Re: Power Supply capacitor physical size

[Adrian Graham]

On 03/09/2016 23:27, "John Robertson"  wrote:

>>> Similar size - then no problem!  But, some new cap types are
>>> VASTLY smaller than the caps from 40 years ago.
>> Hence my question, I'll stick with the same size but higher voltage.
>> 
>> Cheers!
>> 
> 
> You do have to consider where in the circuit the capacitor is. If this
> is a switching power supply (as I suspect) then if the cap is after the
> switching transformer it MUST be a low ESR, high temp cap - otherwise it
> won't last very long. If this is on the primary side and is simply
> filtering the input rectified AC then ESR is not as big a problem, but
> you need a good physical size if the switching supply puts out a fair
> bit of current due to heating effects of low frequency ripple.
> 
> So, it all depends.
> 
> For general repair I would get the best grade of capacitor - say
> Panasonic - with a nice low ESR and away you go.

Panasonic and Multicomp as it happens, identical capacitance and similar
size but higher voltage rating. The mentioned heating effects worried me so
I went big.

Cheers,

-- 
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?

Re: Power Supply capacitor physical size

[Ian S. King]

I try very hard to match physical size and since, as has been noted, that
usually means higher working voltage, it's not a negative.  If you're
preserving something as an historical artifact, be sure to document what
you've done!  Otherwise, someone will be really confused 10-20 years from
now when, trying to maintain the machine, they see a different value on the
board than on the printset.  :-)  IMHO -- Ian

On Sat, Sep 3, 2016 at 10:07 AM, Adrian Graham  wrote:

> On 03/09/2016 17:39, "Jon Elson"  wrote:
>
> > On 09/03/2016 10:56 AM, Noel Chiappa wrote:
> >>> From: Jon Elson
> >>
>  needs new caps since one of the 1000uF 16V ones has bulged badly.
>  ...
>  If I go up to 25V I can get 16mm diameter which is the size of the old
>  ones.
> >>
> >>> Capacitors that are subjected to high AC ripple current may need the
> >>> large surface area for cooling.
> >>
> >> Interesting point - but in his particular case, he should be OK
> replacing the
> >> old 16V cap with a similar-sized modern 25V cap?
> >>
> >>
> > Similar size - then no problem!  But, some new cap types are
> > VASTLY smaller than the caps from 40 years ago.
>
> Hence my question, I'll stick with the same size but higher voltage.
>
> Cheers!
>
> --
> Adrian/Witchy
> Binary Dinosaurs creator/curator
> Www.binarydinosaurs.co.uk - the UK's biggest private home computer
> collection?
>
>
>


-- 
Ian S. King, MSIS, MSCS, Ph.D. Candidate
The Information School 
Dissertation: "Why the Conversation Mattered: Constructing a Sociotechnical
Narrative Through a Design Lens

Archivist, Voices From the Rwanda Tribunal 
Value Sensitive Design Research Lab 

University of Washington

There is an old Vulcan saying: "Only Nixon could go to China."

Re: Power Supply capacitor physical size

[John Robertson]

On 09/03/2016 10:07 AM, Adrian Graham wrote:

On 03/09/2016 17:39, "Jon Elson"  wrote:


On 09/03/2016 10:56 AM, Noel Chiappa wrote:

From: Jon Elson

needs new caps since one of the 1000uF 16V ones has bulged badly.
...
If I go up to 25V I can get 16mm diameter which is the size of the old
ones.

Capacitors that are subjected to high AC ripple current may need the
large surface area for cooling.

Interesting point - but in his particular case, he should be OK replacing the
old 16V cap with a similar-sized modern 25V cap?



Similar size - then no problem!  But, some new cap types are
VASTLY smaller than the caps from 40 years ago.

Hence my question, I'll stick with the same size but higher voltage.

Cheers!



You do have to consider where in the circuit the capacitor is. If this 
is a switching power supply (as I suspect) then if the cap is after the 
switching transformer it MUST be a low ESR, high temp cap - otherwise it 
won't last very long. If this is on the primary side and is simply 
filtering the input rectified AC then ESR is not as big a problem, but 
you need a good physical size if the switching supply puts out a fair 
bit of current due to heating effects of low frequency ripple.


So, it all depends.

For general repair I would get the best grade of capacitor - say 
Panasonic - with a nice low ESR and away you go.


John :-#)#

--
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
 www.flippers.com
"Old pinballers never die, they just flip out"

Re: Power Supply capacitor physical size

[Adrian Graham]

On 03/09/2016 17:39, "Jon Elson"  wrote:

> On 09/03/2016 10:56 AM, Noel Chiappa wrote:
>>> From: Jon Elson
>> 
 needs new caps since one of the 1000uF 16V ones has bulged badly.
 ...
 If I go up to 25V I can get 16mm diameter which is the size of the old
 ones.
>> 
>>> Capacitors that are subjected to high AC ripple current may need the
>>> large surface area for cooling.
>> 
>> Interesting point - but in his particular case, he should be OK replacing the
>> old 16V cap with a similar-sized modern 25V cap?
>> 
>> 
> Similar size - then no problem!  But, some new cap types are
> VASTLY smaller than the caps from 40 years ago.

