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Topic: Supro pickup question |
Paul Sutherland
From:
Placerville, California
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Posted 6 Jul 2011 10:59 pm |
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What output, in terms of ohms, should I be getting from my Supro string though pickup? I've heard this should be a high output pickup, but mine seems really weak. My little multi-tester reads only 209 ohms!!
That's so low I doubted the reading at first, but then I tested my Emmons and got about 19K, and my Strat and got about 5k; so I think the meter, and my testing method are reasonably correct.
Any thoughts? |
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Denny Turner
From:
Oahu, Hawaii USA
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Posted 7 Jul 2011 7:23 am
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Are you reading the coils with the pickup lead unsoldered / disconnected AT the volume pot input? If not then you might be reading the resistance of the 250K volume pot ...or c.e. 200K if the 1Meg tone pot happens to be set at that resistance, or a combination of volume and tone pots settings in parallel to ground, ....since any of those cases would be the least resistance for the meter to read to ground which is where (ground) the other whole p'up output lead is connected to (one lead to the volume pot "input" and the other lead to case ground). The route(s) inside the pot(s) that the resistance would travel depends upon which of several correct pot(s) wiring schemes are hooked up. Forgive any typos or brain farts here; It's 5:00 AM and I'm pretty dizzy finishing up a lonnnnnnnng day, ...although eyeball editing looks right.
The coils resistance should be around 2.5K for each of the two separate bobbins coils (they're 2 separate 3-string pickups wired in series between the volume pot "input" and case ground) to make one 6 string pickup; Or resistance should be around 5K between the whole pickup's leads reading the 2 pickups in series:
http://dennysguitars.homestead.com/BillRicklesSuproP4.html
Other pretty good insights into Valco bunker pickup Steel Guitars can be found here (scroll down to Valco):
http://www.dennysguitars.com/CustomerReportsAndWorkExamples1.html
Hope that might help.
_________________
Aloha,
Denny T~
http://www.dennysguitars.com/
Please help support humanity:
http://www.redcross.org/en/aboutus |
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Paul Sutherland
From:
Placerville, California
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Posted 7 Jul 2011 8:09 am
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I took the ohm reading off the tip of a 1/4 inch jack on a cord plugged into the output jack (which is probably not original, I gather). I made sure the volume knob was all the way up. I tried to set the tone to full treble, but the knob is missing. I think I got the shaft fully rotated to the treble position.
Your website, and the links you provided, are immensely helpful. I not sure what the problem is, or even if I have a problem. But now I have a much better idea what to look for. THANKS!! |
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A. J. Martinez
From:
Ca.
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Posted 7 Jul 2011 11:24 am
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| Paul...I had my pick rewound by Jared Brandon. His # 419-559-9056 now they sound great ( 8.2k) His web site ( jared@brandonwoundpickups.com)the best $40 I put into that guitar. you will not believe its the same guitar. A.J. |
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Charlie Vegas
From:
Tampa Bay, FLA, USA
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Posted 7 Jul 2011 12:32 pm
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| Does your pup have two magnets or one (and a wood dummy)? |
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Denny Turner
From:
Oahu, Hawaii USA
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Posted 7 Jul 2011 1:00 pm
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| Quote: |
| I took the ohm reading off the tip of a 1/4 inch jack on a cord plugged into the output jack..... |
Assuming that the vol pot is fully functional, then the chances are good that your 209 ohms is the volume pot resistance to ground since that should be by-far the least resistance to ground regardless of where the knob / wiper is set. The reading could be an accurate reading of the pot's resistance which can be confirmed by turning the knob up and down while reading at the guitar cord plug to see if the resistance to ground goes all the way down as the knob wiper reduces the resistance to 0, ....or by reading the resistance of the pot directly, ...and the reading at the guitar cord tip would be slightly low at full volume setting because the pickup coil is in parrallel to ground and could reduce the reading slightly.
Your guitar cord also has resistance in the extended circuit you created with the cord. If your jack is a phone jack you can cut the last foot or-so off of an old cord's working end, skin the wires back and read from there; Or if your guitar's jack is amphenol you can read directly on the center contact of the jack.
