Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › eXStatA Build Thread II
New Posts  All Forums:Forum Nav:

eXStatA Build Thread II - Page 38

post #556 of 567

I just found out that the lower part of the cable is an adapter. It seems, then, that two of the wires were switched. Mystery solved. Thanks again Sachu.

post #557 of 567

This is a weird one. Maybe. I fired up the amp with the top off, turned on some tunes, and everthing was sounding great. Then I reached my left hand in to touch

the PS heat sinks and zappo! Turns out that the exposed metal can portion of the negative rail filter cap is at -315V. Would that indicate that the cap is

somehow shorted internally. I removed it, and all seems normal. Any thoughts?

 

BTW, no problem with the positive rail cap.

post #558 of 567
Quote:
Originally Posted by funch View Post

This is a weird one. Maybe. I fired up the amp with the top off, turned on some tunes, and everthing was sounding great. Then I reached my left hand in to touch

the PS heat sinks and zappo! Turns out that the exposed metal can portion of the negative rail filter cap is at -315V. Would that indicate that the cap is

somehow shorted internally. I removed it, and all seems normal. Any thoughts?

 

BTW, no problem with the positive rail cap.

 

Capacitor cans are always somewhat hot, and you can definitely get shocked by them. They end up floating somewhere between the two poles of the cap, but they actually have some energy to them (in fact the can of a cap can pass limited DC to at least one of the terminals, I forget which)

 

If you want some laughs, google "captret free energy" where people invented a three-terminal component called a captret, which is an electrolytic capacitor with the can as the third terminal. They claim you can extract infinite free energy from the tret terminal.

post #559 of 567
Quote:
Originally Posted by funch View Post

This is a weird one. Maybe. I fired up the amp with the top off, turned on some tunes, and everthing was sounding great. Then I reached my left hand in to touch

the PS heat sinks and zappo! Turns out that the exposed metal can portion of the negative rail filter cap is at -315V. Would that indicate that the cap is

somehow shorted internally. I removed it, and all seems normal. Any thoughts?

 

BTW, no problem with the positive rail cap.

yeah.. i always tape up the top of the rail caps with insulation tape just for this reason..especially so on HV builds before even firing them up to test.

 

You should be reading over -300V on the negative rail caps. This is normal and fine. seems like you are good to go. If its working, don't mess with it. Have a listen and enjoy the tunes brotha beerchug.gif

post #560 of 567
Quote:
Originally Posted by funch View Post

This is a weird one. Maybe. I fired up the amp with the top off, turned on some tunes, and everthing was sounding great. Then I reached my left hand in to touch

the PS heat sinks and zappo! Turns out that the exposed metal can portion of the negative rail filter cap is at -315V. Would that indicate that the cap is

somehow shorted internally. I removed it, and all seems normal. Any thoughts?

 

Not sure what dude_500 is saying, because the can of the cap is connected directly to the negative terminal. On a single rail power supply this naturally sits at ground and there is no problem. On a dual rail power supply it sits at the negative voltage below ground, which is a problem.

 

Life lessons well learned, eh?

post #561 of 567

Just like to add in 20s/30s/40s/50s tube  radios many smoothing/reservoir  caps were like that NEG attached  to cap case . Also came across them in Tex    tube scopes I used to repair. Some had insulators     stopping the case contacting the chassis . Still have some spare ones.Split rail is mainly a newer invention[although there are some specialized usually government equipment that is older]  .allowing removal of the output cap in an amp and larger voltage swing at the output. Multiple capacitors in the one case were popular to save money. Many went faulty[interaction].  Do not  use those types  in audio. 

post #562 of 567
Quote:
Originally Posted by Beefy View Post

 

Not sure what dude_500 is saying, because the can of the cap is connected directly to the negative terminal. On a single rail power supply this naturally sits at ground and there is no problem. On a dual rail power supply it sits at the negative voltage below ground, which is a problem.

 

Life lessons well learned, eh?

 

Interesting, I've tested quite a few caps and never found one that was electrically connected to the negative terminal. You can do cool stuff with the case like connecting it in a certain configuration with all three terminals to make a dead 9V battery have a higher voltage the next day (no I don't claim it's free energy, some chemical reaction probably but still interesting none the less).

post #563 of 567

The old caps  had cases that that WERE connected to the negative. I hold in my hand as I type one taken from  a 50s UK tube  radio I repaired  25yrs ago. =HUNTS-capacitors[well known UK  capacitor company] cap-1-32UF-275V-DC --2-16UF--275V-DC -3-25UF-25V--max ripple=250MA---CAN NEGATIVE. I have 100s of them !! You want the makers serial no?=KDQ 854G -    THH -.The casing of ALL those  types of caps have soldering tags ALL round them for the NEGATIVE connection and ALL are CASING NEGATIVE. Things arent different in the US I also have many US caps with identical working connections.Yes the same isnt done in modern times but I was hard  put to find a cap relating to those eras without saying -casing negative.

post #564 of 567

Thanks to all who responded.

 

After I posted the question, I got curious and did some research and discovered that the can is in fact connected to the negative

rail. I went one better than sachu and painted the top of the cap. This amp is sort of a second-hand commission. The original builder backed out on the owner

who is local, so he asked me if I would build it. This the first build I've done with a hi-voltage dual supply, so the hot cap kinda' surprised me.

post #565 of 567
Quote:
Originally Posted by funch View Post

so the hot cap kinda' surprised me.

 

Huh, that is a very diplomatic way of describing the cursing that follows a 300V+ electric shock.

post #566 of 567

That's when you know that it really hurt; when you can't even curse.   wink_face.gif

post #567 of 567

Hey Guys,

Sorry if I'm resurrecting an old thread. I have my first three DIY projects on their way. I would like to build this someday, but have read that this should only be attempted by someone who has a reasonable amount of experience in DIY audio. Could anybody recommend some sources that I could use (esp. video tutorials) to help me get better at this, so I can do it in around 6 months time, maybe less? I need to get better at everything, from soldering to reading schematics. 

Thanks,

Chris


Edited by ChrisCaubin - 11/21/14 at 10:12pm
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › eXStatA Build Thread II