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| Adding digital audio and ac3 RF to 50 disc auto-changer https://forum.lddb.com/viewtopic.php?f=23&t=10084 |
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| Author: | willis [ 25 Oct 2021, 17:22 ] |
| Post subject: | Adding digital audio and ac3 RF to 50 disc auto-changer |
Trying to get both digital audio and ac3 RF out of my lc-v200 50 disc auto-changer. I started with digital audio figuring it should be the easiest. The two players within the changer have the same EMF decoder as the player found in the linked thread below (CXD2500AQ) Pioneer CLD-M90 now modded for AC-3 RF and Digital Outputs Both decoder chips feed to a DAC which is located on the door of the changer unit. But before the signals go into the DAC both digital out circuits are fed to a chip (ic201 positions 2 and 3) that select which signal to output depending upon which player has been commanded to run. The output side of ic201 at pin 22 a single digital out signal exists that goes into the onboard DAC. To capture my digital signal I tapped into the circuit the pin 22 location, prior to a resistor (209) which resides between the DAC and ic201. I used the same pcb purchased from eBay found in the thread above, I have proper 5v power as the red optical light is working, however I do not have any sound from either coax or optical source. I'm not the most knowledgable on circuit designs and was hoping someone here might be able to compare the diagrams and tell me where I'm going wrong. The manual for the auto changer is loaded to the database here, and the information can be found on page 66 (ic201) and 109 (EMF decoder). Any help would be much appreciated. I wanted to tackle this first before attempting the ac3 rf mod. |
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| Author: | krbahr [ 26 Oct 2021, 00:30 ] |
| Post subject: | Re: Adding digital audio and ac3 RF to 50 disc auto-changer |
The thread you pointed to will give you the details to make the connection to a single player so for the digital output you need to either run 2 digital outputs or design a simple switch/relay circuit that sends the active player signal out. As for AC-3 RF it depends on if there is 1 or 2 analog audio circuits as this has nothing to do with the digital audio circuitry. AC-3 signal is the right analog audio channel. Again if you have 2 analog audio decoder circuits (one for each player) then you'll need 2 each AC-3 outputs or again design a simple switch/relay to output the active player signal. |
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| Author: | willis [ 26 Oct 2021, 15:22 ] |
| Post subject: | Re: Adding digital audio and ac3 RF to 50 disc auto-changer |
The unit actually already switches the signal at ic201, both digital out signals converge into this chip which switches depending upon which player is commanded to play. It appears the signal is amplified prior to this chip (looking at page 66 of the service manual) and I am wondering if this possibly has something to do with the issue. Does anyone know what the raw signal from the EMF decoder chip measure so I can compare that to what the ic201 chip is outputting? For the ac3, there is a similar chip that switches the RF signal (ic502), I'm hoping to grab the RF signal there. I just need to buy or build a ln ac3 RF board. |
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| Author: | cplusplus [ 27 Oct 2021, 01:59 ] |
| Post subject: | Re: Adding digital audio and ac3 RF to 50 disc auto-changer |
Are we looking at same schematic? I see one DAC IC201 with one digital input at Pin 8. |
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| Author: | ldfan [ 27 Oct 2021, 05:14 ] |
| Post subject: | Re: Adding digital audio and ac3 RF to 50 disc auto-changer |
I considered replying but I was so confused regarding the service manual and how the two players interact with the CO unit. Is there an instruction manual available on how to set-up the system? If not, some images of the jukebox connected to the CO unit would be appreciated. |
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| Author: | willis [ 27 Oct 2021, 14:19 ] |
| Post subject: | Re: Adding digital audio and ac3 RF to 50 disc auto-changer |
cplusplus wrote: Are we looking at same schematic? I see one DAC IC201 with one digital input at Pin 8. The service manual is a bit confusing. The DAC handles the digital audio signal for both players at ic202, where pin 8 is the digital in. I believe this is the chip you are seeing on the schematic. Both players send the digital out signal to ic201 to pins 2 & 3, then depending upon which player is commanded ic201 outputs a single digital signal on pin 22. Pin 22 feeds the DAC at pin 8. I believe I may have found the issue, the digital signal voltages are dropped from 5v to 2.4v prior to entering into the switching chip ic201. In the post I linked to they tapped the EFM decoder chip digital out signal which is at 5v. |
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| Author: | willis [ 27 Oct 2021, 14:42 ] |
| Post subject: | Re: Adding digital audio and ac3 RF to 50 disc auto-changer |
ldfan wrote: I considered replying but I was so confused regarding the service manual and how the two players interact with the CO unit. Is there an instruction manual available on how to set-up the system? If not, some images of the jukebox connected to the CO unit would be appreciated. The co unit doesn't do anything except command the players on, command the disc loader, and allow the karaoke portions to work (mixing the mic audio and such which I don't use). So the co unit doesn't really play into modifying the disc changer unit. All of the audio circuitry takes place on a pcb mounted to the door of the changer unit. Instead of doubling up on audio circuitry they removed all of it from the players and had them share a single pcb using a switching circuit which the co commands. You can put in multiple disc requests at one time and the co unit simply loads the discs requested and commands the player on which holds the requested disc. All audio and video can be input into the co unit but isn't necessary. I run both audio and video straight from the disc changer into my receiver. |
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| Author: | cplusplus [ 28 Oct 2021, 00:23 ] |
| Post subject: | Re: Adding digital audio and ac3 RF to 50 disc auto-changer |
Not my brightest moment. I was looking at LD-V200. You could use some data select IC to take in IC201 2,3 and have 5 as the selector. Not sure if there is an easier way though. This is an interesting one. I wish I had this unit! |
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| Author: | krbahr [ 28 Oct 2021, 03:26 ] |
| Post subject: | Re: Adding digital audio and ac3 RF to 50 disc auto-changer |
From all my past experience the digital out signal generates from the signal processing chip before the DAC and it is a separate output pin than the output pin going to the DAC. I'm not sure what the signal differences are but if you are using the signal output that is supplies for the internal DAC I would suspect a difference in the signal control, signal level, or the data in the signal. I would recommend in looking into why the digital output pin and the digital pin to the DAC are always separate pins. |
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| Author: | willis [ 06 Dec 2021, 15:32 ] |
| Post subject: | Re: Adding digital audio and ac3 RF to 50 disc auto-changer |
Two digital signals (one from each players DSP cdx2500aq) are routed to the VAPB board which is found on the door of changer. These two signals are sent to PD0052. This chip can receive up to three digital input signals (pins 1,2,& 3), then output a single signal based on voltage input into pins 4 and 5. The chip can output both a data signal (pin 22) and the raw selected digital signal (pin 6). The data signal (pin 22) is passed to the DAC (lc7883k) and pin 6 is unused. I changed my approach and grabbed the signal from unused pin 6 on PD0052 and now everything works as it should. The PD0052 chip handles switching which players audio is commanded and all unwanted noise when players are changing so far has been eliminated. I found a schematic (technics SHX1000) that uses the PD0052 pin 6 for digital output and they route the digital signal through a cmos inverter (TC74HC04AP). This exact chip is found on the disc changer VAPB board, the two digital signals go through this prior to entering into PD0052 pins 2 & 3. I am unsure of the reason to send pin 6 digital signal back through TC74HC04AP but it works fine without doing this. Maybe someone out there who understands the cmos inverters can explain if this is just a good practice to do and the benefits of doing so. Next is getting AC3 RF out......... |
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