Contents:
These are not going to be covered by any warranty! Of course, not mentioned
below are: fire, flood, falling from a tenth story window, getting run over
by a bulldozer, or being plugged into the wall outlet instead of the stereo,
etc. :-).
(Portions from: Lasse Langwadt Christensen (fuz@control.auc.dk)).
1. DC bias across speaker will cause the voice coil to overheat. Windings may
short out or open up. Also see (3), below. This usually results from an
amplifier output stage failure - shorted capacitor, for example.
2. High power clipped signal:
* A clipped signal contains a lot of high frequency energy and that could
burn a tweeter, because the voice coil overheats.
* The clipped signal could have a amplitude so large that the voice coil
hits the magnet and is bent. It's a permanent damage but not always
terminal, because the might still work, but make a scraping noise. If
you play loud with it for a long time (and it doesn't burn out - see (3),
the part scraping against the magnet might wear off.
3. If the speaker is overheated, because of high power for a long period of
time, the voice coil could expand and scrape against the magnet, and perhaps
short some of the turns. This is not always permanent, and some
manufacturers use Teflon on the magnet, so that it's less likely to cause
damage.
As noted above, if you are dealing with a high quality system, leave these repairs to professionals or obtain an entire replacement as some reduction in audio quality may result from the abuse you are about to inflict on the poor defenseless driver. We will address two types of repairs: physical damage to a speaker driver cone and an open voice coil (actually, wiring outside the voice coil). However, serious damage to the cone or just plain deterioration of the suspension components may require replacement of the entire driver unless a close enough match can be found. For more information on loudspeaker repair, see: "Speakers (big, small, in between)" also at this site.
Minor damage to the cone can be repaired using a flexible adhesive like weatherstrip cement and a piece of thick paper to reinforce the seam or hole if necessary. Since this will not totally perfect match with the original paper cone, there could be audible distortion at certain frequencies particularly at higher volume levels. However, such a repair will be better than nothing. Cut the paper in a shape and size to just overlap both sides of the torn area or completely cover the puncture. Use just the smallest amount of adhesive to fasten your 'splint' to the cone. The less material you add, the more likely that the audio effects will be minimal. (From: M. Przytarski (m.r.p.@ix.netcom.com)). I have repaired many field-coil speakers, and there is one sure proof way my grandfather showed me (and several Tube Radio rebuilding mags suggest the same). Take a milk glue (Elmers or such), and rub it around the crack. Then take a piece of brown lunch bag and rub it with glue. Place it over the crack, and rub some glue on it, pressing it in place. The glue should by now soak the paper of the cone and bag. When dried you cant tell the difference in sound and its as sturdy as ever. This also works for those units that a animal (or kid) has put a hole in. I repaired a speaker that was missing almost half of the cone from mice. It sounds great and was cheap to do.
