Replacing electrolytic capacitors with ceramic?

[Orihalcon]

Hello all,

I'm working on refurbishing some VCRs that originally used relatively low capacitance electrolytic mini capacitors as part of the Video/RF signal right after the video head before the RF signal is decoded. The capacitors in question are all 10uF or lower.

I am wondering if there are is any reasons NOT to "upgrade" those electrolytic capacitors to ceramic (or some other capacitor type) other than cost?

[T3sl4co1l]

So, signal coupling capacitors?

Distortion and microphony are the main downsides.  Distortion might not matter, depending on how they're being used (active clamp DC-restore per line/frame?), but microphony has the interesting effect that you'll see horizontal luma bars when tapping on the circuit (or there's enough ambient audio).

The ideal choice here is tantalum, actually.  At least, electrically speaking -- but their cost (in general, plus externalities, i.e. Ta is a conflict mineral) may be sufficient reason to stick with electrolytic.

Or film, but large values in low voltages are prohibitively large; film just can't be stretched as thin as ceramic can, without succumbing to thinning or pinholing.

On the upside, they see very little if any ripple current, or heat, so shouldn't need replacing unless they were poorly made in the first place.  (Seals can go leaky, electrolyte can corrode, etc..)  This is one place where an ESR test (in circuit should even be reasonable) is preferable over a general "replace everything" policy.  Anyway, modern electrolytics will be good for at least another couple decades at room temperature, so it's not like you're dooming the unit by replacing like with like.

Tim

[factory]

What is the age of the VCRs? Are they surface mount or through hole parts? Is the board covered in fine traces and/or a multilayer PCB?

Certainly smaller values can dry out with age, leakage (peeing) can be a major problem, it doesn't matter is the seals are rubber or plastic, they degrade with age & fail, even well known brands fail in this way.
In my experience stuff from the late 80s & 90s seem to be worse than much older parts.

David

[MathWizard]

What about electrolytic caps that are 0.1-1uF ? I've never bought any EC's that small, so I've always just used those green coated, higher voltage Mylar caps, or ceramics in any circuit/repair.

IDK if small 0.1-1uF EC's were ever cheaper than large ceramic's, but yeah I guess it depends on the circuit, and the pro/cons for each type of cap.


I'm still just talking about under 1uF caps, not +1uF multi-layer ceramics, but are small EC's getting rarer though ? I haven't worked on that many repair's, but I feel they are getting less common. So are the other types getting better at what an EC can offer, or maybe it's the types of circuits used these days match better with ceramics.

One of these days I need to compare so caps side by side on a scope, and see IRL.