AIWA 990 - WHAT A PAIN !!!!

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SUCCESS

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May 14, 2009
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Hi people

I've bought an AIWA TRP-990.
The boombox itself looks like new. It's mint, but, guess ..... the deck isn't working and so is he FM
Ok, let start whit the MOST important, the cassette deck.
And when I opened this beauty .... I felt both surprised and frightened.
Surprised by it complexity. Really the most complex boombox I've opened.
Solid, well made and definitely service-unfriendly.
No conectors, all the wires are soldered. I managed to take the main board out (without unsoldering wires). Then I saw the mecha. WHAT A PAIN !!!!!!!!!!!!! The mecha is a soft-touch built around a common mechnical one (very similar to my 955) but it has a black -box in it's botton, that pushes the mecha buttons. This black-box is a servo mechanism, very complex, with one shaft per key (never seen that) driven by one motor.
All the servo system was jamed. Many buttons was pressed at the same time (I noticed that when I purchased it) , mising springs ... The systems itself is quite complex to guess what is going on.
I spent all the afternoon figuring out how this servosystem works. Eventually, I managed to get it working (some functions) powering the motor with a supply and seeing how the servosystem moves to press the buttons of the mechanical deck used in the 990.
I need a little help. Only if you have the photos from a previous work of the exploded diagram of the mecha.

Here the photo of the servosystem ....



The question is about the function button marked with the red arrow ... It supposed to has and spring, because, If I press it, it doesn't return itsefl, like the others ... But I can't see where the supposed spring goes.
Don't get confused, I added two springs to the mecha no get the other functions working properly.

Here is a photo of the mecha (the cassette drive itsefl), which is mechanical !!!!




Pretty box, good sound, superb design .. but I HATE ITS DECK !!!!!!!!!
 

ahardb0dy

Member (SA)
SUCCESS said:
Hi people

I've bought an AIWA TRP-990.
The boombox itself looks like new. It's mint, but, guess ..... the deck isn't working and so is he FM
Ok, let start whit the MOST important, the cassette deck.
And when I opened this beauty .... I felt both surprised and frightened.
Surprised by it complexity. Really the most complex boombox I've opened.
Solid, well made and definitely service-unfriendly.
No conectors, all the wires are soldered. I managed to take the main board out (without unsoldering wires). Then I saw the mecha. WHAT A PAIN !!!!!!!!!!!!! The mecha is a soft-touch built around a common mechnical one (very similar to my 955) but it has a black -box in it's botton, that pushes the mecha buttons. This black-box is a servo mechanism, very complex, with one shaft per key (never seen that) driven by one motor.
All the servo system was jamed. Many buttons was pressed at the same time (I noticed that when I purchased it) , mising springs ... The systems itself is quite complex to guess what is going on.
I spent all the afternoon figuring out how this servosystem works. Eventually, I managed to get it working (some functions) powering the motor with a supply and seeing how the servosystem moves to press the buttons of the mechanical deck used in the 990.
I need a little help. Only if you have the photos from a previous work of the exploded diagram of the mecha.

Here the photo of the servosystem ....



The question is about the function button marked with the red arrow ... It supposed to has and spring, because, If I press it, it doesn't return itsefl, like the others ... But I can't see where the supposed spring goes.
Don't get confused, I added two springs to the mecha no get the other functions working properly.

Here is a photo of the mecha (the cassette drive itsefl), which is mechanical !!!!




Pretty box, good sound, superb design .. but I HATE ITS DECK !!!!!!!!!
remind me to never buy one of those and feel free to slap me around if I ever talk about doing so
 

Superduper

Member (SA)
Well, I know it's a complicated deck but I don't think it's the most complex or painful cassette mechanism I've ever worked on. Sure, having a different belt for every function makes it easier to understand and I think unfamiliarity is a big part of the problem. On mine, my motor didn't work but luckily, replacing an open power resistor did the trick.

It's been quite some time since I've worked on mine so there's nothing in my memory banks that would help but....

As to your request for info, the following should be helpful to you.

http://home.pacbell.net/normanwc/tpr-990.pdf
 

Aiwa

Member (SA)
May 7, 2009
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yo -it took a while -but it was much easier than a zxl repair.... :lol:

nevertheless succes -good luck-I`m sure you`ll make it workin`again!
 

SUCCESS

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May 14, 2009
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Reading the pdf I've noticed a mistake when assembling the "MD-1" thing.
Also the pdf gives another useful info, like adjusting the microswitch ....
Has anybody done that ?.

Basically I want to know what happens when you press a FR function (FW or RW).

