Generally, the only symptom is a CD players that sounds unhappy - there are no audio or tracking problems. However, in severe cases, there may also be audio degradation described as "muddy sound". (No doubt, a non-Sony approved weight would work equally well for the solution below.) (From: Lance Edmonds (firstname.lastname@example.org)). The whine problem usually occurs with KSS240A and KSS213A optical pickups, and is caused by a mechanical resonance. There are at least 2 service bulletins describing the fault and the cure. Sony sells a special weight to fit to the pickup, and also a felt pad to add to the bottom of the top clamp assembly. Both these items cure this problem. Some machines may only require the weight. In rare circumstances the resonance can interfere with the tracking/focus servos enough to cause skipping. Usually the problem is not easily repeated, however certain light weight disc's may trigger the problem repeatably. Note that the resonance usually only occurs on the first few tracks if at all, and some disc's will play with the problem never showing up. Seems to be a disc weight/thickness/density problem. Contact your official Sony service office for the part numbers etc.
(Refer to the photo of the Sony CDU-31/33A CDROM Optical Deck for parts identification.) Both these drives use similar optomechanical technology. The CDU31A is 1X (though I have heard that some versions of this may be 2X, unconfirmed) and CDU33A is 2X. Many have complained about the lack of a motorized tray. What this does provide is a very simple robust mechanical design. A solenoid latch keeps the drawer shut. When the solenoid is activated (or the emergency release is pressed) the drawer pops out about an inch. Pulling the rest of the way is manual. The movement of the drawer clamps/unclamps the disc to the spindle with a powerful magnet. Except from gross abuse, there is little to go wrong mechanically. There are only two major components: the Printed Wiring Board where all the active electronics are located and the Optical Deck including laser, optics, and pickup worm drive mechanism. The other parts include the upper plastic casting and metal shroud, solenoid latch assembly, right and left guide rails, drawer assembly, and front bezel, two springs, bottom plate, 6 screws. There are only two electrical connectors inside: one flat printed cable linking the PWB and optical deck and a two pin connector supplying power to the eject solenoid. This is in pleasant contrast to some other CDROM drives I have seen with a half dozen or more small connectors spread all over the PWB making removal and testing very difficult and risky.
The only major cautions are to not lose any of the small screws or springs and to avoid damaging the multi-conductor flexible cable linking the electronics to the optical assembly. The following procedure takes about 5-10 minutes: 0. Place the unit upside-down on a soft surface. 1. Remove 4 philips head screws securing bottom cover. Set bottom cover aside. You will now have access to the electronic adjustments for focus, tracking, etc. If this is what you are after, no further disassembly is needed. 2. Unclip the front bezel. Slide it out with the tray as far as it will go. You may need to manually activate the eject mechanism with a paperclip. 3. Remove 2 philips screws securing Printed Wiring Board (PWB). Gently lift PWB and disconnect connector to latch solenoid assembly in front of unit. 4. Gently lift PWB further and disconnect flexible cable connector on optical assembly. Mark the orientation so there will be no doubt about getting it correct if you need to reassemble on the workbench for testing. There is a latch at each end which you push away from the connector 1 mm or so. The cable will than come out easily. You now have partial access to the optical assembly sled drive. Cleaning and lubrication of these components is now possible. 5. Lift the latch solenoid assembly up, remove and set aside. 6. Using a pair of fine needlenose pliers or tweezers, disconnect and set aside the two tray retraction springs. Note their position and orientation. 7. Remove the two plastic guides - one on each side. There are little tabs that you will need to depress and then lift each guide straight up. 8. The entire deck can now be slid forward and lifted off. The opto/mechanical assembly can then be removed from the tray. Set the tray aside. The mechanism shown in the photo of the Sony CDU-31/33A CDROM Optical Deck is screwed into the rubber shock mounts. 9. If you prop up the PWB and reconnect the flexible cable - note the orientation marks you made previously - you can then run the drive with full visibility of the mechanism and optics. With a CD in place, there is no danger to you from the laser beam. Just make sure the PWB cannot short to anything and that the whole affair cannot tip over. Reassemble in reverse order. Be especially careful reinstalling the flex cable. Make sure no wires are being pinched and that nothing is obstructing free movement of the optical pickup. This is actually pretty easy for this drive.
