JVC HR-S8000U Won't Rewind
 

Hello, I'm new to the forums.

I'm having issues with my JVC HR-S8000U. It won't reliably rewind. Usually it just attempts to rewind, then stops. Sometimes it'll rewind for a little bit, then stop. And on very rare occasions it'll rewind normally.

Play & Fast Forward work fine. Play used to not work reliably, but I loosened the tension belt a tiny bit, and now the Play seems to work fine.

Below is a video I made so you can see the issue. You can see I attempt to rewind several times, but it doesn't work. Fast Forward is fine. Play is fine. When I was attempting to troubleshoot it, I thought I had it reliably working by covering the Supply Sensor. But the next day when I went back to continue trouble shooting, even covering the Supply Sensor didn't help much.

I'm hoping someone else has run into this issue and might have some advice.

The chassis board that has the supply sensor is getting 12.5v (a little high, supposed to be 12v), but the Phototransistor is getting 5v on the dot like it should. I recapped the power supply because it had a bad cap. I also removed all the glue and adhesive pads from the various PCBs. The rewind issue has persisted.

https://youtu.be/KzowZIwONzU

Thanks for any help.

The end sensors need covered as it's exposed to light without the enclosure
There should be reel sensors under each reel.
Check the pulse on those.
Usually under the reels is a reflector with black stripes.sometimes
The black comes off or the reflector is dirty
If you clean just use water.
The optical sensor it uses may be weak also

Is the mode switch clean?

Yeah, I had the end sensor covered. If it's not, the VCR will fast forward indefinitely looking for the beginning of the tape and won't let you change modes.

I remember the black stripes on my RCA. I don't recall seeing any when I removed the reels to oil the bearings. I'll take another look. Thank you.

Oooh, I forgot about this. I read that it's a common point of failure for a lot of VCRs. That would make sense if it's all crusty and not engaging correctly. I hope it's not buried inside. The only way to get to the lower functions of this particular model is complete and utter disassembly.

I'm not familiar with your model but it was built shortly after my HR-D470U. The mechanism looks similar but not exact. On my model the bottom panel comes off and if I remember correctly, you have to unsolder a couple of wires to gain access to the mode switch. I could be mixing this up with changing the mode belt too. LOL

Looks like my reels have crenelations with an IR LED and photosensor on either side that reads the light as it passes.

Mine is behind a plastic cage. Some of the stuff is accessible.

So, here's the back of the unit:

http://www.clickwidget.com/vcr/HRS8000U-back.jpg

And somewhere under here is the mode switch:

http://www.clickwidget.com/vcr/HRS80...haassembly.jpg

Even with the service manual, I couldn't figure out how to remove the mecha assembly. It doesn't tell you what screws to under, or in what order to disassemble things.

I removed all the screws and desoldered the board, but I couldn't figure out how to disengage it from whatever it was hung up on. I also have zero idea what the mode switch looks like.

Edit: Sorry, I can't get inline pictures to load.

It gets hung up here:

Attachment 206897

Well, now I have to take it apart. The belt is slipping on the motor there in the lower right. I wonder if that was the reason all along.

Edit: Nevermind. Removing the mech assembly gets me nothing.

The mode switch will look something like this..
https://kpcomponents.co/products/jvc...9444c846&_ss=r

I'm not saying that is the exact one for your model. Look at the SM for the part number. It may be called a slide switch.

Be careful if you remove that bottom plate to change the belt. Things must be kept in time. There should be information in the service manual.

I've run into the problem that I can't get any further than I have. As mentioned above, it's stuck around something. I was able to determine it's stuck around a pin that connects to an arm. And that arm is either riveted to the mech chassis or screwed in inaccessibly from the opposite side. As far as I can tell, it would require that I completely disassemble the entire chassis just to get access to the section I need to replace the belt and gain clean the mode switch.

Unless someone else has worked on this model and can point out a different approach, I just don't see how it's even possible. I don't want to take it apart further than I have because I don't have a scope that would almost certainly be required to realign everything.

Attachment 206900

The service manual is not very detailed from a mechanical standpoint. It doesn't tell you in any great detail what to do. I assume from the order things are laid out, I disassemble the head assembly, followed by the Audio Control assembly (which is attached that arm that I can't remove.), followed by the tension band assembly, followed by the control arm assembly, followed finally by the control cam assembly. I guess? ¯\_(ツ)_/¯

And nowhere does it tell you what type of screws, in what order, or where they're even located.

