How to service a Linn Lingo (mk1)

Recapping and calibrating a power supply for the iconic Linn LP12 turntable.

Linn’s Lingo, the first outboard power supply for the LP12 turntable, was introduced in 1990 and sold in its original form for about a decade. Because of their (relatively!) compact form factor and first-party branding, early Lingos (“version 1” or “mk1”) remain popular on the used market. These power supplies have now reached the age where their electrolytic capacitors can become marginal or dried out, and for optimal operation they should be “serviced.” This consists of a new set of capacitors followed by a voltage check/calibration. I did this to a Lingo recently, and seeing no other comprehensive guides online, I’m writing this one.

Disclaimer: This is a best-effort guide and is not guaranteed to be free of errors. If you discover any, please let me know. Also, during calibration, live voltage including mains voltages is accessible; mains electrocution can injure or kill. Only work with live current if you know how to do so safely.

Performing this service may correct (or head off) motor-related problems of low torque, no-start, or difficulty getting to speed. This guide won’t fix a power supply that has non-capacitor-related issues; for other concerns, look around for a Lingo service manual or take it to an expert.

Experience required

This is mostly straightforward desoldering and soldering, but given that the market value of a used Lingo still runs to a few hundred dollars, probably not recommended as a first-time project if you’ve never done anything like this before.

Tools

Phillips head and hex screwdrivers, desoldering pump/gun/braid, soldering iron, digital voltmeter. Bonus: bench isolation transformer.

Parts

There are 20 electrolytic capacitors (“caps”) on the Lingo board, and if you’re bothering to do any, you should just replace them all. The three largest caps are axial (leads coming out each end) and all others are radial (both leads coming out one end). Axial style caps have fallen out of fashion and are increasingly difficult to find in some specs. If you can’t source them, you can substitute a radial of the same values — they’re functionally identical — but it will be more fiddly to connect securely.

  • (3x) 33μF, 350V axial.
  • (2x) 2200μF, 25V
  • (2x) 1μF, 450V
  • (3x) 220μF, 16V
  • (2x) 100μF, 63V
  • (8x) 22μF, 63V

As always, replacement capacitors should match the original capacitance (μF), and must be rated for at least the original voltage — you can replace a capacitor with one that can handle a larger voltage but never the opposite. General use capacitors (including the original Lingo parts) tend to have an upper operating temperature spec of 85°C. If you use higher-temp parts (105°C) you’ll pay a bit more but they’ll likely last longer in warm environments, like the inside of a power supply. You’ll also want to use caps from respected manufacturers: look for Nichicon (the audio cult favorite), Rubycon, Kemet, Vishay/Sprague, Panasonic, Illinois, CDE. A good rule of thumb is that anything you buy from DigiKey or Mouser will be of good quality; and anything that comes in bulk assortment kits off Amazon for cheap should be avoided.

Step 1: Open the case and remove the PCB

With the Lingo unplugged (obviously), flip it upside down and remove the four screws that secure the board sled to the outer case (near the four rubber feet). Once done, you should be able to slide the outer case away from the sled; set that aside.

You can remove the plastic front panel by removing the two screws on the very front of the bottom, and the screw on each upper-side of the panel. Be careful, because the plastic is thin in parts and can crack or break around the screw threading nuts. (You may not need to remove the front panel but I found it useful to understand how to free the switch.)

Remove the power switch assembly from the case front by taking out the two screws that hold it down on the inside. Leave the switch mechanism intact, it can just dangle there away from the sled.

Using a small hex screwdriver, remove the four screws holding the PCB to the sled, and the two that secure the turntable connection socket. There is one final screw that comes in from the underside of the sled into the transformer; remove that as well. You should now be able to lift out the PCB.

Before or during its removal, unplug the power connection on the board. You can use a flat screwdriver to carefully jimmy it if necessary.

Lift out the board, taking care not to scrape its surface on the case, and set aside the sled. You’re ready to replace the capacitors.

Step 2: Replace the capacitors

For each capacitor, desolder the connection on the underside of the board. I recommend taking photos along the way so you can always refer back to which part came from where and which orientation they were in. You’ll need at least a solder sucker or some facility with desoldering braid to do this well; the ne plus ultra is a good desoldering gun which are wildly expensive but worthy investments.

⚠️ Note that some care is required here; the Lingo board is two-sided, and some of the capacitor legs are soldered to pads that are part of conductive channels back through to the top side of the board. You don’t want to separate or break any of these.

