JVC Dynamic Drum Ultimate Fix

[zxck]

This is awesome, thank you for finding and sharing this! Only took 4 years from when we first suggested it for someone smarter than us to do it!

There is also an eBay seller who sells JVC's with the DD disabled, though no indication of how they are doing that.

Hello. I am reviving this thread after i found out of a youtuber that has made an emulator for the Dynamic Drum System of JVC.
Here is the Video on his youtube channel.
https://www.youtube.com/watch?v=gmhKEJlBkJA

[dellsam34]

Thanks for sharing the video, this is what we've been looking for, I've contacted him via e-mail to see if he can share his thoughts in this thread.

[lordsmurf]

EDIT: Post removed, benefit of the doubt given.

[dellsam34]

YT does delete comments automatically for hate speech and spam, I learned that sometimes writing words in alpha numerical or changing the spelling can fool the algorithm, Also avoiding words such "check out my" or "it is in this", also any words against the establishment and main stream believes. Not saying YT members can't or won't delete comments though.

[Aristarhos]

Thanks for sharing the video, this is what we've been looking for, I've contacted him via e-mail to see if he can share his thoughts in this thread.

I also contacted him by email and he replied. His name is Heikki Korpimaa from Finland.
He has developed a module that he is selling.* EDITED
https://www.youtube.com/watch?v=gmhKEJlBkJA

Here it is:

"Thank you for the interest in DD emulator!
I created DD emulator as a hobby, but realized, that there are today quite a many people who repair and refurbish these vintage VCRs. It's quite a new device from me, but I have tested it with very good success during past 2 months. I can produce small series for those interested.

The price is 70€ + packing & postage 10€ to EU and Great Britain. Freight to other countries based on actual cost. Buyer is responsible for possible TAX and DUTY in his own country if outside EU.

I have attached 2 documents with technical information regarding to Dynamic Drum System and DD emulator mounting considerations.

BR
Heikki Korpimaa
Tampere, Finland"

[zxck]

"...praising the mod..." = "It's an impressive mod, but..."
"...offering suggestions..." = Next 6 sentences telling him all the things he did wrong.
"...inviting to the community..." = Character bashing someone on multiple forums whom you know nothing about because your comments weren't adored.

Yeah, I probably would have deleted it too.

I reached out to him directly, and got an immediate, professional response with all the information I needed.

Thanks for sharing the video, this is what we've been looking for, I've contacted him via e-mail to see if he can share his thoughts in this thread.

Don't bother.

I wrote a comment on the video, praising the mod, offering suggestions, and inviting to the community to discuss it.
It was deleted.
I wrote about it here: https://www.digitalFAQ.com/forum/vcr-repair/9777-jvc-dynamic-drum.html#post101056

I've read where Youtube automagically deletes comments. But others have said that's just a BS cover story from somebody that was caught deleting comments. Who knows. Too many Youtubers are snowflakes. Unless you're stroking their ego, they delete your comment. This is why Youtube is such a damned joke when it comes to video advice.

[dellsam34]

He hasn't replied to me but basically I want to ask him if we can use the system for playback of problematic tapes, shrunk, stretched, miss-aligned recordings ...etc. This off course is kind of the opposite of what he did since it requires a perfectly working DD system, a manual knob will be added to tilt the head in either direction for a perfect picture during playback.

As far as cracked gears, I got a new 8k high resolution 3D printer just for this purpose and I will be experimenting with different resins to find the perfect match for the application that meets the mechanical characteristics of an injection molded gear in terms of strength, elasticity and durability.

[dellsam34]

I would also like to point out that with this MOD it is possible now to replace the DD head with no DD one, provided it has the same number of heads, the same pinout on the ribbon cables of both the rotary transformers pack and the motor stator.

[lordsmurf]

EDIT: Post edited, benefit of the doubt given.

YT does delete comments automatically for hate speech and spam, I learned that sometimes writing words in alpha numerical or changing the spelling can fool the algorithm, Also avoiding words such "check out my" or "it is in this", also any words against the establishment and main stream believes. Not saying YT members can't or won't delete comments though.

I've posted a much shorter comment. Let's see what happens.

