artto Posted January 9, 2023 Share Posted January 9, 2023 I have several SET amps, all with tube rectifiers. The amps haven't been used in approximately 12+ months. They are all relatively new (< 2yrs old). Do I need to fire up these amps slowly with a variac to reform the caps if they have a tube rectifier? Quote Link to comment Share on other sites More sharing options...
seti Posted January 9, 2023 Share Posted January 9, 2023 You can do that to be on the safe side. I only do it for amps I do not know the history of but ones I know I just power on. Quote Link to comment Share on other sites More sharing options...
OO1 Posted January 9, 2023 Share Posted January 9, 2023 I use a Variac when the amplifier is out of commission for 1 year or more , no matter which type of amplifier ...just to be safe Quote Link to comment Share on other sites More sharing options...
artto Posted January 9, 2023 Author Share Posted January 9, 2023 Thanks guys! I was just hoping that having a tube rectifier might alleviate the need to pull out the variac. So variac it is. Quote Link to comment Share on other sites More sharing options...
henry4841 Posted January 9, 2023 Share Posted January 9, 2023 I have many amps I have not used in a year or two. I just fire them up with no problem. Reforming caps usually means many years or even decades old caps not recent ones. 1 Quote Link to comment Share on other sites More sharing options...
henry4841 Posted January 9, 2023 Share Posted January 9, 2023 Just thought I would add, unsold electronic equipment may sit for years in the storeroom before finding a home. 1 Quote Link to comment Share on other sites More sharing options...
seti Posted January 10, 2023 Share Posted January 10, 2023 For really old gear I use an oscope with a curve tracer to check cap condiiton. It can do this in circuit. A friend who was a tube tech for many years turned me onto this tool and it is the most useful dam tool I have. 1 Quote Link to comment Share on other sites More sharing options...
opnly bafld Posted January 13, 2023 Share Posted January 13, 2023 On 1/9/2023 at 2:28 PM, artto said: I have several SET amps, all with tube rectifiers. The amps haven't been used in approximately 12+ months. They are all relatively new (< 2yrs old). Do I need to fire up these amps slowly with a variac to reform the caps if they have a tube rectifier? Just power them on and enjoy. 1 Quote Link to comment Share on other sites More sharing options...
the real Duke Spinner Posted January 15, 2023 Share Posted January 15, 2023 On 1/9/2023 at 3:28 PM, artto said: I have several SE The Tube Recto comes up slowly anuwaysmps, all with tube rectifiers. The amps haven't been used in approximately 12+ months. They are all relatively new (< 2yrs old). Do I need to fire up these amps slowly with a variac to reform the caps if they have a tube rectifier? No Letter rip ..the Tube Recto comes up slowly anyways Quote Link to comment Share on other sites More sharing options...
John Warren Posted January 15, 2023 Share Posted January 15, 2023 Electrolytics age while under load. The life expectancy of an electrolytic (say 4000h) is based on it operating typically at 2x its max. continuous ripple current and max temperature (usually 105C). Temperature is the big driver. Most electrolytics are rated to 105C max (220F) which is quite hot and sitting at that temperature with no power will shorten life. In real world circuits, electrolytics rarely exceed 40C and, at design ripple current, will last much, much longer. 1 Quote Link to comment Share on other sites More sharing options...
henry4841 Posted January 15, 2023 Share Posted January 15, 2023 When doing repairs to electronic equipment I find heat to be the biggest contributor to electrolytic failure. When I see a board upside down inside the chassis of an old receiver I know most if not all the capacitors on that board will need replacing. Quote Link to comment Share on other sites More sharing options...
artto Posted January 20, 2023 Author Share Posted January 20, 2023 So, how slowly do you guys increase the voltage when reforming caps on a reasonably new tube amp ( <10 years old) that hasn't been turned on for more than a year? AND, how slowly do you guys increase the voltage when reforming caps on a old tube amp ( 30+ years old) that hasn't been turned on for more than a year? Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted January 20, 2023 Share Posted January 20, 2023 On 1/9/2023 at 5:16 PM, seti said: For really old gear I use an oscope with a curve tracer to check cap condiiton. It can do this in circuit. A friend who was a tube tech for many years turned me onto this tool and it is the most useful dam tool I have. Any recommendations for a particular oscilloscope? Quote Link to comment Share on other sites More sharing options...
seti Posted January 20, 2023 Share Posted January 20, 2023 10 minutes ago, tigerwoodKhorns said: Any recommendations for a particular oscilloscope? I'm using a late 1940's HP Scope and it is fine for this use. Best diagnostic tool I've ever had. 1 Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted January 20, 2023 Share Posted January 20, 2023 37 minutes ago, seti said: I'm using a late 1940's HP Scope and it is fine for this use. Best diagnostic tool I've ever had. Yea, I am updating my electronic tools lately as I have several amps that are due for caps and refresh and I need to brush up on my skills with these. So any scope? Quote Link to comment Share on other sites More sharing options...
seti Posted January 20, 2023 Share Posted January 20, 2023 9 minutes ago, tigerwoodKhorns said: Yea, I am updating my electronic tools lately as I have several amps that are due for caps and refresh and I need to brush up on my skills with these. So any scope? Yeah there are some cool ones out there I have HP, Tektronix, and a sencore. The sencore is cool because it can measure voltage at the same time but you wouldn't want to tie up that scope for one purpose. I really like the tektronix scopes. There are lots of them and they are affordable. I am rebuilding my workbench from scratch which should be fun.... lol scary..... 2 Quote Link to comment Share on other sites More sharing options...
henry4841 Posted January 20, 2023 Share Posted January 20, 2023 I have a number of scopes and like Seti really like my old analog scopes. Crap shoot finding a good working one but when you do you will love the trace it provides. Still I probably use my digital scope more being it is so easy to get numbers. Nothing fancy for me, a Hantek DSO5102 is plenty good enough for audio work. 1 Quote Link to comment Share on other sites More sharing options...
seti Posted January 20, 2023 Share Posted January 20, 2023 Here is what I used to setup as curve tracer. Being able to step through caps and parts while in circuit is invaluable tool. Here is a terrible pic of mine. It is also fun to restore scopes of course it helps to have one as a curve tracer to start with.... Check your craigslist I bet there are a handful to choose from. 1 Quote Link to comment Share on other sites More sharing options...
henry4841 Posted January 20, 2023 Share Posted January 20, 2023 8 minutes ago, seti said: Here is what I used to setup as curve tracer. Being able to step through caps and parts while in circuit is invaluable tool. Here is a terrible pic of mine. It is also fun to restore scopes of course it helps to have one as a curve tracer to start with.... Check your craigslist I bet there are a handful to choose from. Now that is an old one for sure. I have 6 or so old scopes but none that old. My repairs of old scopes has been hit or miss. Most times it is a power supply problem though. But getting back to reforming old caps, unless the equipment is decades old I do not go through the trouble myself. Does not hurt to be too careful though. To answer the how question, slowly bring the power up to approximately 60V's and hold it awhile there then slowly bring it up to line voltage from there. Quote Link to comment Share on other sites More sharing options...
pnort Posted January 20, 2023 Share Posted January 20, 2023 Can one of you experts please provide a tutorial on how you use an oscilloscope to evaluate caps. Thanks Quote Link to comment Share on other sites More sharing options...
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