It is currently 29 Mar 2024, 00:06




 Page 1 of 1 [ 15 posts ] 
Author Message
 Post subject: Salvage Demod Chips / Circuits
PostPosted: 11 Jan 2017, 01:48 
Honest fan
Honest fan
User avatar

Joined: 16 Mar 2014, 01:05
Posts: 93
Location: United States
Has thanked: 2 times
Been thanked: 0 time
Well, I'm a little late to the game, but have focused on Pioneer gear, and their AVRs that incidentally had RF inputs.
It's gotten to where I now have 3 (VXS-09, 39, 59tx...) and only use the 59.
I can find no buyers for the 09 and 39 (old, heavy stuff, yet not quite classic) and would throw out them but...

I would really like to have 2 small demods to feed into small room systems, powered by USB connectors, about the size of a band aid box.

Anyone have any experience with gutting the demod circuit out of Pioneer AVRs?

If I had 10 I could justify the time by recovering 8 or so for others but just 2 will be quite a project.

Anyone else tried similar?
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 11 Jan 2017, 09:45 
Hardcore fan
Hardcore fan
User avatar

Joined: 28 Jun 2014, 05:59
Posts: 1451
Location: San Francisco, CA USA
Has thanked: 415 times
Been thanked: 527 times
I've never done it but I can see one possibility that it could work.

If the AC3-RF Demodulator is like a separate board inside any of the AV Receivers in question, it could be as simple as just unplugging it from the main board and saving it for a future project. All a board like that would need is essentially 5v of power and all the connections needed to send the data to an S/PDIF output.

Unfortunately, if the Receivers are built anything like my Sony, SDP-EP9ES, the RF Demodulator section is essentially part of the main board and trying to extricate it would be nearly impossible especially if one does not know what all the circuit traces feeding it are designed to do.

I guess if I was in your shoes and space was not a major concern, maybe I keep the receivers for a rainy day. You could use the entire receiver as an external RF Demodulator if any of the units have an S/PDIF optical or coax output (assuming these get fed w/ the proper signal from an AC3 RF source which I assume they would).

Dave
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 11 Jan 2017, 12:57 
Honest fan
Honest fan
User avatar

Joined: 16 Mar 2014, 01:05
Posts: 93
Location: United States
Has thanked: 2 times
Been thanked: 0 time
I get that, but since I have that 70 lb monster in the main rack, that leaves 50 lb monsters sitting in the floor just to decode for the office or bedroom system.
I had never thought about them being a daughter board - possible, but I doubt it.
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 12 Jan 2017, 19:47 
Absolute fan
Absolute fan
User avatar

Joined: 18 Apr 2012, 18:02
Posts: 1614
Location: United States
Has thanked: 71 times
Been thanked: 88 times
Did a service manual googling - on the 09 at least there's an AC3 board with demod and decoder. Biggest issue would be dealing with the voltages, the analog parts want +/- 16v, +/- 6v, and +5v - the digital bits want +5v and +3.3v if they can be talked into working without the analog bits.

https://www.elektrotanya.com/pioneer_vs ... nload.html
_________________
Happycube Labs: Where the past is being re-made, today. [meep!]
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 13 Jan 2017, 23:24 
Honest fan
Honest fan
User avatar

Joined: 16 Mar 2014, 01:05
Posts: 93
Location: United States
Has thanked: 2 times
Been thanked: 0 time
That board idea was brilliant!
I got it out, working up an insertion into a Denon 606 clone

UPDATE:
Turns out my player has a 504 power board, anyway, I only need 5 and +-15, so far.
I have a print for my board, and for the Pioneer Demod RFD-1?, and they are 98% exactly the same.
A few pins tied hi/lo vs switched, and a panel light rather than a LED.
Gonna' power up tomorrow!
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 19 Jan 2017, 02:32 
Hardcore fan
Hardcore fan
User avatar

