Help! I need a fresh pair of eyes to look at a VERY
mysterious problem I am having with a repair.

I am repairing a 582 that has lost the ability
to record/erase tapes.

I have replaced the faulty caps in the bias oscillator
and checked the frequency. The bias oscillator
function has been restored and is right on spec.

I was just about to start checking/calibrating the
deck's EX/SX/ZX record bias, when the deck lost
its ability to go into PLAY mode.

It simply cannot enter PLAY mode. When you
hit PLAY, the deck goes into PAUSE
mode instead.

PAUSE = PAUSE
PLAY = PAUSE

I have checked the reference voltage at the
sliding contact of the cam control
10k volume pot, and the voltage is definitely
LOW for both PLAY and PAUSE
functions.

PLAY voltage reads 1.04VDC.
PAUSE voltage is identical.

It's as if PLAY and PAUSE functions have
merged and are now the EXACT same PAUSE
function, with a complete loss of PLAY function.

Adjusting VR401 (the Play mode voltage adjuster)
does nothing. A preliminary check of all related
transistors and diodes on the logic board has
produced no clues. Everything checks out OK.

I am starting to suspect op amp 4558C
(IC405), but am not sure how to proceed.

SOME INFO: The Play and Pause modes both
involve negative DC voltages. The 10k "volume"
pot previously mentioned is an internal motor-
driven pot that gets voltages directly from the
deck's logic board. This pot SHOULD be getting
slightly less than 3VDC in PLAY mode, but instead
gets just over 1VDC.

Here is the service manual:
http://www.analogstereo.com/nakamich...ice_manual.pdf

What should I be checking that I haven't checked
already?

Any help with this "tough dog" will be most appreciated.

On Tue, 4 Dec 2007 19:38:59 -0800 (PST), EADGBE
wrote:

What should I be checking that I haven't checked
already?

Replace the open "stop" lamp. And wire a several
hundred Ohm resistor across it to prevent future
logic issues.

All good fortune,

Chris Hornbeck

"Chris Hornbeck" wrote in message
...
On Tue, 4 Dec 2007 19:38:59 -0800 (PST), EADGBE
wrote:

What should I be checking that I haven't checked
already?

Replace the open "stop" lamp. And wire a several
hundred Ohm resistor across it to prevent future
logic issues.

All good fortune,

**Bugger! Beat me to it. I concur.

Trevor Wilson

Thanks for the tip, but the stop lamp is the
very first thing I checked. It is working just fine.

If it were just the stop lamp, the deck would
go into the PLAY mode, but then it would
immediately stop.

This deck physically cannot go into PLAY
mode. The heads only come up as far as
the PAUSE position. They never engage
the tape, and the pinch rollers never touch
the capstans.

This is due to an improper control voltage,
but I am going crazy trying to find the point
at which the voltage drops. All of the logic
board components I have checked so far
check out OK.

The two voltage regulators are spot-on. No
issues whatsoever. Perfect +12 and -12
DC voltage output from them.

I have found one or two resistors with
a positive voltage on one end and a
negative voltage on the other, which may
or may not be a clue.

On Wed, 5 Dec 2007 07:14:37 -0500, EADGBE wrote
(in article
):


Thanks for the tip, but the stop lamp is the
very first thing I checked. It is working just fine.

If it were just the stop lamp, the deck would
go into the PLAY mode, but then it would
immediately stop.

This deck physically cannot go into PLAY
mode. The heads only come up as far as
the PAUSE position. They never engage
the tape, and the pinch rollers never touch
the capstans.

This is due to an improper control voltage,
but I am going crazy trying to find the point
at which the voltage drops. All of the logic
board components I have checked so far
check out OK.

The two voltage regulators are spot-on. No
issues whatsoever. Perfect +12 and -12
DC voltage output from them.

I have found one or two resistors with
a positive voltage on one end and a
negative voltage on the other, which may
or may not be a clue.

Is there, by any chance, a hardwired remote control jack that needs a dummy
plug like the old Revox A77?

Regards,

Ty Ford


--Audio Equipment Reviews Audio Production Services
Acting and Voiceover Demos http://www.tyford.com
Guitar player?:http://www.youtube.com/watch?v=4RZJ9MptZmU

"EADGBE" wrote in message
...

Thanks for the tip, but the stop lamp is the
very first thing I checked. It is working just fine.

If it were just the stop lamp, the deck would
go into the PLAY mode, but then it would
immediately stop.

This deck physically cannot go into PLAY
mode. The heads only come up as far as
the PAUSE position. They never engage
the tape, and the pinch rollers never touch
the capstans.

This is due to an improper control voltage,
but I am going crazy trying to find the point
at which the voltage drops. All of the logic
board components I have checked so far
check out OK.

The two voltage regulators are spot-on. No
issues whatsoever. Perfect +12 and -12
DC voltage output from them.

I have found one or two resistors with
a positive voltage on one end and a
negative voltage on the other, which may
or may not be a clue.

**Just a wild thought: Do the pinch rollers move freely on their pivots? If
the pinch rollers are jamming....


Trevor Wilson

On Thu, 6 Dec 2007 06:57:57 +1100, "Trevor Wilson"
wrote:

"EADGBE" wrote in message
...

