Talking of caps, I have an Audion Megavox Pre 2 (single 6922 valve per channel) that needs to be refurbished. The output caps are Aerovox 2uF 600V "oil-filled" cans. These are 25 to 30 years old and need to be replaced. What would be the most suitable caps to use here?
Your advice will be greatly appreciated.
Your advice will be greatly appreciated.
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Not by measuring the performance of the cap. You can identify the manufacturer based on the markings and labeling they place on their product.
P.S. This should tell you the importance of determining the cap's manufacturer: if you can't detect this by examining the cap's performance, why would it matter?
Oil filled capacitors do not degrade or wear out over time. They do not need to be replaced unless they actually fail. I'd leave them alone, unless you specifically want to change the sound of the preamp.
Thanks very much for the feedback gents, it is highly appreciated.
When I tested them (2 - 3 years back) they were measuring at 2uF. The cans are still good, so there shouldn't be any issues. They are in fact solidly bolted onto the chassis base. With only a single 6922 the pre does not get very warm (nicely ventilated on top.) I may very well play around with a few different type of caps when I eventually get to the refurbishment, just to listen to any differences. I have a few high voltage caps around (Solen MKP and Panasonic 600V) and will also try some large diameter 'lytics when I get there. That is likely to only happen next year though. Too many other things keeping me busy - not necessarily HiFi related.
Regards, Kevin
P.S. I am very new to electronics, and have enough knowledge to help myself and do basic troubleshooting. Also to know when to ask for help. Very aware of dangerous voltages used in all forms of electronics, so very careful with my valve gear.
When I tested them (2 - 3 years back) they were measuring at 2uF. The cans are still good, so there shouldn't be any issues. They are in fact solidly bolted onto the chassis base. With only a single 6922 the pre does not get very warm (nicely ventilated on top.) I may very well play around with a few different type of caps when I eventually get to the refurbishment, just to listen to any differences. I have a few high voltage caps around (Solen MKP and Panasonic 600V) and will also try some large diameter 'lytics when I get there. That is likely to only happen next year though. Too many other things keeping me busy - not necessarily HiFi related.
Regards, Kevin
P.S. I am very new to electronics, and have enough knowledge to help myself and do basic troubleshooting. Also to know when to ask for help. Very aware of dangerous voltages used in all forms of electronics, so very careful with my valve gear.
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Smaller caps dry out quicker I guess.
Does anyone have experience with Aluminium polymer electrolytics - they allegedly can't dry out (being polymer electrolyte), yet still have a rated life that's not particularly impressive compared to regular electrolytics.
Not by measuring the performance of the cap. You can identify the manufacturer based on the markings and labeling they place on their product.
P.S. This should tell you the importance of determining the cap's manufacturer: if you can't detect this by examining the cap's performance, why would it matter?
shreekumar is online now shreekumar
diyAudio Member
Join Date: Oct 2018
Thers no marking of manufacturer on this cap.
The one I have has a little discoloration probably due to heating up I assume.
Hence would want to buy and stock a few for 2 of my my cx1000 Yamaha Amp
Rgds
Shree
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In AB class amps that don't run hot good quality elcos have surprisingly long life. It's not unusual to take out old PSU elcos and measure them after 30 years of use and find that they have nominal capacitance. Small elcos last less but I've measured small ELNA 10u DC blocking signal elcos from 30 years old Yamaha cassette deck and they were perfect, in spite of being improperly polarized with negligible voltages. I hear that modern elcos are much better than elcos produced 30 or 40 years ago.
I hear that orientation of elcos have influence on longevity. It seems that it is useful to have elco standing upright with leads facing down towards pcb. I do not know how elcos longevity is influenced with elcos in horizontal position. It seems that if the leads are on the top some bubbles are formed inside can that tend to leak around leads and that shortens cap life. Bubbles tend to go towards top of can.
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