JVC 30K Bandwidth Fix - Page 7 - AVS Forum
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post #181 of 305 Old 11-26-2005, 06:36 AM - Thread Starter
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Quote:
Originally Posted by JohnHWman View Post

Just finished the schematic of the JVC update with the use of AD chip :
JVC 30K/40K video filters update schematic
This schematic is quite obvious and the update requires low count components

- The IC inputs are directly linked to JVC HD/SD video processing board with very short wires from J1.
- It is powered by the JVC power called "AL5V" on the JVC schematics (60mA max)
- The "1080_L" signal is derivated from "1080_H" signal (inverted by Q836 on the JVC MB) to change the polarity of the signal to be compatible with AD IC video BW selection (36MHz in HD and 9MHz in SD mode)
- The IC outputs are feed directly to the JVC back panel RCA plugs with RG179B/U 2.5mm diameter 75 ohms coaxials (BA7623F-X IC will not be use anymore).
- The coupling is DC on both inputs and outputs for better signal integrity.
- The IC size is very small : 9x6mm , so the PCB
- Because of the IC video Gain x2, R818/R830/R842 (current to voltage conv.) on the MB must be updated with there values divided by 2 factor (135R/75R/75R)

I'm gonna start the PCB layout (which is very simple )

John

Good Job John!

I have a few of the chips on order as well, and have been waiting for them for weeks. I'll test one here, and will also get one off to Tim for testing.

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post #182 of 305 Old 11-28-2005, 01:48 AM
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Quote:
Originally Posted by mp20748 View Post

Good Job John!
I have a few of the chips on order as well, and have been waiting for them for weeks. I'll test one here, and will also get one off to Tim for testing.

Thanks Mike
I've also ordered some AD ICs as samples but it will take some weeks to get'em (I should have them by the end of this year ).
If you want (and for Tim too), I can provide some PCBs for you tests, then this will ease the implementation of the chip inside the JVC unit.
As soon as I'll get some PCB, I'll send them to you .

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post #183 of 305 Old 11-28-2005, 02:12 AM
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Hi Tim,
Quote:
Originally Posted by VideoGrabber View Post

Not really. 18 MHz would be the appropriate setting, in this case. That's correct, for consumer-grade equipment running 4:2:2 or 4:2:0. Unless you're running pro 4:4:4, the half-bandwidth chroma setting (0:1) for 18 MHz BW is preferred, since it reduces chroma noise and hash outside the bandpass.

Fine, I should update the schematic to reflect the BW change between Y and Pr/Pb.
Quote:
Originally Posted by VideoGrabber View Post

The new circuit looks good, and seems promising. Keep us updated on its performance. I'd offer to check it for you, but my spectrum analyzer tops out at a bit over 40 MHz, so any spurious high-end products wouldn't be visible (at least not directly... I could check for any components that "wrapped" back into the bandpass to see if any were above the -80 dB noise floor of my analyzer). I think my other "spectrum analyzer" can go quite a bit higher, but it's an FFT-based DSO with 350 MHz BW, and getting all the sampling settings right for maximum BW results from the FFT is something I'd have to do some reading on first, since I've never done more than "play" with it so far, and there's some fairly complicated interactions based on those settings (max 400 MS/s, single channel, one-shot; 10GS/s repetitive).

Your tools can be good enough to check the JVC video BW after the update. I may check the update too if I can have access to Tektronix HD5000 video test equipment in my company. The only thing I missed is the DVHS DVE test tape ...
John

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post #184 of 305 Old 11-28-2005, 07:18 AM
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John,
> If you want (and for Tim too), I can provide some PCBs for you tests, then this will ease the implementation of the chip inside the JVC unit. <<br />
It would be good if the PCBs came from somewhere, since I have no time to do them myself (plus, it would be redundent effort).

> Your tools can be good enough to check the JVC video BW after the update. <<br />
Yes, I think you're right. The critical region will be to see how 26-37 MHz fares, and I can go to 40.2 MHz directly. I had just been thinking about looking for 74.5 MHz residuals.

