3M Cantata 700 Player - Part 2
Where in part 1 I took the entire device apart and cleaned it for the most part, here we continue with the actual repair of the device.
Do you recognize a Cantata 700 in it?
March 16, 2022
A day before the expected delivery date, the doorbell rings, the package with capacitors has arrived!
In the box a number of bags with caps together with the order forms, first I check whether the order is complete and correct. After confirmation I can almost start replacing but I was already prepared for a new problem that would arise.
The new capacitors are not only smaller than the old ones, but the problem is in the length of the feet. These are not long enough and will not reach the soldering points without a modification. I'm still going to work and in the meantime come up with a solution for this problem.
As mentioned on the previous page, I don't have much room to turn the circuit board. There are many short wires attached to it that hinder the freedom of movement of the print. Fortunately, a few are stuck with clamps. They're also numbered, so with this in mind I'm disconnecting the wires, including those from the speaker and one from a potentiometer that has a gear mounted on it. This gives me enough space to work on the circuit board.
I have to admit, I've messed around with printed circuit boards before, but I've never replaced capacitors before. So I also consult the internet in advance for information. My method may therefore deviate from what is recommended. However, I will do my best to follow the guidelines.
A few lessons beforehand, a 'standard' capacitor is officially called an Electrolytic Capacitor, in this case in full: Aluminum Electrolytic Capacitor. The name is not important now, but what does count with this type of capacitor is the polarity (ie the + and - sides of the capacitor). current can only flow in one direction, if you connect the capacitor incorrectly it would not work or worse damage the capacitor.
To indicate the polarity you can look at two things. The length of the feet and otherwise the inscription of the capacitor itself. The short foot is the - side and the long the + side. There is also a - symbol on the electrolytic capacitor on the side of the short foot (which is not indicated on every electrolytic capacitor).
In addition, it is important that you do not bend the feet from the bottom, but leave some space. A locking pliers offer me a solution in this. There are several reasons given but the most logical I have read are that otherwise the pins can short-circuit the housing of the capacitor, on the other hand you risk damaging the seal of the capacitor if you bend the feet from the bottom. Yet again I read statements that contradict this. I take no risk and follow the first advice.
I also read some posts from others asking if a difference in voltage and farad can cause problems when replacing one capacitor for another. It is of course best to replace the old one with an electrolytic capacitor of the same values. But it may happen that these are simply not available. In that case you can assume that there is always some slack possible, the question is rather what effect this has on your equipment that is controlled by it.
To make it clear for the reader:
- Ampere (or current) is equal to the amount of energy.
- Voltage (or voltage) equals pressure.
- Ohms (or resistance) is equal to how much 'resistance' a material gives to the energy flowing through it.
- Farad (or capacity) is equal to how much an electrolytic capacitor can store in this case.
A higher voltage would generally do little harm, it is also recommended to go for a higher than a lower voltage, otherwise the electrolytic capacitor might not work at all. Of course, too high is not justified. The only problem with this is that an electrolytic capacitor with a higher voltage is also physically larger, so it must of course still fit on the printed circuit board.
As far as farad is concerned, I can give the same advice, only it is more strictly speaking here, it is advisable not to deviate too much from the original value.
I won't go into detail about the limits on how much the voltage or number of farads can deviate, otherwise I might as well write a separate page.
I'll add my sketch again. We start with the largest electrolytic capacitor (1000 μF 25V).
So my method is as follows. Although I have to deviate for this first capacitor because the feet are too short. I have now found a possible solution for this.
It doesn't deserve a beauty prize, but I didn't have any other idea so quickly. The only bad thing is that I can only see if this works when I have replaced everything and have partly reassembled the machine.
With the first electrolytic capacitor replaced I can continue on the rest. It is also worth mentioning that the old electrolytic capacitors are firmly glued to the printed circuit board. The residue that remains is not a danger and I leave it alone.
I almost forgot to mention it. There are also four 2.2μF 16V capacitors. I couldn't find any standard replacements for this, after some searching I came to the conclusion that I can also use 'Tantalum capacitors' instead of the old ones. So here are three of this type of elco. Also here I have to extend the feet.
