Volume Poti acts tonewise like a on/off switch on a stock 1968 Telecaster

[gmanella]

Hi everybody,

I'm Jörg from Germany and own a 1967 CAR Telecaster with changed electronics and
a stock 1968 blonde Telecaster which I acquired last Friday from the second owner
who bought it from the first owner in 1974.

To me everything looks stock and untouched.

When I roll of the volume pot, within a few milimeters (metric over here) there
is a complete absence of bass & middle and a very trebly tone is present with almost
no change over the the whole control range.

What can that be?

Thanks in advance

 

[AJBaker]

Could we see some pictures? Is it a problem on both guitars?

I think that those models had a 1M pot, and a treble bleed cap (.01uF if I recall). When you turn down, the frequencies are being sent to ground (lost) EXCEPT for the high end which can always pass through the treble bleed cap to the amp.

Late 60s teles have a bunch of factors making them VERY bright: 1M pot instead of 250k, low-output pickups, and the aforementioned treble bleed.


To me it's hard to say what exactly the problem is, but it could possibly be that your 1M pot has a very steep taper, and that the treble bleed effect is kicking in very fast.

A possible solution might be to just clip out that cap, but that depends on whether you're willing to modify these guitars.


(Sei gegrüsst, mein teutonischer Freund!)

 

[skunqesh]

Hi Jorg

could you provide pictures of the troubled potentiometer ?
actually - Both guitars would be great to view they sound amazing!

My best guess is - the pot's resistor / metal contacts have oxide or "crap" on it, and needs to be cleaned.

a little bit of spray-in Deoxit (electronics cleaner), and mechanically moving the pot clock wise/counter clockwise (rapidly, many many times) might help.

good luck!


edit: does this problem happen when both pickups are selected? or does it only happen on the bridge or neck pickup?

 

[cousinpaul]

Might be an oversize treble-bleed cap. I've seen .005uf used in some older tele's.

 

[Timbresmith1]

I suspect you have a pickup with an open winding. If you can, take a resistance reading across a guitar cable plugged in to the guitar.

 

[Antoon]

To me it sounds like a cracked carbon track in the pot. Apparently it only makes contact when the wiper is at the end of the track. I presume that you do not want to desolder any connections but you may want to verify if the pot still measures 1Meg or 250k on the outer terminals. With a broken carbon track it would measure open. Problem is that you can only measure the pot plus the pickup, so you may have to measure the pickup separately to know the pot resistance.

 

[gmanella]

Thanks everybody so far.


The blonde '68 is complete stock while the CAR '67 has changed pickups (Häusel Big Mags & electronics)
have kept the original neck pu & switch. The original bridge pickup got lost.

The CAR has turned almost copper on the frontside and kept more of the red on the sides and back.
Due to the guy I bought it from, the finish was like this when he bought it new out of are store-window in the early seventies.

The 67 is on the heavy side while the 68 is very light.
Will get myself a hanging scale and tell you later.

Conserning the pot-issue...it is present on both pickups.
Both are working and great sounding with the open pot.
Will measure or trying to clean later.

Pictures are the currency here:

 

[Telekarster]

Hopefully others can see an issue here, cause I can't, but man.... those are some SWEET Tele's! Congrats on such a nice collection Good luck and hope you find the issue!

 

[AJBaker]

a. Could you type out the letters and numbers on:
- The small cap that is on the volume pot
- The back of the volume pot.

b. If you have a multimeter, could you measure:
- Resistance of pickups (measure at jack, pots up all the way)
- Resistance of the volume pot (measure the outside lugs)
- Taper of the volume pot (set volume to 50% on the guitar. Measure from left lug to middle, then from right lug to middle).

 

[AJBaker]

And also:
Very pretty guitars!

 

[Asmith]

Nothing looks out of the ordinary to me at least. To avoid any unnecessary modifications I would measure potentiometers with a digital multimeter. Check they measure at 1M ohm (it will be a bit off) for all the rotation of the dial and also plot the resistance on the middle lug of the pots to one of the outer lugs.

