Help with National NV-780EM VHS
the problem in this video when i press vtr
its turn on for a second and off. the clock working what the problem ...??? |
Re: Help with National NV-780EM VHS
Sorry don't know the model but would suggest worth checking the power supply for bad capacitors. Very common on some Panasonic units. Just a starting point maybe others can elaborate.
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Re: Help with National NV-780EM VHS
i think it is not in the power
i have another power it's the same problem |
Re: Help with National NV-780EM VHS
Not sure if this model has automatic power-up when inserting a tape, but worth trying if it has. Also check the VTR switch isn't sticky or damaged; clean the mode switch; check for dry solder joints.
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Re: Help with National NV-780EM VHS
I have the service manual for this machine. This model has a switching power supply since it is 110-240 volt automatic. And it is a multi system too.
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Re: Help with National NV-780EM VHS
Try heating the power supply with a hair dryer. If the situation improves while it is hot, it has bad capacitors for sure. If the situation doesn't improve, it can still be anything.
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Re: Help with National NV-780EM VHS
When you press the operate button can you hear the capstan motor rotating?
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Re: Help with National NV-780EM VHS
Yes
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Re: Help with National NV-780EM VHS
When the capstan rotates check if the supply reel table also rotate
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Re: Help with National NV-780EM VHS
Yes
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Re: Help with National NV-780EM VHS
The second display below the deck (function display) works ok???
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Re: Help with National NV-780EM VHS
Yes work but shut down in second the clock still working
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Re: Help with National NV-780EM VHS
Check the zener diode and the caps in the switching power supply.
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Re: Help with National NV-780EM VHS
Check the All Voltage in the PSU.
You need Schematic and SM of this VTR, to check the voltage's are coeherent with the schematic. Libra |
Re: Help with National NV-780EM VHS
This is a relatively early front loader from the mid 80s. D deck.
If it's the one I'm thinking of, it has a transformer PSU. On powerup, the mech should 'shuffle' the reel idler. If this doesn't happen, then the drive belts should be replaced and the mode switch cleaned. That shoud solve this fault. There was also a resistor of very low ohms/safety type, that used to go high, cannot recall if it was in the PSU or on the main PCB where the voltage lines come in. Will try and find some info. |
Re: Help with National NV-780EM VHS
I think that one is on the main PCB. At least in the NV-830 and NV-850 which may be related models. R1001 or something close to that comes to mind.
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Re: Help with National NV-780EM VHS
You can download the service manual from here
http://freeservicemanuals.info/en/se...sonic/NV780EM/ These type of panasonic/national mechanism (D1) when the VCR operates the mechanism proceed a <<selftest>> the capstan motor rotate the suplly reel table and the loading motor make a small movement (rotation). if the self test find a failure the VCR rotate for a few seconds the capstan or the loading motor (it depends from the failure) and then turn OFF. |
Re: Help with National NV-780EM VHS
I believe the person who the machine belongs to has tried another power supply and still has the same fault?
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Re: Help with National NV-780EM VHS
thank you all
I will do everything |
Re: Help with National NV-780EM VHS
My money is on the mode switch being faulty or having dirty contacts.
I had a lot of trouble with this series not doing its switch-on 'shuffle' and then shutting down due to the mode switch having dirty contacts. Tony |
Re: Help with National NV-780EM VHS
I agree with boxdoctor. My Sharp VC-799 did the same beucase the loading belt was off. Some VCRs do a self test when powering on.
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