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Older reel-to-reel decks (maybe even some cassette decks) likely use an AC induction or synchronous motor driven from the power line. Speed selection is usually done by switching in different sets of motor windings and the use of slip-on capstan/pinch roller sleeves. Speed problems are most likely a result of * Decayed rubber parts - belts, idler tires, pinch roller. * Gummed up lubrication or worn bearings. * Dried up or otherwise faulty capacitors in the motor circuitry. * Faulty switches or wiring in associated with speed selection. * An actual bad motor is possible but not that common. See the appropriate sections in the chapters: "Turntables" and "Motors and Relays" for specific information on these types of problems.
OK, you have found the magic screw, but how to set the speed accurately? Sometimes, there will be strobe disks on tape decks which will appear stationary under fluorescent lighting (magnetic ballasts only - electronic ballasts are usually high frequency and do not modulate the light intensity at the power line frequency) but not usually. So, you do it by ear: Make a recording of a single tone on a tape recorder you trust - one with accurate speed. Suitable sources include: a signal generator, electronic instrument, Touch-Tone phone tone, PC sound card output or PC speaker, etc. A frequency around 400-1000 Hz should work well. Then, adjust the speed while listening to this same source simultaneously with the tape being played back on the unit to be adjusted. As you adjust the speed, you will hear the pitch change. As it approaches the correct setting, you will hear the tones beat against each other. When you are set correctly, the pitches will be equal and the beat frequency will go to zero. Even if you are tone deaf, you will easily be able to adjust pitch accuracy to better than 1/10 of a semitone using this method. Recording the 60 or 50 Hz power line (through a suitable isolated attenuator) and using this as a test tone will work if you have an oscilloscope. Trigger on 'line' and adjust playback speed to stop the trace from drifting. However, this is too low a frequency to be used accurately with your Mark I ears! Some alternatives: (From: Helling Bernie (helling@uwindsor.ca)). A while ago I hit upon a way to set the speed on old cassette decks that have gone out of speed. Use an electronic guitar tuner They cost about $40, can be borrowed, etc... Find a pro cassette deck that is in speed, (the local campus radio station had a nice one) and record a tape full of A tone. My guitar tuner puts out tones too, so that was easy.... Play the tape in the suspect deck, while adjusting the motor trim to replay a A tone perfectly on the tuner meter... Tadah.... I never did have the patience to learn to play the guitar, so I got some use off the tuning meter.... (From: Paul Temple" (mri@earthlink.net)). Get a song on CD and a tape of the same album. Play both at the same time and adjust away!
If your prized Walkman suddenly develops a severe case of warbling sound check: 1. Batteries (where appropriate). Almost dead batteries will greatly increase flutter. Use of Nickel-Cadmium rechargeable batteries in place of alkalines may result in problems due to their lower voltage (1.2 V vs, 1.5 V per cell). 2. Tired belts - loose flabby deteriorated belts will produce varying, probably slow, speed as well. 3. Dirt or goo on pulleys. Sometimes a glob of stuff gets stuck to a pulley and produces a periodic variation in speed. I picked one up at a garage sale that had this problem. I thought it was a bad motor until a careful examination revealed that the belt was jumping a mm or so on each rotation of an idler pulley. 4. Lack of lubrication - a dry or worn bearing may result in a variety of speed problems. 5. Bad speed regulator - either mechanical or electronic including bad solder connections or cracks in circuit board traces. 6. Bad power supply. 7. Bad tape. Don't overlook this obvious possibility, try another one.
This may be an almost inaudible tick, click, or pop which occurs fairly regularly. Its frequency may be dependent on many factors including temperature, humidity, even whether you are at the start or end of a cassette! I may occur even if no cassette is present but the motors are running. The tick is probably due to a static discharge though other causes are possible including mechanical problems and bad capacitors in the power supply. (From: Paul Grohe (grohe@galaxy.nsc.com)). The problem is with a plastic or nylon gear, in contact with a rubber belt or tire, generating a charge and discharging to some nearby metal. (It acts just like a miniature Van De Graff generator --- sam.) You have to listen around for it. Murphy sez it will probably be buried deep in the "guts" of the machine ;^) I found it by touching a small wire to each of the pulleys until it stopped "snapping" (actually, I got a little "snap" when I found it). My "cure" was to use some stranded wire to create a "brush" that lightly brushed against the pulley to bleed off the charge to the chassis. I would first check the two big capstan flywheels and anything powered by the main motor belt. Look for any plastic, or metal with plastic bushings and parts in contact with belts or tires. (From: Ylo Mets (ylo@mango.mef.ki.se)). I have experienced similar ticking in an old two-motor deck. There was some dust collected between the takeup/wind motor shaft end and the metal chassis, which evidently generated static electricity. Cleaning the dust did the trick, although at first I thought the shaft was too close to the metal chassis. You can check for the static by breathing slowly into the mechanism. The damp air should discharge the static and the frequency of ticks decreases. Such ticking is especially annoying because it is not exactly regular.