(I have not dealt with any of these places personally - these are all based on recommendations of others.) * Simply Speakers, 11203 49th St. N., Clearwater, FL 34622, Voice phone: (813) 571-1245, Fax: (813) 571-4041, http://www.simply-speakers.com, provides speaker repair services and also sells do-it-yourself refoaming kits for repairing foam edge surrounds on most round 4" to 15" and oval 6" x 9" speakers. * Stepp Audio Technologies, P.O. Box 1088, Flat Rock, NC 28731, 1-704-697-9001. * The Circuit Shop, 3716 28th Street, Kentwood, MI 49512, 1-800-593-0869 or 1-616-285-1144. (From: Raymond Carlsen (rrcc@u.washington.edu)). Various sizes of paper cones and foam-edge replacements are available from MAT Electronics @ 1-800-628-1118. They range in price from less than a dollar to about $5 for the largest (15") drivers. The downside is there is a $25 minimum. However, they also sell electronic components like flybacks, video heads and belts, ICs and transistors, etc. So coming up with a minimum order may not be too difficult. (From: Johnion (johnion@aol.com)). I was given a pair of infinity speakers and ordered replacement cones from The Speaker Plac. As long as the problem is just the cones, the kit is great (and cheap). These are the numbers I used around a 1-1/2 years ago: * The Speaker Place - NEW FOAM, 3047 West Henrietta Road, Rochester, NY 14623, Phone: 1-800-NEWFOAM (1-800-639-3626), Fax: 1-800-2FXFOAM (1-800-239-3626), Voice Mail: 1-800-FOAMMAIL (1-800-362-6624). Email NEWFOAM@msn.com, Web: http://www.NEWFOAM.com. (From: T Schwartz (toschwartz@worldnet.att.net)). I've had excellent results sending drivers to Millersound Labs: * Millersound Labs, 1422 Taylor Road, Lansdale, PA 19446, Phone 215-412-7700, Fax 215-412-0542 They can re-foam or re-cone depending on what is needed, they are fast, easy to deal with, and IMHO, reasonably priced. Call them for a quote. (From: jl (jlager@tir.com)). * Orange County Speaker, 12141 Mariners Way, Garden Grove, California, 714-554-8520. * (From: Aan Jerig (ajerig@gate.net)). Lakes Loudspeaker, 4400 W. Hillsboro Blvd., Coconut Creek, FL 33073, 1-800-367-7757.
An open driver can sometimes be rescued by tracing the input wires through the cone and under the center protective dome. The most likely places for these wires to break are right at the place where they pass through the cone and just after they pass under the dome. Note: some drivers have replaceable voice coil units. If this is the case, you should probably just replace the entire unit. First, scrape away the insulating varnish on the front of the cone where the wires emerge and head toward the center. Use your ohmmeter to test for continuity here. If you find that you now are measuring a reasonable resistance - a few ohms, then trace back to determine which of the two wires is broken or has had the solder connection come loose. If it is still infinite, you will have to go under the dome. Use an Xacto knife to carefully remove the dome. Use a shallow angle and cut as near the edge as you can. Take care not to puncture the paper cone which may continue under the dome as the voice coil may be of a smaller diameter than the dome. The shallow cut will also provide a base to reattach the dome if you are successful. Carefully scrape off a bit of the enamel insulation as near to the voice coil as possible and test with your ohmmeter once again. If the resistance is still infinite, there is nothing more you can do but salvage the magnet for fun experiments or erasing floppy disks. There is essentially no way to replace just the voice coil unless your driver has a removable voice coil unit (in which case you would not be reading this). If the resistance now measures normal - a few ohms, trace back to determine which wire is broken and use some fine (e.g., #30 gauge) wire to bridge the break. You will have to scrape off the enamel insulation to permit the solder to adhere. Make sure it is secure mechanically first - a speaker cone is a rather violent environment for soldered connections. Finally, use some flexible adhesive to protect and reinforce the solder connections, to glue down your new wire along its entire length, to protect and reinforce the place where the wire passes through the cone, and finally, to reattach the central dome. Let the adhesive dry thoroughly before playing the finale to the 1812 Overture.
Assuming that the cabinet is in reasonable condition, the question arises: is it worth replacing broken, damaged, or worn out drivers or faulty crossover components that are not repairable rather than just dumping the speaker systems? It is very straightforward to swap drivers as long as you get ones with similar characteristics. It all depends on what you want out of a loudspeaker. If you are basically happy with them, then it will be a lot cheaper than replacing the entire speaker system(s). However, speaker system quality has improved considerably in the last 15 years so now may be the time to upgrade. As far as crossover components are concerned, these are basically common electronic parts and replacement is probably worthwhile. However, if one driver has a deteriorated suspension, it is likely that its mate does as well and that other drivers may not far behind. Replacing **all** the internal components of a loudspeaker may not be worth it. Radio Shack as well as places like MCM Electronics and Dalbani have a variety of replacement drivers, and crossovers and parts.
