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Replacing two 37 year old filter caps; where do I start?

S

Saffire

Active Member
Please excuse my ignorance, I'm new to the world of recapping vintage receivers. I have an original Pioneer SX-50 that's getting up there in age, and I'd like to start by replacing the main filter caps for good measure. They're a pair of Nichicon 8200uf 50v caps with an 85c rating. What would be a good replacement for these two caps?
 
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So that's about 27mm diameter (if you want them to fit into any existing clamps) and 50mm high--new ones will probably be smaller, at least in height. I'd stay as close as possible to the 8200uF capacitance but you can go 50V and higher with the voltage rating. If there's room to install a slightly wider diameter cap you'll have more options--I did a brief search at Mouser for you and found that most of the Kemet caps in that value range are a bit wider than 27mm. I like Kemet for filter caps but have also used Nichicons. Be careful when handling the existing caps as they can hold a charge and zap you, even with the power off. Note where the + and - terminals are hooked up and draw a diagram/take photos/etc. before desoldering. I desolder one cap at a time, replace it, then move on to the next cap so I don't get confused. Good luck and welcome to AK!
 
birchoak said:
So that's about 27mm diameter (if you want them to fit into any existing clamps) and 50mm high--new ones will probably be smaller, at least in height. I'd stay as close as possible to the 8200uF capacitance but you can go 50V and higher with the voltage rating. If there's room to install a slightly wider diameter cap you'll have more options--I did a brief search at Mouser for you and found that most of the Kemet caps in that value range are a bit wider than 27mm. I like Kemet for filter caps but have also used Nichicons. Be careful when handling the existing caps as they can hold a charge and zap you, even with the power off. Note where the + and - terminals are hooked up and draw a diagram/take photos/etc. before desoldering. I desolder one cap at a time, replace it, then move on to the next cap so I don't get confused. Good luck and welcome to AK!
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Great info, I'll be sure to unplug the stereo 24 hours before I start the job, thanks!
 
I've personally had less issue with the big cans than small value caps, but thats my 2 cents.

and metric calipers are your friends for capacitor sizing. Often you'll have to compromise on dimensions, picking the one that is more important to mounting. I've often ended up with short, fat capacitors in order to make them fit the clamps correctly. Sometimes there is nothing that will fit the clamp and you have to bulk it up with foam or something to mount them.
 
W9TR said:
Just curious, how do you know they are bad and need replacement?
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So far, the receiver has been working completely fine, but I'd still like to replace the caps for reliability reasons. After almost 40 years, they have to be either dried up or out of spec. The sound quality is still very good, but I feel like I can make it sound even better by recapping, if that makes sense.
 
Saffire said:
So far, the receiver has been working completely fine, but I'd still like to replace the caps for reliability reasons. After almost 40 years, they have to be either dried up or out of spec. The sound quality is still very good, but I feel like I can make it sound even better by recapping, if that makes sense.
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First of get in the Pioneer forum- will help a little better than DIY specifically. Your large can chassis/filter lytics are a common replacement. Its not just about type but mainly size. You can always make just about anything fit. Seen, have had done, and used foam etc to pad between the metal mounts, or your own idea it they are a little larger. Here- the LKG from Nichicon are extremely popular and have been used by AKers for decades in Pioneer amps, receivers, etc: https://www.mouser.com/ProductDetail/Nichicon/LKG1H822MESCBK?qs=4lWw5qRttGIULP5vC8OjIQ==
 
KKnight said:
First of get in the Pioneer forum- will help a little better than DIY specifically. Your large can chassis/filter lytics are a common replacement. Its not just about type but mainly size. You can always make just about anything fit. Seen, have had done, and used foam etc to pad between the metal mounts, or your own idea it they are a little larger. Here- the LKG from Nichicon are extremely popular and have been used by AKers for decades in Pioneer amps, receivers, etc: https://www.mouser.com/ProductDetail/Nichicon/LKG1H822MESCBK?qs=4lWw5qRttGIULP5vC8OjIQ==
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My SX-50 doesn't have metal mounts, actually. The filter caps are glued directly to the PCB. But I'll check out the Pioneer forum, thanks!
 
W9TR said:
Just curious, how do you know they are bad and need replacement?
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Test them for ESR using an ESR meter like the Capacitor Wizard--failing that, caps that are pushing 50 years are drying out and likely out of spec. If the amp or receiver just doesn't seem to have any life, sounds dull, doesn't have the clarity you'd expect from, say, a Marantz 2230, chances are it needs at least a partial recap. I partially recapped a Yamaha CR-800 (power supply, EQ sheet, main amp) and it sounded pretty good but when I finally knuckled down and replaced ALL of the remaining caps in the audio path (well, not the ones in the FM or AM boards) that thing came to life--I had no idea how much bass it was capable of putting out until I finished recapping it.
 
Saffire said:
So far, the receiver has been working completely fine, but I'd still like to replace the caps for reliability reasons. After almost 40 years, they have to be either dried up or out of spec. The sound quality is still very good, but I feel like I can make it sound even better by recapping, if that makes sense.
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Totally makes sense. Great to start with just the filter caps and get a feel for the process. You can soften the glue with a hair dryer or craft heat gun to aid removal. Sometimes I cut it with an Exacto knife, too. For those of us paranoid about "losing the vintage sound," you can save the old caps, but you won't want to. It's like saving old car tires.
 
Saffire said:
I'm considering buying this cap, should I be worried about ripple current at all?
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Great question--I get the capacitance matched as close as I can, then make sure I have the same or higher voltage rating, and (obviously) pick something that will fit onto the board. If the filter caps are going to get super hot (like in a Yamaha CR-800) I look for the highest temp rating I can find.

I haven't lain awake nights thinking about the ripple rating, to be honest. I figure if it's a brand name cap and those three factors have been met, it should work. Don't go with a cheap cap you've never heard of or buy from an unknown seller--I suppose you could always ask a human at Mouser or DigiKey about your specific application.
 
Saffire said:
So far, the receiver has been working completely fine, but I'd still like to replace the caps for reliability reasons. After almost 40 years, they have to be either dried up or out of spec. The sound quality is still very good, but I feel like I can make it sound even better by recapping, if that makes sense.
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Makes sense if you are going to keep the receiver for awhile. Electrolytic caps are funny - they can be perfectly fine after 40 years, they can leak, or they can dry out slowly and go out of spec for esr and capacitance.

Without an esr meter you are shooting in the dark and so probably better to replace them.

The ripple current rating is for switch mode power supply use and does not apply to a normal transformer/rectifier/capacitor power supply found in most receivers.

Enjoy the ride, working on your gear is very rewarding.

Tom
 
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