This gears have two stop positions .... one at half gear turn and the other when a full turn has been done.
The rest of the gears have only one stop position (a full turn needs to be done to reach the stop position)
Depending of the microswitch adjust, the FW oR RW gear stops when only a half turn has been done (the metal piece that pushes the button remains UP), or after a full turn (the metal piece goes UP and eventually goes down). The last posibility is the common as seen in the other gears.
I was wondering if the FR and RR have a lock at the mecha (I don't need the FR or RR gear stop at a half turn ie the metal piece UP pressing the mecha button all the time) or not.

Another interesting thing is that in the PDF, the "button pusher" (the MD-1 thing) and the mecha itsefl are separate things.
Clearly, they have adapted a mechanical deck to be used as a soft touch. Not so clever fro me .. morever when I've seen other soft touch designs from another brand made at the same period ...
 

Superduper

Member (SA)
Could someone have tinkered with your mechanism and messed it up previously? If so, it could explain a lot of the problems you are having. I did try to adjust the microswitch without benefit of the manual and noticed only later after assembly that when pressing a function it starts and immediately stops 1/2 the time, like it didn't engage all the way. Pressing it a second time will usually be OK and then it plays fine. I'm sure I messed up in the adjustment (I actually did it without reading that portion of the manual til later) but didn't feel like I wanted to disassemble the whole thing all over again to fix that, which I consider a minor nuisance. I don't consider this a mechanical deck at all since the mechanical actuation of the mechanism is accomplised by a motor. Quite an ingenuous design actually. Slight application of mechanical force (pressing the button) actuates the motor which does the remainder of the work.
 

SUCCESS

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May 14, 2009
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First of all, perhaps you know if the 990 has fast foward and how it operates (readign from the owner manual).
That is:

It works with FWD holded by hand and when you release it comes back to play mode ?
It enter in FWD mode when you press the FWD key and exits when you press it again ?

Both arpoaches are valid for me.

Adjusting the microswitch let both posibilities. Both the second is more tricky .... You have no tolerance at all to make the FWD or RWD gears stop at half turn .... and I noticed that other gears fail to complete its rotation since the microswitch is regulated close to the OFF limit.
With the first, as long as you hold the FWD or RWD key, the gear stops at a half turn and as long as you release, the gear completes the turn and stops.

From what I've learnt about other mechas (I don't have the owner manual of the 990) I wolud chose the first option.


I was thinking on the PM-1 as the mechanical deck. The whole assy is a soft touch deck for sure thanks to the nice MD-1 actuator.

Could you tell me how is supposed the FWD and RWD function to work from the manual (if you had it).
Many thanks for your help !!!
 

Superduper

Member (SA)
I don't have an owners manual so I can't help you there. The service manual... you have most of it there. The rest are schematics, parts list and some adjustment info for tuner. The schematics: Can't scan that because it won't be legible. The graphics are so small and voltage test values are in color that it's hardly legible as it is with my poor eyes. A scan copy will be virtually useless unless you have a large tabloid scanner that can reproduce in super high resolution. I imagine the resulting file size will be montrous.

As for the FF/RW. Here is what mine does:

In PLAY mode:
Pressing FF (momentarily). Player will cue until you press FF again. Pressing RW while it is in FF-cue mode has no effect.
Pressing RW(momentarily). Player will R-cue until you press RW again. Pressing FF while it is in R-cue mode has no effect.

In IDLE mode:
Pressing FF (momentarily). Player will FF until you press Stop button. In FF mode, toggling the play/RW button has no effect. You must press stop first. The same is true of RW function.

So as far as the options you indicated: The second option is true for me (when in play mode). Neither first or second option is true for me in idle mode. In other words, momentarily pressing FF will engage FF mechanism. Pressing it again has no effect. It will return to idle by pressing stop.

Hope my description doesn't make things even more confusing.
 

SUCCESS

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May 14, 2009
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Thanks for your help !!!

This weekend I'll try to assy and test the whole mecha outside the boombox.
Also there are two cut wires in my 990 :-O :-O ..... Would you mind helping me with this later ?.
I'll ask you when I've finished the mechanical work :-O in the 990.

Pedro.
 