Scroll down to the correct shematic on this page (not the circuit fault schematic):
http://dennysguitars.homestead.com/BillRicklesSuproP4.html
Notice that the jack's "hot" lead goes to the volume pot input where the resistance path encounters a "Y" path through the pot resistor to ground AND to the pickup coil. Your meter will read the lowest resistance to ground (slightly reduced by the nominal resistance of the pickup coils). The tone pot at 1Meg would block it's path to ground and be negligible in it also being parallel to ground.
You might want to take this question / discussion over to the SGF *Electronics* section / board; They "live for this stuff" ...the challenge of talking through multiple-choice problems, finding the fixes and helping others.
Gotta run; "terribly" busy day ahead.
_________________
Aloha,
Denny T~
http://www.dennysguitars.com/
Please help support humanity:
http://www.redcross.org/en/aboutus |
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Paul Sutherland
From:
Placerville, California
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Posted 7 Jul 2011 3:17 pm
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Charlie: Two magnets. If I install them so they attract then the first and sixth strings are real loud and strings 2-5 have much less volume; but if I install them so the magnets repel, then all six strings are reasonably balanced. Seems bizarre.
Without the magnets or top plate the volume goes way down. These magnets don't feel very strong. Maybe I need to get these magnets recharged, or get new ones. Any recommendations?
Denny: I removed the pickup/bridge assembly from the body and inspected things. Nothing looked obviously wrong. The volume pot had these numbers: 220-1 & 304447. Does this mean manufactured in the fourth week of 1947? The tone pot numbers were 220-2 & 304033. Does this mean manufactured in the third week of 1953? Judging by the patinas, the tone pot is newer than the volume pot.
The volume pot seems to work properly as I play. On the meter the ohms go evenly from 209 at full volume down to 0 ohms when the volume pot is completely shutting off the sound (counter-clockwise).
The tone pot rotates in reverse from the volume pot and when rotated entirely to the no treble position (full clockwise rotation) there is no output to the amp, but the ohms reading remains constant at about 209.
Not sure what any of that means, if anything.
I still wondering; do I need to have the pickups rewound, or get the magnets recharged, or is something else wrong. The output to the amp is still very low. I only get bedroom volume out of my steel amp (Session 400) when the amp is set for outdoor concert volumes if I were using my PSG.
Last edited by Paul Sutherland on 7 Jul 2011 11:26 pm; edited 1 time in total |
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A. J. Martinez
From:
Ca.
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Posted 7 Jul 2011 4:01 pm
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| Paul...i tried everything with my supro that was so weak and thin sounding. i bought new magnets, i bought new pots, new capacitors, rewired it completely new and it still was weak and when i turned the tone knob all the way off it would go dead.upon my research i went to vintage fender guitar pickup specs( google that) if you scroll down why do fender vintage pickups die? you will read a sure sign of a dead pickup is turning the tone knob off then it kills your sound. i know it's not a fender pickup but a pickup is a pickup. so i ended up getting it rewound, put all the original pots and capacitors back in and now it is my strongest pickup of all my laps. it really sounds like you need to have your pickup rewound. even a pickup that has broken wire will still work very weak. a.j. |
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Paul Sutherland
From:
Placerville, California
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Posted 7 Jul 2011 5:04 pm
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| Thanks AJ. Between your recommendation of Jared Brandon, and Denny Turner's sound advice, I should get this issue resolved. |
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Steve Ahola
From:
Concord, California
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Posted 7 Jul 2011 10:30 pm
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Paul:
Your reading of 209 ohms indicates some sort of problem. The resistance of both coils should be somewhere between 4k and 10k. With the controls set to 10, taking measurements at the output jack will not affect the reading that much. If you add a 250k pot load to a 10k pickup the result is around 9.6k.
With a reading of 209 ohms you need to disconnect the pickup leads from the control and take another measurement. If you still get a reading like that you might try taking the pickup apart to see if there are some wires shorting out. Or you might want to send the whole pickup to Jason Lollar. He can replace the magnets or rewind the coils- whatever it needs.
BTW for proper operation you do want the tops of the two magnets to repel each other. And once the ohm problem is corrected you might experiment with using just a single magnet. For testing purposes I have a water bottle cap that is exactly the same height as the magnet, 1 inch. IMO you get a clearer sound with just one magnet, and a stronger sound with two.
