Tweet
I'll post this for anyone wanting to replace a broken pot and wanting the amp be as stock as possible since the original pots are not available. Thanks to the guys from my other thread for information on replacement pots that would work.
I needed to replace the treble pot but all of the pots are the same except for the drive pots which are 1M sealed plastic so this should work on any of the other pots.
I ordered this 100k linear pot from Digikey
I really wanted to keep the pot on the board like the original. The original has 4 legs that attaches to the board and the new one has just 3 short terminals.
Installing this pot without modifying it would mean having to mount it on the faceplate and then running leads to the board... It would have worked but I didn't like that idea. I also saw someone else cut the three legs off the original pot and solder them onto the terminals of the new one so it soldered to the board, albeit without that 4th hind leg. I still wasn't 100% satisfied with that method either. Both pots are exactly the same size and construction except for the terminals so I ended up disassembling both pots, swapping the shaft and reassembling the original pot with a new shaft. It was not that straight forward however....
Here is the original pot disassembled.
Here is the replacement
I swapped the original contact from the old shaft to the new one (fits perfect BTW) and then put it back together to test.
The flat on the shaft is 180 degrees off.. nuts. there is a stop on the back on the body that contacts a molded extension on the back of the shaft. No problem!, i'ill just rotate the back 180, rotate the contact 180, and done. Nope, the back won't fit on because of the relief that is cut out for the three leg side is now on the other side and the back contacts the leg support and will not seat.
So, two options here... either grind away the metal in the way or bend the old stop out of the way and create a new one 180 degrees from the old one. I felt the latter was the better solution so I went with that. I tested the metal and it was quite malleable so I didn't have any reservations going ahead with it. I cut two slots with a Dremel and used a punch to bend in the new stop and bend out the old one. After a little adjustment to how far the stop stuck out it worked perfect.
I reassembled the original pot with the new shaft, original contact rotated 180 on the shaft, original back in the same position with the new stop.
and soldered it back on the board. Done! Nope, not yet. The new shaft stuck out about 3mm further than the original. Motherffff...
Ok, at this point I'm committed. The knob will hide the shaft so then I decided to use a hacksaw blade and cut away the excess metal to match it to the original. It worked! The original knob fit perfect and is set to the same depth as the others. Looks completely stock and works great!
Lastly, I ordered a repro knob from eBay that looked exactly like the original knob and label "Sunn Beta knob" in the listing, but it is slightly different and does not match, but it will do for now until I can find a used original one. You can see the new knob mounted on channel B on the level control, I felt it looked less obvious there than right in the middle.
Hope this is helpful to anyone wishing to repair a broken potentiometer. Thanks to you guys on this thread for helping me find the right part.
I needed to replace the treble pot but all of the pots are the same except for the drive pots which are 1M sealed plastic so this should work on any of the other pots.
I ordered this 100k linear pot from Digikey
I really wanted to keep the pot on the board like the original. The original has 4 legs that attaches to the board and the new one has just 3 short terminals.
Installing this pot without modifying it would mean having to mount it on the faceplate and then running leads to the board... It would have worked but I didn't like that idea. I also saw someone else cut the three legs off the original pot and solder them onto the terminals of the new one so it soldered to the board, albeit without that 4th hind leg. I still wasn't 100% satisfied with that method either. Both pots are exactly the same size and construction except for the terminals so I ended up disassembling both pots, swapping the shaft and reassembling the original pot with a new shaft. It was not that straight forward however....
Here is the original pot disassembled.
Here is the replacement
I swapped the original contact from the old shaft to the new one (fits perfect BTW) and then put it back together to test.
The flat on the shaft is 180 degrees off.. nuts. there is a stop on the back on the body that contacts a molded extension on the back of the shaft. No problem!, i'ill just rotate the back 180, rotate the contact 180, and done. Nope, the back won't fit on because of the relief that is cut out for the three leg side is now on the other side and the back contacts the leg support and will not seat.
So, two options here... either grind away the metal in the way or bend the old stop out of the way and create a new one 180 degrees from the old one. I felt the latter was the better solution so I went with that. I tested the metal and it was quite malleable so I didn't have any reservations going ahead with it. I cut two slots with a Dremel and used a punch to bend in the new stop and bend out the old one. After a little adjustment to how far the stop stuck out it worked perfect.
I reassembled the original pot with the new shaft, original contact rotated 180 on the shaft, original back in the same position with the new stop.
and soldered it back on the board. Done! Nope, not yet. The new shaft stuck out about 3mm further than the original. Motherffff...
Ok, at this point I'm committed. The knob will hide the shaft so then I decided to use a hacksaw blade and cut away the excess metal to match it to the original. It worked! The original knob fit perfect and is set to the same depth as the others. Looks completely stock and works great!
Lastly, I ordered a repro knob from eBay that looked exactly like the original knob and label "Sunn Beta knob" in the listing, but it is slightly different and does not match, but it will do for now until I can find a used original one. You can see the new knob mounted on channel B on the level control, I felt it looked less obvious there than right in the middle.
Hope this is helpful to anyone wishing to repair a broken potentiometer. Thanks to you guys on this thread for helping me find the right part.
Attached Files
Comment