Originally Posted by bleech2
I recently received an HD XL (658-000) with lifetime service as a hand-me-down, which was purchased in August 2009 and used non stop until it was replaced with a Roamio in late January. Although it doesn't currently have any problems, I read about the issues with the power supply capacitors while researching replacement hard drives. I bought a used power supply on Ebay for $35 as a backup, but upon comparing it with the existing power supply, I immediately noticed the layout of the circuit board was completely different than the existing one. The footprint, connectors, and screw holes are exactly the same, as well as the Tivo part number (SPWR-00011-000 Rev B0), but the manufacturers are different (AcBel (new) vs. 3Y (existing)). Luckily, neither one has bulging capacitors.
Is it safe to assume the power supply is compatible?
Think of the power supply as a "black box".
It has to meet certain requirements--circuit board size of x times y, screw holes in certain locations, outputs that meet certain voltage and amperage specs and terminate in a certain kind of plug intended to mate with the socket on the motherboard.
Within those parameters the subcontractor who makes them decides what parts and circuit designs to use to get the job done.
The one which also provided the similar (but not interchangeable) supply for the TCD648250, original S3 (the one with the clock on the front), turned out one that's basically a re-working of that original S3 supply with the 7.5V line for the OLED display left out.
The other company did it differently.
Both models mount the same and provide the needed current at the right voltages to the right pins on the motherboard and hard drive, so either one can be used in an HD or HD XL.
And both are susceptible to "capacitor plague" because the global capacitor supply chain was so badly polluted.
The good news is that it's a fairly cheap and easy fix.