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AIWA 990 - DECK WON'T ENGAGE


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#1 Cpl-Chronic

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Posted 25 November 2014 - 12:43 AM

Hey all, 

 

I am working on a TPR-990 & the radio/line in works ok.  The radio sounds good & powerful, no issues but the deck is dead.  The flywheel motor is fine & you can hear it clicking but the carriage is stuck, almost engaged but, not quite enough to start the wheels turning, so to speak.  If I lift the carriage the last 2-3mm to engage the pinch-roller to the flywheel pin, everything starts moving & I bet I could hear the tape if I could fit one in there.  The Play LED & Pause LED are lit & I hear a click, every few seconds like something wants to engage or release, etc.

 

Plus, all of the buttons for the cassette on the front are stiff, as if they can't move at all....even pause & stop....

 

Any ideas?

 

Cpl



#2 JVC Floyd

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Posted 25 November 2014 - 12:57 AM

i would try turning the flywheels until  the heads drop down this resets the gears and the head position , also make sure the belts are tight enough that theres no slipping.



#3 Cpl-Chronic

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Posted 25 November 2014 - 02:38 AM

Cool....I could try that.  What about the motor for the carriage,e tc.  The belt for the flywheel & that motor is fine.  All spinning normally, no rubbing.  It's the 2nd motor& gears for the carriage, I am wondering about & the tape keys seem locked solid too.....can't eject the cassette door...Play & Pause LEDs are lit....

 

Cpl



#4 JVC Floyd

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Posted 25 November 2014 - 11:41 AM

i would try just moving the assembly by hand if possible , if theres flywheels or gears instead of belts in the second motor then if the belts went out could have bound up the mech or got things spun out of alignment , you can check for power at the motor just to be sure its working .



#5 Cpl-Chronic

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Posted 25 November 2014 - 01:58 PM

OK,  yeah, I could move the plastic pulleys at the carrage motor & the heads are almost engaged but that's it.  Belts for the carriage mech are on & in-tact.  I have a feeling the controls are jammed somehow & this is way, way beyond my skillset.

 

I'm gonna take it back to my guru who told me it was a simple fix of the flywheel motor but obviously, now that I've got that fixed, there's more to it.

 

Thanx Floyd for trying to help me out.

 

Cpl



#6 monchito

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Posted 26 November 2014 - 05:05 PM

Ok fyi these 990 have 2 fusible resistors on the board one for the main motor the other for the logic motor. I have the 990 and had the same problem I ordered the fusible resistors though mouser electronics make sure you get the half watt ones its under a lot of load so a smaller 1/4 watt will burn up right away. These resistors will be found toward the top right hand section of the mainboard where the switches are. The tpr 968 also has those to.. I believe they are of 1 ohm I have to look to make sure if that's the correct one :-)  :-)



#7 BoomboxLover48

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Posted 27 November 2014 - 07:21 AM

"can't eject the cassette door...Play & Pause LEDs are lit"!!!!!!!!!

 

That could be because of what monchito is talking about.

 

It is getting enough  kick to lock the mechanism. Even if you manually make it happen the next time it won't work.

I have seen problems like that on my boombox tape decks. Can't remember which one because I have so many. :-D 



#8 docs

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Posted 17 June 2018 - 10:34 AM

Ok fyi these 990 have 2 fusible resistors on the board one for the main motor the other for the logic motor. I have the 990 and had the same problem I ordered the fusible resistors though mouser electronics make sure you get the half watt ones its under a lot of load so a smaller 1/4 watt will burn up right away. These resistors will be found toward the top right hand section of the mainboard where the switches are. The tpr 968 also has those to.. I believe they are of 1 ohm I have to look to make sure if that's the correct one :-) :-)

Anyone can help identify why r302 (fusible 1ohm 0.5W) burns up when replaced?
I recognised r302 which is for the motor at the cogs was fried so replaced it like for like but the new one burnt up too. Cogs are lined up and the deck worked for a few seconds.

