HOW-TO GUIDE
How to Solder a Replacement Potentiometer Onto a PCB
By the OhmSavvy Research Team ·
Power off, discharge, then heat
- Unplug the device or remove its battery. In amplifiers and other mains-powered gear, filter capacitors can hold a dangerous charge after unplugging, so discharge them before reaching inside.
- The iron tip runs at several hundred degrees. Use a stand, and hold hot leads with pliers, not fingers.
- Ventilate or use fume extraction, wear eye protection when using a solder pump, and wash your hands after handling leaded solder.
1Match the replacement potentiometer
Read the markings on the old pot before anything else. A code such as B10K means 10 kΩ end to end with a B taper. On most current parts B is linear and A is logarithmic (audio taper), with C used for reverse log, but some older and European parts used other letters, so confirm against the datasheet when the code is ambiguous. Then match the physical details. A pot with the right value but the wrong pin spacing will not fit the board, and one with the wrong shaft will not take the knob.
| Attribute | How to check it | If it is wrong |
|---|---|---|
| Resistance value | Printed code, e.g. 10K, 103 or B10K | Control range, gain or timing changes |
| Taper (A, B, C) | Letter prefix; confirm on the datasheet | Control feels bunched at one end |
| Pin spacing and layout | Measure the pitch with calipers; count rows | Pins do not line up with the holes |
| Mounting style | Vertical vs right-angle, tab positions | Shaft points the wrong way or tabs miss |
| Body size | Measure the diameter (9 mm and 16 mm are common) | Pot fouls nearby parts or the panel hole |
| Shaft | Diameter, length, D-flat, knurled or slotted | Knob will not fit or sits too far out |
| Gangs and switch | Count the pins: 3 per gang, extra for a switch | Stereo channel or power switch lost |
Note the power rating too if the pot carries real current, and photograph the board before you start, including which way the shaft faces. If you are not sure the old part is faulty, check it first with the method in how to check a potentiometer wiper with a multimeter; a scratchy pot sometimes only needs cleaning.
2Remove the old potentiometer
Pull the knob, then undo the panel nut and washer so the board can come free of the case. Look at the underside: a typical board-mount pot has three signal pins in a row plus two or more mounting tabs. The tabs are thicker than the pins, are often bent over against the board, and are frequently soldered into ground copper, so they need noticeably more heat.
- Clear the three signal pins first with a solder pump or braid. Add a little fresh solder and flux before pumping; a fresh joint melts through faster than a dull, oxidised one.
- For the tabs, switch to a larger chisel tip, flux, and load the joint with solder so it carries heat down the hole. Once the solder is cleared, straighten any bent tab with pliers while heating it.
- Work back and forth until every pin and tab moves freely in its hole. Never lever the pot out against solid solder; that is how pads and barrels tear out.
If the old pot is definitely scrap and the tabs will not release, snip the pins and tabs from the top of the board and remove each stub on its own with tweezers while heating it. Single stubs come out far more easily than a whole part. The general methods are in how to remove solder from a circuit board, and the same multi-joint problem on larger parts is covered in how to remove solder from a multi pin PCB connector.
3Clean the holes and pads
Each hole must be open before the new pot will drop in. Heat the pad from one side and pump from the other, or run fresh flux and braid over each pad. On a double-sided board a thin film of solder often stays inside the barrel; the techniques in how to remove solder from a plated through hole deal with that. Hold the board to a light: every hole should show a clean ring.
Then clean off old flux with isopropyl alcohol and inspect each pad. If one has lifted or torn away from its trace, fix it now, before the new part covers it; see how to repair lifted PCB pads after desoldering.
4Fit the new pot square to the board and panel
Insert the new pot with the shaft facing the same way as the original. Most pots have a small anti-rotation lug on the bushing that locates in a notch in the panel; keep it on the same side. Press the body down so it sits flat on the board, with the tabs fully through their slots.
Align with the panel before soldering
Dual-gang pots, used for stereo volume and balance controls, have two rows of three pins, and the rows are not interchangeable if the circuit treats the channels differently; match the front and rear gangs to the original. Switched pots add two more pins for the switch, often at the back of the body. If the new part's pins are slightly longer or thicker than the old ones, do not force them: check that you have the right footprint before opening up a hole, because drilling removes the plating that links the two sides of the board.
5Solder the pins, then the tabs
Tack one signal pin first, check the pot is still flat and straight, and reflow that joint if it is not. Then solder the other two pins with a small chisel tip at a typical 330 °C to 360 °C for leaded solder or about 350 °C to 380 °C for lead-free; check the solder maker's guidance. Each joint should take a few seconds and finish as a smooth concave fillet that wets both the pin and the pad.
