I replaced a bulging 2200mfd 16v in a TCD24008A power supply and that did the trick.

I suspect that, except for the capacitors, the components in a TiVo power supply are of reasonably good quality.

Bad electrolytics plague a lot of consumer electronics these days, not just Tivos.

badcaps.net and lcdalternatives are both good sources of info and quality caps.

Get out your soldering iron and get busy.

I replaced the two bulging capacitors as mentioned above. I put the power supply in a good DVR and IT WORKED!!! What a pleasant surprise. Now I'll try it in the other defective power supplies.

A few more details. I cut away the rubbery foam around the capacitors. Then desoldered and removed them and used a needle while applying the soldering iron to open the holes on the PCB. There are lots of instructions on the internet about soldering/desoldering. My power supply originally had caps with 2003 dates and the solder was probably lead/tin since it melted easily and quickly. I think it was a few years later that they switched to lead free solder which has a much higher melting point.

I was surprised to find the type of capacitor used has a design lifetime of 5,000 - 10,000 hours. A year is about 8700 hours so it is no surprise that they fail in a device like a DVR that is always on. Presumably the actual lifetime is much longer if the cap is operated well below its 105 degree C max temperature. Obviously, having a functional and unobstructed fan is critical.

Oh, by the way. The no load voltage on the hard drive connector before replacing the caps was 5.05 and 10.94. With the new caps it was 5.05 and 11.95. Maybe that below spec voltage is an indicator of bad caps. Test under load is probably better but I didn't do that.

Obviously, anyone who attempts to measure voltage or replace the caps should have some knowledge and experience and should be careful. Full 110 AC line voltage is present and exposed on the power supply when the DVR cover is removed. That can kill you!!

Here is the report on all three power supplies that I attempted to repair. I replaced the two caps (2200uF 10v and 16v) in all three of the defective power supplies I had. I am delighted to report that all three now work fine. Five of the six caps were TEAPO brand, four of which were slightly though noticeably bulging. The sixth was another brand and was not bulging. None of them showed any leakage. The replacement caps cost about $0.70 each.

On the third unit, I made some voltage measurements on the drive cable as follows:
a) with original caps, no load: 5.08v and 10.36v
b) with new caps, no load: 5.03v and 11.88v
c) with new caps, under load: 5.00v and 12.08v.

Two of the three units were significantly below 12v before replacement so that may be a useful indicator of cap problems.

..Paul..

A couple of things to note about replacing bad caps in switching power supplies:

1) If you find one or two bad caps (bloated top or bottom, or leaking) replace ALL capacitors of the same manufacturer over 100uF, if one is visibly bad, it's pretty good odds that the rest are either bad but not bloated/leaking, or have about a week left before they bloat or leak.

2) The capacitors in switching power supplies are NOT general purpose capacitors, replacing them with GP capacitors may work for a short while, but trust me, they'll go poof even faster than the garbage the manufacturer originally used.

3) When replacing the bad capacitors, the following are important:

A) Capacitance in uF must be at least as high as original, you can almost always go one size higher, ie 1500uF is usually safe to replace a 1000uF.

B) Voltage must be equal to, or higher than, original capacitor, the only exception to the rule is when the board uses 10V caps on the 5V rail. This is usually done because the 10V cap has lower ESR (see below) than the 6.3V version. As long as the replacement has better ESR and Ripple Current, 6.3V is plenty on a 5V rail.

C) Equivalent Series Resistance (sometimes called ESR or impedance) must be equal to, or lower than, original capacitor. To find the ESR, type the manufacturer of the bad cap (IE, Capxon, Rulycon, Teapo, OST, etc.) into Google with the series number, which will be a 2 or 3 letter code somewhere on the capacitor, and you should find a PDF of the capacitor series in question.

D) Ripple current as high or higher than original capacitor.

E) Physical size! Usually not a problem, unless they're right next to another component, or they have to be super short so the cover can close.


In the US, www.digikey.com is a great place to get high quality capacitors. My all time favorite is the Panasonic FM and FC series, they will last forever, and are of such low ESR and high ripple current that they will replace just about anything, the only down side is they may not fit, as they're not the smallest. Nichicon HE, HM, and HN are great for tight fits, as they usually come in smaller sizes.

Just go to http://search.digikey.com/us/en/cat/...luminum/131081

Filter by general purpose, through hole, radial can, and in stock.

Then choose the series, manufacturer, diameter, height, voltage and or capacitance you need, and happy hunting. USPS will be the cheapest form of shipping.

Assuming you have the room, save yourself some time and just get Panasonic FM's, they'll last forever, they'll meet or exceed the specs of anything you're going to replace, and they're just a few cents more than the Nichicons.


BTW, the life expectancy ratings on capacitors are max load, and max temperature, and double with each 10 degree Celsius drop, so a 105 degree cap with a 2000 hour life will last:

105= 2000hrs
95= 4000hrs
85= 8000hrs
75= 16000hrs
65= 32000hrs
55= 64000hrs
45=128000hrs

45=55 degrees is the hottest you're likely to run into even inside a DVR or PC.

The reason the original caps failed was because the manufacturer grossly overrated the cap's specs, or the designer grossly underrated the cap requirements, not because the cap hit it's end of life rating. A good capacitor working in a circuit that does not stress it past it's "real" ratings will last essentially forever.