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 Post subject: [Sony MDP-605] AC3 modification issues (solved)
PostPosted: 05 Jan 2018, 05:14 
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Hello, and thanks for checking out my post. I am in the process of installing an AC-3 mod board in my Sony MDP-605. However I am having some issues finding the correct place to pickup the signal the board needs. I have tried a few different points on the audio demodulation circuitry but none of them produce an AC signal out of the AC3 board that is close to .6 volts. I purchased the kit from Benedictus.de. His website claimed that he had instructions for an MDP-605 but he either did not or couldn't find them. He did send instructions for the MDP-650, but it is a completely different player. I do have a digital oscilloscope and was looking for some insight as to what the input signal should look like and the amplitude of the signal that goes into the AC3 board. I'm including a picture of two places that I've already tried with no success. In addition I've also tried the pin labeled A RF.
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 Post subject: Re: Sony MDP-605 AC3 modification issues.
PostPosted: 05 Jan 2018, 05:15 
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I will probably have to attach the images tomorrow at work where I have a better internet connection.
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 Post subject: Re: Sony MDP-605 AC3 modification issues.
PostPosted: 05 Jan 2018, 05:37 
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Please do post pictures, I'm not a tech but all of this info should be posted.
Thanks and good luck with your player.
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 Post subject: Re: Sony MDP-605 AC3 modification issues.
PostPosted: 05 Jan 2018, 23:47 
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Here is a picture of the Audio demodulation circuitry. Perhaps I need to move back further in the circuitry to get the AC3 input signal I need.


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 Post subject: Re: Sony MDP-605 AC3 modification issues.
PostPosted: 06 Jan 2018, 02:34 
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You see in this image a block marked FL301. This is the band-pass filter that splits the audio FM into left & right channels for demodulation. Just before this, at the output of Q303, looks to be where you should be picking off the AFM signal for your AC-3 output. I suspect the big circled dot on the trace from Q303 to FL301 marks a test point where you can very easily attach.
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 Post subject: Re: Sony MDP-605 AC3 modification issues.
PostPosted: 06 Jan 2018, 04:27 
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If you haven't already recap the LV-20 board!
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 Post subject: Re: Sony MDP-605 AC3 modification issues.
PostPosted: 08 Jan 2018, 06:12 
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publius, that is where I had originally tapped in when I installed the kit. Unfortunately it didn't work there either. My preamp would occasionally lock in an AC3 signal but I wouldn't get any sound. At this point I'm beginning to suspect something is wrong with my kit. The AC3 input worked correctly with my first player that I have since sold.

happycube, The first thing I did when I got the player was to recap the LV-20 board. It's a beautiful one owner player with all the original packaging and paperwork. I just wish I could get the AC3 to work on it.
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 Post subject: Re: Sony MDP-605 AC3 modification issues.
PostPosted: 08 Jan 2018, 15:40 
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The picture I posted of the schematic is very hard to read. The schematic is available in the service manual on page 42.

http://manuals.lddb.com/LD_Players/Sony ... l_Scan.pdf

Thanks,

Ben
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 Post subject: Re: Sony MDP-605 AC3 modification issues.
PostPosted: 08 Jan 2018, 17:10 
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I finally emailed Benedikt out of frustration. I hate to bother the guy but I was really running into a brick wall with this mod. He told me that he makes a special kit for Sony players with a potentiometer to boost the RF signal to the correct level. That all makes perfect sense since my RF waveform looks perfect, it's just too small at .2 volts instead of the required .6 volts. Luckily I want to mod my LX-900 Panasonic as well so I will be ordering another kit from Benedikt with the correct Sony style board and using my current kit in the Panasonic. I will let you all know how it goes after I get the new kit.
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 Post subject: Re: Sony MDP-605 AC3 modification issues.
PostPosted: 10 Jan 2018, 20:43 
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topdollar69 wrote:
I finally emailed Benedikt out of frustration. I hate to bother the guy but I was really running into a brick wall with this mod. He told me that he makes a special kit for Sony players with a potentiometer to boost the RF signal to the correct level. That all makes perfect sense since my RF waveform looks perfect, it's just too small at .2 volts instead of the required .6 volts. Luckily I want to mod my LX-900 Panasonic as well so I will be ordering another kit from Benedikt with the correct Sony style board and using my current kit in the Panasonic. I will let you all know how it goes after I get the new kit.


Well since from your earlier post it seems he should have been aware this was for a Sony player you think he could have supplied you the 'special Sony' version in the first place? At least if you have use for both that saves the need for an exchange with shipping, but I'd suggest trying the kit you have in the Panasonic first just to be sure....
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 Post subject: Re: [Sony MDP-605] AC3 modification issues.
PostPosted: 02 Feb 2018, 17:54 
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The mod was somewhat successful on my Panasonic LX-900U. It works for about 30 minutes and then starts cutting in and out. If I let it sit overnight it will work correctly again for the same amount of time. That will require a little bit of investigation, but I should be able to figure it out. At least it sort of works. I am still working on the Sony. I still need to hookup the RF pickup point and adjust the output signal to the correct level. Hopefully it will be up and working by this same time tomorrow. I had a broken washing machine and a pinewood derby that I've been dealing with for the past month.
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 Post subject: Re: [Sony MDP-605] AC3 modification issues.
PostPosted: 08 Feb 2018, 16:45 
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I have an update on both my Panasonic LX900U and my Sony MDP-605 AC3 mods. The issue with my Panasonic ended up being a problem with the internal demodulator in my preamp. I swapped it out with a different one I have and it worked fine for over an hour. I have also made some small progress with the Sony. The only useable signal I could find is on pin six of the filter pack. Unfortunately the signal is very small and even with the variable output board I can only get 150 mV of final which is enough for the demodulator to partially work. It cuts in and out though since the signal should be about 650mV. If I can just figure out how to get more gain I will have the Sony up and working as well. Hopefully Benedikt gets back to me so we can figure it out. Now I need to fix my preamp with the bad demodulator.
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 Post subject: Re: [Sony MDP-605] AC3 modification issues.
PostPosted: 16 Feb 2018, 23:42 
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I never did hear back from Benedikt, I can't say as I blame him too much. So I figured it was up to me to reverse engineer his design. I was able to get about 400mV of signal verses the 150mV that I was getting with the changes I made. Hopefully that will be enough for my preamp to work. Time to unhook the Panasonic again... Wish me luck, or it's back to the drawing board again for the sixth time.
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 Post subject: Re: [Sony MDP-605] AC3 modification issues.
PostPosted: 19 Feb 2018, 04:55 
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Good news, I finally have a Sony player with working AC3 audio output. This time the preamp has a good lock on it with nice clear sound. What a hassle this project turned into. Hopefully fixing the built in demodulator in my TA-E9000ES preamp will be as simple as a few bad capacitors. Thanks for all the help everyone.
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