(From: Frank Fendley (frank.fendley@datacom.iglou.com)). Wiring speakers in series increases the impedance of the load, generally allowing less expensive output chips and smaller heatsinks, due to reduced current. It also decreases the amount of output audio power in most cases, since power is inversely proportional to impedance for a given voltage. Many cheaper home stereo receiver and power amps are configured in a similar manner. If you have a switch and output connectors for "A" and "B" speakers, in some cases when you turn the switch to "A+B", the two left speakers and the two right speakers are wired in series. To find out if this is the case on your stereo, hook up only one set of speakers to the "A" jacks. Turn the speaker select switch to "A+B". If you have no audio through the speakers, then your receiver or power amp is configured to place the speakers in series with both sets of speakers are connected. On better stereo equipment, if you have only one set of speakers and select the "A+B" switch setting, your speakers will still function, indicating that the speakers are wired in parallel in the "both" position. Bottom line - the answer is money (isn't the answer always money?). It's cheaper for the manufacturers to design for speakers in series.
When loudspeakers - even those little speakers that came with your PC - are near TVs or monitors, there may be problems with the fringe fields of the powerful magnets affecting color purity, convergence, or geometry. Speakers designed to be used with PCs in close proximity to their monitor will likely include some internal shielding. This may even be effective. However, the large powerful loudspeakers used with high performance stereo systems will likely not have such shielding. The best solution where display problems have been traced to the loudspeakers is to move them further away from the TV or monitor (and then degauss the CRT to remove the residual magnetism. Where this is not possible, shielding of the speakers may be possible: (Also see the document: "TV and Monitor CRT (Picture Tube) Information".) (From: Lionel Wagner (ck508@freenet.carleton.ca)). Put a Tin can over the magnet. This will reduce the external field by about 50%. If more shielding is desired, put additional cans over the first, in layers, like Russian dolls. (Note: a Tin can is actually made nearly entirely of steel - the term 'Tin' is historical. --- sam) (From: Nicholas Bodley (nbodley@tiac.net)). While both electrostatic and electromagnetic (E/M) fields can affect the paths of the electron beams in a CRT, only E/M fields are likely to be strong enough to be a problem. Magnetic shields have existed for about a century at least. Some decades ago, a tradenamed alloy called Mu-Metal became famous, but it lost its effectiveness when bent or otherwise stressed. Restoring it to usefulness required hydrogen annealing, something rarely done in a home shop (maybe one or two in the USA). More-recent alloys are much less fussy; tradenames are Netic and Co-Netic. Magnetic shields don't block lines of force; they have high permeability, vastly more than air, and they guide the magnetism around what they are shielding; they make it bypass the protected items. I have been around some shielded speakers recently, but never saw any disassembled. They looked conventional, must have had the "giant thick washer" (my term) magnet, and seemed to have a larger front polepiece than usual. They had a shielding can around the magnet; there was a gap between the front edge of the can and the polepiece. I suspect that a second internal magnet was placed between the rear of the main magnet and the rear (bottom) of the can, so there would be minimal flux at the gap between the can and the front polepiece. Holding pieces of steel close to the gap between the can and the polepiece showed very little flux there. Modern magnets are not easy to demagnetize, in general. (From: Dave Roberts (dave@aasl.demon.co.uk)). The *good* so-called magnetically screened speakers rely on two means of controlling stray flux. The static field from the magnet on the speaker (which would cause colour purity problems) is minimized by the design of the magnet. This is often at the expense of gap field linearity, leading to greater distortion - not that most users seem to worry about that...The mains varying field is minimized by use of a toroidal mains transformer, but the more recent mains powered speakers seem to be coming with *plug top* PSUs, which take the problem further away.
* Connections to 'Plain Old Telephone Service (POTS)' is via two wires.
POTS is the type nearly everyone currently has to their residence. Newer
ISDN or fiber lines use different techniques.
* The wires are called 'Tip' and 'Ring'. This terminology has nothing to do
with telephone ringing but is historical; Tip and Ring were connected
to the tip and ring respectively of the plug used on manual switchboards.
