Add capacitors to RF 25 to Life Punch 150 - diyAudio
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Old 27th February 2009, 07:20 AM   #1
diyAudio Member
Join Date: Aug 2008
Location: Lafayette, Louisiana
Default Add capacitors to RF 25 to Life Punch 150

I can't seem to find this anywhere, but I recall reading a while back that extra capacitors could be added to the 25 to Life Punch 150 in the missing spots. I would like to know what, if anything, would be gained by filling the blank spots:

Click the image to open in full size.

I guess my next question would be is that circuit board as hard as I think it is to remove from the heat sink?

Lastly, insomnia sucks!
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Old 27th February 2009, 07:26 AM   #2
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Join Date: Nov 2003
Location: Louisiana
It's unlikely that there will be any audible improvement by adding the capacitors.

The circuit board comes out easily. Remove the T15 screws from the MEHSA strips and the circuit board and it lifts out.
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Old 27th February 2009, 07:37 AM   #3
diyAudio Member
Join Date: Aug 2008
Location: Lafayette, Louisiana
So in other words, it would be a waste of time, money, and effort. I want to say what I remember reading on them said that the only benefit was extra capacitance on the power supply side.

Oh well, this was one of those "I wonder if" situations that popped into my head while counting sheep

Thanks for the reply Perry!
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Old 27th February 2009, 08:29 AM   #4
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Join Date: Dec 2005
Location: Northern California
Perry is correct in his statement that you most likely will not "Hear" any difference. It all depends on how poorly the supply was designed in the first place and the musical content you may be listening too also.

BUT, sometimes benefits may not be heard, but will be only seen in the overall performance of a amp design.
I have found in older amp designs that they suffered from a lack of stored energy in the supply. This was seen as a cooler running amp, and a reduction of over temp cut-outs under heavy demand after the addition of suitably matched caps to the supply rails.

Also a significant reduction of current draw and or 12 volt "hit" can be seen after such a upgrade. As the extra stored energy can smooth out the transients the Dc to Dc supply has to deal with. Although for the most part SMPS can handle just about anything music can demand of them speed wise, < recovery wise>, I am a firm believer in a very solid supply design and this means lots of micro-farads of storage. < but this is a small school of thinking in the real world>

Also this same board was most likely used for a similar design by RF so it still has the markups for the different amp design on the board. And that amp design may have a need for those extra caps power wise.

Also when you build big multi-cap banks like this you may also need to consider passive or active voltage balancing across the caps to keep them all operating in balance of one another.
You see this in those 12 volt mega caps using 200 little caps all adding up to one big value. resistors for passive and diodes for active balancing are pretty much the norm when you try to add that many caps in a circuit and try to get them to operate properly. the same effects may also happen on smaller banks like in your 25 to life.

Is it worth it ??? Who knows unless you try it and measure the differences it may or may not impart on your amp. As I said earlier on older 80's amps i found that it was noticeably an improvement up to a point, but after that given point it was simply a waste and the damage amp suffered upon failure could end up being magnified by the addition of TOO much energy storage.
I used to do this a lot in the past, so I am speaking from practical experiences of trying these ideas.
Adding the caps most likely won't hurt, unless you fail the amp. then it might show itself as a whole bunch more damage then you would expect to see in a un-modified amp... been there , done that , and got the Tee shirt...
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Old 28th February 2009, 12:02 AM   #5
jol50 is offline jol50  United States
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Are those amps sagging rail voltage at high output? I've read newer PS are smaller and more capable, but I do have old amps with BJT PS and sometimes wonder what difference there is. I don't yet have the setup to check rail voltage near clipping, but have checked amps where it dropped under heavy load. They were not mine so out the door they went.
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Old 28th February 2009, 06:19 PM   #6
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Join Date: Dec 2005
Location: Northern California
Early BJT power supply's were not as efficient at the switching frequency's as mosfets are, so they had a tendency to make heat that ended up on the sink along with the amps outputs stages heat load. Changing to Mosfets just made the supply more efficient and faster. Mosfets were designed with high frequency switchmode power supply's hence the no brainer to leave BJT's behind as a switch....
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