"I have a Teac 2300S reel to reel. 7" reel capacity, 1/4" tape. Two problems. First, right channel doesn't play back. Second, pinch roller doesn't come up to the capstan unless it's gently pushed." (From: Davetech (dnesbitt@mindspring.com)). I've repaired a few reel-to-reels in the past and generally find that they all need three main things done: * They need all the rubber parts - belts, tires, rollers - replaced. Also the brake pads. * They need all the controls and switches cleaned with a de-oxy type cleaner. (This may be the cause of your right channel problem). * They need all the mechanical pivot points cleaned and re-lubed. (This may be the problem with your pinch roller). The last one I did, the old grease had hardened up so much that the heads would not come up to contact the tape - and the grease was so hardened that I could not get the linkage pulled off even using pliers and pulling as hard as I could. I had to heat the post with a propane torch before the old grease would soften enough that I could separate the parts. I put enough time in the last unit that I could have fixed 3 or 4 VCR's, so I'm not real big on taking them in. They are generally very time consuming to disassemble and reassemble and overhaul. But not usually technically difficult to fix.
"I have a Sony reel-to-reel tape recorder. When I play a tape, after a few seconds or minutes of playback, I can watch the tape creeping up the capstan between the rubber roller until it comes out the top and off the capstan." The first thing to check - as with a VCR with similar symptoms - is the condition of the rubber parts, in particular, the pinch roller. Next, would be tape path alignment and wear: (From: Jack Schidt (dbutler@airmail.net)). Check the reel height as well. Capstans are upset if the reel tables have shifted. Use a straight edge between the two reel tables. There are set screws that sometimes get loose on some of these machines. Check for a worn capstan bushing. Disconnect the drive belt (if any) and see it there is lateral play in the capstan. If so, perhaps you can shim it (either the motor [if equipped] or the idler). Also make sure the tension is simply not too high. You should be unable to pull the tape through, but ridiculous force (as in something is BENT) will cause this problem as well.
These compete with turntables for classification in the Jurassic era. 8-track
equipment uses a cartridge with a single reel and enless loop tape (tape is
pulled from the center and returned to the outside). The tape can only move
in the forward direction - rewind is not possible.
There were also similar competing but incompatible 4-track systems as well
as quadraphonic 8-track (when quad was all the rage).
Four pairs of channels allow for many hours of stereo playback without
changing cartridges. A pair of playback heads is mechanically shifted
among the 4 possible sets of tracks when a metallic strip on the tape passes
over a set of contacts which operate a solenoid.
Most common problems are - you guessed it - mechanical with the cartridge or
in the drive or head shifting mechanism. General comments with respect to
cassette decks apply here as well.
If you are really interested in resurrecting that 8-track player found under
the steamer trunk in your aunt's attic, there are many links to information on
8-track equipment, books, history, dealers, collecting, and everything else
8-track related that most people probably don't care much about anymore at the
following web site:
* http://www.bway.net/~abbot/8track/resource.html.
There may be links for specific 8-track player repair information but I could
not locate them at this site.
