Faulty IR sender

[RusselBarnes]

My Tivo wont change channels on my DSE STB.

An electronics friend tested the IR sender with a CRO, and compared the signal to that received from the DSE remote control. The signal from the Tivo IR sender was nothing like the signal from the DSE remote control. It did not have the "bars" like the DSE remote control - just a continuous signal for the time the Tivo was sending a channel change signal

Has anyone seen this problem and can it be fixed?

[Darren King]

Has the TiVo previously worked for you with this or any other brand STB?

While there *could* be a fault I will very much doubt it is hardware as in all my time fixing TiVo's it is very rare indeed for the IR controller to fail, and if they do it is a "go or no-go" mode, not a disparity in waveform analysis.

A little more information would be handy, including the model number of this STB and the IR code number you have tried to use.

[RusselBarnes]

The Tivo is a HDR212, bought from Hobotech in 2006

I tried several STB a few months ago, but neither were in the list of STB for which IR codes had been mapped. However they did respond to IR codes, but not all channels were changed successfully. The IR sender was working then

Since then I re-imaged the Tivo by removing the HD and loading the latest image. This was because the image was 1.4, and the program mods to change to a new data source didnt work. Easier to start afresh than to find the error I had made in the code

The Tivo works fine with the new image. When I restart the tivo, I see Version 3 and 1.6.2

I recently bought a DSE G1955 STB which is in the list of STB for which Tivo has IR codes. I setup Tivo for this STB and could get no responses from the STB, ie trying to change channels.

Then i took the Tivo and STB to my electronics friend who compared the output from the STB remote control with the output from the Tivo IR sender using a CRO. We could see the coded output in the waveform from the STB remote control. The signal from the Tivo IR sender looked very different - for instance there was no high/low pattern in the waveform (which we figured were the characters in the code).

We tried another IR sender which produced the same result - the picture on the CRO looked the same. No highs and low pattern in the waveform

Any suggestions of where to look for the problem would be welcome

[petestrash]

Was your friend able to test the built in IR sender in the front of the TiVo?

Peter

[RusselBarnes]

I didnt know there was a sender in the front of the Tivo, so we didnt test this.

I tried holding the DSE STB in front of the Tivo and changing channels but there this didnt operate the STB

I could test the front of Tivo IR sender with the CRO but it requires a long trip to where rthe equipment is located. Can you suggest other tests I can do first or while I am there?

Is there some way to tell if the problem is in the software rather than the hardware?

Much appreciate your help.

Russel

[petestrash]

A basic test to see that it works would be to watch the eye on the front through a digital camera while changing channels. You should see it flashing when it sends the data.

Peter.

[RusselBarnes]

Peter - I think the IR device on the front of the Tivo is a receiver for the Tivo remote, not a sender

[Darren King]

It is both. On the IR sub board there is an IR receiver chip for receiving commands from the TiVo remote, and beside that is an IR LED that can transmit commands to an external STB.

[RusselBarnes]

Thanks for confirming Darren and apologies Peter! You were right.
I watched the IR sender on the front of the Tivo (with a digital camera) while changing channels, and it does flash. I put the IR sender which plugs into the back of the Tivo alongside and I can see they flash in unison

What do you suggest next in investigating the problem? Is there some way to tell if its hardware or software?

[Darren King]

Based on my past experience (as hinted to in my original reply) I've only ever known an IR transmitter fault to be "go" or "no-go" rather than what looks to be a working transmitter but what you believe is incorrect code information.

Given that the transmitter is driven almost directly out of one of the controller chips, that failure is something rarely seen by myself (generally the IR sender componentry is very reliable) and that the IR is indeed sending "something", and also that you mention the IR sender used to "talk" to a different STB, I would have to say most likely software issue at this stage.

The only way to know "for sure" is to test your TiVo against another TiVo with a known working STB, and then swap the hard disk and see that your TiVo can still control the STB. That poses it's own logistical can of worms for most, unfortunately.