Help: Sylvania VCR problem: VCR switches to stop in the middle of play
Jonathan G Harris
we will be playing the tape and it suddenly switches off as if we had hit
the stop bottom, but nobody touched the controls. I assume this is caused
by the tape jamming in some way? We also have had frequent problems with
bad picture or no picture, but the picture becomes fine after one cleaning (at
least for a short while). Now Even after running the cleaning tape through,
we still have the problem of the VCR stopping in the middle of the tape (very
frequently in some tapes, so that they are essentially unplayable).
I just replaced the belt hoping to relieve some of the problems. I have
heard that a number of problems can cause what I am seeing. What is the
easiest procedure. Is there a test to isolate the problem or am I better
off just replacing components until it works? Which components should I
replace first[The age of the machine is about 5.5 years]? It is probably
cheaper to replace the machine than to pay $80+ to have it repaired (
also considering that after the repair I still have a 5+ yr old machine
that may break down again)
Thanks,
---Jonathan
--
Jonathan G. Harris
Department of Chemical Engineering, MIT Rm 66-450
25 Ames Street, Cambridge, MA 02139
har...@athena.mit.edu (617)253-5273 Fax 252-1651
Dave Mcdonald
The problem is likely a dirty cassette down switch.
When you say it is probably cheaper to replace, just remember, the new machines you will be
to get 2 to 3 years of service from them. The new ones are getting
to be very unreliable. Back in the early 80's VCRs never wore out heads.
Now you are lucky to get 1000 hours on them! I say lucky, as I have had one
customer that has worn their heads out 3 times in the past 2 1/2 years.
The guy's wife is addicted to soaps, and runs it for about 6 hours a day.
A set of heads lasts him abouy 8 months. He gets 1 set under warranty, and
wears them out in abother 8 months.
Andy Green
: My Sylvania 2-head VCR keeps stopping while we are watching a tape. That is
: we will be playing the tape and it suddenly switches off as if we had hit
: the stop bottom, but nobody touched the controls. I assume this is caused
: by the tape jamming in some way?
Well, the machine is detecting a fault of some sort and making a
controlled shutdown. Yes, it does have a certain amount of
self-preservation logic, although it can still eat tapes under the right
circumstances...
The most common repair I know of is replacement of the idler wheel, that
large rubber-tired thing you can see near the front of the machine below
the tape, which pivots from side to side to drive either the supply or
takeup reel spindles. It's a $6 part that requires $74 of labor to
install, hence the $80 repair bill, but if you are reasonably handy with
basic tools, you can replace it yourself. While you're in there, clean
the heads with alcohol and a lint-free swab. You can get a replacement
idler wheel (sometimes you can just buy the tire _for_ the wheel) from
local electronics supply places.
As for why it shuts down, my best guess is that the idler wheel is
slipping as it attempts to drive the takeup reel during playback. There
is commonly an optical sensor under the takeup reel that watches a
pattern on the underside of the reel and signals the machine to shut
down if the reel does not move within a certain period of time.
-- Andy
Nick Austin
> Jonathan G Harris (har...@athena.mit.edu) wrote:
> : My Sylvania 2-head VCR keeps stopping while we are watching a tape.
> : That is we will be playing the tape and it suddenly switches off as
> : if we had hit the stop bottom, but nobody touched the controls. I
> : assume this is caused by the tape jamming in some way?
>
> Well, the machine is detecting a fault of some sort and making a
> controlled shutdown. Yes, it does have a certain amount of
> self-preservation logic, although it can still eat tapes under the right
> circumstances...
The possible faults on this one are endless and one could probably
write a book on the subject!
Without a service manual for your particular machine (which I
don't have) I can only give a very general (and brief) guide to
tape-stopping faults:
The syscon (system controller) microcontroller will make a whole
load of checks while a tape is playing. These checks could include:
The supply spool is rotating;
The take-up spool is rotating;
The upper head/drum is rotating;
The capstan is rotating;
There is a cassette inside the mechanism;
The mechanism's "mode switch" is set to "play".
There is non-blank (i.e. not leader) tape coming from the supply spool.
This is by no means an exhaustive list. And it's possible not all
these checks are being performed by your particular machine. In
general if the syscon doesn't like the signals it receives (from
sensors mounted all over the deck) then it stops play and reverts
to stop (some machines will go to standby instead of stop).
Blank tape from the supply spool signals the end of the tape and
this often makes the machine go into rewind. Carefully watching
the symptoms of the fault and comparing to how the machine behaves
under normal operation can give some clues.
The fault could be:
* A mechanical fault that prevents one of the above actions from
happening.
* A sensor fault (or a cabling/track fault, e.g. a dry joint) so
the syscon only *thinks* that one of the above is happening.
* The syscon is faulty or is being 'reset' because it (1) lockups,
(2) its power supply browns-out or (3) because it is being
'clocked' incorrectly.
Sometimes a sensor is used to detect a magnet mounted on a
rotating spindle or wheel so a broken or slipped magnet could also
cause a sensor to give unreliable readings.
> takeup reel spindles. It's a $6 part that requires $74 of labor to
> install, hence the $80 repair bill, but if you are reasonably handy with
Estimating costs for this type of intermittent fault is almost
impossible. It could be under $20 or several hundred dollars -
Most of the cost will be labor.
If you are lucky your machine will have a diagnostic mode, so that
when the fault occurs it reports (typically via the "clock display")
why it is stopping. This should tell you which of the sensors is
at fault/detecting the fault. You need a service manual for this.
This type of fault is best tackled by close attention to detail
and close observation/inspection of the machine. Familarity with
that particular model of the machine in question will also help.
Good luck!
Nick.
--
| Nick Austin | "5... 4... 3... 2... 1... Pass the Mic!" |
| Southampton, England. | news:alt.fan.michaela.strachan |
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