View Full Version : Video Input Fault

14-01-2007, 09:19 PM
Due to a hardware mod that didn't work as expected I now have a no input video fault ie. blue no input message screen when selecting Watch Live TV.
I first suspected the PAL tuner but have ruled this out to some degree as the fault is apparent on AV0 input (v1.6) as well as tuner (Image works ok on second Tivo).

The Kernel Log increments very rapidly with the main errors being:
I2C arbitration error at 0x4c and
I2c arbitration error at 0x42.

Does anyone know which devices these addresses relate to?
I also have suspicions that the SAA 7114 chip is faulty.

The mod that I was attempting involved the tuner I2C bus and the Micronas I2C bus. I have checked both busses and think that they have no faults on them.

Any ideas?

Thanks in advance

Darren King
15-01-2007, 05:14 AM

Sounds very much to me like a short or something on the I2C line which means you are not getting any messages through and therefore no setup of come critical hardware. If all of this checks out then also look that you have not accidently got a slither of solder stuck somewhere. Also make doubly sure that all PCB traces are intact as the motherboard is very finnicky towards heat from a soldering iron and will open circuit a trace very quickly. Last thing to check is that you have not accidently dislodged another part in the vicinity of the SAA7114H. If all that fails you may be looking at the possibility of the good 'ol static discharge (ESD) frying something.

Further testing can be done but it all depends on what sort of test equipment you have access to. Last resort I could take a look at the board if you like.

29-01-2007, 03:56 PM
The problem was a dead SAA 7114.
Replacement supplied by the ever helpful Darren.
All is well now, I will have to re-think my Mod.


02-02-2007, 12:05 AM
What is the mod you were trying to achive before the 7114 go fried?


03-02-2007, 12:18 PM
I was connecting a PCF 8574 Remote 8-bit I/O expander for
I2C-bus which I was going to use to operate devices external to the Tivo ie. Video switch to switch between two Tivos onto one av input to TV. My test cct had worked some months ago but this time I was connecting it in a tider way and I suspect that have goofed in my connections.

I may try again soon to make this work time permitting.

03-02-2007, 04:10 PM
How did you control the I2c bus to select which TiVo was active for the video switch.


03-02-2007, 05:45 PM
The PCF 8574 would be connected to one of the Tivo's i2c busses and using, initially, Thomsons i2cset4 script to set/reset the outputs of the PCF chip to operate a relay to switch between outputs of two Tivos. The script could be invoked using a trickey sequence.
This would enable remote selection of the Tivo required for input to the viewing TV.
The circuit could also be used to control any other external device using a relay to switch this device on and off (eg room lights) wth the action commanded from the remote (trickey) or a cron job or web (tivoweb remote control).
With further refinement the same device can be used for input to the Tivo from the outside world ie. record start/stop alarm conditions or whatever.

04-02-2007, 02:14 AM
Thanks, It was the control side I was wondering about.

Thought you might have used some magic to watch tivolog to see which TiVo's remote was being actively used. Sending a command to the relay to automatically switch displays to the active TiVo.

Not trying to be smart, but why not just use an out of the box external A/V switch box (either manual or IR controlled).


Darren King
04-02-2007, 08:21 AM
Not trying to be smart, but why not just use an out of the box external A/V switch box (either manual or IR controlled).

Us hardware mob don't like doing things simple... There's no fun in that :D