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How to recap Master PSU, Astec 13830

Posted: Fri Jan 25, 2019 3:34 pm
by VectorEyes
Hi everyone,

I'm attempting to recap a Master I obtained recently. The PSU seems to be a little different to the 'usual' one. It's an Astec 13830. I've found the 10v 200uF Startup Cap -- mounted on a separate board mounted sideways to the main board -- and I've found the 100nF RIFA capacitor, but I can't seem to find a 10nF capacitor.
AA13830.jpg
Just wondering whether anyone has come across this type before and if they could advise me what to do with it?

Thanks!

Re: How to recap Master PSU, Astec 13830

Posted: Fri Jan 25, 2019 4:21 pm
by danielj
You only really need to worry about swapping out the capacitors if it has RIFAs on it - this one doesn't by the looks of things, so nothing doing unless it's not actually behaving properly :)

d.

Re: How to recap Master PSU, Astec 13830

Posted: Fri Jan 25, 2019 5:23 pm
by CMcDougall
Yip, no need to change, but change black start up cap opposite 'Danger'

what I did to all mine anyways 8)

Re: How to recap Master PSU, Astec 13830

Posted: Fri Jan 25, 2019 7:48 pm
by Prime
Oddly I've never needed to change the startup cap, just the Rifas. maybe I've just been lucky :)

Cheers.

Phill.

Re: How to recap Master PSU, Astec 13830

Posted: Sat Jan 26, 2019 12:29 am
by 1024MAK
The X2 type capacitors used as mains interference suppression / filtering will all be at the end of the board near the input fuse.

Not all Master PSUs use Rifa capacitors. For the 10nF and 100nF X2 type capacitors, it is only capacitors made by Rifa that normally need replacing. Unless there is visible damage, excessive radio interference or power supply malfunction,

10nF capacitors may also be marked 0.01uF.
100nF capacitors may also be marked 0.1uF.

Mark

Re: How to recap Master PSU, Astec 13830

Posted: Thu Jan 31, 2019 2:50 pm
by VectorEyes
After I removed the one 100nF RIFA capacitor from the board, I discovered that it's somewhat different from the usual ones, in that it's rated 400V instead of 275V, and is the 'smaller size'. (Usually the 100nF are larger and the 10nF are smaller).

A colleague suggest that replacing it with a 275V one would be fine, on the basis that the voltage is unlikely to go above 250V anyway, and so the 400V capacitor is essentially higher-spec than required anyway. I could probably just drop in a new 100nF, 275V, larger size capacitor, but it feels slightly odd, given that the board was clearly designed with the smaller size in mind, and was presumably manufactured with a 400V capacitor. (It didn't look like it had previously been re-capped, although obviously it's difficult to be sure).

Can anyone think of a reason I shouldn't replace it with one of the larger, lower-voltage ones?

Re: How to recap Master PSU, Astec 13830

Posted: Thu Jan 31, 2019 3:42 pm
by danielj
Depending on the circuit it might be getting more than 250V across it... It was 400V for a reason I suspect! Also it might not be an X2 - post a picture of it?

d.

Re: How to recap Master PSU, Astec 13830

Posted: Thu Jan 31, 2019 4:07 pm
by VectorEyes
Thanks! It looks like this:
400V_Side2.jpg
400V_Side1.jpg

Re: How to recap Master PSU, Astec 13830

Posted: Thu Jan 31, 2019 6:13 pm
by 1024MAK
That capacitor has a 400V DC rating. That is NOT the same as an AC rating!

To get the peak voltage on an AC supply, multiply the RMS AC voltage by the square root of 2. The peak AC voltage should be lower than the DC voltage rating of the capacitor. So with a 240V AC supply, the peak voltage is around 340V. So a 400V DC rated capacitor would be required.

So yes, a X2 250V AC or 275V AC rated capacitor should be fine (assuming this capacitor is actually connected across the mains line and neutral lines, you can test this with a multimeter connected on the low resistance range, between the mains terminals and the capacitor terminals).

Can you post a photo of the top of that capacitor please.

Mark

Re: How to recap Master PSU, Astec 13830

Posted: Thu Jan 31, 2019 6:50 pm
by VectorEyes
Very useful, thanks! I can't post a picture of the top until tomorrow, but from memory it only had "0.1uF +- 10%" written on the top.

Re: How to recap Master PSU, Astec 13830

Posted: Thu Jan 31, 2019 8:55 pm
by 1024MAK
VectorEyes wrote:
Thu Jan 31, 2019 6:50 pm
Very useful, thanks! I can't post a picture of the top until tomorrow, but from memory it only had "0.1uF +- 10%" written on the top.
That’s fine. Just wanted to check it was marked as I expected.

Mark

Re: How to recap Master PSU, Astec 13830

Posted: Fri Feb 01, 2019 2:13 pm
by VectorEyes
Right, sorry to keep on about this, but let's say I wanted to order a correct-sized one just so I didn't feel like I'd bodged it (and because fitting a larger one onto the board is actually a pretty tight fit).



Would this one be OK?

https://uk.farnell.com/kemet/phe840mb61 ... or%200.1uF

Thanks!

Re: How to recap Master PSU, Astec 13830

Posted: Fri Feb 01, 2019 2:17 pm
by danielj
The only thing I'd say here is that the capacitor doesn't look like it's cracked or crazed at all - the RIFAs look quite "stressed" if they are about to go pop and need replacing... As such I might be tempted to err on the "if it ain't broke, don't fix it"...

d.

Re: How to recap Master PSU, Astec 13830

Posted: Fri Feb 01, 2019 3:04 pm
by 1024MAK
VectorEyes wrote:
Fri Feb 01, 2019 2:13 pm
Would this one be OK?

https://uk.farnell.com/kemet/phe840mb61 ... or%200.1uF
If the lead pitch and the physical size is okay, yes.

Just a point you may wish to consider. As long as the capacitor you use is class X2, is rated at 250V AC (or greater) and is the correct value of capacitance, you can use a capacitor from any reasonable manufacturer. You don’t have to keep to the Rifa brand name.

Mark