Introduction: Intro to Cassette Recorder Operation, Maintenance, and Repair
As somebody who lived through the cassette tape era, to see it come around again is interesting and nostalgic. I see lots of groups all over the web dedicated to tape and tape machines but still there's plenty of basic questions that go unanswered.
In this instructable I hope to take you from zero to hero when it comes to cassette deck terminology, machine operation, and basic maintenance and repair. Some of the things we discuss involve opening the machine and maybe even operating the machine with the cover off. You can get shocked if you're not careful. Use your judgement. On any machine that plugs into a wall outlet you can have unguarded mains voltage exposed inside the cabinet. Please be careful and seek help from a trained person if you feel you're in over your head.
What you'll need..
This all depends on what you want to accomplish but I assure you it's all basic stuff. All tape machines require frequent cleaning if used often. For this you'll need Q-tips or similar and head cleaning fluid. What's head cleaning fluid? I'll explain that in the head cleaning part of the instructable. Additionally, Windex or similar and isopropyl alcohol should be part of your toolkit.
For more involved stuff like belt changes or lubing a motor for example you should have a set of good quality basic hand tools (screwdrivers, small pliers, dental pick at minimum), light machine oil, and patience.
The last tool you'll need is a digital camera with good resolution. Nothing beats having pictures to refer back to as you work on something. Your phone is fine for this.
Step 1: Transport Controls, What Tells the Tape to Move
So our first stop will be talking about the controls for the transport. The transport is the mechanism that physically handles the movement of the tape. It's what winds the tape in one direction or the other and what engages the heads for playback and recording. Transport controls can be roughly grouped into two categories, mechanical and electronic.
Mechanical controls actuate rods, levers, and gears and cause the mechanism to do what you requested. The most common of these is the piano key style as seen in pics 1 and 2. Piano key controls are very common on decks from the 60's up until the 80's. You push down on a lever that makes part of the internal mechanism move. Similar mechanisms, though not as exposed, were used in almost every "shoe box" (pic 1) style portable cassette recorder.
Pics 3-8 show some other types of transport controls found on portables. Instead of a lever you push down upon you have a rocker mechanism or a button. Not pictured is the style found on the first cassette recorder which is a lever that moves side to side. There were also some machines that used a knob you turned to do different functions. All are still mechanical in operation. As long as you don't force the mechanism or try to get it to do two things at once, they are fairly robust and rarely require repair.
Pics 9-10 show examples of the controls to an electronically controlled transport. In these, you push a button that is actually a switch which causes a very basic computer system in the deck to actuate a solenoid that engages whatever function you requested. Keep in mind when I say basic computer, I mean the lowest Arduino can run marathons around it!
What's the benefit to the electronically controlled transport? It protects itself from users trying to cycle it too fast or jam it into two modes at once. It also allows for some basic automation. Looking closely at pics 9-10 one deck has an "auto space" function and the other a "search" function. Auto Space automatically inserts a certain amount of blank space at the end of a recording and then stops the deck. Search function is just that, it fast forwards looking for music, when it finds it, it stops, rewinds a touch, then plays. These automations are possible with an electronically controlled transport. Remote control didn't become economically viable until electronically controlled transports came around.
On some decks you may see the term CUE/REVIEW. This allows you to listen to the audio as you are fast forwarding or rewinding. While it makes finding music on a tape easier, it does shorten the life of the heads (part that reads the tape) if used extensively.
One final type of transport control to mention that lies partially between mechanical and electronic, power assisted mechanical. There was an interim time where manufacturers wanted something different but didn't want to spend the money on a still expensive fully electronic transport. They came up with a mechanical transport that uses the tape deck's motor to fully engage a button for you. You still have a mechanical button but when you push it, the mechanism kicks in and greatly lessens the force necessary to activate the function. These decks while novel are very prone to jamming once the belt goes slack. The user hits a button, the mechanism kicks in, the belt starts to slip, and that's it... stuck deck. Easy to fix by opening the deck and turning mechanism by hand but many end up with ripped off doors from angry users trying to extract their tapes.
