JVC HR-S9900U bad ribbon cable, part needed?
 

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.

Many thanks for that link. Looks like I have a project for tomorrow.

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.

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?

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.

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.

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!

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.

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?

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.

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.

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...

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?

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.

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.

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.

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!!!

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.

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?

Well there is two ways you can do it, The sloppy way or the professional way, The latter is removing the mechanism, removing the board and replacing the part, The sloppy way is the easy and quick way, snip both ends of the blown component leaving some wires sticking out, put some flux on the ends and fuse some solder on them, do the same on the new component and solder it on top. I will consider this approach for one specific reason, those machines are old and every time taking them a part and moving their guts around is a potential for future break downs unless you are confident that you can do it properly.

You present me a real dilemma. On the one hand, I'd like it to be done properly but am leery of pulling everything out for the very reasons you mentioned. Plus the fact that I'm not familiar enough with these machines to have much confidence in my abilities. The sloppy method certainly sounds doable for me, but then I don't gain any experience with repairing the unit. I'll have to wait until the diode arrives anyway so it gives me some time to mull it over.
Anything to watch out for or other advice when removing the mechanism and board?

Well, the video drum bottom ribbon cable is easy to break when removing and is a bitch to put back, very thin and it bends on you when trying to insert it in the connector slot.

Removing a board really is not that hard. I can do it in about 10 minutes.

It is not about time, When something breaks the whole VCR is trash, you can't get replacement parts anymore, If the head ribbon breaks the whole head assembly is needed because it's built into the rotary transformers, and because there is no head assemblies available may as well get another VCR.

Or just a "new" head (from a donor parts deck).

Sorry this thread has taken a few turns away from the original topic but I've gained some valuable insight and instructions from the discussion. Thanks for everyone's help.

As for replacing the diode, I pulled the board without near the trouble I thought I would have and have removed the faulty diode. Once the new one arrives I will install it and hopefully get everything put back together correctly. I'll post again if the legacy gods have been kind to me and the unit is working as it should.

Update... JVC HR-S7600U

I got the diode replaced, put the whole thing back together again and attached the new ribbon wire. What a huge sigh of relief when I inserted a tape and everything functioned. Of course Murphy's Law had to rear it's ugly head and pose me with a new problem.

I'm not getting good playback. The bottom part of the screen looks fine but the top part is blank. See attached photo.

Does this look like some sort of adjustment is needed or did I somehow ruin the head when taking the VCR apart? I really was very careful with the disassembly and reassembly but I know these things get pretty cranky in their old age. Any advice appreciated!

That's what I was talking about when suggesting the sloppy way, Anyway before you assume it's a miss alignment try different tapes and make sure the tape transport is dry with no oil or grease in the tape path, Make sure all ribbon cables mating surfaces are clean and firmly in place. Make sure the P guides are not loose when fully locked around the drum, The should feel solid, also the adjusting heads should not be loose when you try to spin them with a fingertip.

All items on your list checked out and everything appears to be fine. Still only half a picture.

Here's another question I have going back to removing the gears. On the bottom of the drum, the 2 little gears that screw into the drum itself; assuming that no gears have been removed, should they be screwed in as far as they can go or should they be somewhat loose? The guide I read said to leave them loose after the gears were removed but this is the working drum assembly with all the gears in place, so I had the thought that since I screwed them in all the way it might be affecting the angle of the head. Is that even possible? Do you think that it could have something to do with the picture problem?

I was under the impression that this is the working VCR that you haven't tempered with the DD system yet, As soon as you take those gears a part your alignment is gone, You will now have to disable the DD system, There is no alignment procedure for the DD gears in the service manual. Whatever you do, DO NOT try to mess with the tape path alignment.

If you must disable the DD system, the final gears (screw gears) have to be free, meaning that they should not be under any load, The springs and pivot points should keep the drum assembly in its neutral position (the position in which the tape path alignment was done in the factory). Also you will have to isolate them from turning which requires removing one thick gear on one side and leaving the other one to keep the tone wheel spinning to avoid the shutdown, Check the procedure again at VH forum.


Edit:
I hate to see a perfectly working DD system disabled, Let's try this:
With the gear system out and only the screw gears in place back them off until they are loose and start tightening until they touch the drum or the intermediate plate (each gear has a function), do one at a time, no pre-load and no play, just touch. Put the gears cage back on making sure the screw gears will not turn while meshing with the rest of the gears, screw the cage in and install the drum, try a tape and let me know.

After your first post I was a bit frustrated and thought about just leaving both units alone for awhile. But before I put them back together and put the covers on I got the 2nd post. And that, my good man changed everything. Adjusted the gears as you said and put the DD back in place. Made sure the ribbon cables were attached firmly. Then I noticed a small smudge on the head so I took a little alcohol to that also. Put in a tape and it played perfectly! Put in another tape and it played as well. Then a did a comparison against the same tapes in my AG-1980 and the 7600 is every bit as good. Maybe even better (sharper) on one of the tapes.

