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 Post subject: Replacing Glitchy Knobs
PostPosted: Tue Jan 08, 2019 12:57 pm 
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My FX2 knob is loose and glitchy. I found that turning FX1 and FX3 also has affect on this glitch. Anyhow, they have affect on each other.

Does anybody have similar problem or any recommendation?
Can I change the mic knob with fx2 knob? Can it work that way?

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 Post subject: Re: Replacing Glitchy Knobs
PostPosted: Tue Jan 08, 2019 4:54 pm 
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You need to replace the pot.
Just buy a new one for the fx knob or do all three while you are in there, do not try and pull out the mic one to put it in another spot, you are only going to ruin the solder pads by repeatedly heating it up and pulling on them. I would assume the mic pot has five prongs, the control pot will be three.


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 Post subject: Re: Replacing Glitchy Knobs
PostPosted: Mon Jan 14, 2019 7:55 am 
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Thanks. I'll do your recommendation, I decided to change all three fx knobs. I hope the problem is not with something else.

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 Post subject: Re: Replacing Glitchy Knobs
PostPosted: Tue Jan 15, 2019 5:39 pm 
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It shouldn't be anything else. I had the exact same issue on a sp505 I just got, fx control knob one was damaged and moving by knob two, soldering in a new pot fixed it.


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 Post subject: Re: Replacing Glitchy Knobs
PostPosted: Fri Jan 18, 2019 12:28 pm 
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I have the same issue with my SP505 too. I'm going to change for both machines :)

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 Post subject: Re: Replacing Glitchy Knobs
PostPosted: Fri Jan 18, 2019 7:06 pm 
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May just need some electrical spray to clean out any gunk in there.

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 Post subject: Re: Replacing Glitchy Knobs
PostPosted: Sat Jan 19, 2019 5:02 am 
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I've done a ton of pot replacements on various models, mostly the SP-404, and it's always worth cleaning the pot out first using something like DeOxit D5 from CAIG Laboratories. In many cases issues can be resolved just by cleaning the pot and D5 also will help prevent future build-up in the pot, but if a replacement is necessary it's not terribly difficult to pull the pot off the board with a good soldering iron (hakko 888D, fat chisel tip), desoldering wick (mg chemicals or gootwick), and flux (amtech 559 is what I use, but any non-tacky flux should be fine for big work like this).

Basically, you're gonna want to disassemble the unit and put the board you're working with on a nice non-flammable surface (I use a cutting board from amazon) then drop a nice blob of flux onto each of the solder joints connecting the pot to the board (typically two large support/ground clips and 3 - 5 smaller joints grouped together). Then take your soldering iron and push the heated tip (375C is my typical working temp) against the solder joint until it gets shiny (aka "flows") and you can move the joint like a liquid by wiggling the iron a little bit. At that point you know that you can bring the joint up to its melting point and you can put your desoldering wick between the heated iron tip and the solder joint. The copper braid of the wick should pull the solder in the joint into the wick once heated (if that isn't happening cut a section of braid off from your roll as that will allow it to heat to the melting temperature faster) and ideally the conductor to the pot should be left in the middle of a clear through-hole. Just continue to repeat that process if you don't get all of it the first time. Repeat the same steps for each of the solder joints for the pot.

Assuming all of the through-holes are clear you should be able to drop in a compatible pot and use new leaded solder plus flux plus your heated iron tip to reattach the legs of the component where the old pot used to be. I'm always happy to help out if you run into any questions so feel free to shoot me a message!


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 Post subject: Re: Replacing Glitchy Knobs
PostPosted: Sat Jan 19, 2019 6:25 am 
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Zukken,

First off welcome to the forum. From your first four post I already like you.

Concerning your supplier that you found for these pots. the part numbers are listed here.

viewtopic.php?f=3&t=25788

and can easily be bought on mouser. The control pots work and are the correct size for most units (202 excluded).
If you would like to add to the thread part numbers as opposed to selling to help the community it would be appreciated.

As for "pulling" the pot off the board, there is no point in saving a .89 cent pot. cut the legs off from the top and pull them out one by one.

Look forward to your mods.


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 Post subject: Re: Replacing Glitchy Knobs
PostPosted: Sat Jan 19, 2019 6:44 am 
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Are you referring to the post where I mentioned messaging me if someone needed the pot? I wasn't suggesting that I was selling them if that's the case. Mouser's cheapest shipping option is $7.99 Ground or $7.99 USPS Priority currently and they charge a ridiculous amount for international shipping in my experience. I ordered about $100 worth of pots so that I can have them just sitting on a shelf for future units and there's no reason I couldn't ship a couple to a forum user in the US for like $2.00 instead of them paying $10 for that $0.89 component.

~

I've never really liked cutting components when they can be removed with an iron pretty easily intact. Since the through-holes need to be cleaned anyway to install the new pot it's kind of moot but I just prefer to remove the solder while the component itself is installed so I typically go immediately to that train of thought when suggesting a repair method.

I can see cutting legs becoming problematic if there are any components mounted on the board in the general vicinity that get damaged (in this case the SMD Capacitors that are right next to the center pin on the FX Pots). Most of these boards are maintaining the traditional single-side component mounting (way cheaper to manufacture incidentally) which means using desoldering braid on the unpopulated side is going to make it pretty difficult to cause any damage with a tool that slips.

~

That LED mod is next on the docket for the unit I'm currently working on. Cheap cheap cheap and a good way to make it stand out during use and when/if you resell the unit. Do you happen to know what SMD Diodes were used?


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 Post subject: Re: Replacing Glitchy Knobs
PostPosted: Sat Jan 19, 2019 7:10 am 
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Yes, that is what I was referring to and that is the type of help (your response) that the forum needs. The shipping there is ridiculous and it's best to stock up. I think it would be great if you sold them for a buck or two more plus the dollar for shipping. You make money and the people here aren't getting ripped off from ebay.

Like the post says, any color you want. The size is around 2mm x 1.2mm, and of course around 3v.

you can pm me if you want. So we don't carry on on this guys thread, although I think this issue has been solved.

As for not cutting the legs I'm 100% for it as every unit I get for $60 from someone reheating and reheating and reheating the legs till the pad breaks off is worth it to me.


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