(From: email@example.com@deltanet.com) Nothing will stop a good lightning strike, but there are things you can do to put the odds more in your favor. For telephone line protection, the place to start is where the phone line comes into your house. Locate the protector and verify you have a good ground close to it. Next, replace the standard carbon protector elements with gas tubes. These often look like large brass hex bolts with no wires attached, but the exact design will vary. Carbon protectors operate rather slowly; gas tubes ionize very quickly and carry large amounts of current. You may have to shop around your local telco supplier to find these. Strictly speaking, these are on the telco side of the demarc and you're not supposed to fool with them, but if you won't tell, I won't either. Or you could call your local telco and ask for the gas tubes... Then add your store-bought protector inside. Make sure it has a good ground, too. It can't hurt, and it might help. But the best place to try and stop the lightning is before it enters your house.
I have heard of someone fighting off a would-be mugger with a tape deck but this is generally not a recommended practice. However, once it happens - your cassette deck fell off its shelf or you prized walkman fell from your hang glider (ok, maybe that will be too much even for miracles) - what should you do? Overall, electronic equipment - especially portable devices - are quite tough. However, falling or being beaten in just the wrong way can do substantial and possibly not immediately visible damage. If you take it in for service, the estimate you get may make the national debt look like pocket change in comparison. Attempting to repair anything that has been dropped is a very uncertain challenge - and since time is money for a professional, spending an unknown amount of time on a single repair is very risky. There is no harm is getting an estimate (though many shops charge for just agreeing that what you are holding was once a - say - tapedeck!) This doesn't mean you should not tackle it yourself. There may be nothing wrong or very minor problems that can easily be remedied. First, unplug the unit even if it looks fine. Until you do a thorough internal inspection, there is no telling what may have been knocked out of whack or broken. Electrical parts may be shorting due to a broken circuit board or one that has just popped free. Don't be tempted to apply power even if there are no obvious signs of damage - turning it on may blow something due to a shorting circuit board. If it is a portable, remove the batteries. Then, inspect the exterior for cracking, chipping, or dents. In addition to identifying cosmetic problems, this will help to locate possible areas to check for internal damage once the covers are removed. Next, remove the covers and check for mechanical problems like a bent or deformed brackets, cracked plastic parts, and anything that may have shifted position or jumped from its mountings. Carefully straighten any bent metal parts. Replace parts that were knocked loose, glue and possibly reinforce cracked or broken plastic. Plastics, in particular, are troublesome because most glues - even plastic cement - do not work very well. Using a splint (medical term) or sistering (construction term) to reinforce a broken plastic part is often a good idea. Use multiple layers of Duco Cement or clear windshield sealer and screws (sheetmetal or machine screws may be best depending on the thickness and type of plastic). Wood glue and Epoxy do not work well on plastic. Some brands of superglue, PVC pipe cement, or plastic hobby cement may work depending on the type of plastic. Cycle the the mechanism and check for free movement of the various moving parts. Inspect for any broken electronic components - these will need to be replaced. Check for blown fuses - the initial impact may have shorted something momentarily which then blew a fuse. There is always a slight risk that the initial impact has already fried electronic parts as a result of a momentary short or from broken circuit traces and there will still be problems even after repairing the visible damage and/or replacing the broken components. Examine the circuit boards for any visible breaks or cracks. These will be especially likely at the corners where the stress may have been greatest. If you find **any** cracks, no matter how small in the circuit board, you will need to carefully inspect to determine if any circuit traces run across these cracks. If they do, then there are certainly breaks in the circuitry which will need to be repaired. Circuit boards in consumer equipment are almost never more than two layers so repair is possible but if any substantial number of traces are broken, it will take a great deal of painstaking work to jumper across these traces with fine wire - you cannot just run over them with solder as this will not last. Use a fine tipped low wattage soldering iron under a magnifying lens and run #28 to 30 gauge insulated wires between convenient endpoints - these don't need to be directly on either side of the break. Double check each connection after soldering for correct wiring and that there are no shorts before proceeding to the next. Also see the section: "Repair of printed circuit board traces". If the circuit board is beyond hope or you do not feel you would be able to repair it in finite time, replacements may be available but their cost is likely to be more than the equipment is worth. Locating a junk unit of the same model to cannibalize for parts may be a more realistic option. Once all visible damage has been repaired and broken parts have been replaced, power it up and see what happens. Be prepared to pull the plug if there are serious problems (billowing smoke would qualify). Determine if it appears to initialize correctly - without shutting down. Play a garbage tape to determine if there are any problems that might damage the tape. Listen carefully for any evidence of poor tracking, tape speed instability, or weak or muddy audio that might indicate that tape path alignment requires further attention. Listen as well for any unexpected mechanical sounds that were not there before. Very likely, the unit will be fine, you can replace the covers, and now find a more secure spot for it to prevent this sort of event in the future. Maybe hang gliding is just not for you!
