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Author Topic:  Absolutely non-techy taking a stab a no output from guitar
Michael Greer


From:
Ontario, Canada
Post Posted 9 Jan 2018 6:37 am     Reply with quote

Morning

Hoping some experienced techs can offer some suggestions to help me try and once again get output from new to me guitar ( 60's or 70's Pierce )

Really appreciate some trouble shoot tips,techniques which for some is an easy .
I do have a multi meter and an alligator clip.

So far, I think I may have isolated defective volume pot but want to be sure and test via bypass?

I plug cord into guitar and multi meter on cord tip
Meter set at 20k in thr ohms section
Black lead on body , red on tip ....result nothing
Then I fiddled with volume knob back and forth and would get a reading....sometimes in the 9 range...a few spots got a reading of 19.....if I turn knob again no reading.....so thinking bad volume pot??
When I had a reading I plugged into amp thinking I would get sonething.....but no output

Any help ,suggedtions,next step appreciated.

Thanks
Mike







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Paul Arntson


From:
Washington, USA
Post Posted 9 Jan 2018 8:10 am     Reply with quote

By nothing, do you mean 20 Kohms ?

Make a careful wiring diagram so you can post it here and someone can guide you through the process. maybe number the connection points on the picture.
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Michael Brebes


From:
Northridge CA
Post Posted 9 Jan 2018 8:30 am     Reply with quote

If the pickup is working properly, you should measure anywhere between 7k and 20K ohms depending on the pickup. I would recommend going up to the 200K range. If the pickup is open the resistance value should be roughly the value of the volume pot. Common volume pot values are 250K or 500K ohms, so put it in the 2M range.
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Lee Baucum


From:
McAllen, Texas (Extreme South) The Final Frontier
Post Posted 9 Jan 2018 8:52 am     Reply with quote

Here is an old discussion about Pierce steel guitars.

Click Here

And another, with a photo.

Click Here
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Michael Greer


From:
Ontario, Canada
Post Posted 9 Jan 2018 10:20 am     Reply with quote

Guys

Thanks....I will make a detailed drawing from pickup to output jack and post a picture and clarify my meter readings

Thanks
Mike
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Michael Greer


From:
Ontario, Canada
Post Posted 9 Jan 2018 1:35 pm     Reply with quote

Picture of the circuit and meter on end of chord

Thanks for assistance to help me isolate cause of no output thru amp.






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Paul Arntson


From:
Washington, USA
Post Posted 9 Jan 2018 2:56 pm     Reply with quote

I added some numbers to make it easier to write the steps:

Also, make sure you are getting good contact on the solder blobs. Sometimes I start with both probes on different spots of the solder blob and make sure
I get near 0 ohms (5 ohms is plenty low). Sometimes there is old flux left over that acts like an insulator.
Also, be aware that your hands might influence the readings so try not to touch the probe tips while reading. Depending on a lot of things, your fingers can go as low as 5K or 10K sometimes.



First we test the output jack and cord.
6 to tip of cord should show close to 0 ohms.
1 to sleeve of cord should show close to 0 ohms.
1 to 6 should be near the value (maybe a tiny bit less) of 1 to 2 at one extreme of the volume pot, and should rise to 250K (or the pot value) plus the pickup resistance at the other extreme.

Next we test the pickup winding resistance:
1 to 2 should show a constant resistance of somewhere between 7K and 25K.
If close to 0, = shorted pickup.
If much higher than 30K, pickup is probably open. You might get a really thin muted output in this condition.

Now we test the volume pot.
5 to 7 should show a range of near 0 up to the value of the pot, probably 250K, as you rotate the pot.
7 to 1 should be near 0 at all times.
***EDITED***
2 to 5 should do the same thing as 5 to 7 but with the near 0 reading at the opposite end of the rotation.

Now we check the tone pot (probably not the culprit, just for completeness)
3 to 4 should go up and down with rotation.

We can also check the capacitor (also probably not the culprit)
1 to 2 should not change with rotation of the tone pot, and should be the same value as the pickup itself.

Let us know what you find. Most likely these tests will find the problem.
_________________
Excel D10 8&4, Supro 8, Regal resonator, Peavey Superslide, homemade lap 12(a work in progress)


Last edited by Paul Arntson on 9 Jan 2018 5:25 pm; edited 1 time in total
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Michael Greer


From:
Ontario, Canada
Post Posted 9 Jan 2018 3:47 pm     Reply with quote

Paul

Thanks for all your time and sharing knowledge.

I can't wait to get home to nite and get to work with your very clear trouble shooting steps.

Thanks again...will report back

Mike
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Paul Arntson


From:
Washington, USA
Post Posted 9 Jan 2018 5:31 pm     Reply with quote

You made a good drawing to work with. One other thing, the reading on the volume pot will change more rapidly at one end of rotation. This is supposed to be that way.

