[SOLVED] Finding a replacement capacitor for old power supply...

[Simon27]

The capacitor in my c. 1980 Apple II Europlus power supply (250V model) has blown and I have been trying to find out what sort of capacitor I should get to replace it.

The capacitor is marked as 0.1µF, 250V and 4.9MHz. Then there's a load of other markings and symbols on it. I've looked up this specific component online and found one forum post where it was decided that cap was obsolete (**broken link removed**).

I haven't seen one like this before and would like to know from you guys what sort I should use to replace it?

Many thanks,
Simon27

 

[karesz]

Hi,
You can order an equivalent/similar type from Wima(Type MP3,Klass X2/Y2) by Farnell, art Nr.:100-6059, for £ 0,70...
https://uk.farnell.com/wima/mp3-0-1uf-20-250v/kondensator-klasse-x2-0-1uf/dp/1006059?Ntt=1006059
Maybe has another pin distance-but its not a issue, & I can not check it from your board
K.

 

[Simon27]

Thanks for your reply - I'll get my order in later today.

The capacitor you linked to has a 15mm lead spacing and my board has 20mm spacing. Should the leads reach this OK?

Just out of interest, what does the 4.5MHz marking on the original capacitor refer to?

 

[karesz]

Hi,
I think you can solder it into your PCB, or if its a double side Print-I would drill a new hole for the actuall capacitor, optionell you can solder to its one "leg" a longer wire below hes volumen...
The 4.5MHz: I dont no ... These kind of capacitors have a lot of (inter)national standard marks on it, I think its a "frequency for some measuring in accordance xxxx standard" ?...
They are RFI capacitors, but 4.5 MHz seems me to be a relative high value by a 100nF, but is not inpossible.
What for you is, in my opinion, interesting:
working voltage =250V AC,
Type =MP3 , X2/Y2

And if their has internal a serial 100 Ohm (or so) than you need some similar to find (a snubber by swithced supply) but it seems to be a simple RFI C.

Is it direct on the mains input to find? Than is these a simple "X/Y capacitor" for RFI usage...
K.

 

[Simon27]

I don't know much about power supplies but I do know that this is a fairly simple switching supply.

I have looked up the circuit in the Apple's manual and attached a scan below.

This circuit is for the earlier and US voltage model so I know there are some differences in the placement of the capacitors. The one that has blown is called C1 on the board but I think it is actually C3 on the circuit diagram (circled), as this is unpolarised.

The cap is on the other side of a small coil from the 250V mains supply.

Hope this helps.

 

[karesz]

...The cap is on the other side of a small coil from the 250V mains supply...

Hi Simon,
Im some confused, than you dont have on the schema a small coil_can see only the line filter, but their must be bulky...
Anyway, if your 100 nF is not on place oc C4 or C32_ must be the correct one...
What is C5 for a capacitor pls?
Btw; if you are on the supply preparing: it will be good to check the input DC-Bus (beteen CR1 + & -) with a scope for hum (rest of 50Hz), but be care with GND-ing!
Your scope MUST BE NOT EARTH-ed!!_ otherweise you will make a mains short :-(
And its very DANGEROUS because yoiu are on mains & ca. +340V & high energy!
Otherwise its testable with a better MultiMeter too in AC & DC read bot displays pls...
I mean it for check your DC-Bus electrolytics(C1 &C2); possible they are no more the original, have some hum (higher ESR as OK)_better to change it too.
K.

 

[keith1200rs]

The exploded capacitor is more likely to be what is called "Line Filter" in the circuit diagram and is directly across the mains input. You should replace it with a class X one.

For 20mm spacing, have a look at Farnell 9717340, RS 206-7724. It is 20.3mm pitch, but should be OK.

I think the 4.9MHz is the self resonant frequency.

Keith

 

[Simon27]

Just been having a look at Farnell 9717340 which is a PME271E610M.

Had another look at my original cap and it reads PME271M610 which Farnel gives me 9717463. The page states this is an X2 capacitor although the number is closer to what I have (it's also in stock).

Would this do instead - is there much difference between X1 and X2? The top of mine just says X.

karesz, unfortunately I don't have a scope to check for any hum.

 

[keith1200rs]

You will be fine with X1. X1 has a higher pulse rating than X2.

Keith

 

[Simon27]

But could I use the Farnell X2 9717463 as they have them in stock? Would it still work OK?

 

[keith1200rs]

Yes, X2 is rated to 2.5kV for domestic use. X1 is 4kV for industrial use.

Keith

 

[Simon27]

I take it that the 2.5kV X2 is OK then?

Sorry to keep asking but I wanted to make sure I got it right!

 

[keith1200rs]

Yes, X2 will be fine.

Keith

 

[Simon27]

Thank you for your help, both of you!

Also thank you for introducing me to Farnell, they have a much wider range than I've seen before.

I'll place my order shortly.

 

[karesz]

welcome!
Farnell is a good component house & is originally from GB, some time are Schuricht / Distrelec or RS-Components not so expensive as farnell & all have a good & wide on stock sortiment -program /all in Germany...
K.

 

[Steph00]

Try speaking with a tech .mouser, avnet or newark