Larger components like electrolytic capacitors are often secured to the circuit board with some sort of adhesive. Originally, it is white and inert. However, with heat and age, some types decay to a brown, conductive and/or corrosive material which can cause all sorts of problems including the creation of high leakage paths or dead shorts and eating away at nearby wiring traces. The bottom line: Most of the time, this stuff serves no essential purpose anyhow and should be removed. A non-corrosive RTV or hot-melt glue can be used in its place if structural support is needed. (From: Richard Rasker (firstname.lastname@example.org)). Are you repairing somewhat older Japanese (Yamaha, Nikko, etc.) equipment, but the problem seems very obscure? Then maybe this may interest you: In some amplifiers and other equipment, the supply capacitors and other large pcb-mounted devices are secured in place by a type of gluelike substance, that after several years causes corrosion to all metal parts that it touches; eventually, the metal connections (like component wire leads and wire bridges) will fail. The substance in question is a dark yellow rubber-like compound, coloring brown and turning rather hard on the places where damage is done to other components. The only solution is to scratch it away completely and replace all components affected. I've already repaired five amps where this turned out to be the cause of trouble - with very vague symptoms, like a missing ground reference to an endstage, an on-board controller that wouldn't start up, etc. The first time it took me forever to find, so if this posting will make even one repair easier for someone, I'm already happy. Hope this makes life a (little) bit easier for all those people out there trying to repair stuff, instead of throwing it away :) P.S. My theory about this process: I think that the substance used is a rubber compound with an excess of sulfur, which will very slowly react with oxygen and moisture to form corroding chemicals (like sulfites). If anyone has a better theory (or the correct explanation), please let me know. (From: Jake Gray (email@example.com)). I have found in a lot of electronical gear and more recently in my monitor. The glue has been designed mainly to hold leads and wires in place, also to hold capacitors in place. It eventually soaks up the moisture from the air, giving it a conductive effect and the places that it is located don't like having a conductor across them. And, as time goes on, the glue seems to carbonize and become an even better conductor. Just keep and eye out for it, it is like a creamy colour and remove it ASAP. With many appliances, especially those with many IC's, I have found that with the removal of the glue, they work fine.
In most cases, a functional repair - using wire to bridge the breaks soldered to conveniently located pads - is all that is needed. This will be at least as reliable as the original foil wiring if done properly. However, there are those times when a complete restoration is desired: Note: If the original cause was chemical corrosion rather than mechanical, ALL of the offending material must be removed and/or neutralized before any sort of reliable repair can be attempted! (From: MKILGORE (firstname.lastname@example.org)). Yes, you can repair damaged/lifted conductors and pads on circuit boards. If you would like to repair the damaged area professionally, track repair kits are available from sources such as Pace. These repairs once completed are almost undistinguishable from the original work. Damaged pad replacement - Using a scalple or Xacto knife follow the run attached to the pad back to a point where it is still firmly secured, at a 45 degree angle, cut the trace loose and remove it from the board and discard. Scrape any solder mask from the end of the trace back about 3 trace widths, and clean the area with an ink eraser, then tin the area. Select a pad with trace from the kit ( various sizes are included ) position it in place of the damaged run and form it so it follows the contour of the board to the 45 degree angle cut and rests on top of the original trace by about 2 trace widths. Now prepare a small amount of two part epoxy and flow it on the board where the replacement conductor will lie, do not get any on the tinned conductor. Lay the replacement conductor in place and allow the epoxy to dry, this can be speeded up with a heat lamp. Once dry simply apply flux to the joint and solder the two pieces together. If this was a plated through hole, or strength is an issue, the kit contains eyelets which can be installed through the board. --- However, if the trace you wish to repair is merely lifted you can simply use the epoxy and secure it back in place.