What is the difference between Aluminum and Tantalum? I hear you say. The shape and capacity compared to its size. Otherwise, the operation differs little. Tantalum capacitors are often more expensive and mainly available in small capacities. But here too the polarity is important. The line on the housing refers to the + side. Although you have to have a good eye to see this, they are very small.
Only at this zoom level do I see how dusty the circuit board actually is. When I'm done with the caps I'll run a brush along here.
A short movie where I replace one of the electrolytic capacitors can of course not be missed.
After a while it starts to pick up speed. Initially it seems to be quite a job which is true, but luckily this is an old circuit board with plenty of room to work as well as I only have to replace fourteen caps, I would have a similar circuit board that is ten years younger I probably would have had a lot more work and a lot less space.
Eventually I also arrive at the defective capacitors, here a view of the still good side and the side that has cracked open. I don't need to explain much more. Also a photo of another electrolytic capacitor where rust has formed on the foot, this is also a bad sign and can lead to defects. I just can't figure out the cause, maybe age is just the culprit here.
Everything seems to go well until I arrive at the last capacitor, I had to extend this already small tantalum, but the leg was not so strong anymore, I still manage to wrap a wire around it, but as soon as I want to connect it to the PCB breaks off the extended piece. Because I did not order any extra replacements, I was forced to put on a new extension here. The result doesn't exactly deserve the top prize, but it works. And with this I am finally done with replacing all caps on the printed circuit board!
Here is an overview of the progress, from old to new.
The circuit board now looks fresh and fruity again after I have cleaned it. An attentive eye also sees a light burn, because the electrolytic capacitor whose foot was rusty was in this place. I saved the old one in a bag, it's quite a big difference when you look at the size of the old versus the new one, not surprising when you know that there is almost 50 years difference between them.
Before I put the circuit board back in place, I spray some contact spray on the potentiometers of the tone and volume knobs.
Only it comes out just as hard at the bottom... Fortunately contact spray can't do much harm on a simple circuit board like this one, it should dry without any problems, but check it with a cloth.
I do the same with the connections for the external speaker and microphone. After this I put a plug through it to spread the liquid, this time I put a cotton ball on the circuit board so it doesn't seep through.
Now it's time to look at the cord whose wires are visible. This one is attached to a panel that I don't know how to remove. With the four screws in the corners removed, the panel will not come loose, so I also unscrew the plug.
It all coming loose now. the panel also falls off immediately so that I can see the fuse and connection itself.
Sometimes it is interesting to see how they come up with solutions to problems, here you can determine whether you want 230 or 115 Volt control by turning the plate.
When I look at the plug itself, it is noticeable that the rightmost connection in this case is further spread out from the middle and left, presumably so that you cannot connect it the wrong way round.
Unfortunately I can't do much about the exposed part because the plug is fused together during manufacture. So I can't open it. I'll have to come up with something else on this one though. For now I'll just put it all back together.
The printed circuit board can be reassembled. First the plugs go back on.
While connecting, I discovered that you can adjust the pin of the external speaker to the correct impedance here. Handy to know if you want to connect a speaker that works at 4 Ohms.
With the PCB back in place I can continue with the mechanical part. When I turned the device upside down, a few things fell out. Including a ball bearing on which the flywheel rests. I immediately take the opportunity to clean the hole of this and smear a big dollop of grease in it.
This part had also fallen off, I will have to consult my previous photos to see how it used to be, I have come to the conclusion that this was no longer in place when I opened the device for the first time.
As you can see here, there is a small bracket on the sprocket, it should hook into a metal hook and is held in tension by a spring. I put everything back as it should have been.
Then I go through points that I think should be lubricated, this mainly concerns plastic or metal parts that rub against each other.
It's time for a first test with the power back on. Here you get a good picture of many mechanical parts in operation.
With the first test over, it is time to reassemble the top plate, but first I clean it thoroughly, this also means that the numbering I applied with marker disappears. But I can now use this first photo as a reference so it shouldn't cause any problems.
I'm going to go through some dots for inspection, here's a view of the hole through which the central axis will come later. You can remove the copper canister, but I can't do much with it. this same system is also in the hole of the capstan.
Now that the plate is not on yet, I can show this part in detail, it is the main drive from the motor to the rest of the machine, a second shaft is hidden under a hatch. I suspect that it is used for a different mains frequency (50 or 60 hertz). The axle that sits on the plate has a narrower diameter. Although the machine is now half apart, it should be possible to exchange this shaft even when the device is completely assembled, this can be explained by the hole that occurs when you unscrew the plate.