I'm still a little nervous about FF and Reverse so I didn't try it. I've got another cheap deck I can use to rewind anyway so no big deal. It appears (knock on wood) that I have a very usable 7600 despite all my efforts to ruin it. I'm very relieved that I can now go back and address the original problem with the 9900. Might take a few days off before seeing if I can get the gear issue figured out. Luckily, I have this thread to guide me through the process again.

Many, Many, Many Thanks!!

At least now we know how to adjust the DD gears in case someone needs to, I never had to do this on my two units, One the DD system still working fine, the other had to disable it due to a cracked gear.

You may have to try FF and RW and frame by frame to see if it locks on the picture, That's the only way to know for sure if the DD system is working properly, Those gears will eventually crack due to a flawed design, it's not a matter of if but it's a matter of when.

Has anyone tried 3D printing those gears? Does it work out or do we have a couple of years to go until the tech is good enough for something like this?

Two problems with 3D printing, Low resolution (less details) and brittle materials. Those gears has to be molded around the center metal hub, it is only possible with injection molding.

Maybe it's because these are not that common. If you look at the DD Walkmans, people have created brass replacement gears that you can then fix to the shaft with some epoxy, maybe if someone had the time and resources this could be done for the VCRs as well.

It is possible with high precision machining of brass or aluminum, But honestly the DD feature is completely useless for playback, it served a great purpose in the hay day of VHS viewing but not so much now.

Though, a feature that could be re-purposed for playback of miss tracking tapes or tapes that are recorded on non standard speeds such as LP, SLP, EP... as well as stretched or shrunk tapes.

Basically a modification of the electronics of a perfectly working DD system in a way that we take control of the DD motor via an external potentiameter, turning the knob to one direction tilts the head in one direction, turning it backward tilts the head in the opposite direction during playback, changing the angle of the video tracks helps playing back any problematic tape no matter how weird its speed is.

This is something I've been studying since I heard about the VHS decode project and the possible integration of such control knob in the VHS decode board itself, so extra wires are added to the existing RF wires that go to the VHS main board.

But I wasn't giving too much emphasis to it since the DD gears are failing, but if some how one can make gears and bring these systems back to life it could be a potential project, I can provide CAD design files of the gears.

Here is how the HR-S7600AM both sides of the gear look like:

http://www.digitalfaq.com/forum/atta...1&d=1580932420 http://www.digitalfaq.com/forum/atta...1&d=1580932420

I don't have time now, but...

My other main hobby is (more like "was") action figures -- specifically photo/video and customizing of the figures. That crowd has grown a lot in the past decade. There are customizers that do custom casting in all sorts of materials. Later this year, if nobody has come up with a DD solution, I may start inquiring about it more. It's actually a dormant hobby of mine, not had time to partake in it for 9 years now. But I still follow what goes on, and want to get back into it, finish old projects that were halted back in the 2000s due to time and later health.

If you have CAD files, that would makes this much easier.

Customs are not easy or cheap. What sort of price ceiling would you put on having the gears made? (Perhaps PM me for that part, the numbers.) Then approaching the customizers will be easier.

BTW, if I give you measurements and photos, could you make a CAD for a toy part I need? I've need to repair something (Robotech Zentraedi Battlepod) since the 90s, but only in recent years is it now viable. But I'm not willing to send out my remaining good part, and do not have CAD or 3D modeling skills.

Then I could approach a customizer with two projects, higher likelihood to do it.

I never though about this as a business approach, I was just thinking about it as an idea of making the DD system useful for capturing. I can participate in the project but I'm not expecting any returns, My skills also suck when it comes to modifying circuit boards and coding or scripting, I wish I was a part of the VHS decode.

I've been watching the 3D printing technology over the years and hi res finishes can be accomplished but the materials physical characteristics are not there yet, plus the cost is high for such newer technologies, here is an overview:
https://www.techpats.com/3d-printing...gies-overview/

As to your part, Sure send me pictures and dimensions, depends on the complexity of the part and the free time I have I'll see what I can do.

Nor was I. :wink2:

However, there's usually a minimum order required, even for customizers. But I'd only want to get enough for us, and anybody else that bought as preorder (other members here who want/need a replacement DD), and maybe 25 extras for latecomers. I'd not buy 100s of DDs, not something I really want to mess with. But I'd need to see if we could raise the initial funds required, as I'd not approach anybody without a budget max known in-hand.

My figure part is pretty non-complex. I'll PM some images in the near future, when I get some free time myself. :)