Hence my question, I'll stick with the same size but higher voltage.

Cheers!

-- 
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?

Re: Power Supply capacitor physical size

[Jon Elson]

On 09/03/2016 10:56 AM, Noel Chiappa wrote:

 > From: Jon Elson

 >> needs new caps since one of the 1000uF 16V ones has bulged badly.
 >> ...
 >> If I go up to 25V I can get 16mm diameter which is the size of the old
 >> ones.

 > Capacitors that are subjected to high AC ripple current may need the
 > large surface area for cooling.

Interesting point - but in his particular case, he should be OK replacing the
old 16V cap with a similar-sized modern 25V cap?


Similar size - then no problem!  But, some new cap types are 
VASTLY smaller than the caps from 40 years ago.



Jon

Re: Power Supply capacitor physical size

[Noel Chiappa]

> From: Jon Elson

>> needs new caps since one of the 1000uF 16V ones has bulged badly.
>> ...
>> If I go up to 25V I can get 16mm diameter which is the size of the old
>> ones.

> Capacitors that are subjected to high AC ripple current may need the
> large surface area for cooling. 

Interesting point - but in his particular case, he should be OK replacing the
old 16V cap with a similar-sized modern 25V cap?

Noel

Re: Power Supply capacitor physical size

[Jon Elson]

On 09/03/2016 08:02 AM, Adrian Graham wrote:

Hi folks,

Looking at the PSU of my Lisa's ProFile after it died gracefully not so long
back and it obviously needs new caps since one of the 1000uF 16V ones has
bulged badly. While I'm replacing that one I'll do the 47uF 250V ones too.
And the mains filters but I've got a stock of spares for them already.

Apologies for what's probably a dumb question, but when it comes to cap
replacement I know I can go up a notch if the required capacitance or
voltage isn't available so 25V and 400V is ok, but what about physical size?
I can get the correct capacitance/voltage but they're physically much
smaller than the ones I'm replacing, like 10mm instead of 16mm diameter. If
I go up to 25V I can get 16mm diameter which is the size of the old ones.

Am I worrying for nothing?


Maybe not.  Capacitors that are subjected to high AC ripple 
current may need the large surface area for cooling.  
Possibly using a low-ESR capacitor will help reduce heating, 
but might have other undesirable effects.
So, you need to know a bit about the circuit and the 
stresses placed on the capacitors to decide.  if the ripple 
current is low, then smaller caps are no problem at all.


Jon

RE: Power Supply capacitor physical size

[Dave Wade]

> -Original Message-
> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Adrian
> Graham
> Sent: 03 September 2016 14:03
> To: Discussion: On-Topic and Off-Topic Posts 
> Subject: Power Supply capacitor physical size
> 
> Hi folks,
> 
> Looking at the PSU of my Lisa's ProFile after it died gracefully not so
long back
> and it obviously needs new caps since one of the 1000uF 16V ones has
> bulged badly. While I'm replacing that one I'll do the 47uF 250V ones too.
> And the mains filters but I've got a stock of spares for them already.
> 
> Apologies for what's probably a dumb question, but when it comes to cap
> replacement I know I can go up a notch if the required capacitance or
voltage
> isn't available so 25V and 400V is ok, but what about physical size?
> I can get the correct capacitance/voltage but they're physically much
smaller
> than the ones I'm replacing, like 10mm instead of 16mm diameter. If I go
up
> to 25V I can get 16mm diameter which is the size of the old ones.

Modern caps are physically smaller so folks who want to preserve the look of
objects resort to Capacitor Stuffing..
.. put a new modern cap inside the old case... 

> 
> Am I worrying for nothing?
> 

Personally I think that it's a valid question. 

> Cheers, from a room not filled with RIFA smoke for once :)
> 
> --
> Adrian/Witchy
> Binary Dinosaurs creator/curator
> Www.binarydinosaurs.co.uk - the UK's biggest private home computer
> collection?
> 

Dave
G4UGM

Power Supply capacitor physical size

[Adrian Graham]

Hi folks,

Looking at the PSU of my Lisa's ProFile after it died gracefully not so long
back and it obviously needs new caps since one of the 1000uF 16V ones has
bulged badly. While I'm replacing that one I'll do the 47uF 250V ones too.
And the mains filters but I've got a stock of spares for them already.

Apologies for what's probably a dumb question, but when it comes to cap
replacement I know I can go up a notch if the required capacitance or
voltage isn't available so 25V and 400V is ok, but what about physical size?
I can get the correct capacitance/voltage but they're physically much
smaller than the ones I'm replacing, like 10mm instead of 16mm diameter. If
I go up to 25V I can get 16mm diameter which is the size of the old ones.

Am I worrying for nothing?

Cheers, from a room not filled with RIFA smoke for once :)

-- 
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?