This might be the case where someone tripped over the AC adapter cord of a walkman or laptop computer thus ripping the jack from the circuit board. (From: KIRTO (Kholson@cris.com)). As you will see in the following, I recommend using something other than the pad to get that strength. I suggest you provide mechanical connection between the jack and the board so that the jack can't move with respect to the board. Techniques include a wire strap over the component near the back and soldered to the board like you see on crystals or adhesive under the jack like you see on large caps in midboard. Another possibility is to put a rubber bumper atop the jack so that the front cannot tip inward when it's in the case. A stick-on foot might be a start, with whatever 'foot surgery' is needed to fit. If the jack has a rim near the front (like a std keyboard connector) you might be able to put triangular braces on either side of it with adhesive and some stiff rubber or plastic. I have seen this problem happen when someone trips on a cord and thus pulls the connected jack at a sharp angle with high force. Warn the customer about this possibility, and suggest using an extension cord on the power adaptor. (From: Hank Sievers (email@example.com)). The best way that I can think of is to bend down whatever part of the leg extends through the board and bridge with a heavy bare wire and plenty of solder to as much of the nearest part of the trace (scraped to the copper, of course) as you can. Then, for good measure put a drop of magic glue or some silcone sealant where the leg comes through the hole. Should be stronger than the original. I am a charter member of the the 'down-to-the-component-troubleshooting fraternity', since I am naturally curious and fortunate enough to have the time, since I am retired. However, I can see where it is often important to the bottom money line, not to spend too much time on a repair and so replace the entire unit. Time is money also!
A (former) relative took your boombox to the beach this summer and now it has sand or perhaps salt in it. Or, maybe you could not resist "sing'n in the rain" and a big bus went by without slowing. Now neither of the tape decks will play. Can this possibly be fixed? Will it be worth the effort? Unless this is a really expensive sophisticated unit, I doubt whether it will pay you to take it anywhere for repair. Furthermore, as with equipment that has been dropped or physically abused, few repair shops will be inclined to touch the job. They really don't like challenges of this sort. That leaves you! If saltwater was involved in a significant way, you can probably forget it. Without immediate attention, saltwater corrosion can set in very quickly and attacks electronic components, circuit board traces, cable wiring, and mechanical parts. The only thing worse is damage caused by forgotten, leaky batteries. Although it is probably too late, the first thing to do when electronic equipment gets wet is to remove the power source - switch it off and pull the plug or remove the batteries if possible. Don't be tempted to apply power until you have determined that it is completely dried out. If power was on when the 'incident' took place, then electronic damage may have already resulted which will not be apparent until after cleaning, drying, and lubrication. The following description assumes a dual cassette boombox. Adjust as appropriate for your patient: If the tape decks are totally dead, you may have serious electronic or corrosion which will make any salvage unlikely. If they sort of move (or even twitch a bit) but the sound is erratic, weak, fluttery, etc. then there may be hope. (Of course, if it got wet, you should not have done this test until everything was cleaned and dried!) NEVER use strong solvents for any cleaning. These may attack plastic parts or cause internal damage to electronic components. Mechanical intensive care: 1. Remove the tape decks. This will be a pain but otherwise you will not be able to get at everything. Make as many as drawings as needed so you will be able to reassemble. 2. Make a drawing of the belt routing, remove the belt(s), wash and dry them, label and set them aside. 