NEC DX3000 VCR - slow rewind problem

[Franc Zabkar]

I need help to solve a slow rewind problem in an NEC DX3000 VCR. I've
changed the caps on the capstan motor PCB, and I've replaced the belts
and tyres. I can't feel any excessive drag in the mechanism, only the
light application of brake pads to maintain a minimal tape tension.
The motor voltage is 7.4V which is correct according to the service
manual. Fast forward is OK, but should probably be a little faster.
The idler tyre has plenty of grip - I can feel the resistance of the
servo in play and cue/review modes. It seems that the motor's torque
is too low at the applied voltage. In fact I can easily stall the
motor with light finger pressure. The drive voltage remains at 7.2 -
7.4V when I do this.

I can work around the problem by adding a 3K3 resistor in parallel
with R618. This results in a drive voltage of around 8.0V.

If anyone knows of any other common faults with this machine, I'd like
to give it a full service. TIA.

- Franc Zabkar

 

[Scott Lane]

Sounds like the motor is bad. I have had some good luck spraying a small
amount of cleaner/degreaser into some electric motors. Used to "restore"
spindle motors on early Pioneer CD players that would be slow and never
come up to speed. Good luck. Scott
********

 

[Andy Cuffe]

Sounds like the motor is bad. I have had some good luck spraying a small
amount of cleaner/degreaser into some electric motors. Used to "restore"
spindle motors on early Pioneer CD players that

That won't do anything for a brushless capstan motor.
Andy Cuffe

[email protected]

 

[Franc Zabkar]

Sounds like the motor is bad. I have had some good luck spraying a small
amount of cleaner/degreaser into some electric motors. Used to "restore"
spindle motors on early Pioneer CD players that would be slow and never
come up to speed. Good luck. Scott
********

The FF/REW idler is driven by the capstan via a belt. The capstan
motor is the PCB type. None of the stator windings appear open.

FWIW, the motor control IC is a TA7262P:
http://www.datasheetarchive.com/datasheet.php?article=3216007

The motor is in the style of the one at the top left of this page:
http://www.wagner.net.au/Catalogue/04_14.pdf


- Franc Zabkar

 

[Mark D. Zacharias]

The FF/REW idler is driven by the capstan via a belt. The capstan
motor is the PCB type. None of the stator windings appear open.

FWIW, the motor control IC is a TA7262P:
http://www.datasheetarchive.com/datasheet.php?article=3216007

The motor is in the style of the one at the top left of this page:
http://www.wagner.net.au/Catalogue/04_14.pdf



- Franc Zabkar

Bad idler, bad reel belt, and I've seen a metal pin come out of a lever
underneath which enables the rewind mode. The white nylon/plastic arm
develops a crack which allows the pin to fall out.

Mark Z.

 

[Franc Zabkar]

Bad idler, bad reel belt, and I've seen a metal pin come out of a lever
underneath which enables the rewind mode. The white nylon/plastic arm
develops a crack which allows the pin to fall out.

Mark Z.

The belt is fine, and the top and bottom halves of the idler lock
together in rewind and FF modes. There is no slippage. The only real
drag appears to come from the weight of the tape. In FF/REW modes the
capstan runs in open loop mode, ie the motor is supplied with a fixed
voltage. The tape is fully retracted into the cassette housing and the
pinch roller is disengaged. Both plastic levers and pins are intact.
I've replaced a sticky brake pad on the take-up lever and the
performance has improved, but it's still a little on the slow side. It
looks like it might be just designed that way <shrug>.

- Franc Zabkar

 

[Mark D. Zacharias]

The belt is fine, and the top and bottom halves of the idler lock
together in rewind and FF modes. There is no slippage. The only real
drag appears to come from the weight of the tape. In FF/REW modes the
capstan runs in open loop mode, ie the motor is supplied with a fixed
voltage. The tape is fully retracted into the cassette housing and the
pinch roller is disengaged. Both plastic levers and pins are intact.
I've replaced a sticky brake pad on the take-up lever and the
performance has improved, but it's still a little on the slow side. It
looks like it might be just designed that way <shrug>.

- Franc Zabkar

Did you look at the lever underneath the unit which is part of the reel
unit? It changes how the reel unit engages.

