it rewound by a guy in Sacramento for about $75, and now the guitar works great.

These pickups are very much like Fender Precision Bass pickups, in that they are two single coils connected in some fashion to create the total output. It is possible that one half has gone dead.

It's also possible that the magnets need to be recharged. Also the magnets could be installed incorrectly, and merely flipping and/or turning magnets could fix the problem.

I'm no expert on this stuff, just sharing my experience.

[Stephen Cowell]

Bronze strings (like the Black Diamonds that were the only ones you could get, at the drugstore) are really dead compared to the newer nickel or steel-wound strings. If you've got bronze strings on there that would explain what you're hearing...big difference between wound and plain.

[Rich Hlaves]

In some of these style PUs there is only one magnet and the piece on the other side is a dummy.

Test magnets, change strings and adjust pole pieces if possible.

[Jon Flynn]

Thanks to everyone for your responses. Very interesting input about strings.

First, as a matter of clarification, I mis-typed my first post - it is strings 5 and 6 that are dead, not 4 and 5.

Over the weekend, I changed the strings. Nothing. Moved the magnet around (only one there with a dummy on the other side as Rich suggested... the magnet, by the way, happens to be on the bass side of the guitar). Nothing. I inspected the pole pieces, but didn't move them as they were already as high or higher than those on the treble side.

I'm starting to wonder if, as Paul suggested, the bass-side half of the pick up is dead and the only reason you can hear the 4th string is that the other half of the pickup is... well... picking it up. Or could there be another explanation?

By the way, since the only magnet is located on the bass side (the "dead" side), can I assume that it has enough power, and is not the culprit here?

[Steve Ahola]

Measuring the DC resistance at the output jack with a meter will give you some idea what is going on. The two coils of the Supro coil are wired in series- off the top of my head each coil is around 2k ohms so the two coils should read something like 4-5k ohms. From your description it is possible that the coil on the bass side has gone bonkers, to use the technical term.

I've been running into strange things with lap steel pickups that I've never seen on regular guitars but that might have to do with them being made in the 40's and 50's. I had a Dual Pro pickup that measured infinite ohms yet it still produced a very beautiful sound. Evidently there were some open circuits in the windings but the signal was getting through due to some sort of capacitive effect.

If you can measure the DC resistance at the output jack please post your measurements. Or just send the pickup out to be rewound.

Good luck!

Steve Ahola

P.S. These steels work great with just a single magnet on the bass side- I think that the sound is a little bit clearer with one magnet instead of two although there is a minimal reduction in signal level. Just my own opinion on that...

[Jon Flynn]

Thanks Steve.. Well, I guess I ran into some strange things, too. First I measured 3 ohms, then infinite, then 4.5 or so. When it read 4.5, I quickly and carefully put everything back together, and.... drum roll please.... Now it works fine. After this experience, maybe I should open up a repair business!

[Paul Sutherland]

On my supro the combined output reads 6.73 ohms. Not sure what significance that has to this discussion. Just a little factoid.

[Steve Ahola]

On my supro the combined output reads 6.73 ohms. Not sure what significance that has to this discussion. Just a little factoid.

Thanks for posting your reading (I like to keep track of stuff like that.) I'm assuming that you do mean 6.73K ohms (6,730). For older pickups I expect a wide range of values- like 4K(Supro) to 12K(Dual Pro). If the reading is in the ballpark and it sounds fine then I don't see a problem.

Well, I guess I ran into some strange things, too. First I measured 3 ohms, then infinite, then 4.5 or so. When it read 4.5, I quickly and carefully put everything back together, and.... drum roll please.... Now it works fine. After this experience, maybe I should open up a repair business!

You would not believe how often sh*t like that used to happen when I used to be an HVAC service tech (that is heating and cooling.) Half of the time it would stay fixed and half of the time it would stop working again. (Over time I did learn the usual suspects that would cause the intermittent problem.)

I am assuming that your readings were 3k and 4.5k. My guess is that the connection between the two coils had gotten grounded, with the treble coil reading 3k and the bass coil reading 1.5k.

Which brings up an interesting issue: I have never measured the individual coils in Supro pickups- I always assumed that both coils would roughly the same. It would be interesting to try flipping around one of the pickups to see if it would change the sound and response.

Steve Ahola

[Paul Sutherland]

Yes Steve; I meant 6.73K ohms.