Remember that these capacitors are polarized (one side positive and one negative), and you must install the new ones in the correct orientation. Caps generally have a white stripe running down the side pointing to the “negative” ( — ) lead. Make sure the replacement caps are oriented the same way as the originals. Sometimes the positive (+) side is marked on the PCB for your convenience, but not always. Fortunately, on the Lingo board, all of the radial caps are oriented the same way (negative leads all to one side of the board) and the three axial caps are all oriented the opposite direction.

Solder in the new caps!

Once done, it’s always good to do a careful visual inspection of your work to ensure that all the capacitors are correct, the orientations are correct, and the solder joints are good and secure with no broken traces.

Step 3: Check/calibrate the output voltage

The way this power supply works is that it generates two sets (phases) of sine-wave signals, offset from each other slightly, which drives the AC motor inside the turntable. The Lingo uses a higher startup voltage to get more torque, and then settles into the steady voltage to run the motor. The steady voltage as measured on the board should be 60V for each of the two phases, and after replacing the capacitors, you should check that this output is still nominal, and adjust it if it’s not.

⚠️ What follows involves powering up the Lingo with the case open, and probing a live circuit. Present on the Lingo board are mains (or higher) voltages, which can injure or kill. Do not do this if you’re not comfortable with how to do it safely. You can reassemble the Lingo without checking the voltage and it will almost certainly work just fine anyway. Don’t take unnecessary risks.

Before doing this, you must replace the board back into the sled. Follow the earlier steps in reverse: lower the board back in, reattach the power plug to the board and replace the six screws that hold it down, as well as the one screw below the sled that goes into the center of the toroidal transformer. You don’t need to replace the front panel.

Connect the Lingo to your LP12; you want to take measurements while it’s actually driving a motor. (How to install a Lingo’s inboard assembly inside the LP12 is beyond the scope of this article but plenty of explanations of that can be found.)

If you have an isolation transformer on your workbench, now is a great time to use it!

It is safest to clip the voltmeter leads to the board before energizing it at all. Set your voltmeter to AC volts, and clip the negative (black) lead to the negative leg of C3 (the axial capacitor that’s by itself). Clip the positive (red) lead to the negative leg of C20 (which is one of the two signal phases):

With your hands out of the case and eye protection on, plug in the mains and carefully switch on the Lingo’s pushbutton power switch.

Nothing should smoke or smell or make weird sounds or explode! Wear eye protection.

Turn on the motor using the switch on the LP12. It should start spinning! If at this point, the motor is not turning, something is wrong. Either with the capacitor replacement you’ve done, or something else.

Assuming the deck appears to be running OK, give it some time (a minute or so) to settle in and make extra sure nothing seems wrong.

Note that the Lingo’s initial output is what Linn calls a “stall mode” at a higher voltage (around 90V) to get the platter to speed quickly. Wait at least 10 seconds or so after startup before taking any of the measurements below. You’re concerned with the steady-state voltages.

Check the voltage on the voltmeter. It should be 60V or within 1V of that. No adjustment may be necessary at all! However if you see a reading below 59V, or above 61V: very gently and very slowly, with an insulated screw driver, adjust the small screw-turn-component labeled POT1 (helpfully also marked 33rpm) until it’s in range.

Turn everything off, move the positive probe to the negative leg of C21 to check the other phase, and repeat. Both phases should be in range as both are controlled by POT1.

Finally repeat the above steps, but with 45rpm selected on the LP12. You’re still looking for 60V here (it’s the frequency of the signal that changes, not the voltage), and this voltage is adjusted with POT2 if necessary.

NOTE: 45rpm mode will not properly engage unless the motor is installed in an LP12 with the platter weight on. If for some reason you’re testing with a bare unmounted motor, you won’t be able to switch to 45rpm. That doesn’t mean your Lingo or motor is broken.

Step 4: Close it back up

Replace the power switch assembly with its screws and then replace the front panel if you removed it. Be sure the power LED is lined up pretty well with the plastic tube that relays the light. Slide the outer case back on and secure it from the underside with the four screws.

Congratulations, you just fully serviced a Lingo! I like to put a little sticker on the inside or bottom of the case indicating the date of the recap so that you, or a future owner, will have a record handy of its last service.

I hope you found this guide handy. If you discovered any errors, or indeed if you didn’t but it was helpful, please feel free to drop me an email at (my Medium account name) at Gmail.com. Text photos above are copyright 2020 by Ben Zotto and cannot be reproduced without permission. Now enjoy that vinyl in style!

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