Failing mode switches in digital BOSS pedals

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Pepe
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Failing mode switches in digital BOSS pedals

Post by Pepe » Tue Jan 21, 2025 6:35 pm

In the last few months I have purchased two BOSS pedals with faulty mode switches: a Taiwanese DD-3 with SMD board and a DD-6.

Both pedals had an issue with selecting certain modes. The DD-3 had the long delay in the knob positions "M" and "L", medium delay was not selectable most of the time. And if it worked, it went back to the long mode after a few minutes. Totally unreliable. The DD-6 did overall produce the longest delay time in most modes, only the shortest and longest delay modes were correctly working; reverse delay and WARP mode also only produced the same sound of the longest delay mode.

I managed to repair both pedals to make all the modes reliable and working properly again. Not to my fullest satisfaction, though.

The problem seems to be that the mode switches are normal potentiometers with detents and with three solder legs. They are not true switches anymore as they were in the past. My guess is that these potentiometers have worn off somehow. The resistor values that they used to have at those certain detent points don't seem to be correct anymore. I think that the electronic scanning of the mode potentiometer does only work with accurate resistor values with very little tolerance.

In both cases I replaced the hard (if not impossible) to come by mode potentiometers (with detents and reduced travel path) with standard potentiometers.

In the case of the MIT SMD DD-3, fixed with a standard potentiometer, the effect was in short delay mode in minimum position ("S"), then in medium and long delay mode at the correct marks of the knob metal plate ("M" and "L"), then for the rest of the potentiometer's range it was in Hold mode, also beginning at the "Hold" mark.

Today I did the same with the DD-6, where I already double-checked everything before ordering a fitting replacement potentiometer. With the new potentiometer all the modes are working correctly again. I have to clean and assemble it yet, but I guess that also in this case all the modes will switch at the correct positions that are marked on the knob metal plate, beginning at the Warp mode at 07:00 up to the 2600ms mode at 01:00.

The only "problems" are that you don't have the detents when using normal potentiometers as a replacement, so you don't instantly feel it when you are switching modes, and the mode knobs will have the full travel path of a normal potentiometer (270° to 300°) and don't stop at the mark of the last mode in clockwise direction. If you can live with that, you can easily fix your faulty pedal this way.

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Re: Failing mode switches in digital BOSS pedals

Post by fuzzbuzzfuzz » Wed Jan 22, 2025 4:12 am

Very nice Pepe.

Experience has taught me to either treat this kind of rotary switch with "kit gloves" or avoid such pedals altogether. In particular EHX pedals suffer the same problem, wizzing up and back down the modes...no good in the long run.

May I ask what kind of pot (manufacturer) that is?

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Re: Failing mode switches in digital BOSS pedals

Post by Pepe » Wed Jan 22, 2025 6:30 am

The original potentiometer was from Alpha (Taiwan), the replacement is presumably a cheap Chinese equivalent, bought at a German ebay shop that offers Arduino stuff.

Here in Germany I simply cannot find the 9mm Alpha potentiometers with the horizontal solder legs and with knurled or D-shaft. For example Banzai Music only offers the 9mm Alpha potentiometers with a full shaft for knobs with screws. The other ones with the correct shaft have angled solder legs that are too thick (where they come out of the plastic case) to simply be cut off to make them fit.
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laurie
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Re: Failing mode switches in digital BOSS pedals

Post by laurie » Wed Jan 22, 2025 11:27 am

You can get them here:
https://www.jaycar.com.au/search?q=9mm%20potentiometer

One of our Australian members might need to help you buy them (not sure if they ship overseas).

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Re: Failing mode switches in digital BOSS pedals

Post by Pepe » Wed Jan 22, 2025 11:30 am

Are these from Alpha? I cannot see any brand name.
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Re: Failing mode switches in digital BOSS pedals

Post by laurie » Wed Jan 22, 2025 11:33 am

Pepe wrote:
Tue Jan 21, 2025 6:35 pm
the mode switches are normal potentiometers with detents and with three solder legs. They are not true switches anymore as they were in the past. My guess is that these potentiometers have worn off somehow. The resistor values that they used to have at those certain detent points don't seem to be correct anymore. I think that the electronic scanning of the mode potentiometer does only work with accurate resistor values with very little tolerance.
Yes. This is what is happening.

It is less likely that the pots have "worn out" and more likely they have become dirty? A little scratchiness doesn't affect a potentiometer when used for volume etc, however, for this application it messes up the scanning.

In the past I've carefully drilled a small hole in the side of the potentiometer and flooded the potentiometer with contact cleaner. If you disassemble an old broken 9mm potentiometer (drill out the rivets) that will give you a guide where to put the hole.
Last edited by laurie on Wed Jan 22, 2025 11:37 am, edited 1 time in total.

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Re: Failing mode switches in digital BOSS pedals

Post by laurie » Wed Jan 22, 2025 11:34 am

Pepe wrote:
Wed Jan 22, 2025 11:30 am
Are these from Alpha? I cannot see any brand name.
Historically they have been. Can't say for sure where the current production comes from.

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Re: Failing mode switches in digital BOSS pedals

Post by Pepe » Wed Jan 22, 2025 11:39 am

laurie wrote:
Wed Jan 22, 2025 11:33 am
In the past I've carefully drilled a small hole in the side of the potentiometer and flooded the potentiometer with contact cleaner. If you disassemble an old broken 9mm potentiometer (drill out the rivets) that will give you a guide where to put the hole.
This is a great advice! I did this with sealed potentiometers in metal cases before.
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Re: Failing mode switches in digital BOSS pedals

Post by bigtone23 » Thu Jan 23, 2025 5:38 am

Great info here.
Knock on wood I don't have to deal with this anytime soon, but if so...

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Re: Failing mode switches in digital BOSS pedals

Post by Pepe » Thu Jan 23, 2025 7:33 pm

I tested the reparied DD-6 today. With the new standard potentiometer all the seven modes are working perfectly again.

I have my doubts that the original potentiometer with the detents could be rescued with tuner spray, because only two of the modes worked with it. I will keep it in my parts bin, but I will leave this DD-6 with the new potentiometer.

Can it be that some of these pedals with failing mode switches have simply been kicked accidentally? I have seen so many bent knobs on pedals and most of them were either on the left or the right side (for example my Taiwanese DF-2 had bent potentiometers on both sides and the two knobs were missing). Those mode switches are always on the right side of the control plate. Since they are switching the effect modes at very exact resistor values, I suppose that they are already malfunctioning if you miss the treadle and put your foot on them with force.

As fuzzbuzzfuzz said, better treat them carefully. I have some pedals with these switches and not a single one has ever failed.
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