> I may check the update too if I can have access to Tektronix HD5000 video test equipment in my company. The only thing I missed is the DVHS DVE test tape <<br />
Nice gear! My spectrum analyzer does have a precision tracking generator, so I'm OK in the bandpass without the DVE tape. In fact, with a -17 dB rolloff, I don't think the tape (the 1080i variant) is a good test source anyway. The FFT from the DSO should reveal products outside the bandpass to at least 100 MHz, and I have a 0-300 MHz generator I can inject a signal from to see if there's any foldover (spurious products) inside the bandpass.

- Tim

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post #185 of 305 Old 11-28-2005, 09:05 AM
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Thanks for the answer Tim,

Always good to know that we can test the tweak with differents tests rigs to be able to check the increase of the video BW with confidence.

I've passed some time to probe the HD_DEC video outputs of the 30K with a good oscilloscope (500MHz analog). I've discovered that there is two different VDAC option inside the unit :

- One is with the use of IC1001 (JCP8037) HD_DEC internal VDAC (COMPY/COMPCR/COMPCB signals),
- One with an external video DAC optionnal IC (IC801=JCP8029 not populated in my unit) a small 80-pin LQFP package chips.

I've checked the PCB and found that COMPY/COMPCR/COMPCB signals from HD_DEC VDACs are all in Unity Gain (x1) with Sync. measured at 316mV. That's a good new since there is no need to change the current to voltage conversion resistors (R1021/R1022/R1023) on the PCB to add the tweak Hope the use of HD-DEC internal VDACs is also major in your units ...

I've also checked the "1080_H" signal states :

Playing 480i tape -> "1080_H" = 0V
Playing 480p/720p/1080i tapes -> "1080_H" = 3.3V
Then Q836 is inverting the polarity of this signal ("1080_L") with 10.5V amplitude.

Just another information : The MPEG2 HD transport stream is decrypted through a specific JVC IC (JCP8044) but unfortunatly, the decrypted TS buses (links to IC1201/IC1001/IC601 BGA) are buried in the inner layers of the digital circuit board : no access in any case for security reason

I've updated the schematic to reflect the change of Pr/Pb bandwith to 18MHz(HD)/9MHz(SD) and "1080_L" amplitude.

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post #186 of 305 Old 11-29-2005, 12:46 PM
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Hello,

Just finished the CAD layout of the JVC video BW update :
JVC 30K/40K video filters update PCB layout

- The PCB size is less than 38x22mm,
- The PCB is 0.8mm thick and dual layer,
- Three 220uF 10V Ecaps have been added to the Y/Pr/Pb output to supress the DC component prior to be outputed to RCAs (AC coupling is decreasing AD IC power),
- The most PCB area is used to hold the three RG179B/U coxial terminaison,
- The "solder side" of the layout is filled with a complete ground plane with no tracks cuts,
- ADA4412-3 IC power decoupling is very good,
- Video paths are optimal, so the video signal integrity should be maximal,
- PCB mount / fix is still under study.

John

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post #187 of 305 Old 11-29-2005, 03:02 PM
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Looks great John (being a pcb designer myself).
I have to admit though that I will probably just solder 3x RG179 cables directly to the board for simplicity. This depends on assembly layout though.
Great stuff.

Regards,
moggy
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post #188 of 305 Old 11-30-2005, 12:51 AM
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Hi Moggy,

Thanks again for your help on this project. The JVC30K schematic was helpfull for me !

About RG179B/U footprints on the PCB : it's indeed direct solder of the coaxial on the PCB (tip inside a throug hole pad and shield lay down on the sqare pad and soldered on it). This solution is cost and size effective. This also ensure 75 ohms impedance continuity between the coxial and the PCB (no impedance break).

The next question is how much of this PCB should I make ?