Carefully I put the plate back on the machine, you will have to guide it a bit because the many shafts that protrude do not immediately end up in the right hole.
It may be difficult to see, but not all points come across neatly, here are a number of openings where the screws will go back in later. I try to get most of them right in front of the hole but this doesn't work on all points. Once I put the screws back they will snap into place when tightened.
It is now important that the recess fits well in the back of the machine, when it is in place I can start on the screws.
Step by step I put different parts back in place. Pay close attention to the first and second photo, because here I put back the axle that was loose in the machine when I loosened the top plate. As mentioned before, this keeps the program wheel in place when it is not allowed to rotate. I also lubricate the moving parts that come into contact with each other.
The lamp also goes back into place, I just have no idea what type of lamp this is now. If it concerns a light bulb, it can be quite difficult to replace it if it breaks, but my suspicion is based on a neon lamp (as you often see in the orange switch of an extension box. A neon lamp would also be my preference because these last much longer and often do not get as hot as an incandescent lamp.
Time to grab the paper and put the screws back, as mentioned before the screw holes automatically snap into place when I tighten the screws, the machine makes a few creaks when they snap into place but it shouldn't hurt can I hope...
Step-by-step the pinch rollers and the playback head also go back into place, I still use this moment to clean everything well beforehand.
Finally, I squeeze the pin back into the central shaft, after which I slide the wooden cabinet back around the machine, and then reconnect the loudspeaker. Now it's time for the most exciting part, testing the machine!
In my enthusiasm I forgot that the mechanism is not yet attached to the housing, because of this the parts slide away from each other during use, so that the test does not run as planned. I screw the two parts together first and go for the third test with hopefully better results.
It's not quite right yet, the program system doesn't seem to work quite right when it has to turn the playback head up, but with each test it seems to be getting better, maybe everything should start up again after the extensive repair. The biggest problem remains the scraping of the spools against the housing of the cassette. The central axis still seems to cause problems here. So the device has to be disassembled again to find and solve this problem...
Nevertheless, the electrical part seems to work well so I can say with relief that the capacitor replacement was a success, although I have to replace the external speaker and still test the microphone.
March 20, 2022
We are now a few days further, I have not been sitting still in the background, after the last test I found out that I secretly still had a lot of work to make the device work optimally again. Since I have other things to do in addition to this, I have spread the work on the Cantata over the days, taking the time every day to pick up every point of interest. So here's an overview of all the peripheral work I've done.
I ended up having to disassemble and assemble the device about five times. Because I didn't want to stick the screws on paper every time, I invested in a handy container whose compartments I numbered. It has already earned its money with the Cantata alone I can tell you!
The biggest defect remains the central axis, which is not completely straight (here, by the way, an exaggerated representation). But the cause was not yet known to me. The axle is attached to a plastic wheel that was also not quite straight, so my thought assumed that the wheel was the cause.
The only remedy I could come up with was to put soft pads under the wheel in question, in the hope that it would then run more stable and the axle would stay straight. It was to no avail because the axle was still skewed and due to the friction of the pads on the wheel the speed was no longer correct, with the result that the music no longer sounded right. I then removed the pads again...
Not all cassettes lie nicely straight on the record, it might help if I apply pads here to get it nicely stable? But no, the scraping of the spools was fixed but the tape no longer came out properly at the playback head with the result that you hear two songs at the same time. So I could also remove these pads again.
After trying everything, I ran out of ideas and could only come up with one solution, straighten the shaft itself. After hours of watching and carefully bending the shaft each time and testing, the scraping of the coils became less and less. In the end, this turned out to have been the problem all along! The cassettes now play a lot better, they no longer scrape and stutter.
During playback you can hear some rattling inside, but I could only hear it when the machine was assembled and a cassette was playing. So I had to look in through the side with a flashlight and look for where the rattling was coming from. In the end it turned out to be one of the many copper rods that vibrates when the machine is on. Because it is very close to another metal part he touches it which gives a rattling sound, the remedy here was a soft pad. The rattling sound was no longer heard after that.
