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Post subject: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Thu Sep 06, 2018 2:39 pm
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hi all!

so i got this amazing all original "blonde" finish Stratocaster of 1976:

Image
Image
Image
Image

i have no comment about the tone and sound, because it is just outstanding and it sounds
like no other strats i have previously owned, but..

there is a problem: none of the two "tone" pots are working!

so i have dismounted the pickguard and
checked what was inside, at first glance everything seems to be original.. even the soldering job..

can anyone point me out how to detect the problem and how to make those tone pots back on the track?

also, does anyone have an idea what does mean that "L" sign on the back of the pickguard?

any help is greatly appreciated, thanks in advance!


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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Sat Sep 15, 2018 11:04 am
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Could be multiple causes, and it's just a burden of checking the whole wiring - all components and solderings...

If you want a wild guess, I'd start by checking (or just replacing) the tone cap...


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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Sat Sep 15, 2018 4:47 pm
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Since neither are working, it is something common to both of them, which would be the capacitor, or the 5-way switch.
If the contact for the common connection on the 5-way is not touching the arc on the wafer, then it will not work.

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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Sat Sep 15, 2018 6:36 pm
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The wiring looks correct, I would give all contact points in the switch a really good dose of contact cleaner along w/ switch movement and follow up w/ a dose in all the pots w/ knob movement, before replacing anything.

Those switches were prone to wear out, have you checked each pickup & corresponding switch position w/ tap test and the volume pot maxed.
With the switches in the correct position, use a meter and test for continuity across the switch. This will test the switch across the input/output lugs to tone pots
viewed with the neck pickup at the top the switch is this way,
topleftLug1=neck top right lug1=common
L2=middle L2=bridge
L3=bridge L3=middle
L4=common L4=Neck
The picture of all the lugs is a little unclear, but appears to be wired neck to tone pot 1 and middle to tone pot 2 bridge not connected to tone control(blurred a little may have a jump wire)

The common tone cap, is the easiest to replace if all else fails.

Rich if the common contact is broken, there would be no volume control. If there is volume control across all three pickups the common input&output lugs are good.


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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Sat Sep 15, 2018 8:10 pm
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sfceric64 wrote:
Rich if the common contact is broken, there would be no volume control. If there is volume control across all three pickups the common input&output lugs are good.

The common contact on the tone side of the wafer.... if that's open (but the solder joint on the terminal is still good) then the signal will still go from the selector across to the volume pot.
The switch is a DP5T switch with the common's wired together.

Also, and it is apparent that this was factory, but the tone cap is relying on the middle pot's contact with the shielding foil for its ground connection. It could be that the foil has become worn and is no longer making contact.
Quick and easy check with the PG not installed, plug in and jumper the body of the tone pot to the body of the volume pot and tap-test.
A piece of wire and two solder spots may be all that's needed.

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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Sun Sep 16, 2018 2:15 am
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CB91710 wrote:
sfceric64 wrote:
,.... but the tone cap is relying on the middle pot's contact with the shielding foil for its ground connection. It could be that the foil has become worn and is no longer making contact. .



+1000
This is the issue. Ground with a foil are never very good.

Tsolight solder two wires from both tone pots body to volume pot body.


ImageCapture d’écran 2018-09-16 à 05.05.51 by [url=https://

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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Mon Sep 17, 2018 7:51 am
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I agree that a common wire to pot ground to star is the best ground type and may indeed be the issue w/ this guitar.


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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Thu Jan 10, 2019 7:40 pm
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sorry if i could not reply earlier, i have kind of lost track of this post, thanks to all of you for replying and narrowing down to the potential problem of not working tone pots on this strat.

to clarify a few things:

this is a 3 way switch original , she sounds and plays just great (even using the oldschool method of stucking in between "1-2" and "2-3" switch position) and the only working pot is the VOLUME one and it even performs pretty well, for its age it is linear, transparent and scratch/cracks free.

so the only problem remain is the two TONE faulty pots, they just don't do any effect on the tone no matter what is the switch position.

as said, i will try to investigate further and test as suggested by Stratele52

"+1000
This is the issue. Ground with a foil are never very good.

