Replacing the last power supply cap

[HF9]

Beautiful builds. What are the small red caps in the one with the big Solen? I assume you bypassed the other two power supply electrolytics?

Thanks!. Yes, that was the purpose of the little red Audiofiler caps.

Nick, if you look at the photo above, you'll see the 159M choke on the left going up to the approximate area where the 270R resistor would have been.

 

[adamct]

It looks like my choices are (1) going for 3 of the oilers from eBay (70uf each), (2) one of these, or (3) a Solen 220uf film cap. Frankly, 3 of the oilers off eBay would cost almost as much as the Solen, but would be much bulkier and require more wiring, so I'm inclined to skip them. Any thoughts on option #2?

Best,
Adam

 

[Grainger49]

On the "OLD BOARD" there was something called a PDMPS, a third stage of filtering.  It stood for Pseudo Dual Mono Power Supply.  I did this with my FP 2 adding a couple of 100uF "Oilers" motor start caps.  I just put another 1k resistor between the mono power supply output and the oilers.  Then the two power supply rails went to the right and left channel. 

It did improve the sound.

 

[earwaxxer]

IMO - i don't think you will notice a sound difference between film caps in the power supply. That would be a guess, but I'd do feel its worth going from electrolytic to film, even from just the peace of mind aspect.

 

[2wo]

Hi Nick, the resistor in question would be the one that connects the 2 high voltage caps together...John 

 

[w0lfd0g]

Hi Adam

I use the 220 uF version of this cap:

http://www.partsconnexion.com/capacitor_film_clarity_tc.html

(Relatively) cheap and some peace of mind offered.  Sonically satisfied, fiscally challenged. 

Not a pretty solution, but it does the job.

 

[adamct]

Yep, that's the other cap I was considering. But I wonder if the $11 film cap from eBay wouldn't be just as good when used in the power supply...

 

[earwaxxer]

Hey Adam - with large value film caps like that, in a power supply, I would go ahead and try the cheapest one you can find. No harm done. Its going to be really hard (expensive) to get any name boutique cap in those values. Money can go other places IMO.

 

[adamct]

Hmmmm....at that price, maybe I'll replace all the power supply caps! 

 

[earwaxxer]

Yes.. Large Caps Increase Your Manhood!

 

[adamct]

Just bought 3 of the 200uf poly film caps off eBay. If MLB tested me right now, I would fail a doping test...my testosterone is off the charts!

 

[earwaxxer]

LoL!!! .. yep.. you are definitely hooked!

 

[adamct]

Hmmmm....fools rush in.....

I just watched a video on the difference between start and run capacitors. The poly caps I bought are start capacitors. Am I correct that those are a no-no for use in the power supply, and likely to blow up in my face?  :-\

 

[Grainger49]

If it has a DC rating equal or greater than the stock cap you are fine. 

 

[adamct]

Therein lies the rub....I think it is rated for AC only...

 

[HF9]

Typically the AC ratings for a cap are notably lower than the DC ratings. I'd imagine the manufacturer probably just didn't anticipate anyone dropping their cap into an amp

 

[Grainger49]

I think you are going to have to try it and see.  If the caps don't destruct in the first 5 minutes they just might make it.  For the test put jumpers on.  Don't remove any other caps just put the new cap, only one, in parallel with the last cap.  Put some paper under it in the odd chance that it lets go.

Then move forward with confidence.

 

[adamct]

Check out this eBay listing, then scroll down and watch the embedded video. How dangerous is it if a cap goes belly up?

 

[earwaxxer]

Interesting.. Now I know the difference between a "start" and "run" capacitor.

 

[adamct]

Grainger,

Do you still think I should try it, or just chuck them in a drawer chalk it up to a learning experience?

I've already ordered two of the 100uf oiler "run" caps at the eBay link to use instead of the last power supply cap. Unless someone tells me they really think it is safe and/or worth experimenting with the poly "start" caps, I'll leave the other two electrolytics in the power supply as-is.

Best,
Adam