I ran into this same deleted comments BS with the vhs-decode guys, the ones that wanted to show highly misleading "proof" that the method was better. You know, the clips where the so-called "traditional" workflow uses a thrift store VHS VCR into a non-suggested Easycap without any TBCs. The "better" image from -decode was full of image defects (especially harsh halo/ringing) that you never get with proper S-VHS VCRs, TBCs, and quality capture cards. People like this don't want us to interrupt their narrative, to invade their echo chamber.

Yeah, I probably would have deleted it too.

Then that makes you a narcissist, unable to hear/read anything that doesn't stroke your ego. Deleting Youtube comments you disagree with is childish.

______

Anyhow, the complete mod, as he showed it, has serious concerns. He risks his tapes, and you risk your tapes if you follow his lead. All that foam acts as insulator, and traps heat. Heat is a reason that VCRs eat VHS tapes, or to strip oxide off tapes, etc. Some foam is even flammable, and those VCRs can get excessive hot internally.

His custom chip is amazing. But the installation needs work.

[dellsam34]

I think his idea behind foam to isolate the board from the chassis is for a minimalist effort, I would put holes in the PCB design so they get cut during the manufacturing, then use plastic standoffs, Or use double sided tape and stick it to the plastic side wall, I don't think the board generates that much heat, I believe those run off of 3-5v with less than half an amp.

[lordsmurf]

I really don't know what he was thinking with the foam.

Over the past decades, for homebrew (and sometimes half-assed) modding, I've done foam, duct tape, random adhesives, random bits of metal or plastic. In my early 90s modding days, I did a lot of dumb things that backfired. In the 00s, I even caused some small fires. So I can just look at that Youtube video, and utter "NO!".

It needs some sort of mounting surface. Because all of the PAL/NTSC DD decks will differ some, my suggestion is a small 3D printed cage, with a thick adhesive pad at bottom (the part that sticks a cage to the VCR floor). And cleaning the floor with alcohol, prior to sticking down.

I liked your idea of zip ties, for that specific model unit. But I know it will not translate well to other models, as some lack the VCR internal plastic struts.

Modding the PCB might work, but it will add costs. And while 3D printing also adds cost, it may be less costs, and definitely less work per deck variation (ie, mounting instructions). Shapeways is fine, your own 3D printer isn't needed. Shapeways shifts all costs to the buyer, he never has to mess with it himself, aside from uploading a CAD design.

My 9800U has irritated me for years, failing DD (but not fully failed/cracked yet). For under $100, I'd do it, a total no-brainer.

But does it works on all/other DD decks? JVC decks had lots of variance between models.

Some people hate that I'm not an instant cheerleader to anything new and shiny. I have concerns, I voice them. (And over the longer term, I'm often validated, I was correct.)

[zxck]

We're all fully aware who the narcissist is, that's been established. And with decades of OG experience you have some good advice. Though you're wasting your time on multiple rants, and buried your best comment: "His custom chip is amazing."

OK, you don't like the foam, we get it. But he's not selling you the foam. He's the genius selling you the chip to resurrect countless JVC's. Buy the chip, mount it however you want, and save yourself from wasting any more precious years being irritated by your 9800U.

[lordsmurf]

OK, you don't like the foam, we get it. But he's not selling you the foam. He's the genius selling you the chip to resurrect countless JVC's.

None of those are facts currently known. All we see is (1) it works with a specific PAL model, and (2) with a chip sitting loose on foam, and it clearly does not have any mounting system.

That's why I asked this to person participate in threads discussing the mods.

Both here, and at https://www.digitalFAQ.com/forum/vcr-repair/9777-jvc-dynamic-drum.html

I guess I've gotten a bit "fire, ready, aim" in recent times, because of having to deal with too many arrogant, narcissist, mouthy pricks, that have invaded video communities as of late. So, to the Youtuber @hkorpim, I will give benefit of the doubt (Youtube will be blamed instead), I apologize for jumping the gun, and it's nice to make your acquaintance.

So that's that, let's move on to discussing the mod, since we're all communicating finally.

EDIT:

See his PDF here: https://www.digitalFAQ.com/forum/vcr-repair/9777-jvc-dynamic-drum.html#post101070

Read the PDF. It's just as I feared.

He has explicitly, in no uncertain terms, stated to use materials as in the video.

On most JVC VCRs there is convenient empty space on left side for placing the DD emulator.
Use isolation material similar to Fig 4. in order to prevent DD emulators electrics getting
contact to surrounding PCBs and metal chassis if not securely fixed.

Fig 4 = the foam you saw in the video.