Thanks for the tip, but the stop lamp is the
very first thing I checked. It is working just fine.

**Just a wild thought: Do the pinch rollers move freely on their pivots? If
the pinch rollers are jamming....

Gummed up pinch roller arm pivots are so common, these
several decades down the road, that a truly serious rework
should include removing the rocker arms for washing to
remove all the old wax (it ain't grease any more) and relube.
Auto wheel bearing grease is great, and easily available.

We're all assuming that the little guy has a good control
motor belt (the one that pulls the head bridge up and down),
the number one failure of the classic Naks, and that the
head bridge moves freely.

Oh, and does the take-up reel rotation sensor lamp still work?

All good fortune, and keep us updated,

Chris Hornbeck

"Chris Hornbeck" wrote in message
...
On Tue, 4 Dec 2007 19:38:59 -0800 (PST), EADGBE
wrote:

What should I be checking that I haven't checked
already?

Replace the open "stop" lamp. And wire a several
hundred Ohm resistor across it to prevent future
logic issues.

All good fortune,

Chris Hornbeck

Dang! I guess I did hear about lamps on these back in the day...

Oh, well - at least got a free PDF service manual out of it...

;-)


Mark Z.

"EADGBE" wrote in message
...

Help! I need a fresh pair of eyes to look at a VERY
mysterious problem I am having with a repair.

I am repairing a 582 that has lost the ability
to record/erase tapes.

I have replaced the faulty caps in the bias oscillator
and checked the frequency. The bias oscillator
function has been restored and is right on spec.

I was just about to start checking/calibrating the
deck's EX/SX/ZX record bias, when the deck lost
its ability to go into PLAY mode.

It simply cannot enter PLAY mode. When you
hit PLAY, the deck goes into PAUSE
mode instead.

PAUSE = PAUSE
PLAY = PAUSE

I have checked the reference voltage at the
sliding contact of the cam control
10k volume pot, and the voltage is definitely
LOW for both PLAY and PAUSE
functions.

PLAY voltage reads 1.04VDC.
PAUSE voltage is identical.

It's as if PLAY and PAUSE functions have
merged and are now the EXACT same PAUSE
function, with a complete loss of PLAY function.

Adjusting VR401 (the Play mode voltage adjuster)
does nothing. A preliminary check of all related
transistors and diodes on the logic board has
produced no clues. Everything checks out OK.

I am starting to suspect op amp 4558C
(IC405), but am not sure how to proceed.

SOME INFO: The Play and Pause modes both
involve negative DC voltages. The 10k "volume"
pot previously mentioned is an internal motor-
driven pot that gets voltages directly from the
deck's logic board. This pot SHOULD be getting
slightly less than 3VDC in PLAY mode, but instead
gets just over 1VDC.

Here is the service manual:
http://www.analogstereo.com/nakamich...ice_manual.pdf

What should I be checking that I haven't checked
already?

Any help with this "tough dog" will be most appreciated.


Does the Timer Play function work normally?

Mark Z.

On Dec 5, 7:15 am, "Mark D. Zacharias"
wrote:

Does the Timer Play function work normally?

Mark Z.

Mark:

I tried it.

No, the deck cannot enter PLAY mode under
any circumstances.

On Dec 5, 7:47 am, EADGBE wrote:
On Dec 5, 7:15 am, "Mark D. Zacharias"
wrote:



Does the Timer Play function work normally?

Mark Z.

Mark:

I tried it.

No, the deck cannot enter PLAY mode under
any circumstances.

1) was it able to enter play before the bias osc was repaired?
2) is the timer switch in record mode?
3) I think the voltage you are reading at the wiper is the voltage
from the pot and indicates what position the cam is in. You need also
to read the volatge that the machine is commaning the motor to go to
so sometinh is amiss with the circuit around Q430 in fig 2.3.22

4) see fig 2.3.22 what is the voltage at Q430 collector in play and
pause. This is an interesting circuit, it looks like the macinh
gnerates a voltage for each mode and then the motor moves the cam
until it is in the correct position to null the voltage at the op
amp...so you have determined that the cam is not moving correctly by
reading the pot voltage, but you need to determine is the voiltage
wrong becasue the circuit is getting the wrong commmand or maybe it is
physically stuck and unable to move to the correct position.

5) The votage on the op amp IC405 input pins 6 and 5 should be
"virtually" equal. If they are not equal, then the there should be a
voltage on the motor and it should be trying to turn.
If they are equal, then the mechinsim is doing what it is told and it
is being told to do the wrong thing and the problem is in the command
voltage inputs.

6) It looks like the only differnce in the comman between play and
pasue is due to the different values of R511 and R514. Make sure the
logic signal to them is correct. These different values shoulsd
create a differnet input to the op amp and the motor should move and
move the cam pot so the voltage on pin 6 and 5 is equal again. This
is a big mechanical feedback loop that tries to keep the voltage on
pin 6 and 5 equal.

Very nice manual by the way...thanks good luck , let us know what you
find.

Mark