Half-bridge fix

[ratdude747]

thanks to some generosity I have the psu from here in my possesion...

So far i have replaced the fans and since these fans have tach wires on them, I added two tach extensions to allow fan rmp monitoring. I also stole some parts from an ultra V 550w so both fans are socketed on the fan control board.

I plan on recapping it... but as stated in the linked thread, it is a "half-bridge" and that from what I understand is very bad.

I know there is a way to fix that using a small daughter board... my question is how exactly does one make the conversion? I have never done much upgrading to a PSU other than recapping so this is my first time trying the mod.

this psu is perfect for the mod since the secondary heatsink has a second set of tapped holes for another board mount.

Advice? (some instructions/schematics would help as well)

[ratdude747]

Re: Half-bridge fix

some stuff I forgot to add (from the linked thread):

there is something wrong with the 5vsb circuit involving a high pitched noise when in standby that goes away when powered on.

also, the original owner, Everell, said about it in the thread:

"PWM chip is KA7500C so it is a half bridge. Supervisory chip is a Weltrend WT751002"

I assume fixing the half bridge/2 transistor thing might fix the squeal?

[everell]

Re: Half-bridge fix

The 5vsb conversion from two transistor circuit to pwm chip is not too difficult, and will probably eliminate the squeal. I can give some details if you want.

Conversion from half bridge is something else. It would require an adapter board with a new pwm circuit. The switching transistors are two transistors stacked which adds to the problem because in those circuits one winding of the driver transformer secondary is connected between the two transistors. This winding provides a feedback voltage thru the transformer to boost the voltage on the primary side of the transformer to increase the voltage applied to the two driver transistors on the primary side. So you would be messing with the dynamics of how the switching transistors drive the main transformer. This could get into a real engineering nightmare.

I suggest you play with modifying the 5vsb and get everything working as a half bridge. You might loose some efficiency, but it will be a stable work horse power supply.

[ratdude747]

Re: Half-bridge fix

well, adapter boards are not a problem... there is a second set of tapped holes on the secondary heatsink that I could mount a circuit board to. the first set is used for the fan controller.

I thought half-bridge was a bigger issue than that... if it isn't a safety issue and just efficiency, I can let it be I guess.

So, what are the details of the two transistor fix?

[370forlife]

Re: Half-bridge fix

No need to fix half bridge, they actually have a few advantages like good transient response times. Half Bridge just has low efficiency and got a bad rap for being used in so many poorly designed cheap units. When designed well they can be quite potent. Wintech is really good at designing a good half bridge unit (with cheap ass caps) and this unit can actually do 600W. It's not a stellar performer, but it does 600W and it does it in spec.

[mockingbird]

Re: Half-bridge fix

everell -

Were you the one who did the 5vsb mod in the Antec SP thread? Your instructions were a little obscure, I was hoping you could post a more thorough walkthrough for those less technically inclined.

[ratdude747]

Re: Half-bridge fix

No need to fix half bridge, they actually have a few advantages like good transient response times. Half Bridge just has low efficiency and got a bad rap for being used in so many poorly designed cheap units. When designed well they can be quite potent. Wintech is really good at designing a good half bridge unit (with cheap ass caps) and this unit can actually do 600W. It's not a stellar performer, but it does 600W and it does it in spec.

noted. although the fact that a bare piece of wire is bridging two pads; the wire crosses a few traces... so good soldering is not their strong point.

its crammed full of components so this one will be "fun." Now I see why he sent it my way for free, just kidding.

on that note, i think I know why he got it free in the first place... the fans were beyond hosed (dried up, noisy). the 5vsb issue hadn't shown yet (give it a month or so and it would be a mobo killer!)

back on topic:

at least a part list would be nice here... since I will have to digikey the caps anyway (BCN doesn't carry 16v 6800uf monsters), I'll get twhat i can there while I am at it.

[everell]

Re: Half-bridge fix

That power supply was a freebie to me also, but I had no use for it and did not want it to go on a shelf somewhere perhaps permanently. What I still need is a Tbird cpu!

Give me a couple of days and I will work something up for your DM311 mod for ole blue.

[everell]

Re: Half-bridge fix

everell -

Were you the one who did the 5vsb mod in the Antec SP thread? Your instructions were a little obscure, I was hoping you could post a more thorough walkthrough for those less technically inclined.

Yes, I am the one. I have another Antec SP that needs this mod so I can do a walk thru for you.....................but please help me with what you need and are considering obscure. Before we hijack this thread too badly, how about you starting a new thread for doing the mod to your psu and I will add what is needed.

[ratdude747]

Re: Half-bridge fix

That power supply was a freebie to me also, but I had no use for it and did not want it to go on a shelf somewhere perhaps permanently. What I still need is a Tbird cpu!