The following information applies directly to the Sony Playstation but other CD/CDROM based systems use similar technology. Note that the Playstation (and other newer game machines) are programmed to only work with discs released for the same country or general geographic location in which it was purchased. Thus, if you got a good deal on a used system, you may now know why: it might only work with Japanese software! :-(. I believe Sony has a flat rate ($100 or so) repair fee for these - probably toss the guts and replace them - but this is barely justifiable for a $200 system. Many complaints are similar to the following with symptoms of marginal play of audio or game discs, skipping, erratic operation, etc. Other service centers have both cheaper and DIY kits for Playstation repair. For example, Video Specialties advertises a $45 flat rate and also sell a repair kit they say will handle loading, skipping, and other optical pickup problems. I have no idea of its price or whether these claims are accurate.
(From: Jerry Jessop (email@example.com)). Quick test for symptoms of no power: With the Playstation top cover off and no CD installed press down on the door switch. What should happen is the CD will not spin, but the laser pickup should move up and down attempting to focus on a CD. WARNING: Laser is exposed - don't stare into it! See the section: "SAFETY". --- sam. If the above does not happen the following problems may exist, in order of probability: 1. Door switch broken 2. No 8 VDC to CD, usually a blown ICP "fuse" on the motherboard, or bad power supply. 3. CD controller toasted (bad)
(From: Jerry Jessop (firstname.lastname@example.org)). For no response from controller problems: The controller port ICP (integrated circuit protector) is blown and you are not getting 3.3 VDC to the controller ports. Check for continuity on each ICP, they are near the front of the PCB just below the CD ROM ribbon cable. They will have a 15, 20, 50 etc labeled on each. The one labeled as 15 is blown :). It is an 800 ma fuse. BEWARE of non-Sony approved peripherals as they blow these fuses, especially non-Sony mem cards inserted with the power on.
"I have a Sony Playstation, it starts up OK as in power-up etc. But, insert a disk and it does not seem to want to read the TOC. The disc spins up to speed and the laser goes through the motions of focusing, but then zilch, nada, no-zinks! Funny thing is it seems to play audio disks correctly, but not Playstation game disks" Of course, first clean the problem discs and lens. See the relevant portions of this document for instructions and other general troubleshooting tips. All the usual problems of normal CD players and CDROM drives apply. Note that in general, it may be possible to play music discs with few or no problems and still not be able to reliably play games (or as applied to CDROM drives, reliably access data). Readout of programs and data must be totally error free while errors can be tolerated for audio tracks with little or no detectable degradation in sound quality. Another reason is that audio is always read at the 1X rate; the system may be more tolerant of a marginal disc or servo alignment at the 1X compared to 2X or higher rate. Some of these problems may actually be a result of poor design due to extreme and unacceptable cost cutting on Sony's part. After all, the Playstation reader is essentially the same as a 2X CDROM drive - which should be mature technology by now! (From: Rusty Burke (email@example.com)). A common problem on Playstations is the lens 'sled positioning' assembly. The lubricant that they used on this gets 'a little' solid. Solution: remove old lube (all the way back to the motor worm gear) and use a long-lasting lubricant. I use a mixture of tri-flow and graphite grease. This seems to cure the problem. Apparently what happens is that the CPU requests a read of a certain sector of the CD, and the sled can't get the lens to the proper location quickly enough. (From: (firstname.lastname@example.org)). A lot of Sony Playstation had this problem. Sony knows this problem, and they suggest to adjust the optic laser power to 1 V p-p (at the RF test point) or change the optic. CAUTION: adjusting laser power is always a risky operation. Replacing the optical pickup may not be a realistic option as Sony probably charges more for the replacement part than for an entire Playstation! --- sam. (From: Malik Dad (email@example.com)). Check the focus bias adjustment. These machines are really very finicky when it comes to laser alignment. There are many machines out there with similar problems to yours. This is usually caused by a laser servo that has been badly set up. The symptoms are jumping and/or skipping on the FMV (full motion video) intro sequences and jumping and/or skipping on the music. In the worst case, certain gold (CD-R) discs will not boot. The pits on CD-R are never as well defined as a pressed disk resulting in around a 1/4 to 1/2 volt reduction in the RF eye pattern. The problem can generally be cured by