If I owned a scope, the service manual would be invaluable as it shows all the waveforms for everything.

The service manual is not very detailed from a mechanical standpoint. It doesn't tell you in any great detail what to do. I assume from the order things are laid out, I disassemble the head assembly, followed by the Audio Control assembly (which is attached that arm that I can't remove.), followed by the tension band assembly, followed by the control arm assembly, followed finally by the control cam assembly. I guess? ¯\_(ツ)_/¯

And nowhere does it tell you what type of screws, in what order, or where they're even located.

If I owned a scope, the service manual would be invaluable as it shows all the waveforms for everything.

NO do not remove the stuff from the top. Remove any plugs , wires etc. Remove the loading mechanism.. should be a couple of screws. Now you should see 3 or 4 screws holding the whole mechanism to the plastic frame. These should be pretty large screws. Now lift the whole mechanism out and flip it over carefully on a towel or something soft. Now you can get to the mode switch and mode belt.
The SM that I downloaded is missing parts of the exploded views. I'm guessing yours is the same.
Try this manual. I believe the mechanism is the same as yours....
https://freeservicemanuals.info/en/s...950E/HRD950EG/

This video might be helpful to watch. Your mechanism is different but you can get the idea of how to remove the mechanism.
https://youtu.be/0bbJ-7tXMf8?si=ogz4QHSyXqxTSi_S

Yes, mine is missing the mechanism sheet. I could extract these pages and make a complete manual. It even has the cable I couldn't figure out how to disconnect, which was also covered by 12voltVid's video. Very helpful. I watched a lot of his videos before posting here trying to find an analogous VCR troubleshooting video that would help. I was tempted to send my VCR to him for repair, but the shipping would be cost prohibitive.

Unfortunately I still don't see how to access the mode switch without removing the entire mode assembly, which is interconnected with the A/C head assembly. That's what is stumping me. However, once I have the whole thing out, maybe it'll become more clear and easy. I'll also be able to take better pictures.

Thank you everyone for the help! It's been invaluable.

Well, here's a 12voltvids with a professional VCR with the same mechanism, with exactly the same issue I'm having. Even he thought it might have been the sensor at first, which was my initial conclusion. Such a weird issue.

https://www.youtube.com/watch?v=__PFQlKia68

Unfortunately it doesn't look like he did a Part 2. Or at least I can't find it.

When you remove the mechanism, turn it over and you will have to remove a couple of items to access the mode switch. You may have to unsolder a PCB or remove the plate that holds the cam gear. I think it will be more apparent with the mechanism out. You will not need to mess with any heads or alignments. The gear timing is critical but should be obvious with it in front of you and the pictures from the SM.

OK, fully extracted. The mode switch (highlighted in purple) is beneath the motor & board highlighted in orange, which is interconnected with the mode switch motor assembly to the right.

As I suspected, this is looking like I'm going to have to completely disassemble it both for replacing the witch motor belt and cleaning the mode switch itself. This will, I would assume, require a full calibration, which I am completely unequipped to do. :worried:

Attachment 206903

Pictures are not showing. You should not have to make any adjustments or calibrations.

Here is a picture of the mechanism..
https://web.archive.org/web/20201126...com/mbk-42.htm

You do not have to disassemble anything needing re-calibration.
You may have to unsolder a couple of wires and maybe drop the capstan motor down to get clearance to get at the mode switch. It may be possible to get deoxit in the switch without disassembly. If you take the cam plate off - or whatever it's called, make sure you understand the timing marks. They are critical for reassembly. Also pay particular attention to where each screw comes from. They must go back in the same place!

I just repaired another HR-D470U with a similar mechanism. Someone was in there before and it was making a horrible clicking sound and couldn't go through the different modes. One screw was in the wrong place causing the mechanism not to be able to cycle all the way through. I put it back the correct way, replaced an idler tire, 2 caps in the power supply and it works.

OK, then. I'll start dismantling it and taking lots of pictures along the way.

OK, it was easier than I thought. The main issue I had with extracting the boards was resolved by removing 3 screws to the big motor. It then lifts out and lets me unhook the mode assembly.

Unfortunately I don't know if my old problem was resolved because it now has a new problem: when I power it on, the mode control motor goes into reverse indefinitely until it hits the end of the gear track, then goes for a bit longer until the failsafe engages and the VCR powers itself off.

This did happen to me once before, but it was only because I had forgotten to plug back in the circuit board connected to the tape chassis. This time, however, it's doing it regardless.