Tsolight solder two wires from both tone pots body to volume pot body.
"

if it happens to be the faulty issue, that will be amazing, because i really want to preserve this strat in its full original state by avoiding to replace any of its original components.

salutations to all


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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Fri Jan 11, 2019 2:50 am
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We give you the answer long time ago ;

There is no ground with tone cap. Shield is no good for ground, you need ground wire between all pots body and output jack and guitar's ground.

Red wires here;

Image[url=https://flic.kr/p/23xcuGz]strat pots[/url

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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Fri Jan 11, 2019 7:35 am
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Bus wire isn't vintage-correct for that year, though.

On a near mint all-original '70s Strat you probably shouldn't add solder joints, nor disturb existing joints.
-----------------
First thing to do: Remove tone knob, undo the mounting nut, lift the tone pot and check the foil. There may be enough of it left intact that you can simply smooth it out or rotate the pot or toothed washer so that it touches the foil.

If the foil is completely shredded, then the least invasive fix would be to get a reissue '62 shielding plate, pop an extra mounting hole in it, and sandwich it between the guard and electronics. No permanent changes and the ground will be fixed.

There are aftermarket non-Fender plates with modern-spaced screwholes (some are copper instead of aluminum).


Last edited by strayedstrater on Fri Jan 11, 2019 7:37 am, edited 1 time in total.

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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Fri Jan 11, 2019 7:36 am
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The 62 plate is a good idea if the existing aluminum is thin foil.
Fender does not use soldered links between the pots on the American Vintage series but relies on the plate to provide earth continuity.
This really needs a multimeter to help fault find.
There's a good chance the side of the switch the tone pots are wired to is faulty.

Service diagram
https://p4.zdassets.com/hc/theme_assets ... A_SISD.pdf


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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Fri Jan 11, 2019 7:49 am
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64Galaxie wrote:
The 62 plate is a good idea if the existing aluminum is thin foil.
Fender does not use soldered links between the pots on the American Vintage series but relies on the plate to provide earth continuity.
This really needs a multimeter to help fault find.
There's a good chance the side of the switch the tone pots are wired to is faulty.

Service diagram
https://p4.zdassets.com/hc/theme_assets ... A_SISD.pdf


They do the AV's that way because it's historically correct. They copied CBS cost-cutting.

Losing the tone ground was a common problem with '70s Strats. Other eras had either metal shielding plates or bus wires -- CBS decided thin foil was adequate.


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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Fri Jan 11, 2019 8:09 am
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Anyway, diagnose the cause of the problem before adding/disturbing solder joints.

Could be the switch. Could be the tone cap.

Having had this exact issue on my '75, my bet is on the foil. But whatever you do, don't start changing things randomly until you know for sure what the problem is.
-----------------
As far as vintage value, replacing a failed cap, reflowing a solder joint that's gone bad, or even replacing a failed switch isn't a big deal.

But disturbing several solder joints to add a wire the factory didn't intend to be there will hurt the value.
------------------
As a player guitar the wire would be a good thing. An improvement over factory stock.

But from the pics, that looks like a clean, original, collector's grade '70s Strat. It's only a virgin once -- think long & hard before making any irreversible changes.


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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Fri Jan 11, 2019 8:23 am
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Also, you praise the special tone that guitar has.

Disconnected tone controls are electrically identical to no-load pots on "10".

Fixing the tone controls will slightly change the tone of the guitar in all positions except the bridge pickup by itself. You'll lose a tiny, tiny little bit of treble and airiness all the time.

Obviously you gain all the darker tones that tone knobs can give you. But you won't be able to exactly get its current tone.


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Post subject: Re: Fender Stratocaster 1976 "blonde" tone pots not working
Posted: Fri Jan 11, 2019 8:42 am
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The pre-62 small aluminum shield plate is made of relatively thick aluminum. Fender part number is 0019640049 and would be more in keeping with the original appearance.
It is still used by Fender on the new Original 50's Strat.


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