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post #189 of 305 Old 11-30-2005, 01:07 AM
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Count on me for 2 PCB
Thanks
Mauro
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post #190 of 305 Old 11-30-2005, 04:55 AM
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Just wondering ...

How about ending the three coax. with 75Z BNCs and put these BNCs somewhere on the back panel of the unit ?

Then, we should be able to A/B compare between original filtered (RCA) and new filtered (BNC) Y/Pr/Pb outputs ...

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post #191 of 305 Old 11-30-2005, 07:45 AM
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JohnHWman inquired:
> The next question is how much of this PCB should I make ? <<br />
Perhaps just a couple in the first batch for inital testing?

I have two of the JVC-30K decks and one 40K myself, and I think once the implementation is validated, there are many here in the Forum with these decks that would love to benefit from what should be a very noticable improvement. Those running D-Theater tapes in particular should see a night and day difference on good displays. So a second run in quantity, once people are made aware of it, would be justified.

- Tim

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post #192 of 305 Old 11-30-2005, 03:31 PM
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now who is gonna come up with a DTS mod?
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post #193 of 305 Old 11-30-2005, 03:39 PM
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Hmm, I sold my deck after it died, now I am tempted again.

Anyone tried plugging a laserdisc into the composite input on the JVCs - from memory they had a great comb filter - anyone know much about that side of them?

DON'T feed the troll.
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post #194 of 305 Old 11-30-2005, 08:27 PM
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I would be interested in one for my JVC30K.
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post #195 of 305 Old 12-01-2005, 12:51 AM
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Quote:
Originally Posted by VideoGrabber View Post

Perhaps just a couple in the first batch for inital testing?

This makes sense Tim,
However, for the PCB manufacturing, because of its size, the tooling cost is quite heavy for two PCBs only. I think that it would be better to count on 5 to 10 units in first batch (the PCB cost excluding tooling is quite cheap).
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post #196 of 305 Old 12-01-2005, 04:15 AM
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Dok

the JVC decks do indeed have a top notch 3D 2/4mb Comb Filter, great stuff

Only guys with LD's in their theater would talk about this stuff eh!!

I keep my LD spinning for rare music LD's like Santana and Malmsteen stuff and all sorts of other LD only goodies

I am thru with D-VHS, but I would love to compare a modified 30k to the 5u using HDMI output, the later is the best damn HDTV image I have ever seen and boy have I been thru HDTV devices and decoders

-Gary
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post #197 of 305 Old 12-01-2005, 09:38 AM
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Hey Gary,

It amuses me when people are "done with D-vhs" when any other recordable, archivable HD media is 3-5 yrs out. Sure 200 hr HD dvrs give some room to work with, but I stil love my t-165 and 30k for hd recording.

God bless...

Mark
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post #198 of 305 Old 12-02-2005, 03:19 AM
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Hmm, maybe I should pick one up just to use as the input for my LD player - they are cheap enough now.

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post #199 of 305 Old 12-02-2005, 04:52 AM - Thread Starter
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Quote:
Originally Posted by JohnHWman View Post

This makes sense Tim,
However, for the PCB manufacturing, because of its size, the tooling cost is quite heavy for two PCBs only. I think that it would be better to count on 5 to 10 units in first batch (the PCB cost excluding tooling is quite cheap).
John

I found another potentially good chip for testing (THS7303):

http://focus.ti.com/docs/prod/folder...t/ths7303.html

I have three of these on order, and they'll be here soon. I'm also going to draw out three boards for them, and we'll also share these to look at.

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post #200 of 305 Old 12-02-2005, 08:39 AM
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Hi Mike,

The TI part -3db point is only 35hz, so wouldn't that be 2 MHZ below ideal of 37mhz to let all detail through? The AD part -3db is 36 mhz right?

God bless...

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post #201 of 305 Old 12-02-2005, 10:03 AM
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htguy,

no, not really. Part of your confusion is that 35, 36, or 37 MHz are "hard" points. We're dealing with analog, and it's all part of the curve.