Step 2: Transport Parts - Belts, Sensors, Motors and Other Bits
Belts.. The bane of the cassette enthusiasts world!
Why belts? Belts allow the transfer of force from the motor to the other parts of the mechanism. The electric motors used in cassette decks don't run 100% smooth, They kind of micro-nudge along and this nudging must be smoothed out. The smoothing out is done by the elasticity of the belt which provides mechanical isolation and by a flywheel. With the exception of one esoteric Eumig brand deck, all cassette decks have flywheels.
In pic 1 you see the inside of a lowly GE shoe box recorder. It's basic operation isn't much different than that of a high end home audio deck. You mash a button, it engages the mechanism, the motor turns on, things happen. This machine has a single motor transport. One motor does it all. This setup is common to entry level machines. One motor can do it all but its not ideal as there's more variables to control AND keep the motor speed from fluctuating.
In that pic you see a whitish plastic pulley on the left, that's the motor pulley. As you follow the belt around, it rides past a large metal pulley, that's the flywheel which drives the capstan. What's a capstan? I'll explain that when we get into the part of the deck the cassette goes into. Finally on the belt's route is a black plastic pulley. That one drives the hubs. The hubs are what moves the tape along in FFWD or REW. This setup is very common on portables and low end home decks.
Pics 2-3 show the transport of a Harmon Kardon home deck. Not a cheap deck but they used a single motor to do everything, obviously done to please the accountants. The deck still achieves very good specs by using a very heavy flywheel and large motor.
In pic 2, right below the number 12 on the motor, you see a small hole. This is a speed adjustment port. A small flathead or philips (depending on motor) inserted there can be used to adjust speed. Not all cassette deck motors have this but a great many do. The screwdriver should have its shaft insulated as some motors have the part in the motor you adjust inside at one electrical potential and the case at another. This is not a fix for a slack belt. This is not a fix for a dragging transport that needs to be cleaned and lubed. This is intended to be used with a speed adjustment tape and a frequency counter. You play a tape that has a tone on it that was recorded on calibrated equipment. The output of the machine you are working on is connected to a frequency counter and the motor speed is adjusted until the correct frequency shows on the counter.
On older top loaders, it's not uncommon to find a large AC motor instead of a small DC can motor. Decks with those large AC motors don't have speed adjustments. If the deck is playing slow, the belt is slipping or the mechanism is dragging and needs to be cleaned and lubed.
Higher end decks can have multiple motors dedicated to specific functions.
In pic 4 you see a belt going to a wheel shaped part. This is the auto stop sensor. The auto stop mechanism does just what the name implies, it automatically stops the machine at the end of the tape. This can be only in play mode as found in very old or basic decks or can be in any mode in which there is tape movement. This is done to lessen wear on the machine when it's left unattended. Auto stop can be achieved two ways, monitor tape movement or a physical lever against the tape that trips when there's too much tension.
The mechanical system uses a plastic finger that reaches into the cassette right next to where the heads go in to read the tape. The finger rides on the tape. When the tape reaches it's end, the mechanism pulls it tight, this puts tension on the lever causing it to trip the auto stop.
The electronic system uses a hall effect sensor or an optical sensor. If the tape is moving, the sensor wheel is turning, the circuit that monitors it says all is well. Once you hit the end of the tape, the counter stops moving, the sensor wheel quits turning, the auto stop sensor detects no pulses and it stops the machine.
It's not uncommon to find the electronic sensor system tied to the tape counter mechanism as is done in pic 4. It doesn't have to be implemented this way but you will see this. The belt that drives the counter is important but not speed critical. In a bind? a rubber band will work for a while.
On either type of auto stop setup, it may be possible to engage play without a tape. This is not a flaw. This makes it easier to clean the capstan and pinch roller. Remember the auto stop is really for detecting the tape is at its end and mechanism is binding up.
Some higher end decks will use sensors to detect how many times the hubs have turned to try to give you an actual time left on a tape versus just a counter that has no relation to time. This is built into the transport and not typically accessed for basic repairs or maintenance.