So ... I want correct all along here. Vindicated.

But it has now been brought to his attention, and will be addressed. I look forward to conversing with him, so that we can make this an excellent safe mod for us all.

[zxck]

None of those are facts currently known.

Known fact: you don't like the foam
Known fact: he's not selling foam
Known fact: genius (until we can brush up our EE chops, I'll stand by that)
Known fact: resurrect countless JVC's
Known fact: arrogant, narcissist, mouthy pricks. I seem to have worn out my welcome!

Sometimes your "inviting" sounds more like "challenging" so I wouldn't expect him to come round anytime soon.

But if the foam is the show stopper, please buy the chip from him and I'll whip up a 3D printed enclosure that I will mail to you for free in order to keep it from shorting on the chassis. Add a little glue, tape, or just let it dangle and report back if it does the job it claims. The video of his test rig seems pretty convincing that it will.

it's nice to make your acquaintance.

Likewise.

[lordsmurf]

Likewise.

Great, let's move on...

and I'll whip up a 3D printed enclosure .

I like the idea of submitting to Shapeways. Do you want to do that?

Not all of these DD decks have the same internals. I can photo and measure those in my current possession. The trick will be to either craft something universal to all, or perhaps several for several model lines.

I'm still concerned about deck model (and PAL vs. NTSC) effectiveness. The DD is, after all, part of the transport, and PAL vs. NTSC have different speeds. Referencing his PDFs, when you discuss "sending pulses", the speed probably matters.

So, is it truly "universal" (and tested as such), specifically for NTSC, or is it just a guess?
How many models has this been tested with?
If he wants to submit a couple of samples, I can always call in a few favors to multi-test decks, for both PAL and NTSC.

[zxck]

Great, let's move on...

Whew, finally! Yes, let's.

I like the idea of submitting to Shapeways. Do you want to do that?

I have 5 3D printers, so I am kind of like my own shapeways. This will be a super simple box with some cutouts for the cable, LEDs, and maybe the USB connector. Heck, you could even throw a few wraps of duct tape around it instead and it would be good. We're just looking for isolation of the circuit board from bare metal. It will only be about 1.5" x 2.5" so about like a pack of gum. You could place that most anywhere inside the machine, or run it out a vent and stick it to the exterior if you wanted.

I'm still concerned about deck model (and PAL vs. NTSC) effectiveness. The DD is, after all, part of the transport, and PAL vs. NTSC have different speeds. Referencing his PDFs, when you discuss "sending pulses", the speed probably matters.

Good question. There are only 2 versions of the DD, the lower end belted version (untested) and the higher end gear train version (known working). He's using a HR-S9700, presumably PAL. But even if there is difference in the speed of the pulses, that's an easy software change. Could even be switchable with the addition of a button or switch on the circuit board.

Let's ask.

[dellsam34]

Considering the tiny size of the PCB and the room available inside all modern VCRs from late 90's to early 2000's, model # does not really matter. On the video format side, I don't believe the DD pulses will be any different from one format to another, It just moves the head, it has no relationship with tape speed, But even if it matters, the firmware can be customized based on the VCR format, a matter of changing one parameter or two in the code line.

[zxck]

I just spoke with Heikki:

"Regarding to question if DD emulator works with NTSC deck is positive. I have tested it in my HR-S9700EU, that is Multi Norm recorder: It has PAL recording only, but it does have PAL, MESECAM and also NTSC playback. I have two NTSC tapes and they play perfectly.
DD emulator is not related to tape speed (For "NTSC standard Play" mode it is 3.335 cm/s (1.313 ips) and for PAL 2.339 cm/s (0.921 ips). HR-S9700 has further even slower LP and EP tape speeds and they all work perfectly). Drum speed for PAL is 50 fields/sec (1500rpm) and for NTSC 60 fields/sec (1800rpm). Nor DD emulator or Dynamic Drum system has electrical relationship to video drum speed."

So there you go. You'd better buy one fast because he has gotten a huge amount of attention and may be selling out soon. Let me know when you get yours and I'll send you your free 3D printed enclosure.

[dellsam34]

The very first order from the US was placed by me yesterday, Will experiment when I get it and post my findings, I will also be trying to control the DD motor from an external 5V/-5V source (both directions) to see if I can improve the playback of some problematic tapes.