Joined: 28 Jun 2014, 05:59
Posts: 1451
Location: San Francisco, CA USA
Has thanked: 415 times
Been thanked: 527 times
Awesome. Love to see pics later on the project.
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 09 Sep 2021, 13:20 
Third post and above
Third post and above
User avatar

Joined: 27 Aug 2021, 15:17
Posts: 5
Location: United States
Has thanked: 2 times
Been thanked: 5 times
Found this old thread because I have a VSX-07TX that I have been using for AC-3 decoding but now the audio section is failing. I'd like to salvage the AC-3 board for a demodulator also. @tshephard, what was the outcome of your attempt?
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 18 Sep 2021, 16:45 
Third post and above
Third post and above
User avatar

Joined: 27 Aug 2021, 15:17
Posts: 5
Location: United States
Has thanked: 2 times
Been thanked: 5 times
EDITED: I had left out the all important step #5!

I have successfully pulled this AC-3 daughter board and fired it up as a standalone RF Demodulator!

Let me preface this with the fact that my old VSX-07TX was kind of toast and was putting out a loud 60hz hum from the amp and pre-outs. I'm not saying the audio had a 60hz hum on it which is a common problem. I mean it had a LOUD 60hz hum INSTEAD of the program audio. On all of the pre-outs. If I banged the unit on the counter a few times while turning it off and on I could sometimes get a clean output and it made a fine AC-3 decoder but it was in its death rattle. The LEDs always faithfully showed it was demodulating and decoding AC-3 RF into 5.1 so I was confident the daughter board was ok.

I considered just adding a Toslink AC-3 output to the unit and let it dangle out the bottom. I was able to find a service manual for the VSX-07TX (and other models) which had full schematics of the AC-3 board but no diagram of the physical layout so I wasn't going to be able to identify any of the soldering points I needed by just looking at the belly of the board. This meant I would have to pull the board out to figure out how to connect everything. If you think you'd like to preserve your receiver and take this approach, I will propose a simple way to do that at the end. Maybe somebody can try what I suggest and see if they are successful at just adding a demod out jack without removing the board. I believe it would be easy to do.

I fully sacrificed my receiver to harvest the board. Here is a description of what I did.

1) First let me say getting TO the board is easy. It has its own cover just under the belly of the unit. Getting the board OUT is another story. This is a ONE WAY TRIP. You will most assuredly render the receiver unusable doing this. There are 3 ribbon connectors from the main unit to the board and they do not have plugs on them. The smaller one at the back end of the board has bare wire ends that are pushed into locking sockets which you have to just rip out. The other two along the side have clip-down "backstop" caps just holding the bare wire ends into the socket. You will want to preserve this backstop on CN9801, the one along the side, closest to the back of the board (the middle of the 3 ribbon sockets if you want to think of it like that). You will have to release the tips of the plastic mounting posts that hold the board to the unit, then unscrew the screws on the back plate of the unit that secure the coax RF and digital input jacks. You need to unscrew the next nearest small backplate support screws like those nearby so you can bend the back plate away far enough to clear the RCA jacks so that you can finally separate the board from the receiver. Now off to the electronics dump with the main unit unless you want to harvest any of its other organs...

2) Now you need to build an S/PDIF output. I chose Toslink because 1) it is a super simple circuit with very few parts needed and 2) I am making NO electrical connection to my modern receiver from my "Frankenstein" board. Don't trust myself to not send some major zapping death pulse to the new receiver... If your decoding receiver only has coax S/PDIF input, then you will need to build the 75 ohm coax type output. There are many examples on the web. I did a small PCB with the Toslink transmitter, one .1uF capacitor bridging the +5 and GND wire like so:

Image

Image
Black = GND; White = +5Vcc; Grey = Vin (S/PDIF signal) Ignore the double wiring, I changed that later. Just +5 and GND DIRECTLY from power supply.

