I'm so sorry, but I actually laughed when I read that
maybe it's a bad connection/wire somewhere or something in the head. Surely THREE PSUs can't all have the same fault !
Senior Member
I'm so sorry, but I actually laughed when I read that
maybe it's a bad connection/wire somewhere or something in the head. Surely THREE PSUs can't all have the same fault !
Senior Member
the boards in the new PSU are a new design. I replaced the same capacitor (different location, but the one that performs the same function) and what do you know... it works again... man these PSU's are a barrel of fun.
Senior Member
So it worked great for a night and now the new cap is dead. Either I got a abad batch or something else is going on here.
Is it possible that the cap is seeing a higher voltage than it can handle due to the tube being a bit high pressure? I'm going to swap out the 25v 33uf for a 50v 33uf cap and see if that helps. Fingers crossed!
Senior Member
Interesting new development.
I measured voltage across the capacitor after the laser has already started. I made sure the polarity was correct and the voltage reads about -3VDC. I'm wondering if the negative voltage over a few hours of run time is what is killing these capacitors...
It also seems like the starting of the circuit depends on the speed at which the capacitor can 'charge up'. I have one of the capacitors here that tests to 33uf on my multimeter, yet it charges VERY slowly. It wont start the board when I just turn the key on, but if I click the key back and fourth a few times (charging the cap) then it lights. Also, if I charge the cap by hand and then install the card it also starts. weird stuff here.
Thoughts?
Senior Member
Yes.Originally Posted by GooeyGus
Replace with polyester, but more worryingly, why is it doing this? you may have a leaky diode somewhere or something.
Senior Member
I dont think it's a fault in the PSU... I think it may be related to the head. I think it could be that the head is a bit high pressure, causing higher than normal tube voltage, which is causing this. I just doesn't make sense for three totally separate PSU's to have the exact same failure. The only constant in this situation is the head.
Oh, also I wanted to add that both caps on both PWM cards read -3VDC. They operate completely independant of each other
EDIT: Also, will a polyester cap have the same performance as tantalum? I assume they are not polarized which is why you recommend them, correct?
EDIT AGAIN: Finding a 33uf polyester cap @ 25v or more is proving to be quite difficult...
Last edited by GooeyGus; 05-08-2009 at 14:57.
Senior Member
Digikey 478-2589-ND
Senior Member
thanks! But WOW... almost 13 bucks for one capacitor... that's nuts!! I guess I'll buy a couple and swap them in here and see what happens. And the thing the huge... 1" lead spacing. Hopefully it will fit with the cover on the PSU!!
Is there any other 'type' of capacitor that would be ok for this application? I really cant see why it needs to be tantalum, especially since it doesn't seem to do much of anything once the circuit is started.
Senior Member
Any thoughts on this guy?
http://www.mouser.com/Search/Product...0VwGLdEQ%3d%3d
Creaky Old Award Winning Bastard Technologist
At 26 cents, might be worth a try I'm about to place a digi order, why dont I save you some woe and put it on my order and then just mail them to you.
Or better yet, parallel a bunch of the mylar/ poly ones here :
http://www.goldmine-elec-products.co....asp?dept=1027
at 50 cents each its not that bad a ouch
Steve
Last edited by mixedgas; 05-09-2009 at 14:01.
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