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 Post subject: FEELER: drop-in pre-assembled AC3 RF Mod Boards?
PostPosted: 11 Oct 2022, 00:18 
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Putting out some feelers to see if anyone is interested. I am planning to manufacture some affordable modification kits for adding AC3 output to Laserdisc players (and other devices). The boards will come assembled and all you need to do is wire them up. Unless I missed something, I can’t find anything like this readily available in the US. The circuit is just the tried-and-true design from LA Audiophile

UPDATE 10/11/22: interest seems to be good enough that I will be ordering prototypes! I have some "beta testers" lined up who will be testing the boards in various players. I plan to order a prototype run at the end of this week (around October 14th) and should have them in the hands of testers by the end of October / start of November.

If the board is successfully approved and people are interested, I’ll put up a page for pre-orders and make up the kits on a per order basis. I would probably leave the pre-order page up for a month and then should be able to get them all made and shipped out 2-4 weeks after closing the preorder. They should be around $25 USD (or possibly $20) plus shipping.

The kit would include:
— AC3 modification PCB, fully populated with all components
(edit) PCB mounted 75 ohm BNC jack OR RCA jack, there will be an option to choose either or
— 2 feet of Canare coax wire for running to the jack
— 2 feet of hookup wire (PTFE mil-spec high-temp)
— bolt with solder lug / ring terminal for chassis ground and nut
— adhesive mounting squares
— total dimensions are 37.5mm x 20.35mm before cutting the jack daughterboard off

Obviously it would be up to you to figure out how and where to wire and place the PCB based on your model player.

Attachment:
File comment: Mockup
2022-10-10---PCB-mockup2.jpg
2022-10-10---PCB-mockup2.jpg [ 174.63 KiB | Viewed 1636 times ]


Boring Details:
I would also include coaxial wire with the kit for running from the main PCB to the jack. 1% resistors, C0G/NP0 capacitors, and the correct transistors. **EDIT** after much feedback, I plan to include an option for either a BNC or an RCA jack. As you can see on the mock-up, the board can be installed in the back of the player as one (jump the JACK+ and JACK- pads with a small piece of coax) or cut/snap the PCB across the perforation and run wire from the main PCB to the jack. I plan to use a plastic threaded jack (TE Connectivity part # 1-1634622-0 for the BNC one, RCA jack will be a different part that I will have to source from overseas) so the sleeve will be fully isolated from the chassis ground, with a 100nf MLCC between the sleeve and the chassis ground (it is important to have this as close to the jack as possible), so you’d have to drill an additional hole for a chassis ground bolt next to wherever you place the jack. The PCB also has a hole for an M3 mounting bolt depending on where you want to put it.

However, you could use a standard chassis mount jack (BNC or RCA) and not the included PCB solder pin one.
You can omit the mute circuit if you want by carefully removing Q2 and then jumping the correct pads. Figured better to include the mute portion than not. 

Here are the sources of the schematic.

Attachment:
File comment: Mockup with more details
2022-10-10---PCB-mockup.jpg
2022-10-10---PCB-mockup.jpg [ 231.74 KiB | Viewed 1636 times ]


Here are the sources of the schematic. This scheme has been around for ages (and I'm pretty sure is based on Pioneer's original one??) so I cannot take credit for it: http://www.laserdiscarchive.co.uk/laser ... pgrade.htm and http://www.laaudiofile.com/ac3mod.html

Attachment:
File comment: Source schematic from LA Audiophile
schematic.gif
schematic.gif [ 7.14 KiB | Viewed 1636 times ]


Last edited by zw12345 on 11 Oct 2022, 18:03, edited 4 times in total.
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 Post subject: Re: FEELER: drop-in pre-assembled AC3 RF Mod Boards?
PostPosted: 11 Oct 2022, 01:06 
Jedi Master
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Wow, I hope this works out for you.

I remember in the past talking to a friend and trying to get him to help me do this type of thing but he wasn't interested and I
didn't have the knowledge of parts etc and he was a stickler not helping :lol:

Anyway hope others can help you out with this and once you take the dive into AC3 you enjoy it :thumbup:
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 Post subject: Re: FEELER: drop-in pre-assembled AC3 RF Mod Boards?
PostPosted: 11 Oct 2022, 05:44 
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I'm sure there are a small number of people interested in a mod kit like this. It would definitely help facilitate more people willing to mod their players if they didn't have to build a board from scratch. I myself did scratch build my last two boards w/ this schematic and I can confirm it does work perfectly (but only for MAH players mainly sold in the US & Japan so please be aware of that; MAL players are mostly European models).

Moving on, I do have some comments....


zw12345 wrote:
It will be configurable with a PCB mounted BNC jack because I like BNC connectors. For those of you who don't like BNC connectors, I'll include an option to include a standard BNC-to-RCA adaptor that can fit right on the jack.


I can understand why you like BNC as it is definitely the better connector design. However, since all AC3-RF hardware was built around the RCA jack, it would probably make sense to simply offer the kit w/ an RCA jack option exclusively.



zw12345 wrote:
You can omit the mute circuit if you want by carefully removing Q2 and then jumping the correct pads. Figured better to include the mute portion than not. 