Mark Z.

 

[Bruce Esquibel]

: The belt is fine, and the top and bottom halves of the idler lock
: together in rewind and FF modes. There is no slippage. The only real
: drag appears to come from the weight of the tape. In FF/REW modes the
: capstan runs in open loop mode, ie the motor is supplied with a fixed
: voltage. The tape is fully retracted into the cassette housing and the
: pinch roller is disengaged. Both plastic levers and pins are intact.
: I've replaced a sticky brake pad on the take-up lever and the
: performance has improved, but it's still a little on the slow side. It
: looks like it might be just designed that way <shrug>.

You know you might not be that far off with that last comment.

I'm not totally sure of the that model number but if this machine is from
the mid/late 80's, I had a DX-5000 bought new and in all the machines I ever
owned, it had the slowest rewind/fast forward.

I mean I'm talking about 7-10 minutes easy to rewind a T-120. It didn't take
long to fail completely, within the first year it couldn't rewind the tape
all the way and from that point, needed the idler tire changed twice a year
if not more often.

At first I thought the generics from MCM were just poor, going to NEC direct
was expensive (whole idler, not just the tire) and didn't help.

Eventually I think I ended up using the reverse scan.

I really liked that machine, was some weird non-standard vhs compared to
everyone else, had some kind of real ram based digital memory with a bunch
of tricks that could be utilized. Was the first vhs that could do frame by
frame slow-motion without noise bars because everything was read off the
ram. Some kind of built in TBC (sort of). Could freeze frame an image and
toss it into a PIP mode with the tape still playing in the background.

But mechanically it ranked in the bottom on my list.

-bruce
[email protected]

 

[David Farber]

: The belt is fine, and the top and bottom halves of the idler lock
: together in rewind and FF modes. There is no slippage. The only real
: drag appears to come from the weight of the tape. In FF/REW modes the
: capstan runs in open loop mode, ie the motor is supplied with a fixed
: voltage. The tape is fully retracted into the cassette housing and the
: pinch roller is disengaged. Both plastic levers and pins are intact.
: I've replaced a sticky brake pad on the take-up lever and the
: performance has improved, but it's still a little on the slow side. It
: looks like it might be just designed that way <shrug>.

You know you might not be that far off with that last comment.

I'm not totally sure of the that model number but if this machine is from
the mid/late 80's, I had a DX-5000 bought new and in all the machines I ever
owned, it had the slowest rewind/fast forward.

I mean I'm talking about 7-10 minutes easy to rewind a T-120. It didn't take
long to fail completely, within the first year it couldn't rewind the tape
all the way and from that point, needed the idler tire changed twice a year
if not more often.

At first I thought the generics from MCM were just poor, going to NEC direct
was expensive (whole idler, not just the tire) and didn't help.

Eventually I think I ended up using the reverse scan.

I really liked that machine, was some weird non-standard vhs compared to
everyone else, had some kind of real ram based digital memory with a bunch
of tricks that could be utilized. Was the first vhs that could do frame by
frame slow-motion without noise bars because everything was read off the
ram. Some kind of built in TBC (sort of). Could freeze frame an image and
toss it into a PIP mode with the tape still playing in the background.

But mechanically it ranked in the bottom on my list.

-bruce
[email protected]

Ditto on the DX-5000 machine. I have one too and you might as well read a
book waiting for it to rewind. The whole NEC line of that era just didn't
rewind with any speed at all. The 7-10 minute waiting time seems very
accurate.

 

[Franc Zabkar]

Did you look at the lever underneath the unit which is part of the reel
unit? It changes how the reel unit engages.

Mark Z.

There is one lever that engages the idler assembly. It's working fine.

- Franc Zabkar

 

[Franc Zabkar]

Ditto on the DX-5000 machine. I have one too and you might as well read a
book waiting for it to rewind. The whole NEC line of that era just didn't
rewind with any speed at all. The 7-10 minute waiting time seems very
accurate.

The supply voltage to the capstan motor is derived from an RC PWM
circuit. I managed to increase the rewind speed by reducing the value
of R (R618). Changing the take-up brake pad also helped.

- Franc Zabkar