3. Use a soft brush (like a paintbrush) to dust out as much sand as possible. Hopefully, you can get it all this way. A vacuum cleaner with a wand attachment may prove handy to suck out sand. Don't use high pressure compressed air - it will just spread the sand around. Any grease or oil on which sand has collected will need to be totally removed and replaced with fresh lubrication. 4. If there is evidence of salt (remember, I said forget it...but), you will need to wash it off. Yes, wash it. Keep water out of the motors. Use low pressure compressed air (a blow dryer on low heat should be fine) to dry so that it does not rust. Ditto if it is still wet with contaminated liquid (we won't say where this came from), wash with fresh water to remove all traces of it as quickly as possible. A final rinse with 91% or pure isopropyl alcohol will decrease drying time and should not damage mechanical assemblies. Degreaser may be used if it is safe for plastic and rubber parts. Lubricate all bearing points with a drop of light machine oil - electric motor oil, sewing machine oil, etc. (Never never never WD40). Lubricate gears, cams, and sliding parts with a light plastic safe grease. 5. Replace the belts and reinstall the tape decks. Electronic intensive care: 1. Remove the circuit boards and label the connectors if there is any possibility of getting them mixed up. If the circuit board(s) are soldered to the rest of the equipment, then you will have to improvise. 2. Wash with water and dry thoroughly. This does work. I use it routinely for degunking remote controls and rubber membrane keypads, for example. The most important objective should be to get corrosive liquids off the components and circuit traces as quickly and completely as possible. A final rinse with isopropyl alcohol will decrease drying time. However, there is a slight risk of damage to sensitive electronic components should some be trapped inside. Moisture will be trapped in controls, coils, selector switches, relays, transformer cores, connectors, and under large components like ICs. Pat dry, then use warm air from a hair dryer (or heat gun on low) to completely dry every nook and cranny. DO NOT operate until everything inside and out is thoroughly dry. 3. Inspect for damage due to short circuits including blown fuses, fried components, and melted traces. These will need to be repaired or replaced. 4. Use spray contact cleaner on the switches and control cleaner on the user controls and adjustment pots. DO NOT turn the internal adjustments without precisely marking the original positions - else realignment will be needed. Exercise the user controls to help the cleaning process. Once everything is reassembled, power the unit up and see what happens. Be prepared to pull the plug or pop the batteries if there are serious problems. Attempt to play a garbage tape to determine if there are any problems that might damage the tape. Look and listen for any abnormalities which may require additional attention. There could still be electronic faults not repairable without schematics and test equipment. Obviously, this description is very simplistic. The important thing is to get every last grain of sand, salt, and other contaminants off of the mechanisms quickly. Similar comments apply to equipment that went for an actual swim - you dropped your portable CD player in the toilet. The most important objective is to clean and dry it as quickly as possible and then relube any motor and other bearings. Use your judgement as to the severity of the dunking in terms of how deeply the liquid penetrated. Surface moisture will not hurt anything as long as it is dried up quickly. If you left it soaking on the other hand.... As noted above, moisture may collect inside certain electronic parts and it is essential that these be dried completely before attempting to apply power to the unit. If you do not, at best it will not work properly and you may do additional serious damage due to short circuits. For the mechanics, the same applies though this is trickier since certain parts need to be lubricated and these may not be readily accessible or obvious. Don't be tempted to overdo the lubrication either - too much is worse that too little. For high tech devices like CD players, some parts of the internal optics or shielded DC-DC convertors may be impossible to access and clean of scum.
