VT100 PSU smelling.

Tothwolf tothwolf at concentric.net
Sat Jan 23 21:33:35 CST 2016

On Sat, 23 Jan 2016, Jules Richardson wrote:
> On 01/22/2016 06:26 PM, Tothwolf wrote:
>> The translucent yellow Rifa (now owned by Kemet) class X/Y safety 
>> capacitors in particular have a 100% failure rate and are on my 
>> replace-on-sight list. They usually begin to show visible signs of 
>> cracking in their outer casing before they finally go out with a bang.
> It's a well-known fault, but has anyone ever known one fail and actually 
> cause any damage (other than to itself)? AIUI, they're there to reduce 
> noise from the device leaking back out onto the AC supply - a system 
> should run quite happily without them.
> I've had maybe four or five fail on me over the years, out of several 
> hundred systems. They're a definite weak spot, but given that I've never 
> heard of one damaging anything it's the sort of thing I'd consider doing 
> only if I was carrying out some other repair work on the PSU.

I've seen blown/cooked series resistors (which I replace with metal oxide 
resistors) and sometimes a blown fuse.

I always replace them whey I'm doing other work on a psu, however I'm not 
sure I'd knowingly leave one in place since they let out a lot of smoke 
when they go.

>> I usually replace them with a film capacitor from Epcos of the same 
>> value and safety class.
> Is the voltage rating on the US ones different (new vs. old)? I can't 
> remember now. I know all the old UK ones seemed to be 250V, while modern 
> parts were rated at 275V.

Higher voltage parts are available but they are more expensive. I've seen 
300V, 350V, 375V and even 400V safety rated parts.

More information about the cctalk mailing list