* Tip and Ring color codes are as follows - this is not always adhered to!
Type A Type B
Phone line Tip,Ring Tip,Ring
-------------------------------------------------------------------
First line (Pair 1) Green,Red White,Blue
Second line (Pair 2) Black,Yellow White,Orange
Third line (Pair 3) White,Blue White,Green
Type A is often simply called 'quad' and is the most inexpensive cable.
However, the conductors are usually not twisted and type A should not
be employed in new installations especially where computer modems or fax
machines are to be used on any of the lines as crosstalk between
multiple phone circuits in the same cable may result in excessive
transmission errors and interference with normal phone conversations.
For type B, the colors refer to the dominant one if the wires are striped.
Each pair is twisted together which greatly reduces crosstalk.
* On RJ11 type connectors, Pair 1 is the central two wires, Pair 2 is the
next two, and Pair 3 are the outer wires if there are 6 conductors - many
RJ11 cables only have 2 or 4.
* Tip will be approximately +50 VDC with respect to Ring when phones (or
computer modems or fax machines) are on-hook. Test with a multimeter.
* Ringing voltage is about 90 VAC. A neon light bulb (NE2) can be used
to test for this if a multimeter is not available.
* When off-hook (dialing or talking), there will be a DC voltage of
approximately 5 to 15 V between Tip and Ring. This is needed for the
phone circuit and also is used to power the dialing in phones without
a separate AC supply or adapter.
* The on-hook and ringing voltages can give you a shock but are probably
not particularly dangerous to healthy people. Still, it is best to
work on phone wiring with it disconnected from the telephone company's
feed or with another phone on the same circuit off-hook.
* Some phones will work with only one of the two possible polarities of
Tip and Ring while others incorporate a bridge rectifier (for power)
and will work either way - test both ways if a phone does not dial
or work at all.
* DTMF refers to the Dual Tone Multi-Frequency dialing touch tone codes.
Each number, *, and #, are represented by a pair of audio frequencies.
(You can hear the individual ones by holding down multiple buttons on
an old style ATT Touch Tone phone). See the section: "DTMF codes".
DTMF (Dual Tone Multi-Frequency) are the tones that phones use. The
frequencies are as follows:
Hz 1209 1336 1477 1633
------------------------------------
697 1 2 3 A
770 4 5 6 B
852 7 8 9 C
941 * 0 # D
Follow the rows and columns to the number you want to know the frequencies
of and this table will show you. The column of letters at the right is on
some Ham radios.
Where an old style ATT Touch Tone phone's DTMF frequencies need to be adjusted,
accuracy of better than 1 Hz is easily obtained without fancy equipment - just
another working tone dialing phone. See the section: "Classic ATT Touch Tone phone 'battlewagon' will not dial properly".
For more information on DTMF coding, decoding, equipment, chips, etc., see
the DTMF FAQ at:
http://www.repairfaq.org/filipg/HTML/LINK/F_DTMF.html
The phone companies would have you believe that installing or repairing phone wiring is somewhere between rocket science and nuclear physics in complexity. In fact: * Installing new jacks consists of two parts: running the wires and hooking them up. The only difficulty with running the wires is getting between floors. Connecting them is a matter of matching the colors of the insulation, stripping, wrapping around screws, and tightening the screws. Even if you are color blind, this is not difficult. * Unless you disturb it, phone wiring rarely goes bad - even in old houses. Thus, if you have any amount of handyperson ability, paying the $2 a month inside wiring insurance is throwing away $24 a year. * Unlike electrical wiring, phone wiring does not have serious safety issues associated with it. However, you could get a mild shock from touching the two wires of an active phone line. The on-hook voltage is about 50 VDC and if someone were to try calling your number at the same time, the ringing voltage is around 90 VAC. Both of these are easily dealt with: put a jumper between the two phone wires where they enter your house while you are working on the wiring. This will result in an 'off hook' condition and outside callers will get a busy signal.
