Re: Stuck VCR tape, DVD not reading


"Art" <scimethod2000@xxxxxxxxx> wrote in message
news:1187927156.859875.312770@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Aug 23, 6:42 pm, "Arfa Daily" <arfa.da...@xxxxxxxxxxxx> wrote:
"Art" <scimethod2...@xxxxxxxxx> wrote in message

news:1187902602.365664.322840@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

I've got a Toshiba SD-V392SU DVC/VCR player, and there's a tape stuck
inside. It won't play, and when you hit "eject", the little "VCR
spool" icon flashes, indicating that there's no tape inside. So, there
ya go: it won't eject or play since it thinks there's no tape inside
to play or eject. Upon opening the cabinet up, I easily found the
little motor that appears to eject the tape. Trouble is, it is a worm
drive setup, and the nylon gear is too small and too slippery to turn
by hand. Taking out the chassis that holds the tape doesn't appear
feasible (a screw that holds it in is only accessible by taking out
the tape), and even if it could be taken out, doesn't appear to be a
step toward solving the problem.

So, I gotta actuate the motor. The motor has 2 easily accessible
terminal that have been soldered to. They are labeled "+" and "-",
indicating the motor is a DC motor. If I hook up an external DC
voltage to the terminals, what voltage should I try? More importantly,
will damage result if the voltage is applied without unsoldering the
motor's terminals? If I hook up my supply by following the "+" and "-"
terminals' markings, will that eject the tape or suck the tape in
harder? Finally, if this is unwise, I might be able to take out the
motor. If so, then eliminating the worm drive gear should allow the
rest of the accessible gear train to turn smoothly by hand...right?
Will this allow me to take out the tape?

Suppose I get the tape out. Now what? What makes the VCR think there's
no tape inside?

Consider next the DVD portion of the player. Tray works, it spins the
disc, but it won't read DVD's or CD's. Is fixing this feasible, or is
there likely some tiny internal problem not fixable?

Art

Try 6v on the motor, but disconnect it first, as you may do damage to the
driver IC if you don't. If you only use a lowish voltage like this, it is
unlikely that you will cause a problem if your first connection attempt
causes it to 'suck' rather than 'blow'. You just can't tell which way
round
to connect it to get eject. The normal running voltage is probably closer
to
12v, but 6v should be enough to get it going. As far as the DVD player
goes,
it is unusual for one to fail to play either a CD or DVD, and unless
there
is a common cause for both the VCR and DVD problems, which seems on the
face
of it fairly unlikely, as the DVD at least does all the right things,
allbeit not finishing up actually reading the disc, then it is likely
that
the laser is faulty, and it won't be cost effective to repair. Did the
DVD
and VCR problems occur at the same time, or was there some common
external
problem such as a storm or sudden power outage prior to the faults
appearing
? It's just possible that there is a supply rail missing or noisy, which
is
shared by both the VCR and DVD, and it is this which is leading to the
problems. Once I had got the tape out - or maybe even before trying to -
I
would measure and 'scope all of the power supply rails, just to make sure
that they are good voltage-wise, and 'clean'

Arfa

Thanks for the advice. I haven't tried it yet, but I'll get to it this
weekend. I don't recall exactly if the problems occurred together, but
am inclined to believe that wasn't the case. Unfortunately, I have no
scope at home (just at work) so I can't check the rails for
cleanliness, just able to do a bare-bones DVM check. How likely is a
blown rail, though, considering all of the other functions (remote
sensor, channel tuning/picture is fine, all panel lights okay, etc.,
sorry I didn't mention this in the OP)?

BTW, I was startled to see the vastly different construction
techniques used in the DVD board vs. the VCR/TV board. The DVD board
uses SMT, but the VCR/TV board uses what frankly appears to be not so
much a printed circuit board as old-fashioned point-to-point wiring
and thru-hole components. From above, the board has components and a
silk screen image for component labeling, but no traces. It does,
however, have tons of holes in which bare wires poke up from below,
travel across a short distance, and then go down another hole. What's
this all about? My technical skills involve a lot of improvisation (I
work in a lab, and am not involved in production), so I'm actually
sort of used to this. But how the hell does it pay for a company
(producing a product in volume) to do this sort of thing? Any ideas?

Art

When dealing with any kind of 'obscure' problem, where a set of
circumstances or symptoms don't seem to really fit a 'typical' fault
scenario - and yours qualifies on this score as it has two problems, which
on the face of it are unrelated, and one of them is a bit 'odd' anyway -
then the power supply is always the first port of call, as it is usually
common to all sections of a multi-function item like a DVD/VCR/(TV?) combi.
It would not necessarily be a 'blown' rail that you would be looking for, as
in a rail being missing. Rather, one that read low on a DVM compared to what
it should. You would then check with a 'scope to see how clean that rail
was. The reason for this is that the smoothing caps on the output rails of a
switch mode power supply, which all of these items use now, are very
stressed due to the high frequency of the ripple currents that they have to
shunt. There are special caps designed for use in these PSUs, but they tend
to be more expensive than bog standard electrolytics, so many manufacturers
will just use the cheap ones, as they will (usually) last out the warranty,
before they start to fail by going progressively higher and higher ESR. As
they fail, the switching noise and general hash on the rail that they are
smoothing, will get worse and worse, and the average voltage level of the
rail will drop, until you get to the point where something important like
the system control micro can no longer operate correctly, and the oddball
fault symptoms start.

The difference in construction techniques indicates only that Tosh did not
design - or maybe even build - this item. Instead, it has been cobbled
together on the 'Lego brick' principle, where a TV chassis has been bought
in from say Vestel in Turkey, a VCR deck and circuitry has been got in from
Orion, and a DVD section, maybe by Tosh, but equally possibly from one of
the other big Japos, and then have all been put together in a single case to
make the product you have. Indeed, it might all have been put together by
the Ying Tong Lucky Strike Consumer Electronics Manufacturing Company in
Korea or some such, and then just 'badged' Toshiba ...

As far as seeing lots of wire links on the board, this is of no consequence
at all, as they are all put in by automatic insertion machines anyway, so
they are just treated by the machine as any other component - a resistor,
say. Sometimes, lots of wire links just indicates that a single board is
used in many configurations for many different (Lego brick constructed)
products, but equally, it can indicate scruffy design done either totally
manually, or with old software that does not have a good rip up and retry
autorouter. It is also a characteristic of single layer boards, where it is
often more difficult (but by no means impossible) to eliminate track
crosses.

Arfa


.

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