(From: John Baker (firstname.lastname@example.org)). I have repaired equipment that has been soaked in salt water and it depends on what type of components it has on the boards. If they have any batteries on them, get them off as soon as possible. transformers are usually good for rusty paperweights. Get the boards out of the salt water and into fresh water ASAP. I have not found any chemicals that will remove the salt deposits and leave the traces. The best bet is to use a small nylon brush along with a chemical called Flux Off-nr, there are several types of Flux-Off, get the one that does not harm plastic parts, it is not as strong but it workes just as well in this case. From there it takes a lot of time. Use the brush and remove all salt deposits, try and get under all components, especially IC's. Most components can take being under salt water with no damage, it is the batteries and metal that cause problems.
(From: Filip "I'll buy a vowel" Gieszczykiewicz (email@example.com)). Greetings. I've recently had the opportunity to rescue several rather expensive electronic units after the owner flipped the canoe and spilled the beans, so to speak. The dead units were: a Casio solar-powered calculator, a car-alarm key ring transmitter, a 10-satellite GPS unit (yowser!), and some smaller items. Note: GPS unit was waterproofed and did not suffer much. Solution (sorry, pun) was: purchase 1 gallon of distilled water, disassemble the units and submerge the PCBs (and keypads and displays) in containers. The devices were left soaking for more than 20 minutes. Then, they were removed and dried with a hair dryer (and fan for less expensive items). Results: excellent. All items have been brought back to life. Some *did* require purchase of new (rather expensive) Lithium batteries but that was a small price to pay. Hint: It is highly useful to have a brush to clean the area between ICs' pins after 10+ minutes of soaking. This helps to remove any minerals that are not as soluble in water as others. This is more of an issue if the items came in contact with flood-stage stream than a sinkful of tap water. :-) Observation: devices that were "on" at the time of the dunking were the most damaged and required the most time to soak. Batteries had to be replaced since they *all& started to leak.
If you have a true antique - really old, and valuable, you should refer to the extensive literature available on this subject. The following applies more to that 30 year old record player/amp found in the storage loft of your garage during spring cleaning. Common problems relate to two types of components: vacuum tubes (valves for all of you on the other side of the lake) and capacitors (paper and electrolytic type). Push all the tubes down in their sockets as well - they will work their way loose with non-use and vibration. However, thorough cleaning of all socket and switch contacts, and controls will almost certainly be needed. Warning: the voltages inside tube type equipment can exceed 400 V - and contact with that can be real painful not to say dangerous. AC-DC type sets are not isolated from the power line. (In some really old equipment, even the chassis may be tied to one side of the line). This could also happen as a result of a shorted component. The electrolytic capacitors can hold a charge for quite a while. Read, understand, and follow the recommendations in the document: "Safety Guidelines for High Voltage and/or Line Powered Equipment". Use extreme care when probing or even touching anything. This isn't 5 V logic! Vacuum tubes: It is not possible to fully test vacuum tubes without proper equipment but the inspection and tests below will find most bad tubes but will not pick up weak tubes. As a side note, when a repair shop replaced tubes, perhaps 20 % of the tubes they replaced were actually bad (I know because the local TV repair shop's trash can was a favorite hangout on pickup day and nearly all the tubes I scrounged tested perfectly good on a real tube tester once they were washed of coffee grounds and cigarette ash!) Whether this represented legitimate preventive maintenance or just IPM - Increased Profit Margin, I really do not know.) 1. Look for a silvery metallic spot somewhere inside the tube. This is the getter and is there to remove the last traces of gasses. If you see this, the vacuum is