carefully adjusting the bias control on the main board near the laser ribbon connector. turn this a little bit clockwise or counter-clockwise until you have decent results. when you are happy leave it alone. It can be tempting to keep adjusting for different disks trying to get it spot on. There are not many machines that will play every single gold disk perfectly. Most will skip and jump occasionally no matter how carefully they are tweeked. DO NOT touch any other adjustments! See: http://www.gpl.net/paulmax/psx for more info on Playstation modifications. Not sure of which of the following it more appropriate. Just make sure you mark the original positions of the pots --- sam. (From: Mike Walker (firstname.lastname@example.org)). Caution: for the following, I would avoid touching the pot on the pickup itself unless you have exhausted all other possibilities - this is laser power and can easily result in a ruined laser --- sam. Sony will not give out any procedure, we have done it before many times... As far as the beam, the adjustment is on the CD sled itself right by the eye. The gain is located on the main board listed as gain, don't mess with the bias adjustment, try moving the gain about 1/8 inch or less clockwise, then check the play of your CD's, most of the time this takes care of the problem, if not try moving the beam focus about the same and same direction. Not to much on either it's been known you can burn out the laser. We like to mark our original postion with a red marker pen, you can lose where you were and really goof it up. Use ESD precautions, the laser is sentitive to static also. Also, try and replace the grease on the gear drive also, we have found that this helps a great deal also. Remove old, use new lubriplate or similar. (From: Jerry Jessop (email@example.com)). You have it backwards, adjust the Bias and leave the gain alone. If you set the bias level on wiper of the Pot to around 1.60 vdc with a CD loading that is "generally" a good figure. Now adjust the gain during an FMV sequence until it stops reading at one extreme. Then the other, and set it in the middle. Regrease the rails using "LaBelle 106" a white grease with teflon designed for plastic components found in hobby stores. Of course more than likely the optical sled has groves worn in it and now the laser azimuth is out of alignment. The only solution is to replace the entire pickup assembly. MCM claims to be getting a new shipment of Playstation optical pickups soon - their price is $39.95 (as of November, 1997). (From: Cyberchaos (firstname.lastname@example.org)). All earlier productions of the playstation utilized a plastic sled rail construction which collapses and causes this problem. These must be replaced with the upgraded steel versions. Cleaning is a very short term cure.
The problem of a shaking picture on some TVs (notably, Zenith models) is due to a problem in the PlayStation sync generation, not really a TV failure. (From: Jerry Jessop (email@example.com)). PlayStations will sometimes slowly "bounce" on older Zenith chassis sets, this is due to the way the vertical sync is outputted on the PlayStation. Call the PlayStation 'hotline' and explain the problem, it is well known and the system will be modified at no charge to you and you will get a free game for your trouble! A small daughter board will be installed that will correct the problem.
Identifying front-end problems in CD players, CDROM drives, laserdisc players, and other optical drives is often thought to be a mysterious and difficult task. This section describes basic techniques confirming functionality of the laser diode, focus voice coil actuator, tracking voice coil actuator, and photodiode array. No exotic test equipment is required. It is strongly recommended that you read and become familiar with the other information in this document. For general optical pickup information, see the section: "CD optical pickup operating principles". For a description of some common types, see the section: "Sony KSS series optical pickups". Don't immediately conclude that your problem is in the optical pickup. It is likely elsewhere and you will not need to undertake the testing described below. If the unit is able to read the disc directory, if even erratically, then these tests are unnecessary (unless you suspect an intermittent in one of these subsystems) as all of major parts of the laser pickup assembly must be properly functioning in order to do this. However, this does not guarantee that there are not some marginal components such as a weak laser diode or shorted turns in the focus or tracking coil - more on these problems later. Don't ignore the trivial: have you cleaned the lens? Sometimes a dirty lens will result in symptoms that may be mistaken for much more serious problems. For intermittents, first carefully inspect the pickup assembly for bad solder connections and hairline cracks in the flexible printed cables. Interlock switches may be dirty or worn. Mechanical problems may result in intermittent behavior as well.
