Posted 17 April 2017 - 07:12 AM
Now the tape deck unfortunately all of a sudden has just stopped working altogether. You can hear the motor. When the radio is powered up you hear a little bit of clicking.. Then when you try to play the tape deck you just hear the tape deck motor engaging. But it won't respond when you push play pause. You just hear that motor going in the background. I wonder if it's trying to reset the cycle. Appears to me to be a mechanical problem. Not something with the fusible resistors for or belts. Maybe a plastic geer that's slipping because the teeth are getting worn down. So can anybody give assistance please? Anybody have the same problem with their M 90.
Posted 17 April 2017 - 09:41 AM
I'd change the belts first as your first port of call.
Posted 17 April 2017 - 11:54 AM
So unless the new belts are slightly the wrong size. It must be another problem. I'm getting some type of mechanical problem mixed with maybe an electrical problem or some kind of problem relating to the Autologic deck. Much more troublesome and then a regular tape deck for example on the M 70
Posted 25 April 2017 - 12:47 AM
This is of course assuming the belts are ok and correct.
Posted 25 April 2017 - 07:56 AM
Posted 25 April 2017 - 08:10 AM
Posted 25 April 2017 - 09:50 AM
Did you ever fix the broken gear that it came with?
Maybe you should fix that
Posted 25 April 2017 - 02:17 PM
Just wanted to know anyone in this group come across The same type of problems with the tape deck I'm having on my am 90. If so were you able to fix a slip in a gear or replace a plastic cog A tape deck and then solve the problem and have the deck work just as it should?
Posted 26 April 2017 - 01:57 AM
You've asked these question already several years ago and back then, you didn't seem receptive to the advice you received. However years later you ask for advice again on that same issue but you already concluded that the advice that folks have suggested to you does not apply. Interestingly, you personally can not provide specific details because only your "friend" whom you trust worked on it. So if you trust your friend who tells you that the belts are good, and I'm presuming that you've changed all 3 (if memory serves me correct), and I'm presuming that all the pulley and belt surfaces were properly degreased and cleaned, and that everything was properly lubricated (including the solenoid to ensure free movement) as well as head transport assembly, and your friend tells you that it's a gear or cog, and I can already tell you that the cog or gear is already no longer available, then what advice do you want us to give you?
Some of the symptoms you are experiencing are common with slipping belts with this model. But you conclude that the belts "can't possibly" be the issue. I've seen belts slip on this model with new belts if they are just a tad too small, or if the belt transport surfaces are glazed or slick (easy to do when handling the belts since they often come in contact with greased parts during the install). Also, during some parts of the mechanical servo action, there are significant torque humps that the motor and belts must overcome. This includes start and stop, and head actuation action. The belts assembly could work fine until it comes up to the torque hump which it might fail to overcome, in which case it may struggle.
Also, you've discounted any possibility of fusible resistor issues. HOW DO YOU KNOW? You said you aren't technical and even afraid to just remove the screws. And yet somehow you can conclude that this common issue likewise does not apply? Let me just tell you that the fusible resistors in this (and many other boomboxes) have very low values and run hot. Over time, the values change, almost certainly higher WHICH INTRODUCES RESISTANCE INTO THE CASSETTE POWER CIRCUITS. There are like 4 of them. Sometimes they fail open and in that case, certain functions won't work. However, they don't always fail open, and if the resistance is too high, then the additional resistance might be just enough to prevent the functions from working reliably. And by the way, the solenoid and even the capstan motor are protected by fusible resistors. Do you think those 2 items I just mentioned need full power in order to function properly? After all, isn't the capstan motor which spins the flywheel and provides the kinetic energy to overcome certain servo functions important?
Here's some observations. Firstly, the microcontroller does not allow more than one function to operate simultaneously. So if you press a button (say stop) and the solenoid is unable to engage, the controller continues to wait. In the meantime, no other function is allowed to be processed until the last function is successfully processed. This is why unplugging the machine is often able to reset the unit. Also upon power up, the machine always performs a reset. If it clatters during startup, it means that it is unable to complete a reset. Also the system also has a stop over-ride switch which actuates when you eject the door. This is to prevent damage to the heads if they are up when the deck is operating. If you don't believe me, just try FF or RW or Play and then press the eject button. The deck will instantly stop before ejecting the door.