Good luck!
Steve Ahola
_________________
www.blueguitar.org
Recordings on electric guitar:
http://www.box.net/blue-diamonds
http://www.box.net/the-culprits |
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Charlie Vegas
From:
Tampa Bay, FLA, USA
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Posted 8 Jul 2011 4:48 am
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| Paul Sutherland wrote: |
| The tone pot rotates in reverse from the volume pot and when rotated entirely to the no treble position (full clockwise rotation) there is no output to the amp.. |
What Supro do you have? This sounds wrong. |
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Steve Ahola
From:
Concord, California
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Posted 8 Jul 2011 4:54 pm
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| Charlie Vegas wrote: |
| Paul Sutherland wrote: |
| The tone pot rotates in reverse from the volume pot and when rotated entirely to the no treble position (full clockwise rotation) there is no output to the amp.. |
What Supro do you have? This sounds wrong. |
I have a Bay lap steel (the sweetest sounding Supro I have played) with the tone pot wired up as Paul describes. And when I got it the tone did get muddy when you turned it to the full treble position (cleaning the pot eliminated that problem). So I think that Paul might have a problem with his tone pot shorting out completely at the full bass position (which would be fully clockwise- right?). However if his steel uses the tone cap to connect the volume control to the tone control (as Supro often did) here is another idea: perhaps at the full bass position the pot body is moving enough to pull on the tone cap, which is then shorting out to ground somewhere.
FWIW if you wire up a audio taper tone pot backwards what you get is a reverse audio taper, which would give you more control over the subtle shadings when turning it down from the full treble position. Conversely it will get bright very fast when you turn it up from the full bass position. That can be desirable in some lap steels (like my Bay), and to be avoided in others (like my 1949 Gibson Century 6 which used a reverse audio tone pot).
_________________
www.blueguitar.org
Recordings on electric guitar:
http://www.box.net/blue-diamonds
http://www.box.net/the-culprits |
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Denny Turner
From:
Oahu, Hawaii USA
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Posted 8 Jul 2011 6:47 pm
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| Quote: |
| Denny: I removed the pickup/bridge assembly from the body and inspected things. Nothing looked obviously wrong. The volume pot had these numbers: 220-1 & 304447. Does this mean manufactured in the fourth week of 1947? The tone pot numbers were 220-2 & 304033. Does this mean manufactured in the third week of 1953? Judging by the patinas, the tone pot is newer than the volume pot. |
For the volume pot: 304 is the manufacturer code for Stackpole Company. The middle digit '4' is the last number of the year manufactured, 1954, 64, 74 etc. ...certainly after 44 in this case since those industry-standard codes were not used until 1947; While the last two numbers '47' says it was made during the 47th week of the year. The numbers 220-1 are the manufacturer's pot model number. So that volume pot is model number 220-1 manufactured by Stackpole during the 47th week of a year ending in 4. ~~~~~~~ The tone pot was manufactured during the 33rd week of a year ending in 0 (1950, 60, 70, etc.) ~~~~~~~ Since both pots have a similar but simple model number I am SWAG'ing that they are an original pair or one or both correct model pair replacement for pot years 1954 for the volume and 1950 for the tone (albeit you said that the tone pot looks newer than the volume pot ....which throws another consideration in that makes such detective work fun ...if not nerve-racking ! ).
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TROUBLESHOOTING YOUR DESCRIBED PROBLEMS:
I highly suggest NOT rewinding nor doing delicate work on the the pickup until you know for sure that the pickup is the problem; It could be something else. It's not difficult to find what componant(s) a problem is in.
The trick to finding a problem is to FIRST find what componant the problem is in; THEN you can address the problem in that componant(S). Here's an easy way:
Unsolder the pickup lead wire from the volume pot. If you don't know good soldering techniques, then get the help of someone else who does. It doesn't take much heat or misunderstandings to ruin an old pot with a soldering iron.
Read the resistance between the removed pickup lead wire and ground. Report back here what resistance you found. Valco's I've worked on all had resistances near 2.5K for each of the 2 pickups that are wired in series to make what appears to be 1 pickup; BUT, it seems that Steve has found readings between 4K and 10K; And the brow in his avitar looks like he knows! With the pickup lead wire disconnected from the volume pot, then the volume pot's and tone pot's operational resistances can also be read directly across their terminals / lugs without one pot scewing the other's resistance readings.