If anyone else wants to chime in or correct anything I said, please feel free. No offense will be taken.
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Michael Greer


From:
Ontario, Canada
Post Posted 9 Jan 2018 8:03 pm     Reply with quote

Paul
I followed the test list and here are the results,a few photos and thoughts

1-output jack
#6 to cord tip-result- 0 ohms
#1 to sleeve of cord -result - 0 ohms
I think this proves continuity and cord/output jack are good? Is its correct?

2 - test pickup
#1 to #2 -result 0 ohms ...I think this is bad? Indicates a short?
Ps..I had a new pickup in box and touched ends to meter and got 7.2 to on firm what test result should look like

3- volume pot
#5 to #7 -result - strange and varied depending on turn of volume knob
Result at 0 volume was.05 ohms
Result at 2 volume was 5.45 ohms
Result at 4 volume was 15.20
Result at 5 and above was 1 . See picture
It's like after volume 5 it stopped reading values?
Does this indicate bad volume pot?
Is the shorted pickup now being read when you get to volume 5?
See two pics below showing above volume pot results







4 tone pot

Results were very similar to volume pot....readings would rise until knob turned to level 5 then stop and
1 . Displayed
Since tone and volume showingsimilar results seems less likely both have failed?
Reading a shorted ed pickup?

One last test result....the results of volume pot testing #5 and #7 ...let's say 15.12 would be measured exactly the same value 15.12 on the cord end and shaft.

I didn't test the capacitor

Well, look forward to your review and comments of my rookie test results.

In conclusion, I may be wrong but it seems like I may have a shorted pickup?


Thanks again for comments and recomendations......have not fixed anything yet but having fun learning

Mike


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Scott Duckworth


From:
Etowah, TN Western Foothills of the Smokies
Post Posted 10 Jan 2018 3:26 am     Reply with quote

A note on testing... make sure at least one finger is not touching the test leads or the connections of the item under test. The resistance in your body can skew your readings.
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Michael Greer


From:
Ontario, Canada
Post Posted 10 Jan 2018 4:32 am     Reply with quote

Morning

Testing update

I retested the pickup points #1 and #2

The reading still is not good it seems but I miss reported last night as 0 ohms indicating a short.

It as reads as per this pic below....I am thinking this indicates an "open" in the winding?
I did put a metal paper clip close to pole pieces and it seems to be magnetized



Well hope this helps us get to the bottom of this.

Seems like pickup bad....not sure of the readings on the pots as reported last night.

Really appreciate help and comments.....thanks to all who have commented

Mike
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Michael Greer


From:
Ontario, Canada
Post Posted 10 Jan 2018 5:06 am     Reply with quote

Additional comments

The volume and tone pots retested same as last night and as shown in the two associated photos

Tutning the knobs from zero to 5 increasing readings....then after 5 as per picture 1 .


Thanks
Mike
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Jerry Jones


From:
Nashville, Tenn.
Post Posted 10 Jan 2018 5:17 am     Reply with quote

How is your volume pot case (7) connecting to your jack ground (1)? I'm not seeing that in your drawing.
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Jerry Jones
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Michael Greer


From:
Ontario, Canada
Post Posted 10 Jan 2018 5:34 am     Reply with quote

Jerry

There are no other leads from the volume pot

#2 in from the pickup

#5 out to the output jack

#7 lug is pushed back to pot body and soldered

Thanks for help

I should add guitar never worked since I recived.

It's hard to tell if wiring is all original but I think so based on looking at a picture of the underside of another Pierce.....but it is fairly crude....

Pots are somewhat corroded so think they are original .
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Jerry Jones


From:
Nashville, Tenn.
Post Posted 10 Jan 2018 5:51 am     Reply with quote

The volume pot case will need to be connected to the ground lug of your output jack. Then you should meter 0 ohms from 7 to 1 at all times. I see Paul stated this above.
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Jerry Jones
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Paul Arntson


From:
Washington, USA
Post Posted 10 Jan 2018 8:29 am     Reply with quote

Short form response:

Check your value between 1 and 2 very carefully using the 200K range and repeat using the 2 Meg range and tell us what you see for both readings.

When you make the test, you might notice that for the first 1/2 second or so, the reading needs to stabilize, so hold the leads on there until you get a steady reading before noting the value. (If it won't stabilize, that is also important to note.)

Check resistance between 7 and 1 and tell us what you see on the 2K range and on the 2 Meg range..

I apologize if this seems a bit tedious, but we will get to the bottom of this.
Sorry I forgot to mention this before.
..............................
Long winded explanation:
(Now you can see why my kids got frustrated when I tried to help them with their homework...)

