Echostar AD3000IP Viaccess - Audio problem

[davjen]

Well, it looks like that we may be getting to the end of the line on this one. In the meanwhile, would it help if I did the checks on R626 or wait and see what you come up with? I appreciate all the trouble that you have gone to on this one - a rather stupid mistake on my part in the first place.

 

[Llew]

It's no trouble Dave. I'm always up for a challenge

i don't think it's a problem on the output side, voltage is OK on pin 49, no short cct there.

I'll give it a bit more time and see if we can get anywhere. Maybe not, we'll see.

 

[Llew]

Dave, can you try this to establish the CX chip is switching correctly -

With a source plugged in to the VCR scart and switched on and running (DVD player etc.), check with your probe that you have its LH audio in on pin 21 of the chip.

Satellite LH audio in should still be on Pin 1, and VCR source LH audio out should be on pin 49.

Just a basic check to see if the fault is a problem with the LH audio from the scart, or a problem with switching the LH audio from TV Line 1 (Pin 1) to VCR Line 3. (Pin 21).

 

[davjen]

Just wanted to confirm - on my "Typical Application Circuit" for the chip, it shows that Pin 21, being the Audio in- LH comes from AUX Scart, Pin 6. It looks like Pin 17 is the one from the VCR scart. I am just trying to get my head round this one. So the LH signal to the DVD inputs from AUX Scart pin 6 to output at Pin 21 and switches to Pin 1. So I need to check at Pin 1 and Pin 21 or Pin 17 if I use the VCR Scart? I hope what I am saying makes some sense.

 

[Llew]

As you say, the chip circuit is typical only. Echostar have the AUX and VCR input lines reversed, probably because of practical design reasons.

So we have -

Satellite encoder audio in - Pin 1 (LIN 1) Pin 63 (RIN 1)
AUX Scart audio in - Pin 39 (LIN 4) Pin 36 (RIN 4)
VCR Scart audio in - Pin 21 (LIN 3) Pin 19 (RIN 3)

LIN/RIN 2&5 aren't used here.

 

[davjen]

Did the check on pin 21 and audio was present, however, there was just noise on pin 1 and also on pin 49. I just want to make sure that I followed your instruction correctly. I connected the DVD player to the VCR scart on the Sat Receiver, played a DVD - no further connections made other than the probe to pins 21, 1 & 49. This doesnt sound good to me.

 

[Llew]

Yes that's the setup. You do of course need the satellite input working as well to have a signal on pin 1.

Is everything still OK on the right hand audio out Pin 51? (satellite audio with no VCR scart connected, DVD audio with Scart connected).

Also when you switch on your DVD player, do you have video and sound switch from the satellite channel to the DVD on your TV? Might be obvious questions, but I just want to be certain I'm not losing track since we began the thread

 

[davjen]

I re-did the checks again after your latest reply and found there was no signal at Pin 21 when running a DVD player, but there was slight audio at Pin 1.
Then I checked RH audio at Pin 51 - no problem there or at Pin 63. No problem when switching on DVD player from satellite. So as far as I can see, the situation is as follows:

Pin 1 - very low signal present.
Pin 49 - same as above
Pin 51 - good signal
Pin 63 - also good signal

Hope this will mean something to you.
Thanks again.

 

[Llew]

Just a quickie - You say you have no audio on Pin 21 even though you are switched to DVD source. Try Pin 17 - your board version may differ to mine regarding DVD/Aux Scart layout (i.e. the same as in the circuit diagram).

If no audio, we may have isolated the problem to the Scart LH output components to the chip.

 

[davjen]

Sorry to say, I did check Pin 17 as well and no signal there.

 

[Llew]

Looks like that might be the problem then. The resistor and/or the electrolytic cap to 21 (or 17) is open circuit possibly. Maybe when you were having a problem with the scart lead initially.We need to identify the components' placings on the board for checking. 6kohm and 1uF if as the circuit diagram.

 

[davjen]

I think what I want to do first is to go through all the checks again to make sure that I have done correctly and detail the results etc. and come back once I have them.

 

[Llew]

A correction to the AUX scart input pin numbering - the AUX LH audio from terminal 6 goes to the chip pin 39 (LIN 4), not pin 17 (LIN 2).

So LIN 4 is used here, making LIN 2 the spare.

The series resistor/capacitor for each LIN are on my board as follows -

VCR Scart terminal 6 - CE617/R603 - chip pin 21

AUX Scart terminal 6 - CE 616/R604 - chip pin 39

In both cases R=6kOhms C= 1uF 50V

You can easily trace if the audio is missing on either of these inputs to the chip pins (21 and 39) due to an open circuit resistor by checking both sides of it with your probe, alternating your Scart plug in the respective VCR and Aux sockets.

 

[davjen]

My latest findings are as follows:
On checking VCR Scart terminal 6, I found that there is contact between R603 and Pin 21, but no contact from terminal 6 to R603 - R603 checked out OK. My conclusion is therefore that CE617 maybe open circuit, I will need to remove the board to check this.
Turning to AUX Scart terminal 6, I cannot find any contact between it and R604 or from R604 to Pin 39.
This is a real strange one.
I also want to check whether there is contact from terminal 8 on the VCR Scart to chip Pin 7, I believe that when I cut terminal 8 that I may have touched terminal 6 causing the short.

 

[Llew]

You won't have any reading from terminal 6 to R603; CE617 is a capacitor, and will show open circuit with an ohmmeter. Do an audio check (with your DVD player plugged in and running through the VCR Scart), first with your probe on R603 (both sides) then on Pin 21.

Don't bother with the AUX scart at present, just be sure you get audio through from the VCR Scart. CE617 could be the culprit, but replacement is the only option if so.