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[MDP-650D] No Ac-3rf from Optical
https://forum.lddb.com/viewtopic.php?f=56&t=10527
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Author:  barry728 [ 03 Sep 2022, 18:06 ]
Post subject:  [MDP-650D] No Ac-3rf from Optical

Hi all,

I got a Sony Mdp650d, and try to get ac3rf working. I hooked up a Optical cable (red led) from the Sony LD to a Harman kardon avr75, but i dont get the ac-3rf signal working. Do i something wrong?? or can het only working with coaxial(digital ) ?? I hope someone knows the answere.

Author:  ldfan [ 03 Sep 2022, 20:54 ]
Post subject:  Re: Mdp650d no Ac-3rf from Optical

The answer is you can't because your player lacks the appropriate output. Thus, you will need to get a player with an AC3-RF output (fairly easy to find) or modify your current player to add it (hard if you are not acquainted with board level electronics).

Here is a pic of what you should look for to do Dolby Digital (AC3) as well as DTS.

Image



Hope this helps.

Author:  barry728 [ 03 Sep 2022, 22:14 ]
Post subject:  Re: Mdp650d no Ac-3rf from Optical

Thanks for the info Ldfan, so i need to modify my mdp650d. I dont know the modifications you can find online(picture) , works in my Sony laserdisc.

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Author:  ldfan [ 03 Sep 2022, 23:57 ]
Post subject:  Re: Mdp650d no Ac-3rf from Optical

I worked on the MDP-455 years ago and modding it was a tad problem prone due to the lack of a workable mute point. It might be the same for your 650D since it shares a common design. However, since it's a PAL/NTSC player, maybe it might be designed differently enough to make it a better candidate for the mod. Here is the write-up I did on my 455 that includes the tap points I used on it (except Mute)....

My old Sony, MDP-455, LD player w/ AC3 Demodulator mod


As for building an AC3 board, this schematic should be fine as it's written for a Mute Active Low player that your 650D may be designed for (if you can find the mute point and verify that the voltage drops to zero when you hit pause or stop).

Author:  admin [ 04 Sep 2022, 06:44 ]
Post subject:  Re: Mdp650d no Ac-3rf from Optical

barry728 wrote:
Thanks for the info Ldfan, so i need to modify my mdp650d.


Yes, that's correct.

Your Harman Kardon AVR 75 is AC3-RF compatible but the Sony MDP-650D will require a AC3-RF out hack to get the signal out.

Julien

Author:  barry728 [ 04 Sep 2022, 11:56 ]
Post subject:  Re: [MDP-650D] No Ac-3rf from Optical

Thanks Julien for the info, i thought only the Optical was enough to get a ac-3rf signal. Its not that simple :lol:

@Ldfan on your mod(Thanks for the link) i see two boards, the bigger board is for the ac-3rf and the smaller board for Optical out ?? Is that right….

Author:  ldfan [ 04 Sep 2022, 19:27 ]
Post subject:  Re: [MDP-650D] No Ac-3rf from Optical

barry728 wrote:
@Ldfan on your mod(Thanks for the link) i see two boards, the bigger board is for the ac-3rf and the smaller board for Optical out ?? Is that right….


I should have better clarified what this MDP-455 mod was about. This was a special mod that incorporated an "internal" AC3-RF Demodulator (the larger board) which is something not common at all. The smaller board is the one you need to make or procure to get your player AC3-RF capable.

To help you along with this, here is the exact instruction provided by "Precision LaserDisc" on modifying the MDP-455 (I disagree with the instruction's mention that Mute is not needed; you will get an occasional loud squeal on the speakers during initial start up of an LD due to the lack of mute control)….

Image


Also, here are a couple of links to my more recent AC3-RF mods of which I used "scratch built boards" to get the mods done (I used to buy the mod kits but they got expensive and also hard to come by).

Scratch built AC3-RF board installed in my ProScan, PSLD43

Pioneer CLD-M90 now modded for AC-3 RF and Digital Outputs

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