To get better help here, post your model number and indicate how much electronic DIY capability you have. (Your not knowing what "cap" means is suggestive.) If you're not comfortable opening the box and replacing a power supply board, or hard drive, or measuring voltages with power on, or (most advanced) removing caps and soldering in new ones, you should consider the current TiVo.com promotion of a refurbished Roamio base model and lifetime service for a total of $300:
For discussion of this see this thread:
I recently upgraded from a TiVo HD (model 652160) using this promotion deal and, although I liked the HD for the 6 years I used it, I really love the Roamio (so far). The refurbs have the same warranty as new ones.