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It is currently 26 Apr 2024, 09:51
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publius
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Post subject: Re: Adding AC3 output to a panasonic lx900 Posted: 13 Dec 2017, 08:41 |
Hardcore fan |
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Joined: 23 Sep 2003, 18:14 Posts: 1391 Location: United States Has thanked: 39 times Been thanked: 21 times
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Looking at a schematic diagram (which, unhelpfully, is mostly in Chinese), it appears that you want to tap at the junction of Q203 & R208. From that point, the signal flows to both input pins of IC201, the audio FM demodulator. Much upstream of that, you'd be getting some version of the full off-disc RF signal, which is likely not to be all that helpful.
I guess the Panasonic design works rather differently from the Pioneer one, in that the two audio FM signals are separated at the demodulation stage, by different time constants in the two parallel detectors. At least, without a proper datasheet for the PA0034A, I think that's what's going on. The only difference between the networks on the two sides of the chip is C216, 270 pF capacitor attached to pin 7, vs C215, 330 pF on pin 36.
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wander
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Post subject: Re: Adding AC3 output to a panasonic lx900 Posted: 30 Dec 2017, 04:17 |
Third post and above |
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Joined: 26 Mar 2008, 01:22 Posts: 4 Location: Canada Has thanked: 1 time Been thanked: 2 times
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publius wrote: I suggest taking the output through the otherwise useless mono audio jack (the one tagged for an RF modulator). W99 on the main board is the AC3-RF tap point
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primetarget
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Post subject: Re: Adding AC3 output to a panasonic lx900 Posted: 31 Dec 2017, 22:50 |
Honest fan |
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Joined: 29 Aug 2016, 21:02 Posts: 71 Location: Chicago, IL Has thanked: 1 time Been thanked: 2 times
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wander wrote: publius wrote: I suggest taking the output through the otherwise useless mono audio jack (the one tagged for an RF modulator). W99 on the main board is the AC3-RF tap point Do you have the mount points for the other wires or instructions?
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cplusplus
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Post subject: Re: Adding AC3 output to a panasonic lx900 Posted: 17 Jun 2022, 22:07 |
Hardcore fan |
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Joined: 13 Aug 2018, 03:18 Posts: 1520 Has thanked: 449 times Been thanked: 588 times
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wander wrote: W99 on the main board is the AC3-RF tap point This should work. W136 could work as well. The yellow components on each side are the BPFs that feed the Pioneer IC. W60 should be mute if I traced it right. Attachment:
LX-900_AC-3_RF.jpg [ 265.52 KiB | Viewed 3890 times ]
I will confirm once I actually perform the mod.
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cplusplus
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Post subject: Re: Adding AC3 output to a panasonic lx900 Posted: 09 Jul 2022, 00:59 |
Hardcore fan |
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Joined: 13 Aug 2018, 03:18 Posts: 1520 Has thanked: 449 times Been thanked: 588 times
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Both W99 and W136 work. For LX-600 use W99 so you do not have to remove the Sub board. LX-900's Sub board is larger and covers both so it has to be removed to tap either. Attached is an image of voltage taps on a LX-600. P23201 is a 7 pin connector, with an empty connection on the left that connects to pin 1 GND. Pin 2 is +5V and pin 7 is -5V. P23201 is also on the LX-900 in the same location. Attachment:
LX-600_Voltage.jpg [ 286.2 KiB | Viewed 3651 times ]
As always, a DMM can be used to trace to easier/safer points to connect to. You will need a DMM to check your mod (whether you assembled it or it was pre-assembled) before connecting it to any player.
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