Rectifier Substitution

[twnc83]

I've got a tv that keeps blowing fuses. Happened when I was trying to fix a computer with a blown power supply. TV was plugged into the same power strip, must have been surged when I plugged in the computer. Anyways, I've tracked it down to a shorted rectifier. It's an IN5406, the local shop has an IN5404 in stock. Will this be an okay substitute? The differences between the 5406 and the 5404 are the 5406 has higher voltage tolerances but the 5404 seems plenty high compared to the incoming voltage (120VAC). Unless I just don't know something about CRT TVs and they have a large DC requirement?

[shovenose]

Re: Rectifier Substitution

i think its ok

[PowerAmpFreak]

Re: Rectifier Substitution

The 5404 is a 400 volt device while the 5406 is a 600 volt device.
For 120VAC operation it would be pretty safe to substitue a 5406 with a 5404.
But I would not do this if the set was operated at 230VAC.

[Th3_uN1Qu3]

Re: Rectifier Substitution

It'll work fine at 230 volts too. But now the question is, WHERE is the rectifier located? If it's the line rectifier before the large filter cap, no problem. If it's in the switcher, they usually have a good reason why they did that. But one of the reasons they used it could have been simply "it was dirt cheap", anyway, substituting a lower voltage part can at worst result in more blown fuses, so go ahead.

[momaka]

Re: Rectifier Substitution

It'll work fine at 230 volts too. But now the question is, WHERE is the rectifier located? If it's the line rectifier before the large filter cap, no problem.

It probably would work, but personally I wouldn't go that close to the ratings. The maximum RMS voltage on the 1N5404 is 280v. The 400v rating is for the DC blocking voltage.

If it's in the switcher, they usually have a good reason why they did that.

If it is in the switching circuit, you definitely don't want to use a lower voltage part. Reason why is because there are often high voltage spikes from the transformer when the MOSFET turns on and off.

[Th3_uN1Qu3]

Re: Rectifier Substitution

If it is in the switching circuit, you definitely don't want to use a lower voltage part. Reason why is because there are often high voltage spikes from the transformer when the MOSFET turns on and off.

That's what snubbers are for.

Never seen FR303s, two discrete diodes joined at the cathode, in Deer power supplies? Do you think they needed 200v diodes on the 12v rail? Nope, it's simply because they were very very cheap.

[PowerAmpFreak]

Re: Rectifier Substitution

The 5404 and 5406 are not suited for switching circuits!
These are slow animals meant for 50/60Hz rectification!
Check Trr of the these diodes and you'll see what I mean.

[momaka]

Re: Rectifier Substitution

That's what snubbers are for.

Yeah, that's what I meant.

Never seen FR303s, two discrete diodes joined at the cathode, in Deer power supplies?

As a matter of fact I even own one! It's still working, too . Been in service for 7 years in a PIII computer, but I took it out for a better (recapped) Deer unit finally.
The FR303's are fast recovery rectifiers, though, not like the 1N5404. Didn't even cross my mind you can use 1N5404s as rectifiers on the secondary.