Not all cassette decks have auto stop. Some of the very early machines didn't have it and it took a while for the low budget machines to implement it. How do you know if your machine has it? On many machines it will clearly say it somewhere near the transport controls. Another way to check is put a tape in that's already rewound and hit the REW button. It should try to rewind and then give up and stop. On some early machines you had auto stop only on play mode. This means when the tape hit the end, the machine would stop but only when in play mode. If it was in FFWD or REW the motor would keep running and a felt clutch under the hub would just slip. Best bet is don't leave the machine running unattended until you verify that your machine has auto stop and it works.
"My deck says auto reverse. What does that mean?"
Auto reverse means the machine is capable of playing both sides of a tape without you having to flip it over. There were some really interesting ways of doing this were some machines actually flipped the tape over. These machines are cool to watch but rare finds. The great majority of auto reverse decks simply change the direction of play and flip the heads around on a rotating mechanism inside the deck. This is by far the most common way its handled. On some home decks, most portables, and car stereos the way they handle playing both sides is the head (part that reads the tape) is setup to read all 4 tracks at once so it's just a matter of changing tape direction and electronically selecting what tracks to listen to. A standard stereo cassette has 4 tracks, 2 per side.
Step 3: How to Tell If a Belt Is Bad & Replacement
How do I know a belt is bad? On a working machine, warbly play, random stopping, incomplete FFWD or REW operations can indicate bad belts. On a non working machine that powers on and things all look normal but nothing happens when buttons are pushed, it can be a bad belt.
"Can I replace the belts myself?"
Maybe. How good are you with mechanisms and how intricate is the machine you are working on? The GE in the picture is a cakewalk. A few screws and your in. Some other machines may require extensive disassembly and the skills of a watchmaker to get everything back together. That's beyond the scope of this instructable but there's only one way to learn and it's by doing. Please keep in mind that even if broken, some cassette decks can be worth hundreds, a few past the thousand dollar mark. Research what you got before using it as a Guinea pig to learn on.
"Where do you buy belts?"
There are a few sources online that sell tape recorder belt kits. The better kits will include some instructions and have all the belts you need in the correct sizes. This is the safest way to get the job done without error but also the most expensive. There are vendors selling belt lots. This can save you a bunch of coin but now you need to be able to properly size the replacement belt (comes with experience) and the quality of those belt lots varies drastically.
"Can I use rubber bands?"
Yes, and the machine will perform horribly. Rubber bands are too springy. Proper tape machine belts have very little give when it comes to being stretched. Give translates into warbly audio due to inconsistent speed. In a bind rubber bands can be used for non critical things like the counter but they don't last very long.
THIS IS GONNA GET DIRTY... you've been warned!
Old tape deck belts can fail in three ways, stretch, melt, or dry rot.
Melt and dry rot are easy to check for. Open the deck up and look at the belt that goes around the flywheel and around the motor. Is the belt present or did it turn into a mess of black goo? DO NOT TOUCH the black goo. It gets on everything and ruins clothes. It's like tar. Magic melting belts are to be expected in old cassette decks. If the belt melted long ago and wasn't disturbed, you may actually luck out and it's gone into a dried out hardened state which is much easier to clean up. Either way, this can be cleaned up and fixed. Got some on you? Ammonia based window cleaners dissolve it and make cleanup easier.
What if the belt is present, not melted, and looks okay? Here's how you check for stretch. Let's go back to the pic of the old GE shoebox recorder for a second. The big metal wheel is the flywheel that's attached to the capstan. The main belt, and possibly the only belt on some machines, runs around that flywheel and onto the motor. With the deck opened up, power it up and hit play. If it won't stay in play, try putting a cassette in you don't care if you loose just to keep the auto stop mechanism happy. A good belt will have grip on the motor pulley. To determine if the belt is still good simply put the machine into play mode and with your finger, stop the flywheel from turning. When the flywheel stops, the motor should stall. If the motor does not come to a complete stop, you have a stretched or worn belt. Don't do this for more than a second or so, it's hard on the motor.