If you have examined the 'RF Test Point' with a scope and found a proper 'eye pattern', then as noted, these tests are not needed as this indicates proper functioning of all the major components of the optical pickup. If, however, any of the following are observed, then testing of the laser diode, focus and tracking actuators, and/or photodiode array is suggested: * The startup sequence does not complete due to obvious failure of the pickup to perform some action. For example, there is no attempt to focus. * Focus appears to be established but the directory is never displayed even though the disc spins at the correct speed - or overspeeds or does not spin in correct direction (clockwise as viewed from the label side is correct for CDs). * The 'eye pattern' is weak, distorted, or missing at the RF test point. Try to eliminate alternative causes before undertaking these tests as there is a slight chance of damage due to accidents or electrostatic discharge. Will it be worth the time and effort? Only you can decide how much your time is worth. There is a good chance that these tests will only confirm that the pickup is dead - not many of the faults you will be able to locate have easy fixes. You will learn something if that matters. However, with the cost of new single disc CD players less than $70 and changers less than $100, any rational analysis of the expected value for this undertaking may recommend the dumpster. But, we all know that hobbiest's time is not worth much - as in free. The descriptions below assume that the pickup is still installed in the player but selected portions are disconnected when required. This enables us to conveniently use the circuitry of the player to control certain functions for the 'live' laser diode and photodiode tests. It is also possible to test the pickup stand-alone but this will require an alternative power supply to drive the laser diode. Since the microcontroller will not be imposing its own will on those parts of the pickup still connected to the player, this may be preferable. However, if you are uncomfortable in providing a substitute power supply for the laser diode, then leave that function to the player. Caution: whenever applying external power to any component, totally disconnect it (by unpluging or unsoldering - label each wire if there is any ambiguity) to prevent damage to the circuitry on the logic board.
Only a minimum of tools and test equipment are required for these testing techniques to be effective. An oscilloscope is desirable but a VOM or DMM can substitute in a pinch since no high frequency measurements are needed. However, we will assume a scope is available. This section does not address mechanical problems in the sled drive, or the drawer or spindle motors. These problems are adequately handled in the elsewhere in this document. It is assumed that these components have been verified to be functional as there correct operation may be required for some of the tests described below. A schematic will help greatly if available. Depending on the design of the unit, you may be able to infer enough about the front-end electronics to get away without one. The design of the components of the optical pickup are sufficiently similar among manufacturers to make the tests relatively model independent. What may differ are polarities of photodiodes, laser diodes, connector pinouts, etc. These can usually be determined fairly easily. Despite the incredible precision of the focus and tracking servos, we can perform meaningful tests without sophisticated or specialized test equipment. Also see the sections: "Troubleshooting tips" and "Test equipment". The following tools and test equipment will be required: 1. Basic hand tools including precision jeweler's screwdrivers. 2. A VOM or DMM. 3. An oscilloscope (for photodiode/RF tests). For most of the tests, almost any scope will do as long as it has a DC coupled vertical amp. As noted above, a scope is not essential but is highly desirable. 4. A 0 to 5 volt variable DC power supply (400 mA). The power supply can be a 4-5 V 'wall wart' with a Variac. Alternatively (but not as desirable), you can use a fixed 5 V supply with a series adjustable resistor (100 ohms for focus and tracking actuator testing, 250 ohms for laser diode testing). A highly regulated supply is not needed. 5. Resistors: 22 ohm 1W, 5 ohm 1W, 50 ohm, 1 M ohm. 6. Assorted test clip leads, a few feet of #24 solid hookup wire (RS232 quad or multiconductor phone cable is good source). 7. IR detector circuit, IR detector card, or IR sensitive camcorder (for laser diode tests). 8. (Optional) Slow speed sweep or function generator (1-10 Hz) with low impedance output or amplifier, see text. For the following discussions, a component CD player is assumed to be the unit under test. Make appropriate adjustments in interpretation if it is a portable CD player, CDROM drive, or optical drive.
Reread the section: "SAFETY" for your own protection. To minimize the chances of damage to the laser diode - which is extremely sensitive to static and excess current - leave its connector plugged into the main board as much as possible and do not attempt to test the laser diode with a VOM (which on the low ohms scale may exceed the current rating of the laser diode - poof, even if only for a microsecond. As with all modern solid state equipment, preventing electrostatic discharges to sensitive components is critical. An antistatic wrist strap is desirable. In any case, work in an area where static is minimized - not on a carpet prone to static. Make it a habit to touch the metal chassis first to discharge yourself.
