40uf 450v cap replacement

[Bushbaby]

Hi All,
Im thinking I might need to replace/re-stuff a 40/20/20uf 450 smoothing cap. I have 20uFs. Would a 47uf be a suitable replacement for the 40uf or would I be advised to go the other way and use a 33uF?

40uF does appear a strange value.

Regards

Rob

[Refugee]

47uf may well be fine but a check of the maximum capacitor value on the rectifier data sheet would be a worth while check.
I have spotted these very useful looking capacitors for restuffing with.
http://golbornevintageradio.co.uk/forum/...p?tid=3756

[Radio Fixer]

I saw the link to those caps but there is no mention of ripple current rating, this def needs to be considered for the reservoir cap. At only 10mm dia I doubt they will have a high rating, size matters ! And if they do have a rating and it sounds too good to be true it is probably at 100kHz or something for inverters. Rating falls a lot by 50 / 100 Hz, typically < to 1/3.

A used rule of thumb for ripple current rating is that it should be at least 2 X the HT current but I would go larger myself and use 105 deg caps for those inside a stuffed can covered with tissue to build them out to the old can diameter.

Is 40mF a smoother or the reservoir? For the first then 47 is no prob, for he later check as suggested the rectifier valve data.

Gary

[pwdrive]

Most of the Rubicons at 450v from the likes of Farnell etc seem to have adequate ripple current rating.

Lawrence.

[pwdrive]

http://www.rubycon.co.jp/en/catalog/e_pd.../e_BXW.pdf

Lawrence.

[Refugee]

I have now added a snippet of the data sheet to the original post.
The values we will need are 200ma or more ripple currant. It would have to be a huge set if it required any more than 200ma. Perhaps a transmitter would need more.
http://golbornevintageradio.org/forum/sh...p?tid=3756&pid=38470#pid38470

[Radio Fixer]

A pretty useful cap, seems they are getting high ripple current ratings in much smaller volumes now. I have in front of me some Sprague Atoms I bought maybe 5 or 6 years ago and they are 40mm long by 20mm dia for 16 mF. Their size always makes me feel confident as I slip them into an 1 1/4" can. If I don't use these as getting short on values then I buy the BVWS ones rated at 500V, ripple current not known but I guess the 'team' considered that.

Sorry to cast aspersion on your find Refugee but it did need consideration.

Gary

[pwdrive]

I restuffed some HT caps including reservior cap in an old Hallicrafters, the ones I used were very small in comparison but according to the specs for the replacements they had a more than adequate ripple factor, I was hesitant at first but they seem to be ok.

Lawrence.

[Refugee]

I will put them on trial in a 25W RMS push pull valve amplifier and see how they go.
They will be running at about 420V with a ripple of no more than 150ma.
I will do a review after they have been in service for three months.