Sometimes the unit will not turn off when a cassette is playing. The plastic wheel with the rubber edge (red arrow) should touch the wheel of the central shaft and start spinning when the OFF button is pressed, but it did not. After looking for hours I could not find a good cause, my suspicion is that the rubber on the wheel is somewhat outdated and does not always grip well on the wheel of the central axle. Another option is the coil spring (green arrow). If I can get a little more tension on this, maybe the wheel will grip better when you want to switch off the device.
I eventually chose to do what has never helped me in the past, shorten the coil spring and re-tension it. Although I've tried this many times on other devices, the results were often disappointing, either the spring got too long or it broke so I couldn't use it anymore. In this case it didn't matter much. The metal of a spring is made to break and not to bend (high carbon content in the steel). This also happened after I tried to bend a new eyelet when I had shortened it. Still I manage to shorten the spring for an hour and for the first time I can say that shortening a coil has helped, the device now stops neatly when I press the OFF button.
At the start of the repair I was talking about loose parts in the machine, which are two plastic brackets that connect the front to the mechanical part. The only thing I could come up with on this is to put everything back together with super glue. After letting this dry well, I was able to put everything back together again. Yet it remains a simple solution because it will never become really sturdy again.
I doubted this for a while, but decided to see if I could dent the grille. The grille is firmly bent on the plastic plate and also glued. First I unscrewed the whole thing, six screws on the inside and three on the bottom before I got it off. I was able to get the grille itself off with a flat screwdriver by bending the tabs. With make-up pads and a small hammer I carefully hammered out the dents. The result is quite an improvement. There were also rubber feet on the plastic so that the grid does not vibrate against it. I replaced these with new pads, but they shine through the grid again, so I colored them black with a marker. After this the grid back and the tabs bent back together with some glue from a glue gun to hold it.
The speaker was also equipped with pads, so I also replace them with new ones.
With all these points completed, one thing remains for me, the on and off buttons are difficult to distinguish when it is dark. At first I thought there was a silver tint applied to the text and border of the buttons. But I don't see this in pictures from other devices. Nevertheless, I had already bought a jar of paint with metal color. Maybe not completely original, but I put it on anyway. The result is not that bad.
You have probably already noticed, but I managed to get my hands on two original buttons. one for the volume knob and the other for the timer. Although I had made a replacement button for this before, I still prefer the original one, so the self-made button can be used separately for another project and the original buttons still work here.
There it is finally, restored to its former glory and ready for use again.
I have tested the microphone connection and it works properly again, only I am still missing the correct connection to also test external speakers, this will have to wait a while. But for now it's time to give it a trial run. He should eventually be able to play flawlessly for hours on end. I can only test this by actually leaving it on for a few hours and staying there to keep an eye on it.
I also tested the timer and it works. The device itself continues to run, but the coils stop for the set time. When the pause time is over, the system will also restart automatically and start playing again.
However, there are still a few small points that I might pick up in the future.
When switching programs, the sound goes away. The only solution I have found so far is to press the ON button again, after which the sound comes back.
When it is on for a while and has warmed up, something inside starts to beep softly. I suspect this is a rubber wheel that starts to make noise after a while, but I don't know how best to go about this yet.
Finally, there is another problem that leads to irritation. There is radio noise from the music. This is a problem I've seen before on Walkmans made of plastic. A solution for this will follow.
With the repair done I can also finish this page, here's a last movie with different cassettes in action. I still have to repair some of the cassettes, the report can be found on this page . Thank you for reading!
March 21, 2021
March 23, 2022
"Faraday's cage" here a link to Wikipedia on this subject.
It would be the solution for the radio noise that comes with the music. But how can I apply it to the Cantata 700?
With nothing less than aluminum foil. As long as contact is made with the rest of the metal housing, the radio noise is suppressed. Now it's just a matter of applying foil and bringing it into contact with the rest.
Step by step I apply the aluminum foil to the inside of the lid. It's definitely not a view, but I'll solve that problem later. For now, this is the only option to properly suppress the radio noise.
Because the foil has to be in contact with the rest, I apply a strip of foil that runs from the aluminum to the hinges.
The result is a big difference. In time I will look to cover the foil itself so that it will no longer be visible when you have the lid open.
- 3M Cantata 700 (Information)
- 3M Cantata 700 cassette (repair)