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Thread: Potentiometers modification question

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    Potentiometers modification question

    Hello.
    I wanna modify some 24 mm pots from soldering lugs to soldering pins one mounted directly to PCB. The only way found, due to layout and pot size ,was to cut completely the lugs and to solder some solid core wires to serve as solder pins. I choose to use Bourns PDA 24 series. It helps a bit the rivets are tubular and can hook the wires through. But have a question: what max temperature this rivets can take to be sure not destroy physical contacts to the carbon track by soldering, please ? May I slder directly to the pot rivets at 320*C / 610*F ?Thanks.

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    Last edited by catalin gramada; 11-21-2019 at 12:36 PM.
    "If it measures good and sounds bad, it is bad. If it measures bad and sounds good, you are measuring the wrong things."

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    Bent Member Chuck H's Avatar
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    As far as I can tell ALL the (EDIT: import) 24mm and 16mm pot wafers are made by only a few east Asian factories and the metal parts, only two or three. Sometimes the different factories parts are swapped around a little. I expect they're somewhat standardized to each other for conveniences. But basically all the pots are now pretty much the same as the import Alpha Taiwan pots we've been buying from Mouser for decades. Though most come out of China now I suspect that the Taiwan pots often did too. The exceptions would be in QC. Bourns, for example, has very good tapers and tolerance as well as offering special bushings and torque lubricants for the industry. But the mechanical parts are all pretty much the same. That said...

    I've ruined a couple of the old Alpha Taiwan pots attempting to solder to the rivets. As far as I know there is no conductive medium between the rivets and the track. They are only compression fit. So I suspect that flux creep was the problem. But then I've successfully soldered many to the rivets also. I think if you use a hot iron, get in and out fast and be sparing with the solder you'll be ok. But my point above is that there's no guarantees. If you find that you have to keep resoldering your make shift pins to the rivets because heat transfer is melting the joint when you solder the other end then you stand a high likelihood of compromising the connection. If you have room you might try clipping a hemostat on the pin to act as a heat sink. Again, use a hot iron and get in and out fast. Maybe 700° instead of 610°. If you have to hold the hot iron to the joint for too long to get flow there will be more heat transfer and risk of re melting your rivet/pin joint.

    EDIT: CTS is making 24mm and 16mm pots. I do not know where they are made, but they are different from all the east Asian import pots.

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    Last edited by Chuck H; 11-21-2019 at 02:48 PM.
    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

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    Soldering to the rivets is risky, They could loosen and cause intermittent problems. If I don't have a pot with pins I mount one with the lugs up and run 3 wires to the board.
    I would never solder to the rivets

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    Bent Member Chuck H's Avatar
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    Quote Originally Posted by dmeek View Post
    Soldering to the rivets is risky, They could loosen and cause intermittent problems. If I don't have a pot with pins I mount one with the lugs up and run 3 wires to the board.
    I would never solder to the rivets
    This is how I've done it most times. If there aren't space considerations this is the best option.

    I was just pointing out that soldering to the rivets can be done successfully. Though not with 100% assurance.

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    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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    FWIW: I've soldered to the rivets plenty of times. Never a problem.

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    Bent Member Chuck H's Avatar
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    The last time I soldered to the rivets was on my own amp. I wanted to piggy back a circuit on the volume control and it's on an angled chassis front and already has a bypass cap of 47p and a bright switch cap of 180p as well as the normal leads and the caps are sort of sandwiched in tight quarters. I looked at it and thought: "Nope. I'm not taking all that "s" apart and redoing it right now."

    I did eventually redo everything with a new pot and no rivet solder though once I finalized the design.

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    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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    Two pots soldered with all my best skills can do... one hit, one miss. Something get loose as pushed gentle the pot get intermitent operation. Maybe some of you guys can do it but for sure is not something I can do...
    I will turn it up and route some wire as was suggested below. Thanks for support.

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    Last edited by catalin gramada; 11-22-2019 at 11:01 PM.
    "If it measures good and sounds bad, it is bad. If it measures bad and sounds good, you are measuring the wrong things."

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    Did you use 600*F ?
    Like Chuck said earlier, lower temp. iron requires more time on the joint, which usually does more harm than good.
    I ordered a 600F tip once just to see what it was like, it takes way too long just to melt solder, I can not use it.

    I know soldering to pot rivets will not always be successful, but I think you have a better chance with a 700F temp than with 600F.

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    Hi , yes 600. I used a magnastat iron and there are only tips I have. As a remark, I saw the wafer melted litle bit. Ordinary plastic perhaps...? Maybe is better to use a pot with more thermal stable wafer. I will take out to investigate what was happen with those broked pot. Thanks

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    "If it measures good and sounds bad, it is bad. If it measures bad and sounds good, you are measuring the wrong things."