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TONE POT & CIRCUIT FAILURES:
A tone pot & knob that operates in the "reverse" rotation of most guitars, does not mean the tone pot is bad; It just means the circuits hooked up to it are hooked up for reverse rotation direction. The pots in a left handed guitar are the same as a right handed guitar's, but is wired for reverse rotation which becomes forward rotation when installed on a left handed guitar. It was / is not unusual at all for tone pots to be wired for reverse rotation operation prior to about 1950. Many pre-1950 Valco's I've encountered had reverse acting tone pots, as did some other steels as well. ~~~~~~~ Don't confuse reverse rotation with a tone pot acting like a volume pot (LIKE YOUR DOES); A tone pot acting like a volume pot means that the capacitor has failed shorted and lets all signal it receives from the pot pass to ground unfiltered by the capacitor, just like a volume pot does, ....or it means that some other wire or lug has shorted to ground between the pot and it's capacitor, voila Steve's similar suggestion. A tone pot that simply doesn't work at all is usually due to a broken or bad connection, or a bad resistor or wiper in the pot, or the capacitor has failed open (rare for an old analog-era capcitor to do that).
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A PROBLEM SIMILAR TO WHAT YOU DESCRIBE, AND WHAT WAS FOUND TO CAUSE IT:
I encountered a Customer's Valco bunker pickup that drove me nuts with poor performance and strange resistance readings. With a magnifying glass I finally found that the metal pole piece screws had worn through their paperboard tubes in the waxed paperboard bobbin, kissed and made contact with the coil wires and shorted out the coil as long as the screws were in place, giving a false reading when the pickup was assembled but a different reading when the pole piece screws were removed which removed the short and thus a different resistance reading. Here is a link to that affair, what to look for and how I fixed it. Notice that the fix worked only because the screws had only kissed the coil wires and not mashed them into shorting each other:
http://www.dennysguitars.com/ValcoElGrande18.html
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PICKUP POLE PIECE ADJUSTMENT:
Volume-wise and dynamics-wise, Valco bunker pickups are very sensitive to the strings pole pieces height adjustment closeness to the strings. Easy setup: Adjust the 1st string pole piece up as close to the string as possible whithout the string vibrating against the pole piece when the string is picked as hard as you will ever pick it; Don't worry about it's tone for now, we're working on volume, ....tone will be next. The first string has the least mass so it's pole piece will be the closest to the string than any others. Now adjust the other pole pieces so that each consecutive string 2, 3, 4, 5, 6 is slightly farther away from the strings than the previous string / pole piece. Now play the guitar listening to how well the strings volumes are balanced with the 1st string, and adjust each pole piece so that it's string is the same volume as the 1st string. AFTER THE VOLUMES ARE SET EQUAL: If the tone is too robust / dynamic and you would rather have a tighter more stable tone, then lower the 1st string pole piece 1/2 turn each time you try it to see what adjustment tone sounds best. Higher dynamics and volume go hand in hand, while more stable tone is at the expense of less volume. Now go adjust the other pole pieces to rematch their volumes with the 1st strings new setting volume.
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MAGNET POLARITY ORIENTATION IN VALCO BUNKER PICKUPS:
When Valco bunker pickup magnets are removed from the pickup & electronics mounting plate, the plate will almost always have been magnetized a little bit by the magnets. That's why the pickup will work weakly when the magnets and bunker top plate are removed from the guitar. So when uninstalling & reinstalling the magnets, here's the process to make sure they are installed in the best / strongest polarity with the electronics plate: When you temporarily place one of the magnets back onto the plate, the magnet strength to the plate will seem stronger with either N or S up or down. The strongest magnetic strength to the plate is the correct orientation of the magnet (unless you want a weaker pickup). Now, ...while leaving that first magnet in place on the electronics plate, ...take the other magnet and try to place it on top of the magnet on the plate; If the 2 magnets pull on each other then both magnets have the correct polairity facing up; So mark the tops of each so they will have the correct polairty facing up when you're ready install them. But if the magnets repel each other when you try to stack them, then flip the top magnet over, make sure it now attracts to the bottom magnet's top, and mark the tops of both magnets to know that correct polarity to put them both back in when you're ready to.