Tape decks can have more than one belt or a combination of belts, gears, and tiny rubber tires to handle the shuffling of the tape. Always replace all the belts when servicing a deck due to a bad belt. Remember, they are all the same age so all are degrading together.
"I've got black goo all over the inside the mechanism, now what?"
Q-tips and Windex or similar ammonia based glass cleaner to the rescue. Pour some Windex into a disposable shot glass or something similar sized, dip the Q-tip in Windex, start cleaning. Windex dissolves the melted belt goo. You will go through MANY Q-tips. Anything that goo gets on, it sticks to. It's vile stuff. Don't stop till it's all cleaned up. Make sure the V groove in the pulleys is COMPLETELY free of black goo. Leaving any in there will accelerate the failure of the new belt and drag down the mechanism speed.
If the machine uses small rubber ringed wheels for part of it's operation, clean those as well. This can be challenging as some will be well hidden but with patience you can clean, move it a little, clean, etc. clean both the rubber tire surface and the surface it rides on.
Step 4: Let's Look at the Parts Inside the Tape Well - Hubs, Pinch Roller and Capstan
In pic 1-4 you see the inside of the tape well on 3 different cassette decks and a microcassette deck (note similarities). The tape well is where you insert the cassette into the machine. This can be via a slot in the door were you load the tape and it aligns it for you as you shut the door or it can be like what's used in some portables where you lay the tape into the mechanism. Regardless of who made the machine, The all have the parts we are going to talk about.
Let's concentrate on pic 1. In the center you see two black nubs with ridges. Those are the hubs. They drive the tape back and forth for FFWD and REW along with taking up the slack as you play a tape. Got a machine that "eats" tapes? Often times it's the take up hub slipping and not spooling the played tape up fast enough to keep it from being knotted up in the machine. You can catch this by watching it as it plays. What causes that? Slipping belts or glazed idler wheels is a common fault. A binding tape can also cause that. Really low end machines that don't have rewind will have only 1 hub and a peg where the other hub would be.
On the rear left of pic 1 you see a vertical metal shaft with a rubber tire behind it. The is the capstan and the pinch roller. These two are responsible for maintaining consistent play back speed. When you insert a tape into a cassette deck, the shell is designed so the tape media threads between the capstan (vertical metal shaft) and the pinch roller (rubber tire). When you hit play, the mechanism mashes the pinch roller against the capstan shaft, pinching the tape in a tight grip, thus being able to control it's speed as it plays. Remember that flywheel on the backside of the mechanism we discussed? That flywheel is attached to the capstan shaft.
What can go wrong here? The biggest fail here is lack of maintenance. Not cleaning old residue from countless hours of tape builds up. Tapes shed oxide. Older tapes and low quality tapes tend to shed the most. They leave a rust looking residue on the pinch roller, capstan, and the heads (we'll talk more about those soon). As the residue builds up, it doesn't happen evenly. At first it just affects the sound, making good tapes sound dull. As the residue gets real bad, it can actually cause the machine to eat tapes by forcing the tape out of alignment. Pic 2 shows what a well used but clean roller should look like. Aside from possible physical damage caused by an angered user, these parts are fairly robust. The rollers on some very old machines can harden causing problems. The only fix is to find a donor machine with a similar sized roller and replace it. Maintenance wise cleaning these parts is all that's usually needed and a tiny amount of oil applied with a toothpick where the capstan shaft enters the mechanism. This is to oil that bearing. Clean off excess with a Q-tip.
pic 3 is the well of an autoreverse machine. Note it has 2 capstans and 2 rollers. This is because the pinch roller that is engaged is always after the head. When the tape direction changes, the roller on one side disengages and the roller of the other side engages. The capstans on autoreverse machines turn opposite directions. The motor doesn't reverse, the mechanism handles direction change.
The exception to this rule (isn't there always?). High quality machines may be labeled as being "closed loop". This means it has two capstans and two rollers that both engage simultaneously, turning the same direction, to keep precise tension on the tape as it goes across the heads. No matter, clean them BOTH.