However, this one seems to be the place to go for step-by-step 8-track
cartridge repair:
* http://www.geocities.com/Paris/4831/ (Jeremy Larsen's Web Page)
(From: Filip "I'll buy a vowel" Gieszczykiewicz (filipg@repairfaq.org)). This will be either easy or very hard. Question: do both of these have SCREWS holding the tape together? If yes, EASY, if not, very HARD! See what I'm getting at? Go to the store and get a quality tape that ALSO has screws holding it together... you will transplant the insides into the new cases. Take off the screws from both (old and new tape, do it one tape at a time). Remove both top covers - make sure you don't lose the thin plastic "lubricant" sheet (if any). Swap the tape reels - BE VERY SURE the old one doesn't go flying off or it's more or less toast. Put the old tape reels into the new case, make sure the tape follows the same path as the one you took out did - so it doesn't get trapped by the case when you replace the top. Put the "lubricant" sheet back on top of the two reels of old tape and replace the top. Put in all 5 screws. There you go. I'd say that this is 100% successful every time I've tried it. If your tapes don't use screws but are, rather, glued together, you're on your own. I suggest a VERY sharp utility knife but tape damage is, alas, a very REAL possibility. Another way you can do this if you want to also replace the REELs (or if it's a sealed unit) is to rewind the old tape, cut the tape LEADER and attach it to the new cassette that you have already gutted. Put the new tape together (2 screws will do) and attach a small motor to the takeup reel. When the tape has been transfereed to the new reel, cut it off the old one (the old cassette is now empty) and open the new one again, attach the tape to the reel and put it back together using all screws. Other than the leader being 2" shorter, you have the old SOUL in a new BODY. Of course, watch out that you wind the tape EXACTLY as it was and not on the other side... etc. etc. I have done this twice. Grrrr. It's a pain in the rear... so do it only if you have to... I wouldn't do this for money..... if that tells you anything.
Here are general comments on oiling dinosaurs, oops sorry, turntables. Usually there is a 'C-clip' or 'E-clip' which holds the platter (the thing that rotates) onto the spindle. It may be covered with a decorative piece which can be easily removed. The clip can be pryed off (gently) with a small screwdriver (just don't lose it, though even this is not a biggie so long as you never turn the thing up-side-down). The platter can then be lifted straight up and off the spindle. You will see several things (this will vary depending on your particular unit): 1. A flat washer, sitting on a ball bearing race sitting on another flat washer (one or both of these washers may be missing. Also, the top one may stick to the platter when it is removed.) The ball bearings, shaft, washers, etc. should all be cleaned with degreaser and then lubed with a light grease. If either the steel balls or the flat washers are corroded, replacement will be necessary or else there will be terrible audible rumble. For now, it will at least work well enough to determine what else, if anything, needs attention. Also clean and lubricate the platter bushing (center hole) and shaft (vertical post on which it rotates). 2. Changer gears etc. These will have varying amounts of grease on them if it is not gummed up, leave them alone. Put a drop or two of light oil on the shafts. Inspect other linkages as well. If the grease is gummed up on the gears or sliding linkages, you will need to clean it off thoroughly with degreaser and then use a small amount of high quality grease suitable for delicate mechanisms. One cause of a changer failing to activate at the end of a record is gummed up grease. 3. Motor. Check to see if the motor shaft turns freely and smoothly even if spun quickly between your fingers. If it does - without squealing, don't do anything else. If it is tight or makes noise, then you will need to carefully disassemble the motor and clean and lubricate the bearings at each end with light oil. Don't lose any of the various washers/spacers that may be present on the shaft as it is removed from the end pieces and make sure to lubricate and return them to exactly the location and the same order they were in originally. 4. Clean the rubber parts with isopropyl alcohol and Q-tips or a lint free cloth until no more black stuff comes off and then dry thoroughly. Now, inspect the belts (if any). If belts are flabby or cracked or if they don't instantly return to their relaxed length if stretched 25% and released, they will need replacing. Check the idler tire (if present). If hard or cracked, it will need replacing as well. Note: Light oil here means electric motor oil or even 3-In-One but NOT WD40. Light grease means something that is suitable for fine mechanisms and is safe for plastics. Automotive bearing grease may not qualify.
Most inexpensive turntables/changers will use a synchronous motor or even just an induction motor. The only maintenance for the motor is cleaning and lubrication. Servo controlled turntables utilize a feedback technique which locks the platter speed to a stable reference - either the power line (50/60 Hz) or more commonly a crystal oscillator. Here is one example: A Sony turntable I repaired used a magnetic stripe pattern on the inside of the platter which was sensed by a magnetic pickup. The resulting signal was phase locked to a stable reference and used to control a brushless DC direct drive motor. Speed would become erratic if (1) the magnetic pattern were damaged, (2) the pickup position was moved too far from the surface of the platter, (3) the Hall-effect sensors in the motor were bad, or (4) the control electronics went bad. In one case, it turned out that one of the Hall effect sensors had failed in the motor. This required disassembling the motor and replacing the sensor - $4 from Sony.
This is likely to be a mechanical problem - a belt that has worked loose and is riding on the rim of the motor pulley or the wrong surface of the platter. For an AC line driven motor (no electronics between the AC line and motor except possible for a power transformer), it is virtually impossible for any fault to result in a motor running faster than normal. A motor may run slow due to dirt, lubrication, or bearing problems. Of course, check to see that any speed selector has not been accidentally moved to the '16' or '78' position! For a servo-locked turntable, a misalignment of the sensor used for speed feedback could result in an incorrect - probably higher than normal (and uncontrolled) speed.
