Quantcast JVC HR-S9900U bad ribbon cable, part needed? - digitalFAQ Forum
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  #1  
12-17-2019, 01:03 PM
BelowZero BelowZero is offline
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My JVC HR-S9900U has succumbed to the dreaded issue of immediately shutting down every time it is powered up. It has happened before but after a while would return to working correctly. This time it appears that no amount of time or jiggling of the gears under the dynamic drum is going to bring it back to life.

So I did what any real man would do and decided to tear it apart. No, I'm not a repair man and have no knowledge of the inner workings of a VCR, but my rational was that 1) I have a Panasonic AG1980 and a JVC HR-S7600U, both in good working order and 2) I'm not going to spend the $$$ to repair this machine when I can purchase another one for around the same amount of money, and 3) If I screw it up too badly I'll sell it for parts and look for another one. Besides, I've always wanted to get better acquainted with the guts of these machines. So, for better or worse...

I carefully removed the dynamic drum and the gear assembly that sits directly below it. I examined the gears and didn't notice anything that looked amiss. All the gears looked to be in good shape and all turned as they should. Then I looked at the gears that sit directly under the dynamic drum and that's when I noticed that one of them was cracked. It was the smaller of the two that sits on the right side (as you look at the dynamic drum from the top). See attached photo.

Well, that has to be the problem does it not? So now I'm looking for someone...anyone who might know where I can get a replacement gear or perhaps the entire dynamic drum assembly. Surely some of you repair men have 1 sitting around the shop. If not, where might I locate this gem without having to purchase a "for parts only" machine?? I do love this model for it's picture quality when transferring to digital and would like to be able to say I fixed it myself!

Thanks for any advice.


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File Type: jpg JVC Gear.jpg (75.1 KB, 22 downloads)
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  #2  
12-17-2019, 05:17 PM
BarryTheCrab BarryTheCrab is offline
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http://www.digitalfaq.com/forum/news...amic-drum.html
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The following users thank BarryTheCrab for this useful post: lordsmurf (01-23-2020)
  #3  
12-17-2019, 05:56 PM
BelowZero BelowZero is offline
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Many thanks for that link. Looks like I have a project for tomorrow.
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  #4  
12-18-2019, 01:26 AM
latreche34 latreche34 is offline
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The thread in here is missing a lot of pictures, I posted the guide in VH with all the pictures and I revised it few times since, They made it a sticky for easy access. -- Images now fixed! -LS

Here is my take on this, Even if you find the entire drum somewhere never used it will cost you an arm and leg and the gears will most likely be cracked, The reason they crack is not the use, it is the design, the center core is metal and the circumference is plastic, overtime plastic shrinks but metal doesn't so it will give up and crack, Sony made the same mistake on the 8mm VCR's where the hub gears are made the same way.
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  #5  
12-18-2019, 12:09 PM
BelowZero BelowZero is offline
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Thanks again to Barry The Crab and latreche34.

I applied the fix, but unfortunately the unit will still not power on.

I've attached two pictures illustrating what I did.

In Picture 1, I removed the 2 small black gears (one of which was the broken one), marked and tightened the 2 tension screws and backed off the 2 remaining gears so that they are loose but still attached.

In Picture 2, I removed the large white gear and left everything else as it was.

The pics that you had posted weren't exactly like my unit so I very well could have misunderstood what stays and what gets removed. Could you take a look and see if it looks correct to you?


Attached Images
File Type: jpg JVC Gear 2.jpg (66.8 KB, 10 downloads)
File Type: jpg JVC Gear 3.jpg (90.5 KB, 10 downloads)

Last edited by BelowZero; 12-18-2019 at 12:14 PM. Reason: Uploaded the wrong picture
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  #6  
12-18-2019, 02:44 PM
BarryTheCrab BarryTheCrab is offline
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I appreciate the mention but I only gave you a link that was the result of other people’s really impressive tinkering.
Hoping you sort it out, I’ll be watching.
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  #7  
12-18-2019, 09:51 PM
latreche34 latreche34 is offline
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You most likely took off the gear that suppose to keep the tone wheel spinning so the sensor would read pulses, if the sensor sees the wheel stopped it will shutdown the VCR. Put that large gear back and take off the small gears only if you can, the small white and the small black ones only.