SUCCESS

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May 14, 2009
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Lets update ;-)

After asembling the drive mechanism and testing it, I noticed that some spring was still missing :-O .
So this assy needed to be taken appart again
I managed to build the missing spring with another spring. I managed to assembly the drive mecha againg.
Again adjust the microswitch. The way I chose is, don't stop at half turn in FF or RR, so the RWD and FWD will work by hand.
When I finished I docked the MD-1 to the PM-1, where the MD-1 is the motor drive and the PM-1 the mecha itself.
When I hoocked both I tested the soft touch operation with an external power supply fedding the motor drive (MD-1)
Although the functions worked fine, there was a lack of torque. The functions cannot be completed unless you done it by hand. At first I though the issue was caused by the power supply (too weak). So I decided to mount all this assy inside the 990 again and give it a try using the boombox supply.
I took more than a hour and a half to put this mecha in the 990, put the door, the soft eject, counter (believe me, is near impossible to conect the belt of the counter)
When I finally put the mecha, I soldered all its wires again (nice desing without connectors).

The first I saw when a pluged was a bit of smoke :-O :-O :-O :-O .... which then stopped. :huh:
The mecha was full-working but the motor drive took too much current from the boombox .
Every time you pressed a function, there was a nasty ripple sound, the battery vu-meter drop a lot and sometimes the function cannot be excecuted :-O :-O :-O . Really a PAIN :annoyed: :annoyed: .
Then the motor drive stops working. I though that it was something related to the smoke. And yes, a power resistor (in series with the MD-1 motor) blow-up.
I replace it, so I get the boombox working againg :thumbsup: .
Then, I finally decided to test the record function (the most heavy in terms of torque) and the function cannot be completed.
Not also the function cannot be completed, the power dissapeared !!!! and the boombox was dead. :sad:

I looked at the main supply where there was a fuse, which was blown (it was 2A !!!!!)
Eventually I decided to change the MD-1 motor, because it's lack of torque and it's high current consuption.

And guess ?????

ALLLLL the mecha needed to be taken appart from the boombox again !!!!!! :-O :-O :-O :annoyed: :-O :annoyed: :-O
I took the MD-1 motor and its pooley, but when I put a new one (I choose a common CCW motor) the polley's hole was too big for the motor !!!!! :-O :-O

Eventually, I managed to install the pulley in the new motor and assembly all this thing again, then put in the boombox againg and connect the new motor.

Hopefully it worked with problems, all functions runs pretty fast, the battery indicator doesn't drop at all, there is no ripple, even the record function !!! :thumbsup: :thumbsup:
The only issue is the functions run too fast (the original motor was slower). But, what can I do ????

I take the old motor appart, and I noticed it was completely burned, the windings were black !!!!!
Look like the jamed mecha stay running for a long long time.
Now, working all functions, but I got some random noise in the left channel (in tape) :huh:
And the FM doesn't work (since I bougth it).


Some suggestions there ??????
 

Superduper

Member (SA)
Success: See my other post about the motor speed controller and see if that'll work for you to slow down the speed somewhat.

As for the tuner, it sounds like you know your way around a circuit so you already know that a non-working FM can be so many different things that there is no 1 suggestion that is probably going to help you. You'll just have to trace back, preferably using a signal tracer. With that, you should be able to figure it out in short order. I've got a lot of things going on right now but I'll see if I can get you a schematic or something to help you out in tracing the circuit.

BTW, my 990 had the exact same blown power resistor but replacing that fixed my deck (along with belts, of course). I think on these decks, when the belts go and the deck doesn't respond as expected, folks have a tendency to start pushing all the buttons 1 by 1. This jams up the mechanism causing undue stress and current consumption which blows the resistor. That resistor has so little resistance that it's primary purpose probably is to protect the motor. You probably wouldn't even miss it by replacing it with a jumper but then the circuit is not protected against overloading.

~Norm.
 

SUCCESS

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May 14, 2009
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Ok,

I get the deck working fine. And while playing I noticed the sound quality of this boombox.
AIWA had done a nicer work there. I can't aggree with it's transport but I love it's sound .. very detailed and clean with warm bass. Ouput power is enough (perhaps a bit more would be perfect).

But, as I told you, I get a noise from the left channel that drives me crazy.

The sound is like WHITE NOISE and some "POPS" are heard also form time to time.
In fact you can see the spaeker cone moving like MAD.
This problem is not present all the time. It appears and dissapears.
That's what I've done (without success)

I cleaned all switches, including the twin record bar, function. dolby ..etc. .
I reworked almots soldering joints in the main board after looking for missconections :drool:
I reworked all the soldering joints at the auxiliary board which holds the dolby, bias switch.
I moved a little some adjust pots in the board, of course I put then in their original position.

BUT NOTHING !!!! the noise is there !!!!!!!! :annoyed: .

Tests:

At first looked that the noise was only present on tape, but actually in all position of the source selector .. but seems to get worse if the amp had audio signal.