[hkorpim]

Good evening everyone on this thread! (It's now 11:00pm in Tampere, Finland)

I have developed the "DD emulator" that has been discussed on this thread since last couple of days.

Thank you for the big interest in my youtube demo https://youtu.be/gmhKEJlBkJA and the "DD emulator" device.
The interest has been overwhelming, which I did'nt expect at all! I was not sure if this thread was alive, because the issues with cracked gears have been on for so many years without solution. And also no messages since a long time. Great! It's alive and you have not yet scrapped your VCRs with Dynamic Drum. I'm glad to be able to help. I have been dealing with video equipment as a hobby since young boy for 40+ years from 1970's.

I was quite surpriced, that there was almost more focus on foam used on demo video, then "DD emulator" itself. I hope it is now clear, that the foam was only used during testing and for the demo of the DD emulator - making it appear better on video. Of course the final fixing of the device will be made properly, don't worry. I keep it loose for now, because I want to test proper function of every device I produce for sale. In near future I will fix the mounting and close the cover, because I also now have developed test software for final testing (using the 2 LEDs to indicate correct function).

I noted, that zxck already pasted my writing regarding to NTSC compatibility: no problem with that, DD system is not related to TV system and tape speed. It allways works. Regarding to compatiblity to 'low end Dynamic Drum gear box', my answer right now is: I don't know. But I am willing to develop the software so, that it will work in future, and using the same harware + switch/selection between devices. All this provided, I get one of these 'low end DD gearboxes' in hand. If I have one available, I can read/record the signals it will produce for the processor. Only well functioning gear box is needed, not the whole VCR.

Regarding the availability of DD emulator, I currently have in shelf parts and PCBs for 5 pcs DD emulator, shipment early next week. I will order more PCBs during next days - supply time is about 2 weeks. All the other parts, including Raspberry pi Pico, I will get in 24 hours.
Sales price for USA is USD 78 + USD 10 for packing and shipping. Easiest to pay with PayPal (paypal.me/hkorpim). POST in Finland informs, that it will take between 4... 7 working days for transport. The device will be shipped in padded envelope and it only weights 18 grams.

I hope this clarifies open questions sofar and doubts presented. Now, that I have joined this forum, I will of course answer all further questions later. Please allow me 1 or 2 days for response, because I may be busy with other things too, but I try to follow this thread regurarly from now.

[dellsam34]

Thanks for joining, glad to have you on board.

[zxck]

For under $100, I'd do it, a total no-brainer.

Quickly, place your order with Heikki for his DD emulator! I really want you to get one of those in your hands and test it.

And when you do, I'll print and send this to you, a 2 piece snap together case to protect it:

[Attachment 85230 - Click to enlarge]

[Attachment 85231 - Click to enlarge]

[dellsam34]

It is not really necessary to encase the board in my opinion, It can be mounted in too many different ways inside the VCR.

[zxck]

I don't think he was referring to a plastic cage for under $100, I think he was talking about the DD mod. Anyway, it is not really necessary to encase the board, It can be mounted in too many different ways inside the VCR.

Yes, I know. He said he'd buy the DD emulator if it was under $100, but he got so wrapped around his own axle about the foam that he couldn't get past that. So I'm encouraging him to quickly buy the DD emulator ($88 shipped, a bargain at twice the price), and know that I'll send him an enclosure for free so he can use the emulator without fear.

[hkorpim]

Good work with enclosure, zxck!

The attached dimension drawing cand be useful.
Also my view is, that the enclosure may not be needed, if the device is fixed inside VCR cabinet using zip ties or 3M double sided tape for example.
For you information, the length of ribbon cable is currently 290mm. If you think, you need longer, I can change the length.
In my HR-S9700 290mm length works fine with some margin.

[aramkolt]

I think what latreche is doing is an interesting concept to control the DD unit independently while the unit is playing, but that would require a working DD unit with all gears intact still physically moving the original unit. I ton't think that'd be too hard to implement assuming the original DD unit is all intact, it'd just be applying a few volts to the DD motor in either direction and I don't think the rest of the circuit is going to really notice. My guess is that the machine only looks at the light gate position sensors when it is actively attempting to move the motor. All it'd take to test is running some parallel wires off of the motor to be powered from the outside with a different voltage source as the machine is running and see if the machine stops playing or not if the motor moves unexpectedly.