Also see the more detailed description (including a diagram) of the typical optical pickup components and operation found in the section: "CD optical pickup operating principles". In order for information or music to be read off of a CD, several systems must work closely together: 1. Laser must be emitting a coherent beam of sufficient power and stability. Optical system must be clean and properly aligned. Laser power is maintained constant via an optical feedback loop controlling laser diode current. Therefore, a weak laser may not be salvageable as the feedback loop may have done all that is possible. 2. Photodiode sensors must be functioning correctly for data recovery and focus and tracking feedback. In a 'three-beam pickup', there are six segments: the central segments A-D are used for focus and data recovery; the outer segments E and F are used for tracking feedback. In a 'single-beam pickup' segments E and F are omitted. 3. Lens must be focused to within a fraction of a um of optimal to produce a diffraction limited spot. This is less than 2 um in diameter at the disc 'pits'. The lens is actually positioned several mm from the disc surface and is maintained at the correct distance through optical feedback controlling the lens position using the focus coil. Note: um = micrometer = 10E-6 meter; mm = millimeter = 10E-3 meter. 1 meter is 39.37 inches. 4. Lens must align to within a fraction of a um of the center of the track. Tracks on a CD are spaced 1.6 um apart. Tracking is maintained via optical feedback controlling the radial lens position using the tracking coil (or radial positioning unit on some rotary positioners). Note that if the behavior while the CD player is attempting to read the directory changes whether a disc is in place or not, (and there is no separate disc sensor), then some or all of these components are functioning correctly. For example, many CD players will not attempt to rotate the spindle until proper focus has been established. Thus, if the CD rotates when in place but the bare spindle does not, it is likely - though not guaranteed - that focus is being established successfully.
In order to perform many of the tests described below, you will have to locate the drive and/or signal connections to the optical pickup. While there are many variations on the construction of optical pickups even from the same manufacturer, they all need to perform the same functions so the internal components are usually quite similar. Here is the connection diagram for a typical Sony pickup: _ R1 +---|<|----o A | +----o F+ +-/\/\---o VR | PDA | ( PD1 | | +---|<|----o B | ( Focus +---|<|--+---+----o PD (sense) | PDB > Focus/ ( coil | +---|<|----o C | data ( | LD1 | PDC | +----o F- +---|<|--+--------o LD (drive) +---|<|----o D _| | _|_ | PDD _ +----o T+ | --- C1 +---|<|----o E | ( | | | PDE > Tracking ( Tracking +--------+--------o G (common) +---|<|----o F _| ( coil | PDF ( Laser diode assembly | +----o T- +----------o K (Bias+) (includes LD/PD and Focus/tracking flex cable with C, R). Photodiode chip actuators The laser diode assembly and photodiode chip connections are typically all on a single flex cable with 10 to 12 conductors. The actuator connections may also be included or on a separate 4 conductor flex cable. The signals may be identified on the circuit board to which they attach with designations similar to those shown above. The signals A,C and B,D are usually shorted together near the connector as they are always used in pairs. The laser current test point, if present, will be near the connections for the laser diode assembly. It is usually possible to identify most of these connections with a strong light and magnifying glass - an patience - by tracing back from the components on the optical block. The locations of the laser diode assembly and photodiode array chip are usually easily identified. Some regulation and/or protection components may also be present. Note: There are often a pair of solder pads on two adjacent traces. These can be shorted with a glob of solder (use a grounded soldering iron!) which will protect the laser diode from ESD or other damage during handling and testing. This added precaution probably isn't needed but will not hurt. If these pads are shorted, then there is little risk of damaging the laser diode and a multimeter (but do not use a VOM on the X1 ohms range if it has one) can be safely used to identify component connections and polarity.