I'm confident I have the V lined up on the mode switch, and I'm confident I have all the holes lined up for the gears on the mode assembly before attaching.

Were you able to open the mode switch and clean it?
Is there a bad solder connection on one of those circuit boards?
Are all connectors plugged in correctly?
Mode belt not slipping?
It must not think it is home if it keeps running then times out.
Are you sure every timing mark is lined up?
With the power off, can you run it through a complete cycle manually? This takes a lot of turns. My model has a spot where you can use a screwdriver to do this even though it's not documented... there's a hole punched in the mechanism chassis for access.

Where are you located?

I watched the video from the first post again. When it's changing modes, I think I hear a little squeal. I'd check to see if that mode belt has enough traction to go through the cycles. You might get by cleaning it with acetone. Clean the pulleys grooves with alcohol.

I may or may not have soldered the mode motor in reverse. :stupid:

(OK, maybe I did.)

Phew. OK. After all of that, I'm back to where I started. It still won't rewind. :sigh:

Oops. Yes, to answer some questions:

Yes, I got down to the mode switch and cleaned it. I also checked the belt. To be honest, it looks like someone was in here already. The switch looked like it had already been cleaned. I cleaned it anyway following 12voltvid's recommendations. The belt looked like it was recently replaced (albeit a bit greasy.) I cleaned both the belt and the pulleys. The retaining clip for the worm screw was broken, indicating someone had taken it out and replaced the belt already. The belt didn't seem to be dried out or goopy.

I took care to follow the service manual for aligning the mode switch V groove. The service manual says to push the plate assembly to the right and line up the holes on the plate assembly with the holes on the chassis, then insert a screw driver to keep the holes aligned. Then align the V groove on the mode switch.

Edit: Also, I'm in Northern California (South Bay Area). So if any enthusiasts are curious and want to see it in person. I could also stream it on Twitch, I have a web camera. I don't know if seeing it in real time would help.

You're too far away for me to help (or help make it worse!). You may want to contact NorCal715 on YouTube. Maybe he is in driving distance and could help you out. He says he's busy so it could take a while.
Maybe take a vacation to Vancouver. 12voltvids is there. LOL
It sucks that there is nobody left to work on this stuff. You have to learn yourself. Then there's the whole parts issue. At least some people have come up with ways of making gears, etc.

You could also try to see if Dave's TV & VCR Repair in Grant's Pass, Oregon would look at it. He's also on YouTube.

That's a 12 hour round trip drive. If I'm gonna spend $100 on gas, I might as well buy a different "known good" VCR.

I'm gonna try nudging the switch one direction or the other and see if it affects the VCR's ability to remain in rewind mode. Or maybe apply a tiny bit of pressure on the switch.

Thanks, I'll send him an email. Maybe I can at least get some advice or a new direction on how to troubleshoot it.

Try to get an oscilloscope .one may come up in your area.most goodwill hubs will let u pu from them save on shipping
https://shopgoodwill.com/categories/...=grid&ihp=true

I pu parts and test equipment at harvest usually cheap sometimes free
https://www.arrl.org/hamfests-and-conventions-calendar

I found a second 12voltvids video with a JVC unit with the same mechanism that won't rewind. It's also the second JVC related video where he does not revisit the issue with followup video with a fix. :(

https://www.youtube.com/watch?v=__PFQlKia68

However, there're quite a few helpful tips in the comments section. One user suggested it could be a warped "pendulum." I don't know where that part would be. Another user said their photoconductor had bad contacts and was causing noise on the signal, making it not rewind correctly, and offered a suggestion for a fix.

So I have some new avenues to explore for troubleshooting. Could still be electrical, but could also be a mechanical issue. I'm going to try to replicate what he was doing to get it to rewind reliably without a tape.

The noisy photoconductor has me intrigued, though, because I initially thought it was the sensor and seemed to get it to reliably rewind when I covered it. But then later it wouldn't rewind even if I did cover it. So if it's noisy, it could be that the first time I covered it, it was just enough to get it to work. Then it got more noisy the next day, and covering it wouldn't make any difference.

Anyway, just an idea.

Could also be the photointerruptor. I could test it by shining a light in there with my multimeter hooked up. See if it's detecting light. That would at least tell me if it's working, but won't tell me if there's noise on the line. I don't have an oscilloscope. They're just too expensive, and I have absolutely no idea how to use one.

Photointerruptors are fine as far as I can tell. They produce voltage when I pass a light in front of them while connected to my multimeter.

Dang it.