JVC Dynamic Drum Ultimate Fix

[Aristarhos]

Thank you Alex...
Maybe a custom steel sleeve with a bolt and nut could be applied directly...
But maybe then a plastic wheel with metal parts would be too heavy...
What do you think?

How about using aluminium washers?
First you glue the crack and then apply a washer of appropriate size with epoxy. That will prevent the gear from splitting again as the metal with the epoxy glue will hold it together.
Sony used plastic gears with very thin washers in small handycams some 20 years ago.

[dellsam34]

I have very good news, I swapped an entire cassette mechanism pulled from a Philips clone VR960B, It's a basic S-VHS deck with DA 4 heads, no FE head, so the head's ribbon cable is slimmer by 2 pins, I just had to slide it to the side of the socket as you can see in the attached video. Everything else fitted like a glove. The receiving machine is a JVC HR-S7600AM multistandard that has the DD bypass board designed by Hkorpim.

We don't know yet if regular VHS decks can be candidates since we don't know if the heads' gaps are similar, but I'm more inclined to believe that the heads are identical, Just the elctronics are different, hope someone can confirm this.

These later machines from JVC and Philips are very easy to work on, 4 screws and 2 plastic standoffs and you pull the entire mechanism out, it can be done in minutes. Just be aware that without the lid the VCR cannot function due to ambien light hitting the cassette sensors, To take the video I had to put the cover on top temporarily to get the playback started and then removed it to be able to shoot.

It's good to know that we can now fix these failing VCRs with other non TBC, non DD machines or even regular VHS machines provided the heads are the same.

[gizka]

Back off the other two drum and lead ring black gears so they don't interfere with their neutral resting position

Could you please clarify how far they should be backed-off? I only did mine by about 180 degrees compared to their original position and playback works fine, but I'm wondering if more would've been better for some reason.

Thanks for the guide.

[dellsam34]

Enough to keep the lead ring and the head drum resting in their neutral position.

[gizka]

Wouldn't the original gear position already be neutral? How can you tell what's enough while you're doing the adjustment, and is backing off too far a concern?

[dellsam34]

You'll have to understand how the mechanism works to be able to know if the those screw gears are in the way, I really don't have any other way of explaining it, Basically if you turn the screw until it starts moving the drum or the lead ring you've gone too far, That's the most basic I can put it.

[MediumDave]

Now, that it's available without ribbon cable, the price is lower: USD 63 + USD 10 shipping (most countries). Ribbon cable adds USD 15.

How do we go about placing an order? Are any currently available?

[aramkolt]

I mentioned it in a few of 12voltvids recent videos as a comment, but you can just put a drop of superglue on each of the four pivot points as the drum should "home" without influence from the two gears with bolts on them. having the screws there does provide some lateral stability if they are barely touching as delisam34 describes without modification.

If you want something reversible, you could just put some hot glue in the gap between the top and bottom halves of the tilting mechanism and that won't allow it to tilt anymore and can be easily removed later if desired by separating the two halves of the tilting mechanism which are just held in by the "springed" screws.

[dellsam34]

12voltvids brought a point in his video that leaving the DD gear system in place helps keep the drum firm which is a valid point however from my personal testing on a drum that the DD gear system has been completely removed and by just tightening the spring loaded screws further haven't had any issues so far, at least with non damaged tapes.

[lordsmurf]

I mentioned it in a few of 12voltvids recent videos .

12voltvids brought a point in his video

Based on the simple newbie-level mistakes/misunderstandings in several of his videos, and his stubborn willful ignorance in the comments, I've come to the conclusion that he doesn't know what the hell he's talking about, when it comes to these upper-end pro/prosumer type gear. He only knows about repairing low-end consumer VHS fodder.

He's admitted as much to people, but only in private conversation (and those were relayed to me).

Don't be fooled. I'm sure not.

If you think something is "off" with his information, it probably is. Feel free to ignore him, as I doubt you've missed something. More like is that he's overlooking something, even a simple something.

[dellsam34]

I have no doubt that he has a solid background in VCR repair, I just don't think it's a good idea that he tweaked the P guides when the DD gears are misaligned, this will put the drum in a permanent tilt and I'm not sure if that's good for the tape, I would remove the gear system entirely, drop the drum and the lead ring to their home position, lock it and if the P guides need tweaking afterwards then so be it, which most likely not, at least in my personal experience.

[Sharc]

Can one extend the lifetime of a still functioning DD by simply NO MORE using any of the functions which would activate DD operation? Means just using Start, Stop, spool forward, spool backward (no picture search, no pausing, no still picture, no playback speed change, no single picture stepping)? Opinions?

[Alex9876]

DD failure is a matter of time. The reason for DD failure has been written about here many times - plastic gears burst due to incompatibility of plastic and metal shaft. Over time, plastic shrinks, but metal does not. This leads to a crack in the plastic part. Even if you don't use the VCR at all, it won't save the DD.

[Sharc]

DD failure is a matter of time. The reason for DD failure has been written about here many times - plastic gears burst due to incompatibility of plastic and metal shaft. Over time, plastic shrinks, but metal does not. This leads to a crack in the plastic part.

