JVC HR-S8000U Won't Rewind

[olePigeon]

I think I'm going to get one of those cheap $80 portable units. I think it should be good enough for me to calibrate and further diagnose my VCR.

But first I need to make a reference tape, with a stereo KHz tone so I can definitively tell if the audio is working correctly.

[redk9258]

Originally Posted by olePigeon

I think I'm going to get one of those cheap $80 portable units.

What unit? Oscilloscope? You want an analog scope! 12voltvids recently compared a couple of scopes to align a VCR. One digital may have worked somewhat.

Here's the video...
https://youtu.be/fE81cljNBgM?si=IymQlq6Ro7qo3WtB

[olePigeon]

I had a few people comment on my YouTube video where I was demonstrating the problem. Thanks go to @Phil-d2i6s, @SUMI, and @vvm2004. So for posterity's sake, here is a compilation of explanations of the issue and how to resolve it for anyone else who may be having the same issue as I did with my JVC:

The problem is caused by the carbon brush and the ring inside the motor being oxidized, in addition, the noise reduction capacitors are aging, causing noise pulses when operating. The reel motor generates electrical commutator noise: not too much during play and search modes when the supply voltage (and current) to the motor is lower, but much more during the high speed winding modes.

In addition to the motors being electrically noisy, the tape end sensor circuits are potentially too sensitive and are only just turned off while the tape is interrupting the IR from the LED. The electrical noise from the motor is seen and amplified by the end-stop phototransistors resulting in negative-going spikes that make the controller think the end of the tape has been reached.

The correct method for repair is to service or replace the motor, and to replace the noise reduction capacitors. However, this may not always work. So in addition to motor repair and recap, adding 100 uF capacitors to the motor and both end-stop sensors may finally resolve the issue.

[redk9258]

Thanks to all for the information! I wonder if there are any technical bulletins out about this problem. Unfortunately there's not a lot of those floating around the interwebs.

So, is your 8000 working now?

[olePigeon]

Originally Posted by redk9258

Thanks to all for the information! I wonder if there are any technical bulletins out about this problem. Unfortunately there's not a lot of those floating around the interwebs.

So, is your 8000 working now?

Mechanically, yes. The right channel is muted (quiet) compared to the left channel. So I have a little bit of diagnosing to do. It was working, then stopped, then resumed, and now is quiet on one channel. It's an intermittent problem, and without an oscilloscope, I'm going to do the old fashion way of just poking at it with my plastic CRT adjustment screwdriver.

I got an RCA to 3.5mm adapter and I'm gonna plug in some headphones with a stereo audio tone playing. Then I'll poke at it until something changes.

[redk9258]

Originally Posted by olePigeon

Mechanically, yes. The right channel is muted (quiet) compared to the left channel.

Is that only the HiFi tracks or Normal audio too?

MISU also did a video on this same symptom and it was a bad coupling capacitor.

[olePigeon]

Originally Posted by redk9258

Is that only the HiFi tracks or Normal audio too?

MISU also did a video on this same symptom and it was a bad coupling capacitor.

Oooooh. Do you have a link to that one? I'm going to order some capacitors and do some preventative maintenance. I might as well replace that one while I'm at it.

[redk9258]

Originally Posted by olePigeon

Oooooh. Do you have a link to that one? I'm going to order some capacitors and do some preventative maintenance. I might as well replace that one while I'm at it.

https://youtu.be/YxUxaVpR8ro?si=LzZ3nXuyAcZZ0ONK

About 18 minutes in.

[olePigeon]

Originally Posted by redk9258

https://youtu.be/YxUxaVpR8ro?si=LzZ3nXuyAcZZ0ONK

About 18 minutes in.

Wow, thanks! That's the same problem I'm having. Right channel is muted. I'm gonna replace those caps.

[redk9258]

Originally Posted by olePigeon

Wow, thanks! That's the same problem I'm having. Right channel is muted. I'm gonna replace those caps.

Do you have an ESR meter? While they do not test every failure of an electrolytic capacitor, it would show the cap you are looking for as open.

[olePigeon]

I have a cheap component tester. But I'd need to get new gator clips. The ones that came with it broke.

[redk9258]

Those may not work well in circuit.

[redk9258]

12voltvids revisited the BR-S605..

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

I haven't watched it yet but suspect he has it fixed because he is talking about adding caps across the motor.

[olePigeon]

Originally Posted by redk9258

Those may not work well in circuit.

Doesn't work at all in circuit. All the in-circuit testers I could find are really expensive. I've always been on the fend about getting one, weighing it against my lazyness to remove capacitors every time I want to test them.

[redk9258]

Originally Posted by olePigeon

Doesn't work at all in circuit. All the in-circuit testers I could find are really expensive. I've always been on the fend about getting one, weighing it against my lazyness to remove capacitors every time I want to test them.

If you mess around with this stuff at all, you should get one! I recommend the Blue ESR meter. If you remove the cap to test, is it worth putting it back in? I've seen knockoff Blue ESR meters on AliExpress that probably would work fine.