Aiwa TPR-990H

Status
Not open for further replies.

docs

Member (SA)
Thanks Norm, I've left it in bits for now til I get a clear head and retry.
I think that the record button should press even with just the bottom piece out and not in place with the upper section. Then i'm thinking that its nothing to do with the bottom section and thats fine but it is something else and not just the recording tab being depressed that allows the record button to be pressed.
Maybe the problem is with the record lockout lever on the lower section as it doesn't really do anything. Sure it connects to a long spring wire and up to the top of the deck to the lever that presses the tab but it doesn't seem to actually engage or move anything at the bottom to then allow the record to be pressed. There must be something I'm missing in putting it back together since all the cogs rotate no problem and seem to be in the correct locations. Every other button works so I think the lower section is fine.
 

Superduper

Moderator
Staff member
All I can say is.........

To anyone contemplating disassembling and servicing this deck:

MAKE ABSOLUTELY CERTAIN, that you do this job slowly, methodically, and document with photos and notes along the way. Even things that looks intuitive at the time of disassembly should be documented because the service could take far longer than you planned for and memories tend to be short.
 

monchito

Boomus Fidelis
norm on another 990 i remember seeing a big lever switch right on the top section where the cassette sits ,,i guess when u place a cassette it gets pushed back to complete the operation ,, its really not visible unless u look toward the top down with the mainboard detached i belive the 950 also has it ,,but i did remember it missing the plastic tabs that were pushed back ,,so u would also have to check that little black box.... :-)
 

docs

Member (SA)
monchito and Norm thanks for all your help. I have a success with the deck :thumbsup: :thumbsup:

I'm just putting the deck back together (again) and leaving that thing forever !!! :lol:

Norm, did you say you had a source for a full service manual please ? I think I am going to need it since the left channel hasn't sprung into life from spraying the switches and pressing the record arm quite a lot.
If so please send me a PM and I'll fully reimburse anything you need including for the pages you sent.

Thanks again guys, you rock and roll! :thumbsup: :thumbsup: :thumbsup: :thumbsup: :thumbsup:
 

docs

Member (SA)
Another update, deck is fully working !! :thumbsup: :thumbsup:

The left channel does not work on playback from tape/radio/line-in BUT if I put it in radio or line-in mode and record to a tape the left channel comes on perfect. hmmm :hmmm:
However the left VU doesn't move :hmmm:
 

docs

Member (SA)
I did try and spray a bit but I need a closer look at the arm as it seems to have two parts and I'm not sure how to best spray it, will give it another try cheers.
 

Superduper

Moderator
Staff member
Did you playback the recorded tape on another box to see if it actually recorded on the left channel?
 

docs

Member (SA)
Just did a test now Norm and found that the recording was only out of the right speaker.
 

Superduper

Moderator
Staff member
monchito said:
did u try spraying the record bar with deoxit and move it back and forth to see if that helps :-)
monchito said:
um dead channel ,maybe the audio ic chip it uses 2 of them :hmmm: :hmmm: :hmmm:

OK, if you are getting sound out of both channels in ANY mode at all, that suggests that the output IC's are sound. This boombox uses a very unique circuitry configuration. It uses (2) AN7146 chips. The AN7146 is a dual amp chip so 2-chips means 4 amps total with each channel using 2-amps in bridge configuration. Many top boomboxes use similar bridged setups so that's nothing unusual. However, what IS unusual is that unlike most boomboxes which use 2 X dual-amps chips (with one dual-amp chip for each channel) this one uses one amp from each IC and bridges them together. In other words, on most boomboxes, one failed amp IC will result in one dead channel. In this model, one failed IC will result in BOTH channels failing since 1/2 of the bridged amp setup of each channel resides in 1/2 of each IC.

Anyhow, I've reviewed the schematic and found that this model also switches the outputs signals (after amp) through the function switch. So also does the meter signals switch through the function switch. I suggest a thorough cleaning of the function switch, perhaps even disassembling it if necessary. This may fix all (or part) of your problems. I would start there and go forward since although it's likely these are all related issues, it's also equally possible that there are multiple problems that are unrelated.
 

docs

Member (SA)
Simply brilliant info Norm thanks so much, i'm gonna give the function switch a thorough workout.
 

Superduper

Moderator
Staff member
While it's apart -- don't forget to thoroughly clean the REC/Playback switch too, like Ramon said. That switch has 20-something poles and many signals are switched across there. So a very thorough workout of that switch(s) is in order.
 

docs

Member (SA)
I've sprayed the function switch thoroughly and given it a top workout. Short of taking it out I think it is working good. One thing I noticed is when the dolby switch is on and I work the function switch between tape and radio I hear a weird noise out of the left channel momentarily while moving the switch. Its not audio just a slight screech and not loud. So I've worked the dolby switch with some deoxit too but to no avail, it seems consistent.
Not sure if its related but it doesn't seem to work on batteries.
 

docs

Member (SA)
Superduper said:
While it's apart -- don't forget to thoroughly clean the REC/Playback switch too, like Ramon said. That switch has 20-something poles and many signals are switched across there. So a very thorough workout of that switch(s) is in order.

I'll get to that now Norm.
 

docs

Member (SA)
Ira :thumbsup:

Ok i gave the record arm a good workout too but the symtoms are the same. If i turn it up a bit i can hear the audio in the left channel but its distorted a bit and ofcourse quiet. After cleaning switches the symptoms seem to remain consistent.
 

Superduper

Moderator
Staff member
I'm pretty sure that the issue is related to the playback and function switches or related connections. The fact that radio/line/tape all have this issue and that you can hear audio in the otherwise dead channel when in record mode really suggests to me that the problem is NOT in the amp, NOT in the radio or line or tape low-level functions. Just because the switches have been deoxit doesn't mean they are trouble free and working properly. Deoxit is hard to get into the R/P switch. Those switches really shouldn't switch high-level (speaker level) signals but they do. As such, it's very possible that arcing and contact deterioration has occured. I have seen contacts completely eaten away (ask Ira and his BB40). As I said, sometimes, those switches need to be disassembled to properly view. If course before removing the switch, you can test all the poles if you have enough patience with a DMM to verify whether all the poles are switching properly. Not saying that it's 100% for sure that the problem isn't someplace else. What I am saying is that when evidence points in a particular direction, that avenue should be thoroughly investigated and ruled out before proceeding.
 

docs

Member (SA)
I hear ya. Ive taken it apart several times to try and get those switches properly worked.
Im not sure i am able to dissasemble the function switch and the record one is definately beyond my abilities. I'll keep trying with it. I have noticed that when on radio and recording to get full audio out of both channels that neither vu meter move now.
 
Status
Not open for further replies.