Help needed for Nakamichi TA-3A stasis receiver

[routhun]

Greetings to all,

Few days back I've picked up this receiver in non-working state. The receiver will not come out of protection mode. After some investigation I found that output of left channel stuck at -ve Vcc which is -54.3V. I've checked all the transistors in that channel, but did't found anything bad. I've tried to compare the voltages with working channel, but this is next to impossible as the PCB routing for one channel is completely different from another channel. Also the PCB routing is complex and it is not easy to trace back the schematic from the PCB. Can somebody help me in fixing this receiver? I will greatly appreciate if somebody can provide me the service manual or schematic of the power amplifier.

Thanks in advance,
Nageswara

 

[anatech]

Hi Nageswara,
There is a power resistor that overheats commonly in these. It supplies the reference for the current sources (off the negative rail). Replace both with a higher wattage.

Now that is the common fault (wish I had the manual still to pin point it). There may be other faults as well.

-Chris

 

[routhun]

Hi Chris,

Thanks for responding. It looks to me that there are couple of current sources in this amp, if you can hint me about which one, I can look at that one. Also the components are crammed and accessing them is very time consuming. If you remember the value of the resistor, please tell me this also helps alot.

Thanks,
Nageswara

 

[anatech]

Hi Nageswara,
Yeah, it's no fun working under the tuner PCB. I no longer have access to my service manuals or I'd give you all that information.

I think it was a 22K 1/2 W. Use a 1 watt metal oxide resistor to replace it with. There is one ccs per channel supplying the diff pair. That's the feed resistor.

-Chris

 

[routhun]

Hi Chris,

Thanks a bunch!!! Hats off to your memory. The 22k resistor is indeed the problem. Once I replaced with 22K, 1W the amp worked like a charm. I've replaced the resistor in the other channel with 1Watt one. The receiver sounds great, it has punch and very good highs too. It has lot of detail some time it gives an impression that the highs were artificially boosted, and its sound is almost as sweet as my Luxman R-1120 receiver.

Thanks again,
Nageswara

 

[anatech]

Hi Nageswara,
The Luxman is yet another good sounding amp.

-Chris

 

[jcro]

Hi Nageswara,
Yeah, it's no fun working under the tuner PCB. I no longer have access to my service manuals or I'd give you all that information.

I think it was a 22K 1/2 W. Use a 1 watt metal oxide resistor to replace it with. There is one ccs per channel supplying the diff pair. That's the feed resistor.

-Chris

Thanks, Chris from another TA-3A owner. Same problem. Same Solution.

I documented my repair (1/2 watt 22K Resistors R309L and R309R replaced with 2 watt equivalents) with a lot of photos. If anyone's interested, I'll be glad to post. I bought the service manual PDF online, so anybody, feel free to ask questions.

The TA-3A comes apart easily enough ... no tricky hidden screws or clips ... it was easy to pull the top boards to get at the main PCB ... easy to remove the bottom too.

I got my TA-3A free from our local Craigslist. A nice guy who wanted the receiver to end up with someone who appreciated it enough to repair it. It came with a CR-4a cassette deck too, although that has a bad left record channel ... my next project. The deck and receiver are linked with a DIN cable allowing control from one remote.

Having spent the last few hours enjoying the clean sound of the STASIS amp, I'm pretty pleased. In many respects it reminds me of my Yamaha RX-596 when operating in Pure Direct mode, although the midranges on the Yamaha are not quite as clear, at least on the baby Advents I'm currently using. Sometime this week I want to check the Nak out on speakers with a bit more bass, but so far, so good.

Thanks again. Maybe two years from now Google will send someone else to this thread, so I'll make sure to give it some nice keywords like Nakamichi TA-3A TA-3 receiver protection circuit power light blinks no sound ... there that should work.

-Jack

 

[urbinab2]

Hello Jcro:
I have the same problem with the protection circuit Nakamichi TA-3A, and want to be able where to find R309L and R309R in the amplifier and change them.

Thank you.

Urbina

 

[urbinab2]

Nakamichi TA-3A

I need help to locate the resistances R309L and R309R that must change in order that the protection circuit does not fail.

With the manual of service or orientation probably could achieve it.

Thank you
urbinab2

 

[jcro]

They are on the main (big) pcb ... you need to move the tuner pcb and the control pcb out of the way to see them.