Now, since YOU have the boombox, and you aren't qualified or able to work on the unit, and YOUR friend is the one who will do the work, then just go back to him. And if you can get him to work on it, then you should seriously consider asking him to to heed the following advice:
1. Check and replace belts if necessary. Just because they fit doesn't mean they don't slip.
2. Clean all belt transport surfaces and deglaze if necessary.
3. Clean all moving parts to ensure free movement, and grease or lubricate where appropriate.
4. Check that sliding levers are free and don't bind. This is very important because many functions depend upon free movement of these slide levers, even if their functions aren't immediately obvious.
5. Check and verify ALL fusible resistors with a low ohm capable meter.
6. IF you conclude that the issue is a bad cog or gear (which I don't think anyone here has ever seen), then either live with the condition or find a used replacement deck since you aren't going to find the gear from JVC.
Frankly, if you aren't capable of working on the unit, I don't understand why you keep asking for technical advice since you can't perform them anyhow. Perhaps it's better if your friend comes on here and provide details on what he did, and didn't do and how he came to certain conclusions. On this model, 95% of the issues can probably be sorted by just following those steps. And if you ask for advice again, be prepared to be asked how many ohms were those 4 fusible resistors -- because I certainly would be wanting to know.
Posted 27 April 2017 - 04:40 AM
Again thank you for all the advice. Perhaps if somebody from this group who worked on the M 90.I don't know if anyone here would be willing to look over my boombox if I sent it to them and possibly repair the problem. That would be great.
I talked to my friend pinned him down and said he wasn't really 100% sure it was a worn cog, or bad gear. So definitely could be some of those problems listed in the detailed response. I don't mean to sound unappreciative I really am appreciative of the advice people are giving. My friend mostly works tube radios turn tables from the 1940s to the 1970s. So yes he doesn't have much knowledge of two boxes. Especially the more complex nature of the M 90
Posted 27 April 2017 - 07:07 AM
Posted 27 April 2017 - 05:49 PM
Most technicians see a boombox and their reaction generally is to recommend just chuck it. They don't usually view boomboxes as serious audio gear. Like getting a Ferrari mechanic to work on or take a pinto seriously might be hard. However, the guys here have the experience to know what the common problems are, especially with well known models like this. If you are going to be asking questions, remember that someone took time to read and consider and formulate a response or suggestion for you. The only thing we ask in return is that you, in good faith, put these suggestions into practice before discounting them and ask for "more suggestions please, keep 'em coming," all the while not actually doing anything. It makes us feel like we are wasting our time. Several years ago, I seem to recall already having invested time in your threads.
In my response, I gave you some insight into how this deck works including the micro-controller. Although it sounds like it's more complicated than say an M70 deck, it's really a better design. It also has 2-motors (instead of 1 like most boomboxes) so that the reel motor functions only for spinning the reels and the capstan motor's purpose is to spin the capstan and the flywheel which provides the kinetic motion necessary to engage and disengage the heads. Separating those duties greatly simplifies the deck so that it does not rely on a single motor to perform all of the various duties which means less parts. I'm sure it's frustrating that it's not working to your satisfaction but you don't sound like you are technically capable of performing the repairs yourself, rather you like to use the product. Nothing wrong with that, so I suggest that if your friend can't fix it, find another tech, one who specializes in decks perhaps, to help you fix it.
Posted 29 April 2017 - 07:50 AM
The main cog on this deck can fail, it has happened to me twice, but when it fails it results in a continious clunking and the deck can not be used...
go with superdupers sugestions you can't go wrong but first get the whole deck cleaned and lubed followed by new official belts, good luck
Posted 30 April 2017 - 04:58 AM
If I can not convince my friend to work on it again. Hopefully I can get him to work on it.