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RECHARGING MAGNETS:
A simple pickup magnets "recharging" machine is quite easy to arrange onto a bench vice:
http://www.dennysguitars.com/PickupRechargingViceRig1P1.html
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Break time's over; Gotta run tackle alligators gnawing at the gunwales....................
_________________
Aloha,
Denny T~
http://www.dennysguitars.com/
Please help support humanity:
http://www.redcross.org/en/aboutus |
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Paul Sutherland
From:
Placerville, California
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Posted 8 Jul 2011 9:21 pm
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Charlie: This steel appears to be a Supro Supreme, base on pictures from Brad's Page of Steel, except it does not have the plastic looking cover over the pickup/bridge. The serial number (V-5580) makes it a 1947, per the Ebay Reviews and Guides article regarding Supro/Valco/etc. lap steels; which is consistent with the story of the old lady that gave me the steel. The tone knob definitely operates in reverse, and things under the hood look like nothing has been touched, other than the tone pot looks newer than the volume pot. The tone capacitor looks really old.
Denny: I got up my nerve and un-soldered the PUP lead from the volume pot. I can't get any reading at all from the pickup. I guess this means the PUP is officially dead, and a rewind is needed.
Testing on the lugs of the volume pot I get 209 ohms when at full volume setting, and zero ohms when the volume is turned off. For the tone pot I get 209 whether the pot is turned to full treble or the treble is fully off.
Maybe there is also a problem with the tone circuit as explained in Denny's prior post. Would it be lap steel hereasy if I bypassed the tone circuit? I really don't want to de-value this instrument, but I'm not trying to sell it either. I've never used a tone control on a PSG, this tone control knob gets in the way of my right hand as I'm playing, it would be cheaper to repair the steel if I just had the pickup rewound, and I think I would never miss the tone control. I could just un-solder the single wire from the capacitor to the volume pot lug, and then remove the tone pot and capacitor from the assembly. Everything could easily be put back in place. How important is a tone control to lap steel players?
Thanks again for all the valuable input you have each provided. |
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Steve Ahola
From:
Concord, California
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Posted 8 Jul 2011 10:29 pm
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Denny: Jason Lollar mentioned that he will often/sometimes rewind the Supro pickups to 10k. I was checking out your website and you certainly seem to know a lot about these pickups!
Paul: I had expected problems with the tone control on my Bay lap steel being right under the palm of my right hand, but with the knob being fairly short and very smooth and flat on the top, it doesn't bother me at all.
I find the tone control to be very important on a lap steel guitar, especially since some of them are extremely bright without one. In fact I consider it to be an early form of noise reduction: the pickup would be very bright but when you turned down the tone control it would remove some of the noise along with the excessive brightness.
Here is a suggestion if you really need to remove the tone pot. Carefully remove both pots and store them away so that you can reinstall them later. Replace the volume control with a dual concentric pot that takes two knobs. Wire it up so that one of the knobs controls the volume and the other controls the tone.
Alternately once the main problem is fixed you could try adjusting the tone control to the position that sounds best to you. You then measure the DC resistance to ground on the tone pot and replace the pot with a fixed resistor of the same value. (For values in between the standard values you can add together 2 or more resistors in series or in parallel. If you tell me the value you want I can do the math and tell you what resistors to use and how to wire them up.
With the tone pot removed you should look in a hardware store for a chrome plug which will fit inside the hole. Or just put some duct tape on the backside of the control plate (to keep the bugs out!  )
You also need to figure out the 209 ohm reading you are getting from the controls. Are you sure your meter is set to ohms? A reading of 209k would not be unusual with a 250k volume pot set to 10.
Having the volume cut out when turning up the tone control is unusual. If the tone pot was shorting out to ground, you would get the full treble cut. And if the tone pot has an open circuit you would have no treble cut. (That is assuming that the tone cap is what connects the tone control to the volume control.)
Steve Ahola
_________________
www.blueguitar.org
Recordings on electric guitar:
http://www.box.net/blue-diamonds
http://www.box.net/the-culprits |
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