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  • More new pots trouble

    You may remember my frustration with some CTS pots that did nothing from 1 to 2, and then jumped to around 24K at 3. Well today a guy brings in a new Tele from a boutique builder that he just received, and the volume would not go all the way down or up. I did find a couple of hinky solder situations, but in the end both A250K Bournes pots were defective. The volume pot readings would jump all over the place from the wiper to one side, in this case the grounded side. Once I installed a new CTS brass shaft (after measuring it first) that was fixed, but then the tone pot cut out. I resoldered the whole shebang, but if I flexed the wires or pressed one of the lugs just right, it would cut out. I even tried a solder repair to the press fit connections, but no go.

    What is with two instances of new defective pots inside of a week?
    It's weird, because it WAS working fine.....

  • #2
    Were they new from a recognised supplier, Mouser, RS, Farnell etc or new old stock, check the date codes and if new, return them as faulty.
    Some fleabay resellers, sell components that were bought as a batch that didn't meet the quality standard so bought as scrap, not to be resold.
    Support for Fender, Marshall, Mesa, VOX and many more. https://jonsnell.co.uk

    Comment


    • #3
      Things ain't now like they used to be. Although I havent' indulged in Bourns pots that fit amps & guitars*, apparently they suffer from the same low quality as CTS. BTW, CTS makes automotive electronic parts, including the pots used in modern USA built vehicles' "fly-by-wire" computer controlled circuits. That should inspire a chilling lack of confidence. Meanwhile as I mentioned Alpha has stepped up their game. 30-40 years ago their pots were sorta crappy. Now they're everything the US manufactured parts should be, but aren't.

      Couple of years ago I noticed Stu-Mac was touting a new line of pots intended for guitar use under the "Emerson" label. They sure look like custom label CTS to me. Customer reviews at the time - only about 10 - half gave poor reviews with the same complaints you have. And the other half look as if they had been written by the sales department, just a bit too enthusiastic.

      CE/Antique had some made-in-Mexico pots a couple years ago. They looked approximately like Bourns. No great shakes there either. And I don't see 'em in the catalog any more.

      Then there are expensive PEC pots from Canada. About $20 for the usual suspects, linear w/solid shafts. PEC's with spline shafts for guitar use now available at CE/Antique, prices reaching for $40. Haven't tried any though I've seen some reports that these also are far from what they should be, especially at these prices.

      * Bourns "blue cube" trim pots still work OK thank hevvins. I don't know what I'd do if their quality took a flop.
      Enjoy. Every. Sandwich.

      Comment


      • #4
        CTS pots have used the same wafer dimensions for decades and I like them because of that. It means I can create dual pots with specific resistance ranges to suit my needs, repair old pots by re-wafering them and keeping the original date codes on the shell as well as the original shaft, which may be specific to a piece of equipment. With many CTS pots they're an assembly of compatible parts - mix and match - for the factory to produce specific pot types.

        At one time though the switched pots had a different track than the regular pots. The switched wafers had a track where the resistance started at zero at the point where the switch turned on. This meant that if you had a switched volume control, as soon as you turned it on the volume was turned right down. At some point in time the regular pots started to have the same track as the switched pots and effectively the starting point for the control to operate is around 2 - the point where the switched version would begin to operate. This is annoying with amp builds as it gives a dead spot in the range. I have had the odd flaky new CTS pot from trusted sources, though nothing a squirt of Kontakt PR did't fix.

        The most annoying thing with CTS pots is the long shaft versions. They used to have a stop collar on the shaft but now that's gone and when you push a brand new knob onto a brand new pot it can open up the tabs and loosen the shell. The only thing that locates everything is the shell being securely crimped on. Really poor.

        I've noticed increasingly that boutique amp builders in the USA are using 24mm Alpha pots, which do have a proper sweep without that 0-2 dead zone.

        Comment


        • #5
          Originally posted by Mick Bailey View Post
          I've noticed increasingly that boutique amp builders in the USA are using 24mm Alpha pots, which do have a proper sweep without that 0-2 dead zone.
          Yes, I have noted the same. You think those booteekies are on to something?

          In the 70's, mil-style Allen-Bradley Ohmite pots were supposed to be the very best. But audio taper Ohmites were hard to find, dual pots the same. Had to special order those at the local supply shop & wait months for them to arrive. I have an Alembic F2B preamp built with those Ohmites. I found they tended to get scratchy. There was no open slot behind the electrodes - you had to pry the cover off and apply a dot of Cramolin. What a pain in the neck. In recent times, PEC pots resemble the Ohmites. Same problem cleaning them.
          Enjoy. Every. Sandwich.

          Comment


          • #6
            Originally posted by Randall View Post
            You may remember my frustration with some CTS pots that did nothing from 1 to 2, and then jumped to around 24K at 3. Well today a guy brings in a new Tele from a boutique builder that he just received, and the volume would not go all the way down or up. I did find a couple of hinky solder situations, but in the end both A250K Bournes pots were defective. The volume pot readings would jump all over the place from the wiper to one side, in this case the grounded side. Once I installed a new CTS brass shaft (after measuring it first) that was fixed, but then the tone pot cut out. I resoldered the whole shebang, but if I flexed the wires or pressed one of the lugs just right, it would cut out. I even tried a solder repair to the press fit connections, but no go.

            What is with two instances of new defective pots inside of a week?
            Well trouble does seem to follow some people or like a boss at the job told me once I had been installing doors and they kept breaking when I would put them on the cabinets. He said well your the only one putting them on who else is it supposed to happen to?(We get the doors from another company and they had started skimping on the wood glue in the joints)

            nosaj
            Binkie McFartnuggets‏:If we really wanted to know the meaning of life we would have fed Stephen Hawking shrooms a long time ago.

            Comment


            • #7
              Is it possible they can't take much heat? I don't know if some measured bad before soldering, but the ones in this guitar could have been over-heated. Sounds like there were other solder issues so maybe it's not the builder's strong suit.
              That the problem had to do with pressure on the lugs is why I mention this.
              "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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              • #8
                Word got back to the builder, and then back to me that the whole batch of Bournes pots were bad. Customer showed me a photo of about a dozen of them in a trash bin,
                It's weird, because it WAS working fine.....

                Comment


                • #9
                  I've bought cheap Chinese trimmer pots, they were labeled Bourn's made in Mexico. Definitely fake.

                  Comment


                  • #10
                    There doesn't appear to be any item, however mundane or inexpensive, that the Chinese won't fake and make of a lower quality in some way.

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