So what do you clean these with? The CORRECT answer is Q-tips or similar, head cleaning liquid on the capstan shaft, and pinch roller cleaner on the roller. What have I been using since the 80's and never had a failure? Q-tips and rubbing alcohol. I can hear the cries of blasphemy as I type... Never had a failure and always been able to produce top notch tapes from my decks. Some folks use 80-90% isopropyl alcohol. I've had zero issues with regular drug store rubbing alcohol on both roller and heads. I own over 100 machines and welcome anyone to come do forensics on them. The concern with rubbing alcohol is it can leave a residue. There's also been concern of drying out the rollers. Ok, once your down cleaning, give everything a once over with a clean dry Q-tip and rock on. I have yet to have issues on everything from Naks, to Sony's.
An added little bonus, literally. The last picture is the tape well inside a microcassette deck. Notice the same stuff, placed a little differently. It does the same, it's cleaned the same.
Step 5: Let's Look at the Parts Inside the Tape Well - Heads
The heads are what erases, records, and reads (plays) the tape. These are the most critical part of any tape player and they cannot be repaired, only replaced on cassette decks. On reel to reel machines they can sometimes be resurfaced (lapped) but not so on cassette decks. Once wore out, they must be replaced or the machine is junk.
Cassette decks can have 1,2,3 or even 4 heads. Lets cover the most common which are the 1 and 2 head machines.
On a 1 head machine, you only have the ability to play tapes. You cannot record. Think Walkman (portable) units, kids players, and boomboxes that have one well for play and one well for play/record. Pic 1 is the tape well in a portable. The head is the silver thing in the middle. It's what reads the tape.
In pics 2-5 you see inside the well of a standard, non auto reverse, 2 head machine. The head in the center is now a play/record head. It does double duty. This is by far the most common setup.
In pic 2 you see a good shot of the layout of a 2 head machine. From left to right, erase head, play/record head, and capstan/pinch roller. The erase head does just as the name implies, it erases the tape and gets it ready to be recorded on. On really cheap machines, they replace that part with a tiny permanent magnet on a swing arm. That setup is bottom of the barrel and only found on very low end machines. You want a machine with a proper erase head.
Pics 3-4 show you two focused close ups. pic 3 is the erase head, pic 4 is the play/record head.
Pic 6 shows you an autoreverse 2 head setup. The erase and play/record head are sandwiched and rotate together depending which way the tape is playing.
So what about these 3 and 4 head machines I mentioned? A 3 head machine has an erase, record, and play head. Top of the line machines are setup this way. In an ideal world, the head used for recording is engineered differently than one used for playing. To extract the absolute best out of a tape, 3 or 4 head machines are the way to go. These machines are also capable of letting you hear your recording as it's being made so you can do some test recordings and tweak on the fly.
What's a 4 head machine? Its a three head in an auto reverse setup. The record and play heads are sandwiched together in the center and rotate, on either side you have a very thin erase head that energized as needed. These machines are rare. Standard 3 head is the way to go.
In pic 5 you see a real clean shot of the inside of a 2 head well. Notice the top of the record/play head. See the reflection on it? Notice the reflection clues you into the fact that surface is perfectly even, no dips or gouges. That's what you want when buying a used deck regardless of head count. The roller is also perfect with no cracks. The capstan shaft has a weird reflection from the light I used so ignore that.
Playing a tape is basically rubbing a rust coated plastic strip across a tiny electromagnet coil. Since there is friction, the head wears over time. Cheap or really old (dull looking) tapes make it worse. The wear is never even. As the head wears, the contact pattern of the tape on the head becomes uneven. This causes high frequencies to suffer. In really worn out machines, even good tapes can sound like someone threw a towel over the speakers.
In pic 7 you see the door taken off a home deck. A great many home machines have removeable doors. You gently lift up and towards you and it pops off. Not all have this but most all mid to high end decks do. This makes it easier to get in there and clean things.
