22000uF filter caps. Fuse blow question

[JW]

This is two diodes in a package sharing the same cathode correct? (See pic)

If so I shouldn't have any pins shorting. I do though. Between cathode and one anode. So, that seems to be the problem right there. Will 2 1N4003's do? I have those.

 

[abbey road d enfer]

This is two diodes in a package sharing the same cathode correct? (See pic)

If so I shouldn't have any pins shorting. I do though. Between cathode and one anode. So, that seems to be the problem right there. Will 2 1N4003's do? I have those.

These are 1amp diodes IIRC; so you can't expect to draw more than 700mA DC. Since the fuse is rated at 2A, I would think the original diode to withstand at least that. If you don't intend to draw more than 500mA at 48V (which allows about 32 channels of shorted mics or at least 50 channels of working mics), these 1N4003 should be adequate.

 

[JohnRoberts]

I can't tell from the picture but as I shared before, failure as a short circuit is common for rectifier diodes that get overheated.

IR has been bought by Infineon and I can't find that exact model.

It looks like perhaps more than 1A and the fact that it melted down would make me cautious about dropping in400x in place.

You could pick up a cheap couple A bridge and just use the one rectified output (+?).

JR

 

[JW]

Thanks so much for the help you guys. How about this one?: https://www.mouser.com/ProductDetail/Vishay-Semiconductors/UG2D-E3-54?qs=sGAEpiMZZMtbRapU8LlZD0HbIjlpuZ44PERzWWHpHCU%3d

I'm not very familiar with spec'ing diodes. The 200V rating is max reverse voltage right? Forward current is what we want, 2A.

Says forward voltage is .95V though. I don't understand this figure. But 1N400x are 1V forward voltage, so must be okay?  I would think we'd need  above 50V  for phantom power rectifier.

 

[JohnRoberts]

I was thinking a bridge like this  http://www.smc-diodes.com/propdf/KBP2005G%20THRU%20KBP210G%20N1746%20REV.A.pdf  or this http://www.vishay.com/docs/88528/2w005g.pdf

Dual diodes don't seem that popular and mouser doesn't have good availability for small quantity I generally use digikey.

You can use half the bridge to replace your melted dual diode, or the whole thing...

JR

 

[abbey road d enfer]

Thanks so much for the help you guys. How about this one?: https://www.mouser.com/ProductDetail/Vishay-Semiconductors/UG2D-E3-54?qs=sGAEpiMZZMtbRapU8LlZD0HbIjlpuZ44PERzWWHpHCU%3d

I'm not very familiar with spec'ing diodes. The 200V rating is max reverse voltage right? Forward current is what we want, 2A.

Reverse voltage is what you want for the voltage you want to rectify; when the diode(s) is reverse-polarized, i.e. not conducting the voltage across it(them) is 2.8 times the nominal ac voltage. For a 50Vac winding it's 140V. For a bridge rectifier this voltage is shared between two diodes, so the 200V rating has a safety factor of almost 3.

Says forward voltage is .95V though. I don't understand this figure. But 1N400x are 1V forward voltage, so must be okay? 

Forward voltage indicates how much voltage is lost in the rectifiers; wheteher you loose 1V or 0.95V is moot. Rectified voltage is always lower than 1.414 times Vac because of this and resistive loss in the windings.

 

[Aref]

Hi,
I got a same exact issue with the studer 089 psu!
Just changed two big screw-mount caps (frako2200uf100v105*) with new ones (non scew 2200uf100v85*). Ended up with a blown fuse!

Someone mentioned to discharge new caps before turning on the psu. Does it really matter in case of new caps?

Tried it once and changed it back to the original caps.
Now it's working again...

 

[abbey road d enfer]

Hi,
I got a same exact issue with the studer 089 psu!
Just changed two big screw-mount caps (frako2200uf100v105*) with new ones (non scew 2200uf100v85*).

You should have chosen 105°C type.

Ended up with a blown fuse!

The cap itself is not at fault. You may have reversed it or have it touching another component.

Someone mentioned to discharge new caps before turning on the psu. Does it really matter in case of new caps?

Not at all. Urban myth.

 

[JohnRoberts]

+1  check for reversed polarity

The temperature rating will not cause the fuse to pop, but the OEM didn't use the higher temp rating for fun.

You can probe the cap out of the circuit with a basic VOM in ohms scale and you should see it try to charge up some...If you measure a short it might be a faulty cap, but those are rare new.

JR