Installing bridge rectifier in place of 4 diodes

[370forlife]

So I have this sunpro "450w" psu I am fixing up for a friend. It has the usual 4 diode treatment. I am going to put a 6A 600V bridge rectifier in their place, but there is no silkscreening for a bridge rectifier.

I tried putting the bridge rectifier in the same way as my deer, but with the positive on the opposite end as the diodes are positioned opposite that my deer's were. This blew the fuse. I then tried putting the leads in the circled holes, like I did with my deer, and this blew the MOV, and hopefully nothing else. So, I am going to put the original diodes back in, make sure nothing else is blown or shorted, and try and figure out what to do.

[etnietering]

Re: Installing bridge rectifier in place of 4 diodes

You should take the board out and look at the traces. the two primary caps are connected in series, so treat this as one big capacitor for this purpose. the + on the bridge rectifier should be connected to the + on the cap, and the - on the rectifier connected to the - on the cap. the other two go to each side of the incoming AC

[370forlife]

Re: Installing bridge rectifier in place of 4 diodes

Thanks, I'll get on that in the morning. 12:27AM right now here in kalamazoo. Been working on this thing all day.

[Toasty]

Re: Installing bridge rectifier in place of 4 diodes

Tracing and following the diodes connections:

Where 2 Cathodes (banded end) are connected on the trace is the + output
Where 2 Anodes are connected (no band) on the trace is the - output
Where an Anode and Cathode are connected is one of the 2 AC inputs

Schematic help: Google this- bridge rectifier picture

Toast

[370forlife]

Re: Installing bridge rectifier in place of 4 diodes

it does show you at least the side that the positive goes on, I think, it has a large plus sign next to the far left diode.

[lucky13]

Re: Installing bridge rectifier in place of 4 diodes

Or you could post a picture of the PCB both sides and I am sure one of us can help you.

[everell]

Re: Installing bridge rectifier in place of 4 diodes

You guys remind me of the days when I was a senior in High School. A lot of the electronic circuits I experimented with went "BOOM". Those were the vacuum tube days, so had plenty of high voltages. In them days I had more courage than electronics knowledge!

When making changes on the primary side of a power supply, WEAR SAFETY GLASSES when powering up. The price of a pair of safety glasses is far less than the cost of losing eyesight. When these circuits go boom, they send little pieces of debris in all directions. Have fun, but safety first.

[everell]

Re: Installing bridge rectifier in place of 4 diodes

Before installing that bridge in the power supply again, get out your ohmmeter and check that bridge diode. You may have shorted one of its four diodes. If so, it will not be usable in your power supply.

[Toasty]

Re: Installing bridge rectifier in place of 4 diodes

>>A lot of the electronic circuits I experimented with went "BOOM".<<

...and still to this day...

https://www.badcaps.net/forum/showthread.php?p=65187



Toast

[370forlife]

Re: Installing bridge rectifier in place of 4 diodes

Well, the placement of the diodes and where the AC goes in and the DC comes out makes it impossible to put in a bridge rectifier without crossing the legs.

Fucking ridiculous design by sunpro. Whoever made this should be shot.

[etnietering]

Re: Installing bridge rectifier in place of 4 diodes

Can you take a picture of it? Both the component side and the solder side, somebody might be able to suggest something

[Toasty]

Re: Installing bridge rectifier in place of 4 diodes

>>impossible to put in a bridge rectifier without crossing the legs<<

Without dragging this into the gutter...

8 holes and 4 legs? It seems very probable to me that it can be done. I can't think of a scenario where it couldn't be done.

Pics top and bottom please so we can see AC inputs and input filter caps connections.

Going by your comment in this thread: https://www.badcaps.net/forum/showthread.php?p=79508

You said that Delta Power PSU looks like the Sunpro in question. Looking at those diodes, a bridge should be a snap.

Toast

[370forlife]

Re: Installing bridge rectifier in place of 4 diodes

The diodes are laid out differently in that sunpro than in this one.


WARNING I made this diagram at 3:22 in the morning.

Those little boxes next to the coil are Y caps

[Wizard]

Re: Installing bridge rectifier in place of 4 diodes

MOV, no. NTC yes. NTC start high then resistance drops as this heats up, and always dull looking.

MOV is always OPEN till specific voltage threhold is reached, shorts out. MOVs is always across each of Neutral and ground, and HOT and ground. The small blue caps across diodes rectifier is to quieten down diode noise. Said devices are usually shiny.

Cheers, Wizard

[370forlife]

Re: Installing bridge rectifier in place of 4 diodes

Yup its a NTC. Like I said, 3:22 in the morning.

Whats interesting is that the two diodes connected to the X cap there were a lot bigger and rated at 3A, 1000v. The two connected to the NTC (labeled MOV on this,) were much smaller and rated at 2A.

[etnietering]

Re: Installing bridge rectifier in place of 4 diodes

I have a junker PSU that has a similar diode configuration - bigger ones on one side of the AC and smaller ones on the other...weird....

anyways, judging from your picture, it should be easy to install the bridge rectifier: The + should go on the bottom left, the - should go on the bottom right, and the two AC pins should go on the middle two on the top.

[momaka]

Re: Installing bridge rectifier in place of 4 diodes

Whats interesting is that the two diodes connected to the X cap there were a lot bigger and rated at 3A, 1000v. The two connected to the NTC (labeled MOV on this,) were much smaller and rated at 2A.

That's state of the art Leadman/SunPro engineering for you. Not sure why, but they always use a mix of different-sized diodes for the line rectifier.

[severach]

Re: Installing bridge rectifier in place of 4 diodes

Nothing wrong with crossing legs. Use some heat shrink tubing or steal some insulation from a wire in the trash.

[Gianni]

Re: Installing bridge rectifier in place of 4 diodes

Whats interesting is that the two diodes connected to the X cap there were a lot bigger and rated at 3A, 1000v. The two connected to the NTC (labeled MOV on this,) were much smaller and rated at 2A.

The reason is that at input 230Vac all 4 diodes work while with the input switch in position 115Vac only 2 diodes work because one input line is connected in the middle of the two input bulk capacitor. In this case at the same output power, the input current is higher.
I don't know how much cents they can save using a 2A diode instead of 3A diode.

I attach here a schematic with colored current path for both configuration full bridge and half bridge.
If you check diodes connection and input voltage switch connection you should confirm this schematic.

Ciao
Gianni

[Toasty]

Re: Installing bridge rectifier in place of 4 diodes

The switch turns the circuit into a voltage doubler.

Toast