I've also thought about using completely different non-DD heads or a completely different deck on DD machines. The solution I found was just moving the whole DD unit off to the side out from under the deck - it just takes an extension cable that plugs into the main PCB where the DD unit normally would. As a bonus, the extension cable method is completely reversible. The pin pitch on the DD unit isn't the standard 2.04mm, it's like 1.8mm I think, but anyway, this is what that looks like:



I'd just mount the DD upside-down as pictured using the original mounting screw holes that it has and washers to space it off of whatever surface mounted to if needed to give room for the gears below.

I did think about putting out a DD bypass service to compete with that $350 one on eBay - mine would only be $50 though including return USA shipping if just the DD unit is sent to me. I've yet to come across a DD unit that I couldn't bypass.

I always thought the "Arduino replacement" mod had to be possible with something like an Arduino pro micro that costs under $10, but I don't have the programming knowledge for it. It also became not needed for me since I don't see a scenario where I wouldn't be able to just move the original DD off to the side if using a different deck in a machine and all original DDs are bypassable. Now if the whole device was like $30, sure I could see not spending the time repairing DDs and just throwing it in there, but for $90, can buy a whole SVHS machine with a low hours deck and build that extension cable with the spare funds AND have a much less-used mechanism in the machine.

The disclaimer is that I haven't actually had to do a deck/head swap into a DD machine just yet since I've come up with the extension cable idea a few weeks ago, but there's really zero reason it shouldn't work. The machine just applies a voltage to the DD until it sees the return signals from the gears/light gates on the DD and the DD doesn't have to be under the drum to do any of that.

[dellsam34]

Applying voltage to the motor externally or moving the head by hand has no effect on the VCR behavior because the feedback is cut off and not going back to the system control anymore, Hkorpim has tried it already per his e-mail. I just want to see if it will be part of the project for a perfectly functioning DD system so that the motor is digitally controlled by steps instead of an analog potentiometer.

Now what I would like to see in future versions is some miniaturization so the new board will be exactly the same size and shape as the original board and can be snapped into place in the original position of the old board and connects to the chassis without needing any ribbon cable, and yes we would like to see lower prices if he can make the design a little cheaper, we are just the early adopters, I also did not need the board, I made my VCRs work already without it years ago, I just wanted experimenting.

[hkorpim]

For experimenting, manually driving the DD gearbox motor, I can share some knowledge regarding to DD gearbox and it’s sensor anatomy.

Purpose of the 2 photosensors:
Sensor 1 (MFG). Counts the revolutions of the worm gear – 2 pulses / rev.
Sensor 2 (ABS). Marks the neutral position of the video head drum tilt – on/off switching position = neutral position. Thus it’s gear position (startup position) must be correctly aligned in relation to drum neutral position.

The gear ratio between the motor and last gear in the row (= gear with half circle cover) is 390:1, so the motor axle turns 390 revs for 1 rev of last gear. In practice the motor turns back and forth generating around 170 pulses in second, but in reality the startup signal is only around 18 (MFG) pulses in both directions from MFG sensor for 1 pulse (on/off) from ABS sensor due to alignment.
Startup initialization = seeking correct neutral position, that may be misaligned for instance due to electrics breakage.

The presence of sensor 2 (ABS) pulse is critical for the functionality. If gear box gets jammed and the processor will not sense ABS pulse, the VCR will switch off. Missing ABS pulse = DD gearbox is faulty.

The purpose of sensor 1 (MFG) pulse is to report to processor the tilt position and most importantly: prevent overrun of the gear drive: The processor must prevent the gears hitting end of travel = boundary of video head drum tilt.

If driving the motor manually for video head drum tilt, it is extremely important not to hit end of travel, because due to high gear ratio, the motor torque is greatly multiplied by the gear ratio, meaning, that it will have the power to smash the teeth on final gear, the gear screw, if overrun against the boundary.

Regarding to the idea of miniaturization and making DD emulator board same fit and form as DD gearbox board, there is a problem of size: There are no Arduino or Raspberry pi boards available, that would fit in that footprint. This also only would make sense, if the gearbox is left under the drum. If operating it manually, I would rather utilize the MFG and ABS sensors on DD gearbox board for safety of gear drive and drive it step by step through Raspberry pi Pico processor: DD emulator hardware could be used as such for driving the motor with PWM output and if utilizing the 2 sensors, also step by step (= rev by rev) including overrun prevention. This functionality would however require experimenting and developing a new software. I might do it, but it will take time. If successful, I will report it in this thread.