Quote:
If the drum assembly to be removed from the chassis then you can remove the tiny black gears and leave the big gears on, the big black gear has to stay on because it drives the pulse wheel. Back off the other two drum and lead ring black gears so they don't interfere with their neutral resting position
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  #8  
12-20-2019, 12:43 PM
BelowZero BelowZero is offline
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The saga continues. I removed the 2 small gears and replaced the large one but that didn't work either. So I decided to look at the drum assembly in my S7600U and see if that would help clarify things for me. To my surprise, the assembly in the 7600 is exactly the same as the 9900. I took that out and placed it in the 9900 and the unit powered on and worked perfectly. So I now know that the drum assembly is definitely the problem.

Unfortunately, when I was removing the assembly and disconnecting the wiring, the end of the white 5 pin ribbon came apart (the plastic piece just came off) so I am now unable to reconnect the wire. Until I can find another wire I will be unable to do any further testing on the unit. Does anyone know where I could find this wire? It's the white 5 pin ribbon (not the short orange one) that connects to the top the drum assembly. Any help locating a new (used) one would be appreciated!
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  #9  
12-20-2019, 03:00 PM
latreche34 latreche34 is offline
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The drum with broken gears must have a bad motor, a jammed motor or a bad optical sensor, the easiest way to know is to hear if the motor spins freely when everything is connected together.

As for the ribbon cable they are hard to find, I had to glue the plastic piece on one of the VCR's it worked for a while and then the connector was bad so had to strip the traces on the ribbon cable and soldered them on the drum motor board.
If you can measure the traces pitch and width of the ribbon cable you might be able to find one.
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  #10  
01-11-2020, 10:39 AM
HBB360 HBB360 is offline
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Quote:
Originally Posted by BelowZero View Post
Unfortunately, when I was removing the assembly and disconnecting the wiring, the end of the white 5 pin ribbon came apart (the plastic piece just came off) so I am now unable to reconnect the wire. Until I can find another wire I will be unable to do any further testing on the unit. Does anyone know where I could find this wire? It's the white 5 pin ribbon (not the short orange one) that connects to the top the drum assembly. Any help locating a new (used) one would be appreciated!
Same happened to me with my JVC HM-DR10000. I strained the metal contacts at the end and used super glue to attach the plastic piece back on, after it dried some of it had gotten on the contacts so I had to scrape it off to get a connection but it's still working fine and a simple fix.

I just realized this is an older thread, how did everything work out?
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  #11  
01-12-2020, 08:56 AM
BelowZero BelowZero is offline
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Thanks. I was looking for a way to secure the plastic back on but haven't tried it yet. What do you mean when you say you "strained" the metal contacts?

