Following a HDMI signal path

[zzattack]

I have an AV receiver with quite a bunch of video capabilities, but unfortunately no HDMI output.
The path is pretty clear to me. There's 2 muxes to support as many as 6 inputs, there's a 4k scaler that can be bypassed by putting the device in 'HDMI Through' mode and then there's 2 output transmitters.
Since neither output provides any picture, the primary suspect is the common denominator 'HDMI Processor'.
Rather than blindly replacing this chip I'd like to confirm whether there is indeed a problem here, but I'm not quite clear on how to do so. Are there signals I can probe to verify the bottom receiver is properly feeding an input into the processor (and so forth)? Can this be done with cheap equipment (I do have a simple scope, but certainly incapable of looking at HDMI TMDS pairs)?

Code: [Select]

                                                                    ______________
                                                                    | HDMI        |
               ___________           ___________             -----> | Transmitter |  ----> HDMI OUT 1
HDMI IN 1 --> | HDMI      |         |           |          /        |_____________|
HDMI IN 2 --> | Processor | ------> | 4k scaler | --o-----|
HDMI IN 3 --> |___________|    |    |___________|   |      \        _______________
                    ^          \-------------------/         -----> | HDMI        |
                    |                                               | Transmitter | -----> HDMI OUT 2
               __________                                           |_____________| 
HDMI IN 4 --> | HDMI     |
HDMI IN 5 --> | Receiver |
HDMI IN 6 --> |__________|

[/clear]
 

[wraper]

It would be way more useful to write actual model and attach a good quality photo of PCB.

[zzattack]

I've omitted those on purpose, as I'm more interested in the general sense of how to approach such a digital video signal issue, regardless of the actual chips used. Right now I'm not quite sure where to start, what signals to probe and what to expect. Filling in the details for this particular PCB and the chips they used is not something I'd want to bother anybody else with.
Now maybe there is no generic kind of approach and the perhaps this issue cannot be answered without knowing more about the PCB and chip datasheets. In that case I will certainly add those details.

[wraper]

I've omitted those on purpose, as I'm more interested in the general sense of how to approach such a digital video signal issue, regardless of the actual chips used. Right now I'm not quite sure where to start, what signals to probe and what to expect. Filling in the details for this particular PCB and the chips they used is not something I'd want to bother anybody else with.
Now maybe there is no generic kind of approach and the perhaps this issue cannot be answered without knowing more about the PCB and chip datasheets. In that case I will certainly add those details.

Your omission omits too much. Something like this cannot be discussed in general as has many specifics. For example it could be something faulty preventing I2C bus connected to all of the chips in the signal path working properly. Faulty LDO or whatever.