I would always encourage everyone to use Mute. Maybe it's only been my experience but of the one player I modded and left the mute off (I shorted the mute line to GND per instructions from a kit I was using), I would always get a sporadic loud bang on my speakers during the initial start up of a disc. However, all my players w/ a working mute circuit never exhibited this issue.
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 Post subject: Re: FEELER: drop-in pre-assembled AC3 RF Mod Boards?
PostPosted: 11 Oct 2022, 15:53 
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ldfan wrote:

I can understand why you like BNC as it is definitely the better connector design. However, since all AC3-RF hardware was built around the RCA jack, it would probably make sense to simply offer the kit w/ an RCA jack option exclusively.


If there is enough interest, I did find a a supplier where I could get a footprint-compatible high-quality RCA jack, in which I would just supply that in place of the BNC to RCA adaptor. That being said, this supplier is overseas where as I can get the BNC jack I designed the board around directly from Digikey or Mouser and haven't been able to find an RCA equivalent in the USA. I'm assuming this is the equivalent of a part that can be found in the USA but I am having trouble figuring it out.

The BNC jack I designed it around is 1-1634622-0 by TE Connectivity. Here is a link to one of the many Asian sellers with the footprint and design equivalent RCA jack and another in Europe. Not sure why I am unable to find a part like this in the USA. I sent an inquiry to the manufacturer to see what their MOQ is or how many samples I could order. There are several sellers on Alibaba / Aliexpress who appear to have the same part, but shipping takes forever from there.
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 Post subject: Re: FEELER: drop-in pre-assembled AC3 RF Mod Boards?
PostPosted: 11 Oct 2022, 17:25 
Jedi Knight
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I like it.

The BNC jack will be useless for hooking up to any and all AC-3 demodulators ever made (AFAIK…) so it doesn’t really make a lick of sense to use it. It will require an adaptor in every single use case which is not ideal. There should be as few solder-less connections as possible. The time it takes to ship some proper sockets from China isn’t going to matter. Most of us won’t get around to putting in the mod for a year anyway. :)

Also if I were you I wouldn’t build/sell anything unless I could test the entire setup myself. You’re just asking for people problems otherwise.

I’ll take two, at least, once they are known to work.
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 Post subject: Re: FEELER: drop-in pre-assembled AC3 RF Mod Boards?
PostPosted: 11 Oct 2022, 17:48 
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signofzeta wrote:
I like it.

The BNC jack will be useless for hooking up to any and all AC-3 demodulators ever made (AFAIK…) so it doesn’t really make a lick of sense to use it. It will require an adaptor in every single use case which is not ideal. There should be as few solder-less connections as possible. The time it takes to ship some proper sockets from China isn’t going to matter. Most of us won’t get around to putting in the mod for a year anyway. :)

Also if I were you I wouldn’t build/sell anything unless I could test the entire setup myself. You’re just asking for people problems otherwise.

I’ll take two, at least, once they are known to work.


I like BNC and have BNC-to-RCA cables that I use for various spdif applications in pro audio, hence why I designed it around a BNC jack, and Redco sells these nice BNC to RCA adaptors for just a couple of bucks and I will get the coax for this theoretical kit from them.

However, seems like most people I've put feelers out have also commented that BNC is not useful to them. In this case, I'll probably just get the RCA jacks from overseas and let people pick what jack they want.
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 Post subject: Re: FEELER: drop-in pre-assembled AC3 RF Mod Boards?
PostPosted: 11 Oct 2022, 18:15 
Jedi Knight
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BNC connectors are great…but using them just because they are cool isn’t proper product design when it means that EVERY installation requires that you use an adaptor to essentially negate the use of BNC in the first place. It slightly increases the price while slightly degrading the signal. It has small downsides but zero upside whatsoever…unless I’m missing something.
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 Post subject: Re: FEELER: drop-in pre-assembled AC3 RF Mod Boards?
PostPosted: 11 Oct 2022, 18:20 
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signofzeta wrote:
BNC connectors are great…but using them just because they are cool isn’t proper product design when it means that EVERY installation requires that you use an adaptor to essentially negate the use of BNC in the first place. It slightly increases the price while slightly degrading the signal. It has small downsides but zero upside whatsoever…unless I’m missing something.


I wasn't aware of BNC degrading signal, in my experience it is a more rugged and reliable connector than RCA obviously with stronger shielding at the jack, but I guess if you have a good RCA cable made with good 75 ohm coax the difference would be negligible from a consumer standpoint, especially in this context. Won't be surprised if I'm the only one who ends up using the BNC :lol:

also, great video in your signature!
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 Post subject: Re: FEELER: drop-in pre-assembled AC3 RF Mod Boards?
PostPosted: 11 Oct 2022, 18:39 
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zw12345 wrote:

I wasn't aware of BNC degrading signal


I'm pretty sure that Zeta implied the need to not include an unneeded adapter that can cause additional signal degradation. I would agree with this too.

RCA jacks aren't expensive if you know where to look. These are the one's that I buy and they work great.

https://www.ebay.com/itm/195104436610?h ... BMyIX3gflg


Last edited by ldfan on 05 Mar 2023, 05:39, edited 2 times in total.
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 Post subject: Re: FEELER: drop-in pre-assembled AC3 RF Mod Boards?
PostPosted: 11 Oct 2022, 18:55 
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BNC connectors are the least lossy connector in their scale, as far as I know. They are better than…anything, also very durable and smooth in operation. They’ve outlived SO MANY dumb new connector designs. But any extra solderless connections are potential voltage drop/impedance/corrosion and something to be avoided, especially inside the unit.
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