Wow and flutter refer to undesirable periodic variations in pitch caused by changes in turntable (or tape deck) speed. Wow would be a slow variation (e.g., once per rotation) while flutter would be rapid (e.g., a motor pulley with a bump). Even if very slight, these faults will be all too obvious with music but may go undetected at much higher levels for voice recordings. Rumble is a very low frequency noise added to the audio caused by vibration due to cheap, worn, dirty, or dry spindle bearings or by vibrations coupled in from some other motor driven component or even from loudspeakers if the volume is turned way up. If really bad, rumble may sound like a freight train in the next room. For anyone only used to listening to CDs, even very small amounts of and of these will prove very obvious and extremely objectionable. Wow, flutter, and rumble are undetectable - for all intents and purposes nonexistent - with even the cheapest junkiest CD player. For a common motor driven turntable, the following are likely causes: 1. Bad belt or idler. Rubber 'rusts'. If it is old, then almost certainly the rubber parts have deteriorated and will need replacement. Unfortunately, replacement parts are not as readily available as they once were. The places listed at the end of this document may have some and there are many other sources but it is not as easy as one would like. 2. Dirty or worn spindle bearing. This will cause rumble. The thrust ball bearing can be cleaned and lubricated or replaced. The platter bushing can be cleaned and lubricated. 3. Lump of crud stuck to motor pulley or idler, usually of unknown origin. 4. Dried up lubrication in motor, idler, or other rotating part. These can be cleaned and lubricated. 5. Bad motor (not that likely) except for lubrication in which case the motor can be disassembled, cleaned, and lubed. 6. Physical damage to platter - something heavy was dropped on it upsetting the delicate balance. If you are attempting to restore a 20 year old turntable from Aunt Annie's attic, don't even bother to power it up before replacing all the rubber parts and cleaning and lubricating the motor, idler, and spindle bearing.
Sound that varies randomly in intensity or where one channel drops out will usually be due to bad connections in the various units. This could be: 1. At the pickup itself. There may be small press fit connectors at the cartridge. These sometimes become loose. Gently remove each one (one at a time! so that you do not mix up the wiring) and squeeze with a pair of tweezers or needlenose pliers. Snap in cartridges may have dirty contacts the springiness may have disappeared. 2. At the RCA plugs under the turntable which connect to the tonearm. Depending on your design and problem, you may need to simply clean with contact cleaner or squeeze the metal shell or center contact. 3. At the receiver, preamp, or amplifier. Same as (2) above. 4. Sometimes the cables themselves will develop broken wires at one end or the other. Easiest is to try a different set of cables.
Tracking force keeps the stylus in the record's groove. Too little is as bad as too much. It is best to follow the recommendations of the cartridge/stylus manufacturer. If you do not have this information, start low and increase until you eliminate skipping or excessive distortion, buzzing, or stuttering. If too low, the stylus will make only partial contact with the groove during high amplitude segments - it will jump from peak to peak (or other portion) of the wave rather than smoothly and continuously following it. If too high, it will gouge the vinyl (or the shellac or whatever depending on the vintage of your records) or in extreme cases, bottom out on the cartridge's suspension. Skating force compensation is applied to compensate for the fact that except at one distance from the spindle (or with a linear drive tone arm where this does not apply), the tone arm is not tangential to the groove. Imagine a perfectly flat record without any grooves. If you 'play' this, the tone arm will be stable at only one position somewhere in the middle - where a line drawn through its pivot point and the stylus is just tangential to a circle at that distance from the spindle. The skating is usually a simple spring which attempts to compensate for this in such a way that the side force tending to move the stylus is minimized at all positions. Otherwise, the inner and outer walls of the groove will experience a different force which will add distortion and affect stereo separate and balance. Skating force compensation is usually set based on the tracking force. Note that if you are used to CDs or high quality cassettes, all the horrors of records will be all to obvious unless you are using high-end equipment (the kind that likely costs as much as your automobile) and meticulously maintain your vinyl record collection. Sonic defects like wow, flutter, rumble, distortion, noise, imperfect stereo separation, skipping, and limited frequency response are all facts of life for this technology which has not changed in any fundamental way since Edison's time.