The circuit board should be marked with the resistor names .... look towards the left front of the circuit board for one of the resistors and towards the left rear for the other.
The numbering is fairly consistent, so if you see things like C308L you know that R309L is somewhere close.

If I locate a diagram I will post it.

-Jack

 

[jcro]

These may help you locate the resistors

Some images to help you find R309L and R309R


http://img291.imageshack.us/my.php?image=locater309lho7.jpgR309L is in the upper left corner of this detail

and R309R is in the upper right of this one

 

[jcro]

This is my web album documenting the repair

Probably more info than anyone needs or wants, but, it was fun to do.

No longer a boat anchor

 

[onlyrick]

Hello
My name is Rick I live in Hamilton Ontario Canada and I am a new member here
not to often I work on these sets so I sent my TA 3 to a fellow for repair you see I
have worked on many radios from the early 1920,s to the 50,s ,but I am not sure he will
be able to repair it,this set I have had since new I love the sound and I don,t want
to part with it ,the problem is after long use it stops playing no power ,if I try to restart
it just makes a click noise and the green light goes on then off and if I keep trying it
will not even try to start no noise no lights and even the two Ex plugs at the back have no power ,my EQ and extra tuner that are plugged in at the back have no power.If I
let the set cool down for a while it will start up and play but after at times 3 hours
and at times it could go all day then it will shut down.If anyone out there could tell
where I could get a schematic for this or where I could take it for repair I would be
very very thankful,I thank you in advance for any help all the very best Rick

 

[onlyrick]

Thanks for the help

Thanks So Much
jcro thanks so much for the info it,s
a lot of help have a schematic in the mail
thanks again all the best Rick

 

[onlyrick]

New Receiver

I could use some help my TA 3 Nakamichi receiver stopped working
it will play for maybe five hours and then stop it won,t start up
again unless I leave it cool for a few hours no power at all when I
push the switch even the dial lights go out,but it will start if left
for some time,I sent it in 2&1/2 months ago the fellow is not able
to fix it as yet,I had him change the resisters you fellows told me
about but no luck.I hate to replace it I loved the sound from this
set.Can anyone tell me what would be a good replacement with
the same sound I had with this set,I don't crank it very loud and
have four speakers and I don,t need sound surround,I think it,s
called a two stage stereo,some stores tell me a Yamaha R-S700
would be my best choice and other stores tell me Anthem is best
I think the stores only try to sell you what they carry.I am
looking at no more than $700 to $1000 dollar range,I would be very
thankful for any advice all the very best Rick

 

[DreadPirate]

I take it the same would apply to the SR-4A, whereas the existing resistors are R707/R807 22K 1/2W, replace with 1W?

 

[b767]

TA-3A

Thanks, Chris from another TA-3A owner. Same problem. Same Solution.

I documented my repair (1/2 watt 22K Resistors R309L and R309R replaced with 2 watt equivalents) with a lot of photos. If anyone's interested, I'll be glad to post. I bought the service manual PDF online, so anybody, feel free to ask questions.

The TA-3A comes apart easily enough ... no tricky hidden screws or clips ... it was easy to pull the top boards to get at the main PCB ... easy to remove the bottom too.

I got my TA-3A free from our local Craigslist. A nice guy who wanted the receiver to end up with someone who appreciated it enough to repair it. It came with a CR-4a cassette deck too, although that has a bad left record channel ... my next project. The deck and receiver are linked with a DIN cable allowing control from one remote.

Having spent the last few hours enjoying the clean sound of the STASIS amp, I'm pretty pleased. In many respects it reminds me of my Yamaha RX-596 when operating in Pure Direct mode, although the midranges on the Yamaha are not quite as clear, at least on the baby Advents I'm currently using. Sometime this week I want to check the Nak out on speakers with a bit more bass, but so far, so good.

Thanks again. Maybe two years from now Google will send someone else to this thread, so I'll make sure to give it some nice keywords like Nakamichi TA-3A TA-3 receiver protection circuit power light blinks no sound ... there that should work.

-Jack

HI jcro, I am having problems with my friends TA-3A. Replaced R309L & R309R, reciever worked great for a week. Now back to same not coming out of protection mode, any advice you can help me with.