Solder the tabs last, with the larger tip again. They need enough solder to fill around the tab, but leave the plastic body alone: holding a tab at high heat for a long time can soften the pot's housing or disturb the wiper inside. If a joint looks gray and lumpy, reflow it with fresh flux, as described in how to fix a cold solder joint on a circuit board. Trim the pins if they protrude more than the original ones did.
6Test end to end and the wiper with a meter
With the board still unpowered, set the meter to resistance and measure across the two outer pins at the solder side. That proves both end joints connect to the track. The reading should match the marked value within tolerance; many carbon pots are rated at ±20%, so a 10 kΩ part reading anywhere from about 8 kΩ to 12 kΩ is normal. Other parts in parallel can pull an in-circuit reading low, so if it is well under the expected value, lift one end and measure again.
Now move one probe to the wiper pin and turn the shaft slowly from stop to stop. On a linear (B) pot the reading should climb steadily from a few ohms to close to the full value, with no jumps to OL. An audio (A) pot climbs much more slowly over the first half of its travel, which is correct, not a fault.
Finally, look for solder bridges between the closely spaced pins, and check that no pin reads near 0 Ω to a grounded tab unless the circuit grounds that end of the track. Only then refit the board and power it up. For the full meter procedure, including the powered voltage-divider check, see the potentiometer wiper guide and how to measure resistance with a digital multimeter.
The swap at a glance
The whole job follows the same order every time. Skipping the matching step or the test step is where most repeat repairs come from.
01
Match the part
Value, taper, pitch, shaft
02
Desolder
Pins first, tabs with more heat
03
Clean holes
Clear barrels, check pads
04
Fit square
Flat, aligned to the panel
05
Solder
Tack, check, pins, then tabs
06
Meter test
End to end, then wiper sweep
Troubleshooting after the swap
| Symptom | Likely cause | Fix |
|---|---|---|
| Control works backwards | Pot fitted reversed or outer pins swapped | Check orientation and pin order against your photo |
| All the action at one end | Taper mismatch (A fitted where B was used) | Fit the original taper |
| End to end reads OL | Open joint on an outer pin, or damaged track | Reflow the outer pins; re-measure off the board |
| Reading jumps while turning | Cracked wiper joint or faulty new pot | Reflow the wiper pin; test the pot loose |
| Hum or noise in audio gear | Tabs not grounded where the original was | Solder the tabs to the ground pads |
| Shaft wobbles in the panel | Board flexed to meet the panel | Reflow tabs with the panel nut fitted |
Irons that suit potentiometer replacement
The signal pins are easy; the grounded tabs are what test an iron. A temperature-controlled iron that takes a range of tip sizes covers both. For more options, see the best soldering irons and our guide to tip types.
Irons from our soldering reviews
100W digital station with a push-button rotary dial; store one preset for pot pins and another for ground-tied mounting tabs.
85W digital, ESD-safe station (70W iron) with tight temperature stability for a dedicated electronics bench.
Up to 88W at 24V (about 60W on 20V USB-C PD) with an OLED display, for portable repairs.
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Frequently asked questions
Can I replace a 10K potentiometer with a 20K one?
Sometimes, but it changes the circuit. In a simple voltage divider the range of the control stays similar, though the load on the source and the wiper output impedance change. Where the pot sets gain, timing or a bias current, a different value shifts the behavior. Match the original unless a schematic or the maker confirms the alternative is fine.
Does it matter which way round a potentiometer goes in?
Yes. The footprint usually only fits one way, but if a pot can be fitted reversed, or the wiring is swapped, the control works backwards: turning clockwise lowers volume instead of raising it. Keep the shaft facing the same way as the original and match the pin order you noted before removal.
Do I have to solder the potentiometer mounting tabs?
Solder them if the original tabs were soldered. They take the twisting force from the knob and panel nut, so the three thin signal pins do not crack their joints over time. On some boards the tabs also connect the metal case to ground, which helps reduce hum and noise pickup in audio circuits.
Why is my new potentiometer noisy right after installing it?
Check the solder joints first: a cold or cracked wiper joint causes crackle that sounds like a worn track. Flux residue between pins on a high-impedance circuit can also cause noise, so clean the area. If the joints are good and the meter sweep is smooth, the noise may come from elsewhere, such as DC on the pot from a failed coupling capacitor.
Can I mount a replacement potentiometer off the board on wires?
Yes, as a repair or a test, though it is rarely as tidy as a board-mounted part. Keep the wires short, twist the three together, and use shielded cable in audio circuits so the wiper lead does not pick up hum. Anchor the pot to the panel so the wires carry no strain, and ground its metal case if the original tabs did that job.