2 important topics:
First:
"Results were very similar to volume pot....readings would rise until knob turned to level 5 then stop and
1 . Displayed"

The "1." display indicates that the ohms are out of range.
What that means is that you are trying to measure a value that is greater than
20K but your meter is set on the 20K range.

What you do in this case is move the range switch on your ohmmeter up to 200K and repeat the test. If you still see the 1. reading, then move up to the 2 Meg range and repeat.

To confirm an open circuit, move the range switch up to 2 Meg and repeat the measurement.
It is likely that in the 2 Meg range, you will see some kind of reading, but you won't necessarily be reading the actual pickup winding, rather just a leakage path.

If for some reason the 2Meg range shows the 1. display, also try the 20M range.
At this point you should be reading any dust and dirt in the wiring.


Second:
You stated you had an alligator clip. Use it to connect point 7 to point 1 and try the guitar, as per what Jerry stated. I think the builder assumed the metal plate on which the pots are mounted would complete the ground path, but it is worth checking, especially because the output jack is not in that plate. That's why the reading between 7 and 1 is significant.

More on this topic later, after the testing is complete.


Check your value between 1 and 2 very carefully on the 200K range and the 2 Meg range and tell us what you see.
_________________
Excel D10 8&4, Supro 8, Regal resonator, Peavey Superslide, homemade lap 12(a work in progress)


Last edited by Paul Arntson on 10 Jan 2018 8:52 am; edited 3 times in total
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Paul Arntson


From:
Washington, USA
Post Posted 10 Jan 2018 8:36 am     Reply with quote

By the way, Jerry, your instruments are incredible! Thank you for all you have done!
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Paul Arntson


From:
Washington, USA
Post Posted 10 Jan 2018 10:00 am     Reply with quote

Michael, if you don't have the original manual for the meter, you might find it here:
http://www.sperryinstruments.com/en/resources/manuals
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Jerry Jones


From:
Nashville, Tenn.
Post Posted 10 Jan 2018 10:23 am     Reply with quote

Paul Arntson wrote:
By the way, Jerry, your instruments are incredible! Thank you for all you have done!


Thanks Paul, you are kind to say so. Smile

I could not tell if the control plate was metal or plastic... either way that #7 lug has got to be connected to ground. A #1 to #7 measure should tell us.
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Paul Arntson


From:
Washington, USA
Post Posted 10 Jan 2018 11:07 am     Reply with quote

I didn't think about it's not being metal. Good catch.
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Michael Greer


From:
Ontario, Canada
Post Posted 10 Jan 2018 12:22 pm     Reply with quote

Guys

With your tutoring on proper meter usage we have new results

#1 to # 2 -result .608 ( at 2M setting

#1 to #2 -result 1. ( at 20k setting )

It did stabilize at .608





#7 to #1-result 00.0 (200 setting)
#7to #1 - result .000 ( 2M setting )




I also retested both the pots at the 2M setting and they measured full range

#3 to #4 tone pot -result .000 to .532

#5 to #2 volume pot -result .000 to .608





I did not try the alligator clips between #7 and #1 as I am assuming that a reading of .000 is a good thing...indicating precede of a ground?? Or some how magically a connection between #7 and #1 ??

Thanks again for input, assistance
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Michael Greer


From:
Ontario, Canada
Post Posted 10 Jan 2018 12:27 pm     Reply with quote

Guys

In addition to previous post above that has new test results....here is a pictorial view...thanks


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Paul Arntson


From:
Washington, USA
Post Posted 10 Jan 2018 1:09 pm     Reply with quote

Based on your measurements, your pickup is open-circuit and it needs to be rewound or repaired.

What is the center to center spacing on the outermost 2 magnet poles and what is the body outline and mounting screw spacing?
It might be easiest to find a replacement.

There are plenty of people on the forum that will rewind it for you if you are worried about keeping the guitar original.

On rare occasions, it is possible to repair a pickup without rewinding it, but it is a really finicky operation. I've attempted it a few times, with limited success.

One final thing to check:
Between point 1 and the strings, do you get close to zero ohms? If so, the guitar is properly grounded, and hum will be minimized.

If it's an open circuit, then you could try sneaking a small grounding wire from position 1 to a stationary part of the metal structure in contact with the strings. I would suspect there's already one hidden somewhere. It might be a little hard to find.

All the best luck. It's been fun helping you track this down. Anything else, just holler. You can find me on Facebook, too.
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Michael Greer


From:
Ontario, Canada
Post Posted 10 Jan 2018 1:49 pm     Reply with quote

Paul

Thanks so very much.....it was fun for me as well and I learned a lot, or at least enough to make me confident enough to diagnose problems like this going forward.

Michael,Lee,Scott and Jerry , I thanks you also for your assistance.

Kind regards

Mike
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