If they show they aren't faulty then it's probably down to the treble bleed and high resistance values of the potentiometers. If there is an issue you can try cleaning them with deoxit or similar.

Report your findings back here first though.

 

[Asmith]

a. Could you type out the letters and numbers on:
- The small cap that is on the volume pot
- The back of the volume pot.

b. If you have a multimeter, could you measure:
- Resistance of pickups (measure at jack, pots up all the way)
- Resistance of the volume pot (measure the outside lugs)
- Taper of the volume pot (set volume to 50% on the guitar. Measure from left lug to middle, then from right lug to middle).

From the picture I think I can make out that the small cap reads 25pF with a 20% tolerance and the code on the back of the volume ends with 1 MEG AUG.

 

[AJBaker]

From the picture I think I can make out that the small cap reads 25pF with a 20% tolerance and the code on the back of the volume ends with 1 MEG AUG.

You have better eyes than me! Thanks!
Zoomed in, I think the treble bleed cap is 0.001uF (1000pF). I doubt it's 25pF, that would be too small to have any effect.

Plug in your phone, you're down to 2% battery!

 

[Sea Devil]

That's the only thing we really need to see more clearly. I've enhanced the photo a bit, but I still have trouble reading anything but the 20% and what looks like 25F, which makes no sense (F means 1%) unless it's just a manufacturer code. Neither does a capacitor code of 100, which would be 10pf. The correct value is .001uf/1000pf, which would normally be labeled 102.

Definitely spray the pot with contact cleaner, and make sure it contains a lubricant. The right stuff usually says that it's intended for moving parts and is often labeled "control cleaner" in English. If it works properly after that, you're done. If not, either the pot is dead or the cap may be the wrong value, whether it's original or not.

Some fanatical purists might take the pot apart and replace the wafer in order to keep the original solder joints.

Have you asked the previous owner how the pot behaved when he first got it?

 

[Telekarster]

Some fanatical purists might take the pot apart and replace the wafer in order to keep the original solder joints.

FWIW I asked about this very thing out here once, cause I was curious what the experts and collectors thought about such an action on an original guitar, the overwelming response was that it was not worth doing i.e. that the guitar performs well is the most important thing in the end... and I for one agree. Parts wear out and when they do, it's time to replace them with acceptable replacements

 

[Sea Devil]

I tried it once. It was a waste of time.

 

[AJBaker]

View attachment 944225

That's the only thing we really need to see more clearly. I've enhanced the photo a bit, but I still have trouble reading anything but the 20% and what looks like 25F, which makes no sense (F means 1%) unless it's just a manufacturer code. Neither does a capacitor code of 100, which would be 10pf. The correct value is .001uf/1000pf, which would normally be labeled 102.

[...]

I think it says "20%" at the top, and "25V" at the bottom.
In the middle, I think it's the image of a cap on it's side, with ".001" written there (the "1" looks like a line joining the two horizontal bars).

To me that would make sense:
It's the correct value for the period, and it looks just like the tone cap, so it's probably original.

You're right about 102 being the correct way to label it these days, but back then I believe they still mostly labelled caps in fractions of micro Farads.

 

[Sea Devil]

Older caps are often labeled like that. Every cap in my 1964 DR is. I agree that 25V makes sense, and would be about right for the cap's size. Just a weird-looking, lopsided V, I guess.

My 60s Tele's volume pot needs a shot of contact cleaner pretty regularly. It's not necessarily a "one-and-done" operation.

 

[cousinpaul]

Hi Jorg. Welcome to TDPRI! Cleaning the pot is a good place to start. If you were to de-solder and lift one leg of the treble bleed cap, you could eliminate that as a problem. A lot of us don't even use one. If it does come down to replacing parts, I'd save the originals. You might even consider replacing the whole control plate assembly and putting the old one aside. You never know, having the original parts might matter to a future buyer.

 

[Sea Devil]

There's pretty much no way that the cap could go bad in a passive circuit without visible physical damage, at least AFAIK.