The noise is HEARD EVEN THROUGH THE LINE OUT- So the problem is before the volume/tone control and power amp.

At this point I'm lost .... I'm worried about the PCB. It's an early 2 layer ... I hope no via is damaged (OPEN) .. because this is near impossible to find :'-( .

Looking at the board, someone had worked here before. The FM/AM IC has been changed (the FM don't work). In the turner I noticed some soldering joints at component terminals (like someone had been inyecting signal)
Also, one of the DOLBY IC's (R channel) had been changed .... :hmmm: :hmmm:

So, I need some suggestion :-/ . I don't want to leave this baby with this issue. FM ins't very important for me.
Line in is the most important feature, and then the deck, which is working perfect now :thumbsup:

Pedro
 

Superduper

Member (SA)
Pedro. Sorry about the troubles you are having. All I can say is keep plugging at it. I had worked on a TRK-8080 with the dual sided board that was driving me crazy. Initially, I thought it was a blown amp but turns out it was even worse. The amp was fine -- problem was in the circuit board and diagnostic time ate up any savings from not having to replace components. Eventually, I did get 'er repaired and it was very satisfying. Just be glad that it's only a 2 side board and not a multilayer board. Those broken vias aren't impossible to find. It's very time consuming, no question but you just need to be patient. Follow the traces and where you see a via, just do a continuity check to see if it passes over properly. To make it easier, shine a strong light from one side and observe on the flip side. You'll be suprised how clear it becomes. Also, I don't know if this board makes use of printed components. Those DO go bad all the time. When I mean printed components, I mean resistors, diodes, etc that are literally "printed" onto the board like you would print graphics. A little scratch can sometime mess them up. I have successfully grafted discrete components to repair those. In my experience, broken circuit board traces is as common, of not more so, than failed components.

Now, since you've already isolated the issue between the selector switch and the tone board, there isn't all that much left. That is the good news. The right dolby amp has been changed but the left has not you say? Perhaps there is something there. Also, I don't know what you have in the way of tools but if you don't have the proper gear, there is no shortcut for you. That means individually substituting suspect components.

THE BEST WAY TO DIAGNOSE THIS: If you have a function generator and an oscilloscope, you can inject a square wave into the line-in jacks. Since you have 1 good channel, that is great news. The reason is that on a dual trace scope, you can see both waveforms together onscreen. Probe corresponding L + R points along the signal path and depending upon whether you are tracing backwards or forwards, when you see the distortion either appear or disappear, you've found the location of the problem. Without the signal generator and oscilloscope, you can also use a signal tracer and probe corresponding locations. With the signal tracer amp, you should be able to hear the white noise (with no signal present). Trace until you find the source of the problem.

Tell you what. These service manuals are virtually non-existent. I'll see what I can do about getting a service manual to you. That is the best and only tool I can help you with my friend. I know you are kind of down on this boombox due to perceived complexities but I assure you that the problems you are seeing is not isolated to this particular radio. Once you've got the hang of this box, you'll find that gremlins can be present in any radio. When it's operating like it is supposed to, it's one great box. Tape transport is quiet and smooth. Good sound and a quality feel to it too. BTW, how did you address the tape speed issue (or was that another box?)
 

SUCCESS

Member (SA)
May 14, 2009
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I understand. It's a mess to follow the PCB totally wired ...
I followed PCB's many times in my previous work. Vias were a serious problem. Many faults come form vias and traks (the manufacturer cannot control this issues very well)
But the PCB's were NEW ... that's ... on a new PCB a via cannot work, two track can be shortenned somewhere ...
But I don't know if a via can turn to "open circuit" later.

I remeber my RX5600. I spent near a week of my holiday (working about 6/7 hors day).
I repaced it, cleaned all, try other heads ...
But the diference of ouput betwen channels reamined there. It drove me crazy.

I decided to give up ... but two days after .. seeing the RX-5200 schem (which uses the same tape preamp of the RX5600) I noticed a pot, that was put in one channel only (to equal thew levels).

And guess, the pot was open !!!


I know that the noise also appears on the line out (which is previous to the tone/volume control in the signal path).
So the noise exists before the power amp and before the volume/tone control. Also is heard at all positions of the source selector .... So the failure is, as you say, betwen the selector and the volume/tone control .. or at least seem to be there.

Would you mind helping with me with an scan of the preamp section ... ;-)


The speed problem were in the motor drive mechanism, that executed the functions too fast (because the motor run too fast since the boombox apply 12V to it.
I installed a standard 2400 RPM (motor+speed regulator). Now executes all functions at "normal" speed.

Pedro
 
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