3) Next you must solder the Vin signal wire of the Toslink out to the board. The point is on the path right before pin 9 into the CD0004AF chip. This chip takes the 4 inputs and does the switching (using receiver's "signal select" button; the "auto" mode is smart switching: AC-3 RF if present, if not pass the other coax or optical) into the DSP for decoding. As a future project, I may try to figure out how to control that chip and pickup my signal on the output side (emulating the Pioneer RFD-1). But for now, I am just picking up the demodulated AC-3 RF and going straight out to the transmitter. !!!!UPDATE!!!! My first attempt at soldering the Vin for the Toslink out was downstream near the input switcher chip, but it gave me trouble so I looked farther "upstream" and found a surface solder point labeled "DEM" (you can see this label under my wire end) right next to the output pin 70 of the PM4007A Demodulator chip. This makes a much more solid solder point and gives me a steady signal, but again, this is only accessible if you have fully removed the daughterboard. Here is a closeup:

Image

This backside solder spot would be the choice for adding demod out without removing the board from the unit (see proposed add-on mod below). This is a very tiny through hole and it will be difficult to solder to solidly.

Image

If soldering to the "bottom side", you may have a better chance soldering to my original spot:
Image

4) Now to provide power to the orphaned AC-3 board. This circuit only needs +/-5V DC, +15V DC, -15V DC and their common to function. All the other voltages are for the DSP and A/D converters that we are bypassing now. All of these power connections are on CN9801 (that "middle" ribbon connector socket that you hopefully salvaged the backstop crimp holder for). Bring these 5 wires DIRECTLY from the power supply. I will use the pin numbering from the schematic in the service manual. They are numbered in the picture below from right to left. The GND for the 5V goes on pin 9, the +5V supply goes on pin 8, the -15V goes on pin 5, the +15V goes on pin 4 and the common for the 15s goes on pin 3. That backstop cap can now be jammed back down to hold your wires in place.

Image

5) The demodulator chip PM4007A needs to be told to turn on. This last step was figured out by comparing the schematic of the VSX receiver to the schematic of the Pioneer RFD-1. The circuits are nearly identical up through the demodulator chip. The RFD-1 just keeps it turned on by a steady +5V on pins 3 & 4, but apparently pins 3 & 4 are signaled by the DSP decoder chip in the VSX receivers. I guess if the AC-3 input isn't selected, it turns off the demodulator. Luckily pin 2 right next to them has the Vcc +5V so I just soldered 2, 3 & 4 together.

Image

Now the board should operate as a dedicated AC-3 RF demodulator to Toslink out. Make sure you split the +5V and GND(5v) for the board and the Toslink transmitter AT the power supply. As you see in my first picture I was splitting at the Toslink and had ground path problems. Once I split at the power supply it consistently fired up and worked every time. Here is my (interim) completed project:

Image

I have ordered a 3 voltage AC/DC adapter power supply that I will wire into it and an enclosure to house it all.

PROPOSED DEMODULATOR OUTPUT MOD TO OPERATING RECEIVER:

In other words, if you don't want to destroy the host receiver, I believe you could just add the demodulated S/PDIF out.

DISCLAIMER/WARNING!!
!!!! I haven't tried this. I do not guarantee that this will work as proposed and you may still end up deceasing your receiver !!!!

1) Of course, unplug everything and remove the AC-3 daughterboard cover from the receiver

2) Build the Toslink transmitter module as in step 2 above

3) Solder the Vin wire from the Toslink out module onto the pickup point described in step 3 above. Here is a broader picture to find the location. Refer to closeups in 3) above for more detail.

Image
The spot on the left is directly opposite the surface solder spot shown above in step 3. The spot on the right is where I tried the first time (note my first sloppy solder attempt) and is right before the switcher chip input. There is more blank board surface at this secondary spot so less chance of solder spilling onto a another trace and causing a short so you may prefer this location.

4) Solder the Toslink +5V (Vcc) onto the back side of socket CN9801 pin 4 and the GND wire on the backside of pin 3.

Image

Don't be confused by the plastic mounting pegs in my pictures. You will see them coming into the board from the other side while yours is still mounted to the receiver. I reclaimed them from the receiver and used them on this side of my board as "feet" to hold it up in whatever project box I end up enclosing it with.