intact. If it is milky white or red, the tube has lost its vacuum and is dead-dead. 2. Use an ohmmeter to test for filament continuity. The nice thing about tubes (aside from their cheery glow) is that you can see inside (at least for the ones with a glass envelope) and locate the filament connections by tracing from the pins - it will be the whitish fine wire in the center of each of the tube sections. (The filament is almost always pins 3 & 4 on a 7 pin tube, 4 & 5 on a 9 pin tube, and 2 & 7 on an 8 pin tube.) 3. You can check for inter-element shorts (but not at normal operating conditions) with a VOM or DMM. For glass tubes, even without a tube manual, you should be able to deduce which elements are supposed to be isolated by visual examination. Now, just jump into your time machine, back about 20-30 years should do it (remember?) when every corner drugstore and TV repair shop had a tube tester. There is, of course a good chance that your local TV repair shop still has one (if they can find it under an inch layer of dust) and it may even work. Capacitors and resistors: If you just dug this thing out of the attic, it is very likely that electrolytic capacitors have dried up and paper capacitors have turned leaky. Professional restorers will often install modern replacements for all of these capacitors without even testing the old ones. To maintain the authenticity of the vintage equipment, they may actually remove the guts of the old capacitors and mount the new ones (which are much smaller anyhow) inside the original cans. Old carbon resistors can absorb moisture and change value. If your measurements do not agree with their marked rating based on their tolerance, consider replacements. However, if within, say, 20 %, for now, leave them alone. Sockets, switches, and controls: Vacuum and/or use a small paintbrush to remove dust, spider webs, dead insects (and anything larger). Use contact cleaner on all the tube sockets and selector switches. Use control cleaner on all the potentiometers and reostats. Apply a drop of oil to any variable capacitor bearings and mechanical dial pointers. Testing (use an isolation transformer with AC-DC line connected sets): Much of this old equipment had schematic diagrams pasted to the cover - really handy if the paper hasn't totally disintegrated. Turn on the power but be prepared to pull the plug in a hurry if, for example, a capacitor should decide to blow up (this shouldn't be a problem if you replaced them all unless some electrolytics are in backwards). It is probably best to use a Variac to increase the voltage gradually. In fact, this will help to 'reform' old electrolytic capacitors that have developed excessive leakage. However, by 'gradually', we may be talking hours or days to reform capacitors! I would still recommend replacement even if this appears to work. Do the filaments light up? If your equipment has a power transformer, the filaments are probably wired in parallel, so if one tube is out, that tube is bad (or its socket). If they are all out, then the power transformer or AC line input is bad. If it is an AC-DC set like a table radio, then the tube filaments are wired in series. If one is bad, they will all be out. Get out your ohmmeter, pull each tube, and check it for filament continuity. Assuming the filaments check out - all sections glowing (for metal tubes, feel the case for warmth after a few minutes though this won't guarantee that all sections are alive) when power is applied: WARNING: It is possible for metal cased tubes to develop a short between one of the high voltage electrodes like the plate and the metal case. Test with a voltmeter before grabbing one of these and keep that other hand in your back pocket! Check for DC voltages out of the power supply. There will be big filter capacitors - check across those. Watch out: we are talking several hundred volts and BIG capacitors - ouch. With no signal, check plate voltages on the various stages - there should something. If you measure 0, then a plate resistor or coil could be open or the tube may be shorted. The rest is just basic troubleshooting. Think of the vacuum tubes as oversize high voltage depletion mode FETs (field effect tubes, why not?). This is not much different than modern equipment except for the bites the relatively high voltages can take out of your hide.