SMPTE recommendations put the -3 dB rolloff point at 34 MHz. As long as that's maintained, you're in good shape. As far as letting "all the detail through" at 37 MHz, that's never running at full amplitude at that point anyway. By the time you reach 37 MHz, you could be 6-12 dB down, and still have some detail come through at 1920 (with reduced MTF). But it is true that 34 MHz amplitude (@50% MTF) is only maintained out to ~1780 horizontal, in the best-case scenario. (And that's far better than 30K owners are currently getting.)

- Tim

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post #202 of 305 Old 12-05-2005, 02:29 AM
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Quote:
Originally Posted by mp20748 View Post

I found another potentially good chip for testing (THS7303):
http://focus.ti.com/docs/prod/folder...t/ths7303.html
I have three of these on order, and they'll be here soon. I'm also going to draw out three boards for them, and we'll also share these to look at.

Yes Mark, seem's quite good one

However, it has 2:1 mux input which is useless for the application. It is also I²C protocol driven : that's make the implementation more difficult since you need a microcontroler to setup the chip operation within the JVC unit.

The 190MHz Bypass mode is interresting to see.

John

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post #203 of 305 Old 12-12-2005, 08:53 AM
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Just a small update on the project :

Just received today two ADA4412-3 chip samples for free.

Now I could launch PCBs manufacturing.

John

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post #204 of 305 Old 02-01-2006, 10:57 AM
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Here we are

Just finished populate two samples of the JVC30K/40K video BW fix :



- The PCB size is less than 38x22mm,
- The PCB is dual layer (bottom layer is 100% ground plane),
- The most PCB area is used to hold the three green RG179B/U silver coaxial terminaisons on the right side of the pictures,
- ADA4412-3 IC power decoupling is very good,
- Video paths are optimal, so the video signal integrity should be maximal,
- PCB mount / fix is using a simple dual side 2mm thick smooth scotch tape located on the bottom side.

Now I can start to modify my JVC 30K to integrate this small update and test it. I will post some pictures of the mod. integration in this thread to help DIY people.

I can provide some samples for only the BOM cost of $20 for people who want to test it (Mike, Tim ??). These samples will be without the AD chip mounted because I've got only two samples of this device so far on hands.

Moggy will got one too for free since he helped me in designing this

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post #205 of 305 Old 02-01-2006, 07:45 PM
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Beautiful baby ! That's a work of art.
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post #206 of 305 Old 02-01-2006, 08:11 PM
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Quote:
Originally Posted by JohnHWman View Post

I can provide some samples for only the BOM cost of $20 for people who want to test it (Mike, Tim ??). These samples will be without the AD chip mounted because I've got only two samples of this device so far on hands.

Very nice work.

I've got two JVC 30K's...

I'll volunteer to install your sample and do an A/B comparison with MP at next month's open house on my G90.
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post #207 of 305 Old 02-02-2006, 02:10 AM
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Looks great. Look forward to hearing the results.

Regards,
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post #208 of 305 Old 02-02-2006, 04:13 AM
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What is really needed to make me buy one of these machines, is an PAL to NTSC HD video input converter so I can record off air PAL HD signals onto an NTSC D-vhs machine.

Anyone got one in their cupboard they want to sell?

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post #209 of 305 Old 02-02-2006, 04:16 AM
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I'm close to finish the PCB mount inside the 30K. This job is not as easy as expected first and requires some care due to the size of the components footprints on the JVC digital PCB .

I'll post later the pictures of my job to let you evaluate the tricky stuff ...

Clarence, are you familiar with electronic parts soldering ? The installation of the sample require thin iron pin, thin solder, one magnifier and steady hands .

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post #210 of 305 Old 02-02-2006, 04:41 AM
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IS the firewire data streams to the D-vhs the same regardless of where the source material is NTSC 1080i or PAL 1080i. Is there a difference or are they the same?

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