Give me a couple of days and I will work something up for your DM311 mod for ole blue.

you still do? I think I have a 1ghz one on my shelf...

edit- If remember right I actually was going to send it your way... I have it somewhere, I just have to find it.

[mockingbird]

Re: Half-bridge fix

Ok, thank you everell.

I hope I am around by then to start the thread. It seems to me now that I am about to be permanently banned from this forum for speaking my mind.

[ratdude747]

Re: Half-bridge fix

Ok, thank you everell.

I hope I am around by then to start the thread. It seems to me now that I am about to be permanently banned from this forum for speaking my mind.

read the rules, I dare you!

5) Keep things civil! There will be no tolerance for flaming, bashing, hateful remarks, racial remarks, porn of ANY kind, and so on.

[mockingbird]

Re: Half-bridge fix

Lose some weight.

[ratdude747]

Re: Half-bridge fix

Lose some weight.

???

totally random post award!

[kaboom]

Re: Half-bridge fix

RD, you were confusing the "two-transistor" standby ckt with the half-bridge- aka the main supply.

You can have a half bridge with:

No standby supply, as used in AT power supplies, such as the one I 'beefed up.' The 494/7500 will have an aux power take off point after the 12V rectifier, before the output inductor.
TinySwitch/DM311 for aux
Two-transistor aux
One-transistor aux (the 'second' transistor in that ckt is for over-current limiting, most all have it now- hence two-transistors)

The two-transistor ckt for the aux doesn't take anything away from the main supply, it just happens to be a half-bridge.

And enough already with your overly sensitive "racism" garbage. Grow up! Let's stop the world already! Someone "offended" somebody else on an internet forum- let's all jerk knees and go to war. I hope you realize how ridiculous this looks.

I dare you to call me a racist. I have problems with barry-o's commie policies. Would you exhibit the 'typical' response and shout, "He's black (which itself is debatable)- you no say nuttin," or would you agree that this 'wealth redistribution' (among other things) bullshit is an out-of-control train ready to derail?

Mockingbird's last post to you was not at all random.

You cited, "no hateful or racial remarks" from Da Rulez as a way of "keeping it going." He countered your 'read the rules' weak punch by calling you fat... A bit premature for you to consider it 'random'.

IB4TL, even though I shouldn't have even posted...

[ratdude747]

Re: Half-bridge fix

RD, you were confusing the "two-transistor" standby ckt with the half-bridge- aka the main supply.

You can have a half bridge with:

No standby supply, as used in AT power supplies, such as the one I 'beefed up.' The 494/7500 will have an aux power take off point after the 12V rectifier, before the output inductor.
TinySwitch/DM311 for aux
Two-transistor aux
One-transistor aux (the 'second' transistor in that ckt is for over-current limiting, most all have it now- hence two-transistors)

The two-transistor ckt for the aux doesn't take anything away from the main supply, it just happens to be a half-bridge.

I already know... did you read the whole thread? I relized my screw-up and now only want to fix the 2 transistor circuit.

And enough already with your overly sensitive "racism" garbage. Grow up! Let's stop the world already! Someone "offended" somebody else on an internet forum- let's all jerk knees and go to war. I hope you realize how ridiculous this looks.

I dare you to call me a racist. I have problems with barry-o's commie policies. Would you exhibit the 'typical' response and shout, "He's black (which itself is debatable)- you no say nuttin," or would you agree that this 'wealth redistribution' (among other things) bullshit is an out-of-control train ready to derail?

Mockingbird's last post to you was not at all random.

You cited, "no hateful or racial remarks" from Da Rulez as a way of "keeping it going." He countered your 'read the rules' weak punch by calling you fat... A bit premature for you to consider it 'random'.

IB4TL, even though I shouldn't have even posted...

move it to another thread elsewhere... if you wanna play ball, then play ball on the right field.

[370forlife]

Re: Half-bridge fix

even though I shouldn't have even posted...

[everell]

Re: Half-bridge fix

Ok, thank you everell.

I hope I am around by then to start the thread. It seems to me now that I am about to be permanently banned from this forum for speaking my mind.

Shovenose is back. I don't think you have a thing to worry about. Let's take a walk from the VIP room where the flamethrowers are busy and walk across the hall to the Power supply design and troubleshooting room. There we can get into a technical thread....along with a few corny jokes!

Go ahead and start a thread describing what psu you have and post a few pictures of it. Then we can get into some serious discussion on 5vsb conversion.

[ratdude747]

Re: Half-bridge fix

everell, Mockingbird mentioned an idea in another thread I wish to ask regardign the PSU in question

could one replace the bad capacitor in the two transistor circuit with a high ESR poly and make it run that way, bypassing the cooked capacitor issue?

[c_hegge]

Re: Half-bridge fix

I'm sure half the 'killer 5vsb cap' problems are just the resut of using bad caps like fuhjyyu and that a panny or ruby in the same place would do fine, although in other cases it may well be because it's under too much stress.