JVC HR-D721EN black image, only sound?

[maricelado]

hello, from uruguay

I have two vhs jvc version HR-D721EN and both play with sound but black image,
I already cleaned the heads and it's still the same, if I fast-forward there you can see the rain but then it's black with the play logo.
any idea how to repair it or a circuit that is wrong.

for some reason it is blocking the image

here a picture

thanks

[hodgey]

What are you using to view the image? A common issue on this mechanism is a capacitor that sits next to the drum on the bottom of the mechanism that goes bad causing playback issues as shown at the end of this video (though I wouldn't suggest cutting the plastic to get to it, disassemble it properly instead. If there is no image at all (unless whatever you are viewing on will blank out the screen on bad signals) it could be something else though.

[latreche34]

Nice technical explanation from 12voltvids on how the video head timing works, I think the OP has no RF signal at all since the VCR still displays system messages such as playback indicator, I would be looking into the RF preamp with the oscilloscope to see how the RF envelope looks like.

[lordsmurf]

Quote:

Originally Posted by latreche34

I would be looking into the RF preamp with the oscilloscope to see how the RF envelope looks like.

I would be looking into getting a better VCR.

[hodgey]

Since OP is from uruguay, and the specific model supports it, It might be for playing PAL-N, in which case the options are a bit limited. No idea how the image quality is on these, but at least they have a solid tape transport. (It has the same mech as the HR-S5800, 6800, 6900 which the buying guide notes as "These decks have known-excellent tape transports,".) I believe PAL-N tapes will play in a standard PAL deck too as the on-tape format is very similar, but the chroma may be a bit off, haven't tested it.

[maricelado]

Thanks,
i've changed condenser of 50v and 3,5 muf
but still the same, i see the logo of play with black image and sound
so don't know what more can i do

[latreche34]

Changed the capacitors based on what? Can you share your troublshooting procedure. You can't just change a component unless you know it is bad otherwise you will be rebuilding the whole circuit board from scratches, I've already mentioned that 12voltvids issue is different from yours, you can't repair a problem based on a different VCR's symptom. Besides, capacitors are not always to blame, Nowadays are blamed for every mulfunction. Toaster not working? just change capacitors.

[maricelado]

Quote:

Originally Posted by latreche34

Changed the capacitors based on what? Can you share your troublshooting procedure. You can't just change a component unless you know it is bad otherwise you will be rebuilding the whole circuit board from scratches, I've already mentioned that 12voltvids issue is different from yours, you can't repair a problem based on a different VCR's symptom. Besides, capacitors are not always to blame, Nowadays are blamed for every mulfunction. Toaster not working? just change capacitors.

based on that nobody was able to give me a valid solution and it was the only thing I saw that could work. Before talking to me in a bad way because I changed something, try to give a solution
if you come to the forum to speak badly go elsewhere
here is just to give solutions
cheap tenement go talk to the neighborhood rabble

[hodgey]

Ah I missed the bit where the play symbol was visible. It's a bit hard to say what the error is exactly, since audio is normal presumably the tracking and servo stuff is working (at least to some extent) so the error is likely with either the head amplifier or video circuit before the IC that generates the on-screen display. Especially tricky if you don't have a service manual as that makes it easier to see what pins do what so you could check if the voltages are there and if power is missing somewhere. If you have an oscilloscope you can also check whether there is rf signal coming out of the head amplifier to narrow down whether the problem is in it or elsewhere.

[latreche34]

I've already gave you a starting point. Troubleshooting a VCR and repairing it is not something that can be done over a public forum, we've said that numerous times, If you don't have the knowledge, the tools required to do the job I suggest post #4.