In pic 8 you see an oddball. There were some decks made that the tape went flat into a slide out drawer. Some of those machines had a little access door up top you pop open and can access the heads and pinch roller for cleaning. The ones that don't have that may require removing the top cover for proper cleaning. There are head cleaning tapes but nothing beats a proper cleaning.
What to clean the heads with? Proper way is Q-tips and head cleaning fluid (pic 9). Like I mentioned before, I've been using pharmacy rubbing alcohol for decades and NEVER had an issue.
Step 6: Connecting to a Home Deck to Make a Recording
I see this question pop up lot on forums quite a bit.. "How do I connect my ipod/phone/pc to my deck so I can record?" Ok, here goes!
On the back of all component (stand alone) type tape decks you will find IN and OUT jacks. These may be labelled PLAY (out) and RECORD (in). In the USA it's common to see RCA jacks as in pic 1. In Europe you may see DIN style connectors that perform the same task. On some but not all decks you may see MIC inputs for left and right as shown in pic 2.
You will be using the line level in, the jacks on the back marked IN, INPUT, or RECORD. Same function, three different ways to name it. What can you connect there? Your ipod, phone, PC, a cd player, or any other LINE LEVEL source. In order to connect an ipod, PC, or phone, you will need a cable that plugs into your player and has a pair of RCA plugs on the other end. Typically it's a red and white one. Red is for the right if you care to keep the music exactly as it was meant to be heard as far as where the musicians/instruments are in the sound field.
The MIC jacks are for microphones and will sound horrible if you try to feed a music player into there. It overloads them and you'll get distortion.
Once you have the right cable, pick the loudest song you'll be recording and we'll setup for that.
Power up the deck, pop in a blank tape, hit record. Some decks require you hit play and record together. Once the tape is moving, turn the record level adjustment up halfway. Some decks have a single control for level, some have separate knobs, some have two knobs that turn together. You want both left and right meters roughly the same. Next, hit play on your source of music and slowly bring it's volume up till you see the meters just barely peaking past the zero mark. All setup, stop the tape, don't touch any levels, rewind the tape, get your playlist cued up on your player, hit record and play on as needed on the deck to get it going with record indicator on, count to 5, hit play on your source. The meters should start moving and you're making a tape!
You now have the basics and are laying down your first tape!
Now to answer a bunch of questions..
1) Why count to 5? All blank tapes intended for music have a leader, a piece of clear tape at the beginning and end. This leader is 5 seconds long and you can't record on it.
2) My deck has no record level control or meters, what do I do? Trial and error unfortunately. Make a test recording starting with volume on player at max and drop down in increments keeping track of how much you dropped each time. Play back the tape you made and see what produced the best sound. Continue using that setting until you get a better recorder with record level adjustment.
3) What's the difference between old style needle in pic 2 (analog) meters and decks with digital meters like pic 3? Functionally the same. They still have the same scale. Analog meters are slightly slower to show fast peaks.
4) My deck is a 3 head and has a tape monitor switch. 3 and 4 head decks allow you to listen to a recording as its being made. You may hear a slight echo in the background when monitoring the recording that was just made.
5) Can I record louder? Yes, by all means but different brands and formulations will react differently to louder levels. Some can take +3 or +6 without issue. To keep it safe and assure you success until you learn your machine/tape limitations, stay under the +3. What happens if it's too loud? Fuzzy distortion.
Step 7: Advanced Recording
Here's some advanced recording info to help you as you delve further into cassette.
Dolby noise reduction - Dolby reduces the hiss that's inherent to all tape recordings. If hiss doesn't bother you, don't bother using it. If hiss is an issue, here's the breakdown of the different Dolby technologies found throughout the history of cassette decks. They all basically compress the signal on record and then expand it back on playback in effect, lowering the noise floor.
Dolby B - The oldest form of noise reduction. Dolby B tapes can be played back on any machine with or without Dolby. The effect of playing back a Dolby B encoded tape on a player without it will seem like boosted highs. This is sometimes welcomed by tapers making tapes to use on portables and such that don't have the performance of a fullsize home deck.