#9 docs

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Posted 18 June 2018 - 04:16 AM

Guess I'll test R450 for a fault but also try and use the DC power instead of the mains AC, see if it makes any difference.

 

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#10 docs

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Posted 18 June 2018 - 01:06 PM

Does same on DC 😩👎

#11 Northerner

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Posted 18 June 2018 - 01:18 PM

I wish I could say something helpful lol

#12 Superduper

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Posted 18 June 2018 - 01:28 PM

Make sure no caps after R302 is grounded and ohm motor winding to make sure it is not leaking to ground or shorting.  Use ohms law to calculate based on the ohm measurement whether it's winding resistance will work with the 1/2 watt resistor rating.   Also, S18 should only operate momentarily, should not operate continuously.  Once the motor cycles to initiate the proper servo action, it's job should be done.  If not, something is wrong.



#13 docs

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Posted 19 June 2018 - 01:09 PM

Ok who put these two resistor looking thingies here?
These must be c1 and c2...

The microswitch is always engaged it seems and the lever opens it further to release the switch...

Norm, sorry, no idea how to so will check continuity to ground and put it down to a knackered motor.



#14 docs

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Posted 21 June 2018 - 11:54 AM

I’m wondering why one of the cap/res things is going from pin 1 to 3 when the sm shows them both going to pin two and each to 1 and 3?

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#15 docs

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Posted 21 June 2018 - 12:37 PM

multilayer monolithic ceramic capacitor axial lead.
Anyone know what I could replace with?
One has continuity through it and the other doesn’t?

#16 Superduper

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Posted 22 June 2018 - 01:34 AM

1), the wiring diagram might not be literal.  You should be able to determine by testing the switch what pins are what.

 

2), you can replace the caps with any ceramic cap, and it will probably work perfectly fine.  Even with no cap, it will probably still work fine.

 

3), why are you replacing them?  Are they shorted, or are you just trying it to see?  If you test them for short (in circuit), and one shows short circuit, keep in mind that the switch will always be in one of two positions which looks like a dead short, so make sure to throw the switch if one cap tests short to confirm.  If you test them and meter shows (counts to) infinity, then changing them won't make a bit of difference in your problems.

 

4), if you have a DMM with an amp function, you can put your meter in series with motor and power it up with the appropriate voltage, preferably (but not required since you have a DMM) with a bench power supply that has a current meter.  See how much current it is drawing.  Use that to figure out how many watts it is consuming.  If it is drawing 1 watt, your 1/2 watt resistor may not long for this world.  

 

5), did you already test C270 for short?  It's far more likely to go bad than the ceramic caps.  

 

Fusible resistors are not like actual fuses -- they take awhile to burn up, not instant, even if spec is exceeded.  The mechanism function shift motor only runs one cycle for each change of deck function.  This cycle is like less than 1-second, not continuous.  And then it stops.  Is it possible that the servo mechanism is not working properly causing that motor to run continuously?  Or are the caps shorted causing excessive current draw?



#17 docs

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Posted 22 June 2018 - 02:15 AM

Hey Norm, you are right, the fusible resistor does take a little while to burn out completely.

C270 I did test but I need to get an exact replacement for voltage and uf to be 100% sure on that one.

The reason I am at the switch is just to make sure it is set according to the manual below but it confused me why the "caps" orientations weren't as per the manual.

I was going to replace them just to see if it made any difference but I will try throwing the switch and testing those caps in either on or off states. Is there a simple check to see if that switch has failed? IE: when its off its not off even though it does click like a microswitch? because in my tiny mind, the switch being broke is a solid explanation for what I am seeing,

 

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#18 docs

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Posted 24 June 2018 - 12:22 PM

Replaced c270 like for like which is 470uf 16v and the deck functions for a few minutes before the fusible resistor blows. Next step, find a replacement switch.