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Old 17th February 2004, 01:53 AM   #1
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Default Replacing power supply capacitors

I need to replace the power supply capacitors in my amp. They have gotten really really bad. My amp makes popy sounds when I turn it on. I usually forget about it and leave it on most of the time. When I play music and turn it up the speakers randomly pop, then seem to get better for a while.

What type of capacitors should I buy. I want to get 10,000uf (i need 4). My amp has one transformer with two windings, and has two seperate power supply boards for each channel, yay. So my right channel seems to be dying and I don't want to blow up the amp, so I have to get on this pretty soon.

So say I order from digikey. Which type of capacitors should I get?

The reciever is a Ward Montgumery Model 450. It pushes about 75 watts into 8 ohms before audible distortion. I can't wait to install new capacitors, I like my music loud. I actually have two sets of speakers right now hooked to it. I'm at college and it rattles the entire basment.

I think I'm going to bias it to when I have the chance. I just need to buy new trim pots so I don't blow up the bias circut (I accidetally did that on my old reciever and haven't gotten around to fixing it yet).
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Old 17th February 2004, 09:55 AM   #2
hacknet is offline hacknet  Singapore
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well, my only recommendation would be to exactly replace the caps on the board. if they are 10,000uf. den replace them with 10,000uf caps of the same voltage rating.

Good luck!
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Old 17th February 2004, 10:23 AM   #3
JohnSz is offline JohnSz  United States
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Since it is a receiver, (wow 4-10Ks) I am assuming the caps are soldered to the pcb, which means you need ones that fit the pinout, same diameter. Height, you probably have some room. Check out the 10K/80V Nichicons at ApexJr I would expect that they are of at least the same quality of whats in there.
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Old 17th February 2004, 06:59 PM   #4
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Opps I was wrong. It only has four 4,700uf 50v caps in it currently. So I guess 10,000uf caps would be WAY to big. I guess I'll go with 4 6,800 uf caps. There souldn't be any reason the transformer can't handle them. The tranny in it is HUGE. I had 4 6,800 caps in my old amp which only had a mono power supply, and it worked good.

My real question is what style cap should I look for? One manufacture makes like 3 different styles of one value. Some manufaturers are even said to be better than others.

In the digi key catalog I can give some examples...
http://dkc3.digikey.com/pdf/T041/0712-0855.pdf

Panasonic
Pg. 730 TSU General Purpose 63v 6,800uf
Pg. 732 TSNH Long Life and High Ripple Current 63v 6,800uf
Pg. 732 TSHA Miniaturized Size, Long Life and High Ripple Current 50v 6,800uf
pg. 735 AA-Series Computer Grade Capacitors 50v 6,800uf
nichicon
pg. 746 VR Series Aluminum Electrolytic Capacitors (Radial Lead) 50v 6,800uf

Other options if i can find a vender,
http://www.vishay.com/docs/28337/156pum.pdf
http://www.vishay.com/docs/25138/eyc.pdf

Ok i give up looking for capacitors online. Anyone now any good places to order them other than digikey? I do like the temperature/lifetime ratings on the Vishay capacitors.

Thanks,
Nick
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Old 2nd March 2004, 03:40 AM   #5
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I doubt it's your power supply caps causing the snap, crackle pop. Most likely it's a coupling cap or three. There are many in this kind of device, and they seem to go bad over the years.

If your power supply caps were bad, you would either have lots of hum, or popping fuses, depending on whether they failed by drying out and going open, or shorting. Usually they dry out. It does no harm to change them out, but it's probably not going to help if it is a coupling cap.
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Old 2nd March 2004, 10:22 AM   #6
tiagor is offline tiagor  Portugal
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It could well be the power supply caps, which have probably evaporated part of the electrolytic. If you want to be sure before buying new caps, swap them between the 2 channels and check if the problem stays on the same channel, or moved to the other.
Remember to discharge the caps and check with a meter before trying to remove them.

Quote:
Opps I was wrong. It only has four 4,700uf 50v caps in it currently. So I guess 10,000uf caps would be WAY to big. I guess I'll go with 4 6,800 uf caps. There souldn't be any reason the transformer can't handle them. The tranny in it is HUGE. I had 4 6,800 caps in my old amp which only had a mono power supply, and it worked good
It has nothing to do with the transformer being able to handle it.
There is no problem increasing the capacitance(just stick to the power rating or use a higher rating), though you probably won't notice any benefits, and will prove more expensive. Remember the larger the capacitance, the longer the cap will take to charge/discharge. Also, I wouldn't worry too much on getting exotic capacitors.

Also beware of the recommendation of JohnSZ.. you woudn't want to end up with caps that won't fit the board

Good luck
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Old 2nd March 2004, 10:27 AM   #7
DRC is offline DRC  United Kingdom
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If you do replace caps, be sure to get caps with a rated temprature of 105 rather than the normal 85. They are bigger and more expensive to buy but will pay for themselves in the long term.
D
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Old 13th October 2009, 02:24 AM   #8
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My multi chanel power amplifier (Carver 705X) has two big aluminum electrolytic capacitors (Phillips) 25,000 uF/ 75v each. Though they still work flawlessly , the power amplifier has been put into service for more than 12 years, so I am planing to replace the old capacitors by a new pair. Please kindly advise:
1. Whether replacing the old caps by the new caps with the same value can improve the sounds?
2. If it makes an improvement in sounds, then what brand of caps that I can replace? I search on the web for the same cap’s value (computer grade), I could not find the Phillips’ but Vishay Sprague, Mallory, and CDE instead. Which one could be the best for my case? I found the most expensive are Vishay Sprague (US$ 38.5 per cap) on www.tedss.com . Is it better than the rest?
3. Is there any one who buy parts on the web www.tedss.com?

Thank you very much in advance for your advices and comments
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Old 13th October 2009, 11:32 AM   #9
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Phillips, Sprague and Mallory are old companies. Philips now BC Components (distribution about Vishay) and Sprague now nichicon, but I don't know about the presently quality standart and life time.
best experience regarded realibility, life time and sound quality I have with the German brand "Fischer & Tausche", go to
Electrolytic Capacitors - FTCap Fischer & Tausche Capacitors Group
I would choise 22.000uF/100V, see about
http://www.ftcap.de/downloads/elektrolyt/GMX.pdf
please call the US-distributor:
Electrocube - Contact Us in Pomona, California
Please replace also the old rectifier
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Old 13th October 2009, 12:10 PM   #10
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in a nut shell ....

going from 4x4700 to 4x10.000 is an upgrade more than that i think its awaste of time effort and money

replacing caps at this size you might need to alce replace the rectifier to somthing a bit bigger ....probably you will get away with it without replacing anything

then for sure i will agree with the rest of the people that said that pops and crucles are not from the main electro's even nif they are half dead the amp will distort and prooduce bad and less sound but in low levels it will work alsmost properly

the full ability of the caps is used at high levels of power in low or very low levels are not realy needed to produce the power ...they are only there to keep your power as clean is possible ....

so .... mechanical errors like dirty loose or bad soleders arround switches and pots is one target
then damaged trimmers leacky electros ( small ones in the signal path /secondary psu /local filtering ) is the second target
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