I understand. So more or less the failure incident is independend of the usage frequency of the DD functionality (which puts some extra mechanical stress on the gear by using these "DD features"). So the answer to my question is no. Not using the "DD functions" does not really contribute to stretching the lifetime.

[Alex9876]

Yes. According to one version - When DD was designed, engineers did not think that someone would watch videotapes in 20 years))

[dellsam34]

Can one extend the lifetime of a still functioning DD by simply NO MORE using any of the functions which would activate DD operation? Means just using Start, Stop, spool forward, spool backward (no picture search, no pausing, no still picture, no playback speed change, no single picture stepping)? Opinions?

They will still spin every time you turn on the VCR, and maybe even going into stop and fast forward or rewind, the best way to prevent it from moving is to install the DD emulator and unsolder the DD board. But what do you preserve it for if it is going to fail anyway?

[dellsam34]

Yes. According to one version - When DD was designed, engineers did not think that someone would watch videotapes in 20 years))

Yes, the shrinking is an age thing, the claimed high failure by 12voltvids in the heyday of these machines is probably due to gears going out of alignment or miss aligned from the factory but I don't believe it was a plague like it is now, I highly doubt it.

[Sharc]

They will still spin every time you turn on the VCR, and maybe even going into stop and fast forward or rewind, ..... But what do you preserve it for if it is going to fail anyway?

My hope was to possibly bring failures down to a "normal" failure rate by simply avoiding intentional operation of the DD mechanism. Sadly this is pretty pointless though.

[lordsmurf]

I have no doubt that he has a solid background in VCR repair,.

Yes, low-end gear. Some of his comments on that video really showcase his limited knowledge on high-end decks.

EDIT:

Ugh. I just watched that full video.

He needs to stay in his lane, repairing Goodwill VCRs. Between the video commentary, and his comments, 12voltsvids is easily becoming a "who not to listen to" for quality VCRs.

Perhaps just watch his videos on mute, to watch him disassemble/fix VCRs. But not to listen to his nonsense opinions -- wrong opinions, based on wrong understandings.

I like how, at 4:15, it shows what I've said for years -- cleaning the mode switch on JVC S-VHS VCRs tends to be entirely pointless, waste of time, and more risky than not. I'm starting to think he's the reason for this false/myth VCR fix-it meme. Perhaps it is/was a problem on cheap low-end VHS VCRs, and he wrongly assumes it's always needed.

Also, in the comments there, "@coastalvideotransfer" is an ignoramus as well. That guy is a dog walker -- I'm not joking -- that converts videos on the side, using the cheap POS thrift stores VCRs he can find. WTF?

[hkorpim]

I was surprised to find three DD emulator install videos by ‘12voltvids’ after reading the latest discussion here. 3 units of DD emulators were shipped to a gentleman in Canada for direct mounting without ribbon cable. Apparently he was the customer of ‘12voltvids’. I tried to send comment to videos, but possibly commenting is closed, because without success.

Precondition for direct mounting is, that DD gearbox must be permanently removed. Otherwise there is not enough space underneath the head drum. Also on HR-S7600U there seems to be a capacitor, that interferes with direct installation. If alignment is still correct, it is more safe to leave the gearbox in place and not touch the gears at all! Thus I do not recommend direct installation of DD emulator to CN3501. Do it using the ribbon cable provided.

Avoiding to use picture search functions does not extend the life of gears. Every time when you switch ON the vcr, Dynamic Drum system initializes running briefly back and forth. It does this to measure/seek neutral position and user cannot control it.

There are two ways to extend the life of Dynamic Drum gearbox:

1) Remote install it and run without load. This works as long as the worm gears are healthy. (If you do this, see comment re gears on 2) below).

2) Do as dellsam34 has instructed in his ‘Ultimate fix’ instructions: remove the gears for drum tilt and guide ring alignment. Don’t do this without full understanding of the functions of gears and how to remove them. I you remove or turn any gears or screws, carefully mark/count their original position and write it down - if you don't do this, you will end up with misaligned vcr, that is difficult to realign.
Dellsam34 also correctly pointed out: don't try to realign using the T posts on tape supply and exit! This misalignment takes place at guide ring (= head drum tapa path). The T-posts maintain their correct settings and are not related to Dynamic Drum system status.

The third alternative is bypassing Dynamic Drum system using ‘DD emulator’.

For information: I have built DD emulators for vintage video enthusiasts in 16 countries during the past 6 months: this kind of interest has been total surprise for me. Many have purchased not just 1, but 2 or 3 pcs.
Contact: ddrum.emulator@gmail.com



DD emulator works with 1st generation (1995 -1998) and 2nd generation (1998 onwards) Dynamic Drum systems. Signals are identical, but pin order on mainboard connector is different. I have attached Technical Documents of both installations for those interested.

[dellsam34]

I will certainly be buying more boards from you in the future, I'm glad that you have the non ribbon cable ones, I just hope you have enough demand to justify keep making them.

[hkorpim]

Good to hear dellsam34! The demand is just right, not too many and not too few, because I build them 'hand made'. All components are ravailable at 24 hour notice and I keep small stock of parts.