(From: Bill Turner (wrt@eskimo.com)). You're bringing back memories. I used to work for the leading Magnavox warranty repair station in Los Angeles and I've repaired hundreds of the good 'ol Micromatics. Assuming there isn't something actually *pulling* the arm across the record (in other words it's just sort of sliding across on it's own) the problem is almost always the needle. Either the tip is worn out, broken, missing, etc or it could have just been dislodged from it's holder. Lift up the arm and look carefully at the needle. The actual diamond tip is on the end of a short shaft which in turn rests in a fork-shaped rubber holder. This shaft is easily knocked out of the holder, and if that's the case, just carefully put it back. Hope this helps. The Micromatic was a fine record player in it's time. Good luck, and let me know if I can help some other way.
So you still have one of those modified potters' wheels on which you place a pre-formed piece of plastic that looks like a flattened dinner plate with a hole in the middle and drag a needle over its surface to produce sound. How can you tell when the needle, err, stylus, has worn to the point (no pun...) of requiring replacement? It used to be that you could take it to any record store. They would look at the stylus under a microscope, and after a few choice utterances of "Oh my!" followed by "This will strip the music right off your LPs", and would then tell you that your stylus required replacement IMMEDIATELY whether it did or not :-). Of course, record stores don't exist anymore. If you have a semi-decent microscope, you can do the same and get an honest answer ;-). 100X should be more than sufficient, though getting the stylus into position to view it may prove to be challenge. The tip of a good stylus looks smooth and is spherical or ellipsoidal in shape. A worn stylus will exhibit edges/corners due to the wear of the tip. Yes, even diamond will wear down if you drag it over thousands of miles of vinyl. Some of your LP record jackets may even have typical photos of good and worn styli so check these out as well. If the stylus is visibly worn: 1. The physical result will be that it will grind away at the grooves in your records. 2. The audible result of a bad needle will be excessive distortion and loss of high frequencies from (1). After you replace it, your old records will still never sound as good as they did before because of (1) :-(.
If it is a basic old fully mechanical record changer, this is usually due to gummed up grease. There is a large gear which gets activated to operate the lift-and-place mechanism. Attached to this gear is a small swinging segment that gets jogged by the tone arm reaching the proper position. The grease gets gummy and prevents this. You have to remove the platter. If it is a fancier changer with fully electronic controls, then it may be a sensor or something in the circuitry. Of course, there was this one I recently worked on where some previous repair person (I am using this term generously) had glued the moving parts of the changer mechanism together so it could not possibly ever have worked again (until I unglued them all).
In this document, we use the terms 'loudspeaker' or 'speaker system' to denote a unit consisting of one or more drivers in an acoustic enclosure perhaps along with a frequency selective crossover, tone controls and switches, fuses or circuit breakers. Connections to the amplifier or receiver are via terminals on the rear. The front is covered with an (optically) opaque or semitransparent grille which provides protection and improves the appearance (depending on your point of view). A 'driver' is the actual unit that converts electrical energy into sound energy. Most drivers use voice coil technology: a very low mass coil wound on a light rigid tube is suspended within a powerful magnetic field and attached to a paper, plastic, or composite cone. The audio signal causes the coil to move back and forth and this motion causes the cone to move which causes the air to move which we perceive as sound. The typical driver consists of several parts: * Frame - a rigid steel or composite structure on which the driver is constructed. The frame holds the magnet and core, cone suspension, and connection terminals. * Magnet - this includes a powerful (usually ceramic, AlNiCo, or rare earth) magnet including a core structure provide a very narrow cylindrical air gap. This accounts for most of the mass of a driver. * Voice coil - a one or two layer coil of fine wire wound on a light rigid cardboard, plastic, or composite tube suspended within the air gap of the magnet and connected via flexible wires to the electrical terminals. * Cone - a roughly cone shaped very light and rigid structure that does the actual work of moving air molecules. The cone in a woofer may be 12 or more inches across. The cone in a tweeter may only be an inch in diameter. This is the part of the driver you actually see from the front of the speaker system with the grille removed. The center is usually protected with a small plastic dome. * Suspension - a corrugated flexible mounting for the voice coil called a 'spider' and outer ring of very soft plastic or foam. Together, these allow the voice coil/cone combination to move readily in and out as a unit without tilting or or rubbing. For most designs, there is a certain amount of springiness to this suspension. Acoustic suspension loudspeaker, however, use the trapped air in a totally sealed speaker enclosure to provide the restoring force. Inexpensive 'LoFi' devices like portable and clock radios, many TVs, intercoms, and so forth use a single, cheap driver. Some have a coaxial pair of cones but this does little to improve the frequency response. HiFi speakers systems will divide the audio frequency spectrum into several bands and use drivers optimized for each. The reason is that it is not possible to design a single driver that has a uniform response for the entire audio frequency spectrum. A 'woofer' is large and massive and handles the low base notes. A 'tweeter' has a very low mass structure and is used for the high frequencies. A 'mid-range' handles the mid frequencies. There may also be 'sub-woofers' for the very very low notes that we feel more than hear. Some systems may include 'super-tweeters' for the very highest frequencies (which few people can hear. This may make for some impressive specifications but perhaps little else.) A 'crossover' network - a set of inductors and capacitors - implements a set of filters to direct the electrical signal (mostly) to the proper drivers. Various controls or switches may be provided to allow for the adjustment of low, mid, and high frequency response to match the room acoustics more faithfully or to taste. Fuses or circuit breakers may be included to protect the speaker system from intentional (high volume levels) or accidental (amplifier output stage blows) abuse.
