Hey
I have a video, when I turn it on, it trys to take a cassete. If there is no cassete inside it turn off it self. If the cassete is inside, it takes her move it down, then take it out and turn it self off.

does anyone know what is the problem?

thansk ahead

 

Most VCR problems are mechanical, it could well be something broken in the loading mechanism.

You should be aware that VHS VCR's use optical detection to detect the end of tape, these are often triggered by ambient light when you take the top off - it makes it quite difficult to fault find because of this.

__________________
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How can I check if all optical detectors are working properly???

 

With something to block and unblock the beam, and a meter (or preferably oscilloscope) on the output of the detector.

But as above, be careful that stray light doesn't fall on the sensors!.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

From the problem description you have given, it seems to me that these are classic symptoms of a faulty or dirty mode-switch. The mode-switch tells the electronics the position of the mechanics at any given time. If this switch becomes dirty or goes faulty, the machine can exhibit some very weird faults indeed, including the type that you describe.

I'm not saying that the problem you have definately IS related to the mode-switch as it could also be any number of other things including the suggestion that Nigel gave. However, the symptom you've described does sound typical of the kind of problem you can get when a mode-switch is dirty so I would advise cleaning or replacing it.

If you're not familiar with this procedure then I would definately advise you get a professional to do it. Cleaning or replacing the mode-switch often requires the entire deck mechanics to be removed from the machine, and the position of the mode switch as well as the alignment of the mechanics is critical when refitting. If you get it wrong, you can end up with a whole host of other problems.

Brian

 

I have to check it but I think that the problem is in this switch...

I think I know where is it, but I am not sure. How can I recognize it?

Thanks...

 

It varies greatly from machine to machine, also mode switches haven't been used for a good number of years now!.

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

I've seen them used in a number of very recent products. The only system I know of whereby a mode-switch isn't used is the Philips system whereby the microcontroller counts revolutions of a fly-wheel in order to determine the position of the mechanics at any time.

Brian

 

Most modern VCR's use optical methods of performing the mode switch function, basically slotted opto-switches with the beam broken by projections on the mechanism.

It was introduced to reduce the high failure rate caused by the mechanical mode switches. I don't think I've changed a mode switch this century :lol:

Going back a LOT further, they used individual micro-switches, they NEVER failed.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

I've never seen a video recorder which uses optical methods in place of a mode-switch. Every model I've ever worked on, including the latest ones, still use a standard rotary encoder. Even camcorders that I've worked on use them!

You must be working on a model of recorder that I don't and vice-versa. I think I remember you saying that you service a lot of Sony products? I don't service any of those, so possibly that's why we're having a difference of perspective here.

Video recorder servicing is becoming increasingly rare altogether these days though. I can go weeks without looking at even one unit now, the things are so damned cheap that nobody wants them repaired anymore.

Brian

 

We don't do camcorders, but I can see that they are probably too small to do it optically?.

Sony VCR's are just bought in from Samsung, and have been for a number of years now, they don't use mode switches, but neither do Sharp ones. What akes are you looking at?.
Very true!.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

In the VCR department we mainly look at Sanyo units which these days are basically LG decks, and Philips units. I'm not sure what decks the Philips units are using but I'd be suprised if they were their own. We've got a couple of Samsung TV/DVD/VCR combination systems but I've never had cause to strip the VCR part down.

Brian