Most answering machines still use one or two tape decks. Most problems are mechanical. Refer to the sections on the relevant tape player/recorder problems. The newest ones are fully digital electronic - forget repairs unless obvious bad connections, physical damage, power supply, or phone line side failure. * Many non-mechanical problems with answering machines are related to the circuitry connected to the phone line. This is subject to the high on-hook and ringing voltage and possible voltage spikes due to lightning, etc. Testing of the components on the phone line side of the coupling transformer is a worthwhile exercise and may reveal a shorted semiconductor or capacitor. See the section: "Checking phones and answering machines for electronic problems". * If the outgoing message (OGM) or phone messages do not record or playback, check for broken wires at the appropriate tape heads and clean the mode selector switches. * With endless loops outgoing message cassettes, the metal strip that is used to sense the beginning can wear or become dirty. Try a new cassette or clean it. * Like VCRs, there may be various 'mode switches' or position sensors. Where these are physical switches, they may have dirty or worn contacts. Optical sensors can fail as well though it is unusual. * Mechanical problems unique to answering machine tape transports are also possible. Some very clever engineering is often used to share parts where two tape transports are used. Parts may have popped off or broken. Springs may have sprung or weakened. Sliding parts may have jammed. Look for loose parts or broken pieces when the unit is disassembled. Careful inspection during operation may reveal whether it is getting stuck due to a mechanical failure.
This may be one of those machines where it has to go through the entire outgoing message (OGM) tape before allowing recording of the phone conversation - If it is, then just get yourself the shortest outgoing message tape you can find and time your OGM to nearly fill it. Also, if you are trying to use an OGM tape recorded on another answering machine, even if the tape is compatible, the frequency or coding of the control tones - the beeps - may not be the same. Try re-recording it on the machine in question. If these are not the problems, the machine may not be sensing the beep code put on the tape when you record the OGM or the beep is not being recorded properly. This is likely an electronic or logic problem requiring the schematic unless you get lucky with bad connections or a broken wire at the tape head.
* If it has a 'telco' and a 'phone' connector verify that you are plugged into the 'telco'. Otherwise, it may hang itself up. Who knows. If someone else attempted a repair, these jacks could even have been replaced interchanged. * Measure voltage on the relay coil. If it actually disappears when the relay cuts out, then something is telling the relay to turn off. If it is just reduced, then there may be a power problem. If it is relatively stable, then the relay may be bad. * Test components near the telephone connection for shorts/opens. Parts connected to the telephone line get abused by the ringing voltage and other transients. Maybe you will get lucky and find a fried part. * If you can identify the power supply outputs, verify their voltages if possible. Check the 'wall wart' if it uses one for proper output. * Make sure that the tape mechanisms have completed their cycles. While unlikely, it is possible that the logic gets confused if one of the tape units has not reset itself due to a mechanical fault like a bad belt. * As usual with cheaply made consumer stuff (as well as cheaply made expensive industrial stuff), check for bad connections. Beyond this, circuit diagrams would be a definite plus.
This is often a mechanical problem. As it goes through the cycle, see if the mechanism is perhaps getting hung up at a certain point do to a weak spring or motor. A cam may get stuck or a solenoid may fail to engage. Gently prodding the uncooperative part (or any likely parts if the appropriate one is not obvious) may convince it to continue and allow you to make a diagnosis. For endless loop outgoing cassettes make sure that the metal sense strip is not worn off and that the sensor is making good contact. Try a new outgoing message cassette or manually short the sensor contacts to see if it will then shut down.
You probably have no way of knowing since you probably never listen to the outgoing message, but did the problem happen suddenly? Does playback of the outgoing message directly to the speaker appear to be at normal volume? Do incoming messaged get recorded at normal volume? First, confirm that the unit is in good mechanical condition. See the section: "General guide to tape deck cleaning and rubber parts replacement". Clean the tape head and inspect for anything that may be interfering with good tape-head contact. Clean the internal record/play selector switches. Dirty contacts can result in any number of symptoms. Assuming that none of this helps significantly, you are left with a problem in the electronics. If local record and playback of the the outgoing message works normally, the problem is not a bad tape head. It is probably in the interface to the phone line. If local record and/or playback do not work correctly, then there are likely problems with that circuitry. One other slight possibility is that you have so much equipment (phones, modems, fax machines, etc.) on the phone line that in your house that the answering machine is not able to drive the line properly and reduced outgoing message volume is the result.