If you have a high quality and expensive set of loudspeaker, then the cost of professional repair may be justified. However, if the problem is with speaker systems you might not write home about, then read on. Playing your music system at very high volume levels, especially CDs which may have peaks that way exceed the ratings of your loudspeakers is asking for trouble - but you knew that! CDs can be deceiving because the noise floor is so low that you are tempted to turn up the volume. A peak comes along and your speaker cones are clear across the county (remember the movie 'Back to the Future'?). Loudspeaker systems are generally pretty robust but continuous abuse can take its toll. Problems with loudspeakers: 1. An entire speaker system is dead. Verify that the connections both at the speaker system and at the source are secure. Check circuit breakers or fuses in the speaker system. Reset or replace as needed. Make sure it is not the amplifier or other source that is defective by swapping channels if that is possible. Alternatively, test for output using a speaker from another system or even a set of headphones (but keep the volume turned way down). Assuming that these tests confirm that the speaker system is indeed not responding, you will need to get inside. It would take quite a blast of power to kill an entire speaker system. Therefore, it is likely that there is a simple bad connection inside, perhaps right at the terminal block. You should be able to easily trace the circuitry - this is not a missile guidance system after all - to locate the bad connection. If nothing is found, then proceed to test the individual drivers as outlined below. 2. One or more drivers (the name for the individual speakers in a loudspeaker enclosure) is dead - no sound at all even when you place you ear right up to it. The cause may be a bad driver, a bad component or bad connection in the crossover network. Test these components as outlined below. 3. One or more drivers produces distorted or weak sound. Distorted may mean fuzzy, buzzing, or scratchy a various volume levels. Most likely this is due to a bad driver but it could also be a defective component in the crossover - a capacitor for example or even a marginal connection. Getting inside a speaker system usually means removing the decorative grille if it snaps off or unscrewing the backpanel and/or terminal block. Use your judgement. With the grille removed, you will be able to unscrew the individual drivers one at a time. With the back off, you will have access to all the internal components. If sealing putty is used, don't lose it or expect to obtain some replacement putty (non-hardening window caulking like Mortite is suitable). Test the components in the crossover network with a multimeter. These are simple parts like capacitors, inductors, and potentiometers or reostats. Confirm that any circuit breakers or fuse holders have continuity. Test the drivers on the low ohms scale of your multimeter. Disconnect one wire so that the crossover components will not influence the reading. Woofers and midrange drivers should measure a few ohms. If their impedance is marked, the reading you get will probably be somewhat lower but not 0. If possible compare your readings with the same driver in the good speaker system (if this is a stereo setup). Some tweeters (very small high frequency drivers) may have a series capacitor built in which will result in an infinite ohms measurement. Other than these, a high reading indicates an open voice coil which means a bad driver. In a comparison with an identical unit, a very low reading would mean a partially or totally shorted voice coil, again meaning a bad driver. Except for expensive systems with removable voice coil assemblies, either of these usually mean that a replacement will be required for the entire driver. Sometimes an open voice coil can be repaired if the break can be found. To confirm these tests, use an audio source to power just the suspect driver. Your stereo system, a small amplifier attached to an audio source, or even a pocket radio (use its speaker output if the headphone output does not have enough power) will suffice. The resulting sound will not be of high quality because you do not have the enclosure sealed and it is only one of the drivers in the system, but it should give you some idea of its condition. Again, comparing with an identical unit would be another confirmation.Go to [Next] segment
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