It would of course be the ideal situation, if we could keep the gearbox alive and in working condition and also keep the nice JVC feature of perfect picture search in all speeds. Sooner or later however this has proved to be impossible (unless new gears become available). Yes, you can save money, by moving the gearbox to the side as ‘aramkolt’ has done – it works as long as the gears are OK, possibly a long time, because it’s running without load. But for permanent fix, DD emulator is the solution and you don’t need to revisit this issue ever again. There are several dependencies between the sensor signals and the motor drive voltage on FWD and REV terminals. DD emulator understands these dependencies and fully replicates the signals normally coming from sensor board. The bypass service: I would be interested to know how it is possible to bypass DD system without feeding the necessary signals to IC3001 SYSTEM CONTROL MICRO PROCESSOR. I first trialed and failed with simple signals and got it working only after emulating the original signals which have some variations on various picture modes.

Regarding the cost and price of DD emulator. Yes, the parts are cheap, but at the moment producing the boards without any automation, one by one, is labor intensive – preparing, placing components, manual soldering etc. There is nothing I can do now. My wife keeps telling to me, that the price should be 100! – the wife’s are always right or what…

So far I have preferred to use the ribbon cable, because I needed to test the device, see it’s function with the help of 2 LEDs, switch it easily to another one and experiment with software. Now that its functionality is proven, there is also the possibility to plug DD emulator board into main board socket CN3501 directly without ribbon cable. Producing the ribbon cable takes time (preparing the cable, soldering pin headers and isolation with heat-shrink tubing). Leaving the ribbon cable out, could potentially have a price effect of USD 15. On the other hand this would mean, that there is no longer room for DD gearbox, because DD emulator would occupy the space under drum. Double sided tape could be used to secure and isolate it from the main board in addition to mechanical pin header connection directly to socket CN3501 on PCB. At the moment the pin header on DD emulator PCB end is 6 pins/2.54mm pitch. For connecting to CN3501 on main board a 6 pin/2.0mm pitch header is required. I will start to experiment this and will show the result on my next message.

I have attached picture showing hand drawn circuit diagram of DD gearbox board (it is not available in service manuals). Also, as an example, startup signals from oscilloscope. When motor turns, the photosensors are cutting 5V input from SW5V terminal to MFG and ABS terminals. Both terminals have voltage status of either 0V or 5V.


[Attachment 85247 - Click to enlarge]

[dellsam34]

Yes making the boards manually is labor intensive, I've made some custom projects in the past that I oredered from a chinese PCB manufacturers and took me hours to assemble even for just through hole style components let alone SMD.

Where the DD emulator shines is when one wants to replace the DD drum with a conventional non DD one, So you may want to make a ribbon-less option available to order for just that purpose so it could be tacked under the non DD drum and connects directly to the chassis motherboard.

The idea of repurposing the DD system for normal playback has to be tested with bad tapes first and proven to be usefull, otherwise there is no need to waste time on something that doesn't serve any purpose, I will get on that as soon as I receive the DD emulator from you, I got plenty of tapes in weird playback conditions. and yes I'm aware of the potential risk of driving the motor over the mechanical limits, I will use the visual feedback and a dual polarity normally open on-off switch, so when the picture starts to get noisy I'll stop and go the other direction until it's clear. I may also have to use a cheap VCR and miss align it and record a tape and use it to test the theory.

[zxck]

It's always funny to me on these kinds of forums that some folks always complains about the price of some fantastic piece of new tech that allows them to keep using the otherwise scrap piece of hardware they love. (I see it on the Apple II forums too.) These are usually the same folks who have already spent thousands and thousands on discontinued VCRs, TBCs, capture cards, etc., etc., but somehow $88 to resurrect a $600 VCR is too much.

@hkorpim, your wife is, of course, correct. The price isn't for a $4 module and some ribbon cable. It is for the hours and hours of R&D, prototyping, and testing you've done, and the hours and hours of engineering it takes to produce a final product that none of us could do.

There will always be someone who says, "well, I'd buy one if it was cheaper" - No they won't, it will never be cheap enough for them. And,
"Why don't you just add [insert edge case obscure functionality here]." It starts feeling unappreciative of the work you have done.

What you have accomplished is amazing. Steady on!