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  #21  
01-30-2020, 01:11 PM
latreche34 latreche34 is offline
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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.
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  #22  
01-30-2020, 05:35 PM
BelowZero BelowZero is offline
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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?
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  #23  
01-30-2020, 09:51 PM
latreche34 latreche34 is offline
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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.
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  #24  
01-31-2020, 12:40 AM
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Removing a board really is not that hard. I can do it in about 10 minutes.

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  #25  
01-31-2020, 12:53 AM
latreche34 latreche34 is offline
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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.
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  #26  
01-31-2020, 01:33 AM
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Or just a "new" head (from a donor parts deck).

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  #27  
01-31-2020, 05:33 PM
BelowZero BelowZero is offline
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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.
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  #28  
02-03-2020, 03:53 PM
BelowZero BelowZero is offline
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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!


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File Type: jpg vcr screenshot.jpg (34.0 KB, 13 downloads)
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  #29  
02-03-2020, 04:17 PM
latreche34 latreche34 is offline
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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.
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  #30  
02-03-2020, 09:11 PM
BelowZero BelowZero is offline
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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?
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  #31  
02-03-2020, 09:31 PM
latreche34 latreche34 is offline
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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.

Last edited by latreche34; 02-03-2020 at 09:59 PM. Reason: Added info
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  #32  
02-04-2020, 01:57 PM
BelowZero BelowZero is offline
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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!!
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  #33  
02-04-2020, 10:23 PM
latreche34 latreche34 is offline
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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.
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  #34  
02-05-2020, 12:35 AM
HBB360 HBB360 is offline
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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?
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  #35  
02-05-2020, 01:12 AM
latreche34 latreche34 is offline
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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.
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  #36  
02-05-2020, 05:42 AM
HBB360 HBB360 is offline
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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.
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  #37  
02-05-2020, 01:58 PM
latreche34 latreche34 is offline
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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:



Attached Images
File Type: jpg IMG_3959.jpg (50.3 KB, 25 downloads)
File Type: jpg IMG_3960.jpg (52.6 KB, 23 downloads)
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  #38  
02-06-2020, 12:13 PM
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Quote:
Originally Posted by latreche34 View Post
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.
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.

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  #39  
02-06-2020, 02:18 PM
latreche34 latreche34 is offline
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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.
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  #40  
02-06-2020, 09:25 PM
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Quote:
Originally Posted by latreche34 View Post
I never though about this as a business approach,
Nor was I.

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.

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