QUESTION: Nakamichi TA-4A Stasis Receiver - NO OUTPUT

[EADGBE]

Hello All:

I found a Nakamichi TA-4A Receiver at a thrift store, and I am
attempting to repair it. I can't find the service manual, so I thought
I would ask around to see what the problem might be, before I start
digging into it. (NOTE: This is a STASIS model receiver with quasi-
class A circuitry licensed from Threshold, so it's worth fixing!)

When I got the TA-4A home, I discovered that even though it powered up
fine, there was no audio output at all - none through the speaker
outputs and none through the headphone jack.

When you click the various buttons for Tuner/CD/Phono/Tape, etc., you
do hear a VERY faint click through the headphones, but absolutely NO
sound other than that. You can turn the Volume all the way up and
still hear no hum or noise of any kind.

I have taken off the top cover and discovered that the PC board where
the speaker terminals are soldered has cracked into three pieces!

Needless to say, I have to repair the speaker connections here, BUT
HERE IS MY QUESTION: Why is there no output even through the
Headphones jack? Is the headphone signal routed through the speaker
terminal PC board in some way?

ALL internal fuses are OK, by the way...I checked them.

Any help will be MUCH appreciated. THANKS IN ADVANCE.....

[Scott Dorsey]

EADGBE > wrote:
>
>I found a Nakamichi TA-4A Receiver at a thrift store, and I am
>attempting to repair it. I can't find the service manual, so I thought
>I would ask around to see what the problem might be, before I start
>digging into it. (NOTE: This is a STASIS model receiver with quasi-
>class A circuitry licensed from Threshold, so it's worth fixing!)

If there is no Sam's on it, Nak should sell you a manual.

>When I got the TA-4A home, I discovered that even though it powered up
>fine, there was no audio output at all - none through the speaker
>outputs and none through the headphone jack.

How about from the tape outputs?

>When you click the various buttons for Tuner/CD/Phono/Tape, etc., you
>do hear a VERY faint click through the headphones, but absolutely NO
>sound other than that. You can turn the Volume all the way up and
>still hear no hum or noise of any kind.

Okay.

>I have taken off the top cover and discovered that the PC board where
>the speaker terminals are soldered has cracked into three pieces!
>
>Needless to say, I have to repair the speaker connections here, BUT
>HERE IS MY QUESTION: Why is there no output even through the
>Headphones jack? Is the headphone signal routed through the speaker
>terminal PC board in some way?

Maybe, but it's also possible something else is broken.

>ALL internal fuses are OK, by the way...I checked them.

The high voltage fuses... is there high voltage between them and ground?

Is there signal coming out of the tape sends?

Is there a loopback connector that joins the preamp section and the amp
section missing?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Dave Plowman (News)]

In article om>,
EADGBE > wrote:
> Needless to say, I have to repair the speaker connections here, BUT
> HERE IS MY QUESTION: Why is there no output even through the
> Headphones jack? Is the headphone signal routed through the speaker
> terminal PC board in some way?

Dunno your amp, but some certainly are. Uses the speaker switching to kill
the speakers if needed.

--
*Prepositions are not words to end sentences with *

Dave Plowman London SW
To e-mail, change noise into sound.

[William Sommerwerck]

> Needless to say, I have to repair the speaker connections here,
> BUT HERE IS MY QUESTION: Why is there no output even
> through the eadphones jack? Is the headphone signal routed
> through the speaker terminal PC board in some way?

Few -- if any -- amplifiers have dedicated headphone circuitry. The simplest
and cheapest method is to drive them from the amplifier's speaker output,
through resistors to avoid over-driving them. Clearly, the board break is
prior to the headphone jack.

Good luck on your repairs.