Do BAD capacitors work less in the cold?

Question

This might seem a very strange question and I'll try and not make this about fixing my damn faulty TV but I will give you the history in why I'm asking.

I have a faulty TV and it repeatedly turns on and off, but after clicking for about 20-30mins, it turns on and continues to work until turned off for at least 1hour, of which it'll do the clicking again.

DON'T LAUGH! ~ but this morning was very cold and I had to turn the heating RIGHT up for the damn thing to turn on! it was awful listening to my partner whine for 90mins

I have done lots of online research and found this to be a common problem with the brand and model that I have, all fingers seem to point to bad capacitors, looking at the capacitors they don't look bulged but it is my understanding they don't need to be after reading this question and answer already on the Electronics Stack.

Anyway... strangely the TV turns on within 5-10mins if the room is warm and even faster if the room is hot. I consulted with a repair guy and I never brought up the room temperature and he said if its clicking, then he uses a hair dryer on the main board and see if it turns on, if not he then repeats the process on the PSU...

I've never heard of this before but then again I don't know much, which brings me to the point!

Question(s):

• Do BAD capacitors work better in warm climate?
• If true... why?

Answer 1

The capacitance of an electrolytic capacitor decreases slightly with temperature and ESR (Equivalent or Effective Series Resistance ) increases greatly. Bad electrolytic capacitors generally manifest by having high ESR rather than low capacitance, so I suspect this effect is what you are seeing. From Nichicon's manual (response of a good capacitor):

ESR increase is as a result of the electrolyte drying out in the capacitor. The aluminum cans are sealed with a rubber bung at the bottom which is crimped into the case and penetrated by the leads.

Another possibility is upward drift of the value of the startup resistor in the power supply. Higher temperatures mean higher gain for some semiconductors and resistors exposed to high voltage DC tend to drift.

The annoying whining noise you are hearing can be mitigated by purchasing a new set- they are very cheap these days.

Answer 2

The condition you describe in electronics might be called an Astable Multivibrator or a Relaxation Oscillator. This is where a voltage is applied until a threshold is reached then the state is reversed until a lower threshold is reached and it tries again repeating the cycle.

It is a well known fact, that both electrolytic batteries and electrolytic capacitors increase in capacitance and reduce in ESR with rising temperature. Although this comes at the expense of accelerated aging.

But what this does in your case may be anyone's guess. A bad Cap may allow excess ripple voltage on top of the DC and exceed some threshold.