Without a laser power meter, it will be difficult to fully verify laser functionality. However, determining that IR is emitted will provide a reasonable assurance of laser operation. For this test you will need an IR detector. A simple circuit is described in the section: "IR detector circuit". This unit is also useful for testing of remote controls and other IR emitters. You can also use an IR detector card - available at an electronics distributor. In a pinch, CCD based camcorders are often sensitive to IR. It will appear as a bright spot if the laser beam is projected onto a white paper screen. However, you will probably need 3 or 4 arms to position the screen, push the play button, and hold the camcorder while attempting to view the detected spot through the viewfinder! You will need to gain access to the lens. This may require the removal of the clamper assembly. Once this is accomplished prepare to position the photodiode of the IR tester within 1/8" of the lens. Plug the unit in and turn it on. On portables, you will need to defeat the door interlock - use a toothpick or bit of cardboard. Sometimes a CD player will have a disc detect sensor separate from the laser assembly - this will need to be defeated in order for this test to work without a CD in place. If it is a simple optical sensor, a piece of black tape or paper should suffice. The first thing that should happen once a CD is in place and the play button is pressed is for the laser to be powered. You should be able to detect this in a darkened room because there is usually a very faint red appearing emission which you can see as a tiny red dot of light if you look at the lens from a safe distance of at least 6 inches at an oblique angle (WARNING: Do not look directly into the lens from directly above as the invisible IR is much stronger than the faint red emission and potentially hazardous). If you see the faint red light, you know that at least power is being applied to the laser diode. With the laser lit, the lens should go through a few focus search cycles - between 2 and 8 typically. While it is doing this, position the IR detector above the lens. If the laser is working, you will get a positive indication of IR in about a 30 degree cone on either side of the lens. While you have no way of knowing if the power output is correct, this is a reasonable indication of laser operation. Due to the wide angle of the beam, the power decreases rapidly with distance so you will need to be very close to the lens for a positive result. Note that if the lens moves smoothly in at least one direction (up or down), you have also confirmed that the focus actuator is functional. If the IR detector does not pick up a beam and you do not see the red dot, then either the laser diode is really dead or there is no power being applied by the control circuits. At this point, you have four options: 1. You can give up. However, you would not have gotten this far if you were likely to be defeated so easily. 2. You can attempt to obtain a schematic if you do not already have one so that you will be able to test the control circuits to determine if the laser diode is being powered. 3. You can attempt to trace the laser power circuits in the hope that you will find something absolutely obvious that is amiss - a bad connection or open resistor, for example, resulting in no power to the laser diode. 4. You can perform some simple but risky tests on the laser diode itself in an attempt to light it from an external power supply. As noted below, laser diodes are easily destroyed and you will have no warning. One nanosecond it will be a laser - the next it might be a DED - Dark Emitting Diode.
Consider the following only if there is no indication of laser output while connected to the player and you do not have schematics or a service manual to determine if the laser power circuits are functional. Typical currents are in the 30-100 mA range at 1.7-2.5 V. However, the power curve is extremely non-linear. There is a lasing threshold below which there will be no output. For a diode rated at a threshold of 30 mA, the maximum operating current may be as low as 40 mA. A sensing photodiode is built into the same case as the laser diode to regulate beam power. It is critical to the life of the laser diode that under no circumstances is the safe current exceeded even for a microsecond! Laser diodes are also extremely sensitive to electrostatic discharge, so use appropriate precautions. Also, do not try to test them with a VOM which could on the low ohms scale exceed their safe current rating. Even connecting the test leads can blow the laser diode from static on a bad day. In addition, always make or break power or test connections with the player turned off. Locate the laser power connector by tracing back from the three pins on the laser diode assembly. Note: the following only applies if the laser diode is directly connected to the cable. If the power regulating circuit is on the pickup, you will need to trace its circuit or obtain the schematic as there are now too many variations to recommend a specific procedure. Use the 0 to 5 VDC linear supply (a switching supply may put out laser diode destroying pulses) with a 50 ohm resistor in series with the diode. This is preferred over the variable resistor power supply as there is less likelihood of any potentially laser destroying overshoot or noise. If you do use the variable resistor, make sure it is at its maximum resistance when you start and that this is sufficient to keep the current under 20 mA. Keep in mind that a wall wart rated at 5 V may actually put out 8 V or more when unloaded - check the current into a short circuit before connecting the laser diode. Slowly bring the current up until you get a beam. Use an IR detector for this! If you get the polarity backwards or are actually measuring across the internal photodiode, the voltage across the diode will go above 3 volts or will be less than 1 V. Then, turn power off and reverse the leads. Note: some laser diodes will be destroyed by reverse voltage greater than 3 V - a spec sheet will list the reverse voltage rating. The ones I have tried out of CD players were fine to at least 5 V in the reverse direction. Without a laser power meter, however, you will have no way of knowing when the limit on safe beam power (safe for the laser diode, that is) is reached. For this test, increase the current only until you get an indication on the IR detector or you see the red dot. You are not trying to measure power, just to see if it works at all. A typical threshold is around 30 mA. Sometimes, the operating current is marked on the pickup. If this is the case, do not exceed this current. If you detect a beam and there was none before, then your problem is most likely located in the player's control or power circuits, not in the pickup.Go to [Next] segment
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