5) Place the cover back over the board while routing the 3 wires of the Toslink transmitter out to wherever you can find to affix it.

I suspect this solution will require the VSX receiver to be 1) powered on, 2) LD/SAT input selected and the signal select forced to "AC-3 RF" (not auto). Just guessing.

Advanced research opportunity for the real electronics experts in this community: Find out how to control the source selector chip CD0004AF to do the smart pass through function and then pickup Vin on the DATA pin (24) of the switcher chip. My guess is some combination of low or high voltage on pins 4 & 5 which seem to be "selector" pins. There are 4 inputs so 2 binary value pins would seem to cover it.

Good luck and please let me know if anybody else makes this work or finds the advanced solution.


Last edited by chrisf16 on 24 Sep 2021, 22:01, edited 2 times in total.
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 18 Sep 2021, 17:51 
Hardcore fan
Hardcore fan
User avatar

Joined: 13 Aug 2018, 03:18
Posts: 1512
Has thanked: 443 times
Been thanked: 584 times
This is fantastic. Thanks for sharing. I have a demodulation board I pulled from a Harman Kardon that I've been planning to attempt the same with.

In regards to soldering, it looks like you just need to buy some flux.
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 18 Sep 2021, 21:37 
Jedi Master
Jedi Master
User avatar

Joined: 03 May 2004, 19:05
Posts: 8093
Location: Dullaware
Has thanked: 1218 times
Been thanked: 841 times
cplusplus wrote:
In regards to soldering, it looks like you just need to buy some flux.

Possible, I had some issues recently with I believe 60-40 solder and it just won't flow, has flux core.
Could be the same issue that we see??
Hard to find really good solder now, Radio Shack used to have great stuff but now its harder to source cheap priced.
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 18 Sep 2021, 21:43 
Third post and above
Third post and above
User avatar

Joined: 27 Aug 2021, 15:17
Posts: 5
Location: United States
Has thanked: 2 times
Been thanked: 5 times
I'm sure y'all are right. I had only hit the spots with a felt tipped flux pen. The target spots are tiny but maybe I should flood with flux blobs like I see in the youtube videos. It's been holding so far so good. Ugly but a decent connection.
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 19 Sep 2021, 01:46 
Hardcore fan
Hardcore fan
User avatar

Joined: 13 Aug 2018, 03:18
Posts: 1512
Has thanked: 443 times
Been thanked: 584 times
rein-o wrote:
I had some issues recently with I believe 60-40 solder and it just won't flow, has flux core.

Yep. I use Radio Shack solder and SRA Flux #125. I usually gob too much on there but I'd rather just clean it up after.
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 19 Sep 2021, 01:58 
Jedi Master
Jedi Master
User avatar

Joined: 03 May 2004, 19:05
Posts: 8093
Location: Dullaware
Has thanked: 1218 times
Been thanked: 841 times
Is it 135? I can't see any 125 online.
Have been doing some guitar parts over the past few years and its hard to find good solder, will look into getting any RS or look at the SRA if they have.
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 19 Sep 2021, 03:22 
Hardcore fan
Hardcore fan
User avatar

Joined: 13 Aug 2018, 03:18
Posts: 1512
Has thanked: 443 times
Been thanked: 584 times
Yep. Typo! SRA Flux #135 Rosin Paste Flux: https://www.sra-solder.com/rosin-paste- ... a-2-oz-jar

Might be better stuff out there but I use it for everything- through hole and surface mount. That 2oz can will last me years.
Offline
 Profile  
 
 Post subject: Re: Salvage Demod Chips / Circuits
PostPosted: 24 Sep 2021, 22:02 
Third post and above
Third post and above
User avatar

Joined: 27 Aug 2021, 15:17
Posts: 5
Location: United States
Has thanked: 2 times
Been thanked: 5 times
I did some re-work and made updates in my original "how to" post above.
Offline
 Profile  
 
Display posts from previous:  Sort by  
 Page 1 of 1 [ 15 posts ] 


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to: