I'm restoring my National RX5600. I started with the tape deck ( nearly dead). After that I've cleaned ALL swithces and the record bar (3 times).
When I was testing it, I noticed that listening from tape, one channel has lower output than the other, and one vu-meter moves less than the other. It's present even through lineout ... Also seems like the weak channel has lower treble tahn the other.

This problems disappears when I put the BBX in mono ... output level equals and both vu-meter moves the same.

If listen from the radio, I have the same output in both chanel in stereo or mono mode.

I guess there's a problem in the tape preamp or the playback head, since radio doesn't have the same problem.

I've clenaed the record bar three times, and move like I were mad but the problem still there.

And I've cleaned the source selector switches

Of course I've clenaed the R/P head .

I'm lost here . I need some help with this.

Pedro.

Hey Pedro
have you tried demagnetizing the head?

No, but it's a good idea . Thanks
One thing that I forgot is that recording gives the same output level on both channels with perfect quality.

I'll try desmagnetizing ....

Pedro

The level doesn't improve after desmagnetizing.
I've used an electronic desmagnetizer cassette.

I think that I will figth against the electronics of the BBX, but in the tape signal procesing I'm lost.

I'll apreciate any help.

I finished the mechanical work (the mecha works 10/10) changing belts motor and pinch roller.
But this issue worries me a lot(is a dificult one) since I'm lost.

Pedro

No anyone has an RX5600 or had worked on it to help me ?.

success i can only say it could be something as simple as cleaning or something more technical. i have worked on a couple of panasonic boxes not that model but i can tell you that some where fixed when the record play switch where cleaned another had a low channel and cleaning the funtion switch made it come back another one had a bad head and there was one with a few leaking capacitors that where bad so not all will suffer the same way you cleaned it you demagnetized the head,the record/play switch may be really be coroded where you may have to take it apart and clean the inside of the switch or try to change the tape head ,if that doesnt do it you may have to dig a bit deeper a bad solder joint my cause havoc too...i hope this helps a bit.. btw make sure all cables are secure grounds make sure they are clean even that can ruin a good day

Thanks Ramon

But after cleaning it, there wasn't any noise if a move the switch a little (not enough to enter in rec mode). I seems clean ...

I guess that perhaps is a bad capacitor ....

Do you remeber what capacitor was bad (value in uF and volts). I'll use it like a guideline ...

I had a schematics of a Nationa RX5200 uses the the same rec/play amp of the RX5600.
The chip is the AN6210 from Mistumi.

Since the chip is the same, the boundary circuit is expected to be similar ...

I'll post a scanned copy so we can look the circuit. Around the head amps there isn't many capacitors (electrolitic type)... only 2 or 3.

Change head ... I don't think so ... I perform a "lack of technician" test touching with hand L and R input of the head amp, and the weak channel produces less hum than the other, measuring it with VU-Meters.

I know, I need a scope ... I have one at work, but bringing the RX5600 wouldn't be easy =(

Pedro.

ok most likely a bad cap cant remember the one make sure to look closely to see if you see any budging on the bottom of the cap or a greenish subtance on the pins of the cap.btw did you clean the funtion switch i have had a few boxes that suffered in that department.......

Yes, I've claned it.
The interesting thing is that the difference is constant, altough I move the switches a lot (function and recod bar). The difference remain the same. If there was a temporary improvement, I'd guess a bad solder, ir a bad contact. But not, the difference is the same.

Thank Ramon.

If I can help you with something PM me.

ok success well i hope everything works out for you..

Lets see the schematics diagram, the tape frontend is the AN6210 ...

still having trouble with it. i tried to post the datasheet for the an6210.what i saw was pins
22 and 19 where inputs and 27 and 16 are the outputs would have to compare both sides to see if indeed you get the same signal on the inputs same for outputs......btw you did not mention which side was low notice that the left side has a adj pot.

The problem is in the rigth channel.
Notice that all the sources uses the AN6210's line amp. Since turner works fine, problem is betwen the tape amplifier. I can see some electrolityc capacitors ...
As I don't have a scope I'm going to use a multimeter in AC and a recorded tape with some frecuency where the mutimeter works fine (mine works up to 450 Hz) and I'll try to guess by comparing channels.
I don't understand the feedback network at all ... I know we need something like a NAB element, but this looks different.
Ineed schematic is from the RX5200, not from the RX5600. But they use the same solution (AN6210). Launched in the same year, is expected that NP had used the same aplicattion design.

well i have had trouble before with those 50v1uf caps on other radios and i think i saw a couple notice c202 and c205 have these caps

I went over the main board of my RX5600.
And saw some bad capacitors around the AN6210



and



and



I'm worried about this. I started to think about my other boxes. Perhaps electrolytic capactiors are near dead also.

In this one, a saw three, but I don't know if there are more ...
Also I'm going to change supply, output capacitor and tweeter capacitors. I don't trust on they.

well i have been working on a sanyo 920 i had to change all of them basicly but it came back to life i have spent like around 60.00 dollars but its worth it,i have a sanyo 9994 that i will be doing the same thing

BAD NEWS.

After about 6 hours of work I changed ALL MAINBORAD CAPACITORS. I've changed about 81 electrolityc capacitors. About fourty percent was bad. But guess ...
When I've finished, the problem was still there !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


Then I took apart the record bar
and openned it. I've cleaned it with alcohol and contact cleaner with a tothbrush. I close and solder it again. NOTHING. The same.

I changed the head (no the same, but a new head to test). NOTHING.

I'm happy because after all this work the BBX don't get worse , but very SAD with the results.

I supposed that I need to give up this. You can't do it right all the times ...

Some Capacitor that I've changed ...

I found the problem. Bad Boy !!!!!

An onboard trim was open, soo, level at right was at the minumun posible (not zero).
I guess they use it at factory to match both channel levels, since it's imposible in designs with 5% or 10% accuary components, so they perform a calibration set-up.

I know, ... why I didn't see this first ?. Ok, I don't have the schematics, but there was lots of bad capacitors. I though they were guilty.
But it's amazing think that even with many capacitors bad, the unit still worked ok.

great success i am happy that finally you found the problem the good thing is that you replaced all those caps you did it now you dont have to do it latter.what i have seen is that you would never think that trim would be bad so your guesses would be clean switches then start the dignoses untill you end up finding the problem,when you have a scematics on hand thats great when you dont then its a pain

Thank Ramon. I strongly agree with you ... at some time this bad capacitors most be changed. Also I put a bigger at the supply filter, since they are little.
I think it sound better now (subjetive ?).
Always love Nationa/Panasonic. This one disapointed me at first. So many bad capacitors.
Ok ... the unit is 27 year old, it isn't endless
But then I became happy again to see that instead of this bad components, the unit worked well. A great design, faul tolerant.


About the trim ... I guess it in the following way ...

Near the head amp are some trimers. I look two that shield a hum noise when I touch so they are on the signal path. Is more quickly than following the PCB. When I found these, I move one (rembembering the original pos). No change on the output (the bad channel). Then I move the other and the level went up and down about 6db. It was clear that those trimer adjust the tape preamp output. I checked that those don't affect other level while radio or aux. They only work with tape.
Then I measure the good one, it shields 500 ohms (ok since the trim was 501). But the other hasn't any reading or reads 200K. It was broken.
I put a new one and the ouput can be adjusted as expected.
I'm thinking of buying a scope ...

well thanks for sharing your fines it good to know this i have a sanyo with simular problem so i will be taking a look to see what i find
i was working on a panny i am almost done with it had a problem with the meters a couple bad solder joints was the culprit so i soldered the whole board and she is working great,that there was a pain for a couple of hours could not feel half of my body it went numb