If a Touch Tone phone that was previously working now does not tone dial from a new jack or new residence (the button presses are totally ignored, but all other functions are unaffected), the red and green wires are probably interchanged at the new jack, or the phone itself is miswired (the wires inside the phone may have been interchanged to compensate for an incorrectly wired jack at the old location). Newer electronic phones will utilize either polarity. The older ATT battlewagons will only dial when hooked up with the correct polarity. This does not affect conversation, ring, or rotary phones.
There are several types of problems with cordless phones that can be diagnosed and repaired without sophisticated test equipment. Anything involving problems with the RF or digital circuitry is not likely to be within the scope of your capabilities, at least not without complete schematics (yeh, right), test equipment, and a miracle or two. 1. Bad rechargeable battery - dead, shorted cell(s), or reduced capacity. The NiCd battery packs in cordless phones are usually easily replaced for around $5-10. This really is the best solution. The problem is almost never in the charging circuits. Replacing individual cells is not recommended. Battery packs can be built up from individual NiCd cells with solder tabs for a modest cost savings. Reuse the old battery pack connector (you may need to do this with a replacement pack as well if the new connector is not identical to the old one), double check polarity, and tape and insulate your homemade pack after soldering to prevent shorts. A NiCd battery pack with shorted cells will either prevent operation totally or keep the 'battery low' light resulting in a weak, noisy, or intermittent connection. If the voltage measured on the battery pack after 24 hours of charging is less than 1.2 V times the number of cells in the pack, it is most likely bad. 2. Dirty keypad - resulting in intermittent, incorrect, or no operation of buttons on handset. This may be due to internal migration of some unidentified substance (how else to describe disgusting sticky gunk that has no right being there on multiple samples of the same model phone) or from external spills. If you are lucky, the keypad can be disassembled without resorting to drastic measures. There may be screws or it may snap apart once access is gained to the inside of the handset. Clean contact surfaces on both the rubber button panel (or plastic keys) and the circuit board first with soap and water and then with isopropyl alcohol. Dry thoroughly. If the keypad is assembled with 'upset' plastic (fancy term for little melted plastic posts), then you should probably try contact cleaner sprayed as best as possible through any openings before attempting to cut these away since reassembling the keypad without the plastic posts will be difficult. However, I have successfully repaired these by breaking off the tops of the posts to remove the circuit board and rubber keys, and then using a dab of windshield sealer on each post as an adhesive to hold the thing together after cleaning. However, I much prefer screws :-). 3. Bad AC adapter on base station - see the chapter: "AC Adapters." This will likely result in a dead base station. 4. Bad phone line connection - don't ignore this possibility - test with another phone. 5. Bad circuitry on phone line side of interface (coupling transformer) - inspect for blown or shorted components. 6. Bad connections or broken circuit board - if the handset has seen violent service, these are likely possibilities. See the section on: "Equipment dropped or abused". 7. You forgot the code number - some phones use a multidigit code number as a marginal security feature which must match on handset and base station. If the battery goes dead in the handset or the AC adapter is pulled on the base station, this code may be forgotten. You do have the user's manual, right? BTW, do set this code to a non-default value. I was once able to dial out on my neighbor's cordless phone using my phone from my house as a result, I suspect, of their phone being set to its default code! 8. Base station and handset out of sync - some models require that the base station initialize the handset before any communication is possible between them. Put the handset on the base station for a few seconds to reset. This can happen at any time due to circumstances beyond human control but will almost certainly happen if you replace or disconnect the battery in the handset of these model phones.Go to [Next] segment
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