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Adding AC3 output to a panasonic lx900
https://forum.lddb.com/viewtopic.php?f=23&t=7494
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Author:  wander [ 12 Dec 2017, 17:40 ]
Post subject:  Adding AC3 output to a panasonic lx900

Any one no where to tap off the RF signal on the main board? I found A RF pin7 on FP22004, not sure if this is correct. If anyone can give me some information on this, much appreciated. :roll:

Author:  primetarget [ 13 Dec 2017, 00:35 ]
Post subject:  Re: Adding AC3 output to a panasonic lx900

Even though you would think it's the RF pin it is probably not. Do you have the 900 instructions he sent you?

Author:  krbahr [ 13 Dec 2017, 04:55 ]
Post subject:  Re: Adding AC3 output to a panasonic lx900

You need to find the audio RF before it split between right and left RF.

Author:  publius [ 13 Dec 2017, 08:41 ]
Post subject:  Re: Adding AC3 output to a panasonic lx900

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.

Author:  wander [ 14 Dec 2017, 02:52 ]
Post subject:  Re: Adding AC3 output to a panasonic lx900

publius: I had a look at the schematic and will try this option. Don't have time right now to do the DIY, but ill let you know if it worked

Author:  publius [ 14 Dec 2017, 07:56 ]
Post subject:  Re: Adding AC3 output to a panasonic lx900

I suggest taking the output through the otherwise useless mono audio jack (the one tagged for an RF modulator).

Author:  wander [ 30 Dec 2017, 04:17 ]
Post subject:  Re: Adding AC3 output to a panasonic lx900

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

Author:  primetarget [ 31 Dec 2017, 22:50 ]
Post subject:  Re: Adding AC3 output to a panasonic lx900

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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