As for the saga, the dynamic drum (as well as the ribbon wire) from the 7600 are now resting comfortably in the 9900 and it is working just fine. The 7600 is just sitting waiting for some attention, which it may never get. I'm considering selling it for parts or someone who is looking for a new project. It will go cheap if anyone is interested.
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  #12  
01-12-2020, 04:13 PM
latreche34 latreche34 is offline
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I would like to try to repair it but I'm not sure about the state of its electronics so it might not be worth even the shipping charge, PM me your address just to see if it is worth an offer.
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  #13  
01-15-2020, 06:04 AM
HBB360 HBB360 is offline
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Oh crap, don't know how it ended up like this! Meant "straightened out" since they were bent all over the place from me trying to insert the cable in the connector without the plastic to hold the pins together.
Glad the 9900 works, I bought two 7700s a while back without realising how worn they were, must've been used for heavy video editing and then stored underwater. I barely got one to work with a new loading belt and the heads are pretty much nonexistent...
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  #14  
01-23-2020, 01:54 PM
BelowZero BelowZero is offline
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Well now that I've completely buggered up the ribbon cable, I'm wondering if any of the lower end JVCs might have used the same 5 pin cable that the 7600 and 9900 used. Thought I'd look for a "parts only" unit on eBay and just steal the cable out of it. Does anyone who's worked on these VCRs know if that might be the case?
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  #15  
01-23-2020, 02:35 PM
hodgey hodgey is offline
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If you mean for the drum motor, I think lower-end JVC units used the same parts for that. Haven't studied the SM in detail but it looks the same on e.g my HR-J658 and HR-S8500. They changed the mechanism a little from x6xx series on, and later on the very last models had a different cheapened mech with more plastic. You coud probably get one from a cheaper unit from the same lineups and grab a ribbon cable from it. For that matter I wonder if one could even swap in the whole drum from a hi-fi deck.
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  #16  
01-23-2020, 03:25 PM
latreche34 latreche34 is offline
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Ribbon cables have different traces count on JVC's VCR's depends on the speeds the drum can perform, So they are not all the same, the same thing goes for drum assemblies, There are the ones with the extra flying erase head, and the DD ones cannot be swapped out with non DD ones.
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  #17  
01-23-2020, 04:55 PM
hodgey hodgey is offline
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The cables/pinouts for the motor (the cable on top of the drum) seems to be the same between the low and high end models that share mechanisms. E.g see the SMs for the 9700ek top of the line svhs and the JVC-HR271MS 2 head vcr. It does look like JVC started using the simplified mech earlier in the lower end models though, and some of the later ones are jvc-badged LG decks with LG mechs. Those have different pinouts. Most of the service manuals I found were PAL models though, not sure which NTSC ones would be compatible.
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  #18  
01-23-2020, 07:52 PM
BelowZero BelowZero is offline
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Thanks for the replies.

Just for clarification, I am talking about the ribbon cable that connects to the top of the dynamic drum assembly. It's getting frustrating that I can't find the same cable anywhere online or that I can't seem to get the plastic piece back on the cable (super glue doesn't want to hold it on). I'm pretty sure that the bare wires have now pulled free of the cable so I doubt it can be fixed. Not sure where to turn to next.

To top it off, it appears that the motor on the 9600 has gone out as I now can't get it to load a tape. Unit powers up (and stays on!) but nothing happens when I insert a tape.

UGH!!!!

-- merged --

I was able to find a matching 5 pin ribbon cable. Plugged it in and powered up the VCR. Everything seems fine as the unit stays on and I can hear the gears adjust themselves. However...

When I insert a tape the head/drum refuses to spin up. I am assuming that I'm not getting any power to the top of the head and that the problem is on the board somewhere but I'm not sure how to test if I'm getting any power through the ribbon cable. Can someone enlighten me a bit? I don't have a voltage meter but I do have a voltage tester. Can I use that to check? If so, where do I ground it?

If there's no power through the ribbon cable what would be the next troubleshooting step? I'll be the first to admit that I'm probably in over my head when it comes to electronics, so I guess the real question is Can I fix this myself?

Thanks for any advice!!!
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  #19  
01-29-2020, 09:45 PM
latreche34 latreche34 is offline
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What happened is when you were fiddling with your bad ribbon cable you shorted out the power to the drum motor, luckily the drum motor driver circuit is protected by a power protection diode, Pull up the service manual and look for it, it is usually located on the right side of the mechanism right next to the power section, in most JVC VCR's is labeled CP4001. Probe both ends with the power on if one end has power the other doesn't that mean it's blown, the link above shows how it looks like, make sure you get the right part number.
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  #20  
01-30-2020, 09:59 AM
BelowZero BelowZero is offline
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Spot on!! Thanks latreche34! That does appear to be the problem. One side lights up, the other doesn't. I've got the diode ordered.

I've never worked with a circuit board so any tips on how to replace the diode? I'm assuming the board has to come out to get to the underside. Is this something I can do or should I look for a repairman?
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