Dolby C - This format works on both highs and mids. Tapes recorded with C sound pretty awful on machines that can't decode it. The mids will be weird.
Dolby S - This was cassette tapes last hurrah. Superior to all other Dolby formats for cassette but not may machines had it. By this time recordable CD was affordable.
Dolby HX Pro - This is a record only process compatible with all machines. It varies the bias (beyond the scope of this instructable) allowing for hotter audio peaks without distortion. If you listen closely, an attentive listener may pickup on the fact it sacrifices lows in order to keep highs from distorting on peaks. Think of it as a parachute to keep you from wrecking a recording if there's some loud passages you didn't account for when you set levels. You want a deck with this feature. Pic 1 shows a deck that has a similar but non-Dolby feature called Dynamics Detection.
Dolby look-a-likes - There were some noise reduction systems out there that worked similar to Dolby. JVC for example pushed ANRS and Super ANRS for a while. It didn't catch on and even they gave up and added Dolby to their decks.
Decks with Auto Calibration pic 2 - This is another great feature to have, like HX Pro. You'll need to find the manual to your machine if it has it so you can read how it works on your particular machine. What this does is it puts the machine into an automatic mode that records a series of tones at different settings on the tape. It then rewinds and plays back the tones listening to them to find the best setting for your particular blank tape. Once complete, the machine rewinds and is ready to record having calibrated its internal settings as best it can to match the chemistry of your tape. You still set record levels and everything else operates as normal. The process is only good till you power the machine off or eject the tape. It clears out the settings once that happens. Since all manufacture's tapes are slightly different, this process helps you squeeze the most performance from the tape. Some machines have a feature like this but it's manual and uses an indicator on the display you line up. This is not a common feature.
Bias settings - Generally speaking, decks from the silver face era and older will require you to set some controls on the front of the machine marked "bias" to the correct setting. Your blank tape should be marked normal, high bias, or metal. Set the switches accordingly for proper sounding recordings. By the time everybody quit making silver faced gear and it was all black, those machines had auto sensing switches that detected the bias notches on the tape and set themselves. There are exceptions to this of course. If you see switches for bias and they say 120uS or 70uS, they need to be set according to what tape you use. Setting it wrong won't break anything, you'll just get a lousy recording.
Tech bonus - On older machines, pretty much all machines from the top loader and the silver face era, there will be a mechanical switch that switches internal circuits from record to play. Got a machine with a dead channel or one that goes bonkers pegging the meters and buzzing when put into record no matter what you do? Try cleaning the internal record / play switch. In pic 3 you see the inside of an older drawer style deck from the silver face era. In the center bottom of the pic are two silver vertical assemblies that are long. Those are the record / Play switches. Pop a recordable tape in the machine (you're not going to record on it and machine should be unplugged) Bathe them in electrical contact cleaner (available at auto parts stores) while mashing the record button, hitting stop, hitting record, hitting stop. You're looking to actuate that switch, repeatedly. You'll see one of the ends have a plastic piece that moves maybe 1/4" or so when actuated. Not all machines have two, some have one. This feature was replaced by chips towards the late 1980's so "newer" machines don't have these.
Got scratchy controls or controls that act up? Same drill, bathe the circuit board side of the switch or control with contact cleaner, cycle the switches or turn the knobs back and forth. They should clear up. These are common problems with old audio gear. Too many stereos get tossed to the curb just because of noisy controls.
Do this outdoors. The fumes from this stuff is strong. Don't forget to let the contact cleaner dry out thoroughly before plugging gear in.
Step 8: Beware! - Collecting Decks Gets Addicting
There's three of mine of repaired. New belts, thorough tape path cleaning and they sing once again. I hope this instructable helped you get an old machine up and running again. Don't be afraid to dig in and try. People that can perform even basic cassette deck repairs are getting hard to come by. Not every deck has succumbed to a major failure. You'd be surprised how many come back to life with these simple tips I posted here.
If you want to learn more about the tapes themselves please check out my Cassette Tape 1101 instructable. More than you'd ever want to know about cassette tapes.
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