Replacing low pot on Roland kc 300

[Sus4]

Does anyone know if there is a video to show how this is done or maybe a service manual?

[DrGonz78]

Half of the battle is getting the thing apart? Have you got the chassis lying on a bench or is it still in the cabinet? If this helps I included the link to how to disassemble the amp. Once you have the chassis out of the cab then locate the large main board. All the nuts and any screws needs to be removed to gain access to the underside of the main board. The service manual is like looking at a map and it is not going to instruct you how to remove a pot. Once the board is free then you need to desolder the old part and install a new one.

This video shows how to use a solder sucker to remove the solder on the legs of a pot to remove it. You can use braided solder remover too.

[The Dude]

And,...... have you tried cleaning it first? It may not need replacing.

[DrGonz78]

Yup it is very possible that the pot is dirty and needs to be cleaned. Yet I envisioned that the pot shaft might have broke off or something. What is the state of that pot?

[Sus4]

Guys, thanks for the replies. Yes, I do have a solder sucker, glad you reminded me of it. I forgot what it was used for. DrGonz78, your video is perfect and thanks for the fixit link in regard to the KC 300.....perfect. I tried squirting Deoxit D5 into the top of the pot, but it didn't do any good. So, when I dissemble I'll probably be able to squirt some Deoxit into the pot if it has a little hole like the one in your video. The question is, if it is dirty I'll have to re-asemble it to check it right?. Then if it doesn't work I'll have to take it apart again and remove the pot and solder in the new one. Can I buy the new pot from Roland or someplace else? Thanks again.

[DrGonz78]

Take a close up pick of the pot so we have a picture for reference. Might be able to try clean it again before you pull the board out. It may be a closed body pot which can be tough to clean.

[Sus4]

I took a picture and it's on my desk top, but this website is not alloying me to post it saying it's to large for this page. I don't understand this. It's just a jpeg picture. It's just a picture of the Low knob pot.

[DrGonz78]

Perhaps it is due to being a new user and it won't let you post till you have a certain number of posts. Anyhow there is a picture of a Roland KC300 on this thread, thanks to Jason. In fact, the first question on that thread is how do you clean these pots.


So yes they are sealed up pretty good. There are four little tabs on the back of the pot that hold it all together. Use a tiny straight blade screwdriver or something similar and bend those out so the pot can be opened. I use the deoxit and sometimes in this situation a qtip to clean the pot to my best ability. Then put the pot back together and hope it worked. If not then I start looking for a replacement part.

The Aliexpress link show the correct pot style but their website does not inform the buyer about the specs of the part. Not too hard to figure out, but first clean it to try to repair it.
https://www.aliexpress.com/item/32997684982.html

[Sus4]

Unless I'm not understanding you, the picture I have is just looking down at the KC300. All you see is the low pot knob which is of course attached to the amp itself. Nothing is apart. The amp is completely all together. The four little tabs you mention are not visible from the outside of the amp. I would have to take apart the amp to see those tabs. I hope this explains it.

[DrGonz78]

Yes everything I mentioned involves pulling out the chassis. Just like that picture in the other thread posted by Jason (Nosaj). If you read that other thread Enzo & the dude (sounds like a possible Hollywood production) mentioned how to clean the pot without taking out the board. Spray deoxit on the back of the pot, the side that has the 4 metal tabs. You want gravity to help so you need to have the chassis vertical with the pot knobs facing down. The idea is to let gravity drip the cleaner into the pot and while doing this you need to rotate the pot back & forth.

[DrGonz78]

This is the link to that other thread. For some reason it was not working when I pasted it in the post.

https://music-electronics-forum.com/...you#post936305

[Sus4]

OK, got it. I will probably tackle the project either this weekend or next week. I'll keep you posted.

[DrGonz78]

As long as the pot shaft didn’t break then cleaning the pot is really easy. Much easier and cheaper than removing circuit boards and components. These particular pots can be a bit of a chore to clean though. So let’s hope that the pot cleans up easily.

[J M Fahey]

I took a picture and it's on my desk top, but this website is not alloying me to post it saying it's to large for this page. I don't understand this. It's just a jpeg picture. It's just a picture of the Low knob pot.

Yet it can be a HUGE picture, and I am talking file size or pixel count , way higher than what can be displayed here.

Go to to https://imgbb.com/ or https://imgur.com/ and upload your picture there.

If you are on a computer or laptop download and install https://www.irfanview.com/, excellent and simple image handler.

It will let you do 2 very important things:

1) if you have, say, a full board picture but only interested in the pot , you can "crop" the picture leaving only the useful part

2) if you want the full picture but itīs too large, you can "resample/resize" it to "half", itīs usually enough.
If still too large, repeat the operation.

If only working with a phone, I guess that there must be online resources to process your pictures *or* some phones allow cropping, typically when you send picture to a WHatsApp contact or something.

[Sus4]

OK, here's the story. I followed the above instructions and they were perfect. It was very easy opening up the the KC 300 and looking inside. I sprayed the pot with plenty of Dioxide and the pot partially responded. Getting an "on off" cracking sound when I turn the knob to the right at about "4 O'clock". That's the only spot where I get sound so it looks like I need to replace the pot. The place you recommended above, https://www.aliexpress.com/item/32997684982.html, is that the only place because I see it's made in China and I won't be able to get it until March 16th. I was wondering if you can recommend a place in the USA where I can get it sooner. If not I'll go with the one you recommend. Any other pointers, I'm open. Thanks.