No front lights post mod

[Skutter]

So, just modded another TiVo, no front lights on the panel.

The lights on the Ethernet port light up, the fan and disc spin up, tv screen is blank (no splash screen at all).

I've checked the power supply volts with a multi meter and all appears ok.

I've had a good look at the chip holder soldering and it appears to be ok.

Any suggestions? I'm guessing I may have to remove the holder and try again.

[Darren King]

Yes. If you are getting that result then it is not reading the PROM chip and the first thing to do is check your soldering work. You'll most likely find a pin that has not soldered to the board properly even if they all "look" like they are.

[Islander]

I check for low resistance between PROM socket pins with a multimeter.
Apart from a couple of pins that a re 30-40k ohm the rest are in the megs. I have found the a couple with low resistance between the pins that clear by heating the affected pin and allowing the solder to flow.
I have had a non booting board that was caused by a solder splatter away from the PROM. A brush with a bristle paintbrush (not nylon) with the board upside down should clear these as they usually aren't well stuck on.

[Skutter]

Thanks for the suggestions. I'll let you know how I go when I get time to look at it.

[HealthyPinch]

Sorry to revive a year old thread, but how did you get on fixing this?

I've got the same problem, but the TiVo was working fine for 12 months before suddenly experiencing the same symptoms; no lights, no hdmi output.

I've reflowed all the solder joints around the prom and checked the soldering, still no joy :(

[Darren King]

Providing you are getting +12V from the power supply on the yellow/black wires and +5V from the red/black wires (or thereabouts it does not have to be dead on accurate) then you are most likely still having a failure to read the PROM.

I've created a document that traces out every pin from the PROM to the nearest top solder point to help people ensure that they have continuity if that helps:

https://drive.google.com/open?id=1kUCVxQ-qR44mceRDQrMPktXyHxoHZsrU

I've got a 400dpi version if you really need it but it is a BIG file.

[HealthyPinch]

Wow, that's a great document you've created for fault finding. Both the 12V and 5V supply are fine, so I'll check the PROM continuity using your document.

[HealthyPinch]

I checked the continuity based on the document and everything checked out. I couldn't check pins 24 and 31 as they go to via holes on the PCB. I tried scraping some of the resist off above the via hole but was worried I'd inadvertently cut through a track.

I also checked adjacent pins for short circuits and didn't find any.

My next guess is the PROM failed, but I've worked on another product in the past which uses the same PROM and I don't recall any failing.

[Darren King]

Rare for it to be the PROM. I'll say you have either a fine blob of solder or debris somewhere or (also rare) something else has failed. From here if there is nothing visually obvious it may need some more advanced assistance.