I have seen a few symptoms that all seem to root from the power supply board on this unit. I have also found that most of these stem from capacitors that just seem to go bad over time. These problems include...

Frequent reboots.
Over Temp error at boot.
Loss of Dolby Digital, but other digital audio ok.
Audio drops out on digital, but analog audio ok.

All the above problems I have been able to resolve with changing out the larger secondary capacitors located under the heat sinks. The two small ones can be swapped without removal of the heat sink if your careful. The other ones require major effort and many hours of work. I know a new power supply is $75 shipped, and that you can find used ones on ebay, but most of the used ones seem to have bad caps on them...

But the most annoying, and so far troublesome power supply issue is the Frequent error message "Please Insert your Access Card".

I have not been able to fix this problem with component swapping at the power supply. Dose anyone know what part is going bad that is causing this issue? Im guessing its still a filter issue, and probably one of the smaller caps. Im also guessing that is has to do with the larger output voltage (33vdc or 7.5vdc)...these odd voltages are not typical of those needed to run digital computer parts---thats why I suspect they are causing issues with the RF signal parts of the tivo. If those supply voltages are not clean, then there will be errors induced into the stream, and those errors probably are causing the false error message about your access card not being valid.

If it is one of these smaller caps, they should be easy to change---but they are not giving the normal tell-tail signs of a bad cap---the domed top.

Before I spend a bunch of hours swapping tiny caps, wonder if anyone knows for certain which one it is, or even if its something else? A search of the net showed me one comment of someone finding some bad diodes on the under side of the board---but these are very tiny tiny, and a ton of them....I guess I could try to meter them all out and see....but due to the intermittent nature of this problem, it just don't seem like a diode problem to me.

Thanks much, and Id love to know if anyone else has been able to fix this Access Card error with a cap swap?