(From: Carl Ratner (firstname.lastname@example.org)). A good place to post problems is rec.antiques.radio+phono. There are often discussions there about fixing vintage electronic gear. Many long books have been written about fixing old radios! If you don't want to do a lot of reading and learn a lot of theory, here are some practical tips: First, give the radio a thorough physical inspection with the power disconnected. Use your eyes and your nose. Look carefully for broken or disconnected wires, charred components, damaged insulation, etc. If you see wax dripping from a transformer or if it smells burnt, there has been an overload of some sort that will need to be identified. If the set has an internal antenna, make sure that it is connected. If an external antenna is required, connect a long piece of insulated wire, say 15 feet, and lay it on the floor. Old sets will play very weakly or not at all if the antenna is missing. Always replace the power cord if it is deteriorated. In radios of 1930s vintage, it's very likely that all wax paper capacitors, as well as the electrolytic capacitors, are bad. First thing to do is replace all the wax paper ones with modern mylar types. If you have the tall metal can electrolytics, you can put modern ones under the chassis (the new ones are tiny). However, you must disconnect the old ones from the circuit... don't bridge the new ones across the old. Be sure to observe polarity of electrolytics. You may leave the old cans in place to retain original appearance. BTW, the old square mica capacitors seldom need to be replaced unless the cases are cracked open of they have other obvious damage. Even if some of the old wax paper capacitors are still good, they are likely to fail within a few days if you start using the set. I've restored hundreds of old radios and have learned this from experience. Get them all out of there and save yourself a lot of trouble. You should also check the value of all the carbon resistors in the set. They tend to go high or open with age. Replace the bad ones with modern equivalents (same resistance and wattage). You may have to disconnect one side of a resistor when testing it, as the associated circuitry can cause a low reading. However, if a resistor reads way too high, you don't have to bother disconnecting it for testing as it is definitely bad. Your set should start playing quite well after you change all the capacitors and possibly some resistors. You noted that you had changed the tubes, and I'll assume that all the replacements are good. Tubes don't fail nearly as often as people would expect, however, and it's possible that the set's original tubes were OK. Once you get the set working, you can substitute the old tubes one at a time to see if the set continues to play. Then just keep the good ones as spares. Set still dead? If you have a multimeter, check the B+ voltage. The audio output tube's plate connection is a good place to do this. This can be 250-350 hundred volts in a transformer set, so work with care. If B+ is absent or some very low value, you have a problem in the power supply. (If you tell me the tube numbers in your set, I can give you some of the pinouts for testing) If the rectifier tube is known to be good, and you have already changed the electrolytics, then you may have a bad power transformer (large black box, usually near a back corner of the chassis. These are hard to find nowadays and very costly. I'm assuming here that you don't have a B+ short somewhere else in the radio. You will know about that because something will be smoking if such a short exists! There are other components that can fail. Inspect the speaker for physical damage. You can test the voice coil and field coil for continuity. Replace if open. A modern permanent magnet speaker can be substituted for an old field coil speaker, but a power resistor of abut 1500 ohms, 20 watts must be added to replace the field coil. Dirty volume controls and band switches can cause noisy, weak or intermittent sound too. Clean them with a good spray cleaner such as Deoxit D5. Avoid the "tuner cleaner" that is sold at Radio Shack. It is worthless for fixing old radios. As a final step, your set may need an alignment. This consists of adjusting all the tuned circuits to factory specifications to obtain the best possible performance from your set. You need a signal generator and an output meter to do this properly. It is strongly recommended that you do not twiddle any screwdriver adjustments on the IF transformer cans or elsewhere in the set unless you know exactly what you are doing. Misadjustment will cause the set to play very poorly or not at all. End of short course in fixing old radios. (From: R.G. Keen (email@example.com)). 1. Use a battery or ohmmeter to verify that the speaker clicks when electricity hits it. 2. Disconnect the output transformer primary and use the battery on the primary to verify that it makes the speaker click, albeit faintly. 3. Power the amp. verify that the plate(s) on the output tube(s) are sitting slightly below B+, and that cathode is near ground, grid more negative than cathode. 4. Touch a probe to the grid of the output tube, listen for a click in the speaker. No click means that the output tube or it's surrounding circuitry is bad. 5. Assuming that (4) worked, go one tube back up the signal chain at a time, touching grids and listening for clicks. When the clicks stop, that tube or the circuitry around it is bad. 6. When you find the bad one(s), measure all the resistors and check the capacitors for leakage. Measure the tube pin voltages for plate high, cathode low and grid less than cathode. sub in a new tube. 7. It could be an open volume or tone pot between stages. Also a bad solder joint. remelt and touch with a bit of rosin core solder every joint in the bad stage. (From: John Mitchell (firstname.lastname@example.org)). Get a hold of the "The Amp Book" (or something like that) by Aspen Pittman. It's stuffed full of dozens and dozens of tube amp schematics plus other info on mods servicing etc.Go to [Next] segment
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