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    Bent Member Chuck H's Avatar
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    Quote Originally Posted by catalin gramada View Post
    Hi , yes 600. I used a magnastat iron and there are only tips I have. As a remark, I saw the wafer melted litle bit. Ordinary plastic perhaps...? Maybe is better to use a pot with more thermal stable wafer. I will take out to investigate what was happen with those broked pot. Thanks
    From pot #1

    Quote Originally Posted by catalin gramada View Post
    I choose to use Bourns PDA 24 series.
    Pretty sure that's FR4 or some other epoxy and fiberglass circuit board material and not "plastic" (as in some single component polymerized product). If it's melting then it would be the epoxy. And there's a good chance there was WAYYYY too much heat transfer. Which is more likely to happen with a cooler iron slow than a hot one fast.
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    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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    In reply to post #2, I've had recent exchanges with the Taiwan Alpha factory to clear up confusion over products being sold as Taiwan Alpha that I suspected were not, as the quality was very poor and the pots crackled from new. Taiwan Alpha pots are always branded and have their logo. Additionally their push-pull pots have red epoxy to secure the terminals - quite often others use green. To confuse matters there's a Korean factory called Alpha that produces pots, though these don't carry the Taiwan Alpha logo.

    There are many Chinese manufacturers of pots and these are being incorrectly described as Taiwan Alpha by resellers and giving the company a bad reputation.

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    Bent Member Chuck H's Avatar
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    Quote Originally Posted by Mick Bailey View Post
    In reply to post #2, I've had recent exchanges with the Taiwan Alpha factory to clear up confusion over products being sold as Taiwan Alpha that I suspected were not, as the quality was very poor and the pots crackled from new. Taiwan Alpha pots are always branded and have their logo. Additionally their push-pull pots have red epoxy to secure the terminals - quite often others use green. To confuse matters there's a Korean factory called Alpha that produces pots, though these don't carry the Taiwan Alpha logo.

    There are many Chinese manufacturers of pots and these are being incorrectly described as Taiwan Alpha by resellers and giving the company a bad reputation.
    Agree! Taiwan Alpha is the best of the "Alpha"s (in some regards). There's also an Alpha (or maybe two) in China and many of their products are "made in" Korea. I have not been able to locate and Alpha in Korea, per se. There's also an Alpha US! But I have every reason to believe that their 24mm and 16mm pot products are assembled from ALL east Asian components not associated with Taiwan Alpha (except for the following)...

    There is, however, only one prominent factory in China stamping and casting most of the common metal potentiometer parts and I believe they also do the majority of the plastic molding (moulding) for wipers, stops, etc. And I believe that ALL the Alpha's (and most other commercial potentiometer suppliers including) are getting their rings, cases, bushings, shafts and wiper assemblies from this source.

    The real difference between all the pots, in my experience, is in the resistance wafers. Their tapers, the quality of the conductive inks used, tolerance and the pin connections.

    Unfortunately the market is a real insiders game. So specific information and who's actually working with who is near impossible to nail down in much detail. Trust me. I've been investigating it quite a lot because I'm currently trying to find a supplier for a potentiometer I want to have fabricated. There are a shit ton of configurations available and all the features I need are available readily on one model or another from different suppliers that have had custom parts made. Trying to work through Taiwan Alpha and US Alpha has so far yielded little cooperation. As it happens some of the features I need would be more uncommon on their products than other manufacturers. I started with these two because they are very accessible. Opening lines of communication with other east Asian manufacturers that may be more open my requirements is something I'm researching, but is not my forte. I sure don't want to shut out any more prospective manufacturers by coming across like an ignorant, green horn nobody from America.

    EDIT: One pot manufacturer for the common 24mm and 16mm sizes that seems to be mostly independent is Alps. But I believe they're out of Japan, so...

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    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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    The only really accessible custom manufacturer for pots in small production quantities I've found is Omeg in the UK. When I contacted them the minimum order was 10 units and the cost was not much more than off-the-shelf. They made pots for lots of UK amps over the years but will still run off discontinued parts or custom units.

    I did locate the Korean Alpha earlier this year but a quick search today didn't turn anything up.

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    Bent Member Chuck H's Avatar
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    I looked into Omeg because they offer a design feature I'll need that no one else offers. Unfortunately they don't offer some of the other features I'll need. I'll have to do some fabrication it seems.

    There are many references in ad print to Alpha Korea, but if you research those products more closely you'll find China and no "Korea Alpha" in existence. Just Alpha and made in Korea. Just as well... Before the POTUS is done Korea will be on a list of countries in full embargo with the US. Then where would I be?

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    "In fact when I run into problems working on electronic circuirts, there are so many times that when I finally track it down, the source of the problem is located between my soldering iron and my seat." SoulFetish

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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