Looking for advice on an Ultra 550 high voltage and other mods

[LDSisHere]

I have been going through my power supplies to see if they have problems since I have seen what happens if you wait until something pops. I remembered this Ultra 550 (ULT-X2550P) supply that I had in an old case. I pulled it out and found a main cap bloated. I also found the strangest arrangement of capacitors. You have to look at the pictures but they stacked two caps in the same space. The top cap has heatshrink on the legs of the cap.

I have already replaced ALL the capacitors and it all seems to work, the voltage is within ATX specifications but on the high side. The main chip is a KA7500 if that matters. Does anyone know if this can be adjusted and how to go about it? Also I would like to do the 5VSB OVP mod to this supply if it is applicable, can anyone tell me if this is the type of supply that needs this done?

12V = 12.01V
5V = 5.19V
3.3V = 3.39V

I really like this supply, so any input on improving it would be appreciated. I have already added a resistor across the thermosistor to increase the fan speed.

Thanks for your time,
Lloyd

[tom66]

Re: Looking for advice on an Ultra 550 high voltage and other mods

Your PSU will rarely have precision regulated outputs. It is completely normal for the outputs to be a little different from the ratings. 12V, 5V and 3.3V have a +/-5% tolerance. That means:

11.4V - 12.6V for 12V line
4.75V - 5.25V for 5V line
3.14V - 3.47V for 3.3V line

are all acceptable voltages.

[goodpsusearch]

Re: Looking for advice on an Ultra 550 high voltage and other mods

This seems capable of doing its rated Watts. Could you make a list of the original capacitors (maker, series, uF) and the ones you used to replace them?

The values you get are ok.

[LDSisHere]

Re: Looking for advice on an Ultra 550 high voltage and other mods

Your PSU will rarely have precision regulated outputs. It is completely normal for the outputs to be a little different from the ratings. 12V, 5V and 3.3V have a +/-5% tolerance. That means:

11.4V - 12.6V for 12V line
4.75V - 5.25V for 5V line
3.14V - 3.47V for 3.3V line

are all acceptable voltages.

I had looked up the specs already, I knew it was within them but I would much prefer it closer to center if it was just the matter of adjusting or minor modding. I however did not realize that most supplies did not have precision output. The Antec I just finished rebuilding was almost spot on on its' positive output and these supplies share the same PWM chip the KA7500. My knowledge on power supplies is very limited but I am trying to improve it so I very much appreciate your input.

I was only running this under a light resistive load so the values may change under a real load. I am waiting to see if I need to do anything else to it before reassembly and real testing.

I have included an image of the capacitor values I used and a spreadsheet. It could be my choices here are a problem as I have just recently came to understand their importance but I am again limited by my knowledge.

[everell]

Re: Looking for advice on an Ultra 550 high voltage and other mods

Also I would like to do the 5VSB OVP mod to this supply if it is applicable, can anyone tell me if this is the type of supply that needs this done?

I have a Ultra LS500 that blew up the 5vsb two transistor circuit. I tried to repair it, and it blew out again. They are so tricky to fix when they blow! So I added a Viper 22A circuit to replace the two transistor circuit. The old saying, if it ain't broke, don't fix it might apply in your case, but here are the schematics of what I did.

[LDSisHere]

Re: Looking for advice on an Ultra 550 high voltage and other mods

Thanks, that information is exactly what I was hoping to get. I will try and determine how well mine matches the schematics, maybe they are close. I did not want to take the time for this on my other supply as I considered it a complete experiment that would never live again. This supply may be my best one overall, I have just recently started to learn the importance of good supplies and how badly some of them are made so I wanted to fix this one before it blew up. I also want to take the time to do it as best I can as I will be using it on my best machine shortly.

Do you use the Viper 22A in most of your 5VSB projects? I want to figure out if I may should order a few extra for future usage or not.

I am sure I am going to have a few questions about this after I have a chance to look at the supply and compare it.

Thanks,
Lloyd

[momaka]

Re: Looking for advice on an Ultra 550 high voltage and other mods

I have included an image of the capacitor values I used and a spreadsheet. It could be my choices here are a problem as I have just recently came to understand their importance but I am again limited by my knowledge.

The cap choices you made are good.

As for adjusting the output... there may be a potentiometer for that, but it could also be used for OCP or OPP, so you will have to trace the circuit to make sure it's for adjusting the voltage. If not, post #5 in this thread shows how to mod a half-bridge PSU like yours.
https://www.badcaps.net/forum/showthread.php?t=22129
I think the only difference between your KA7500 controller and the TL494 is the pinouts.

But most importantly: this is a group-regulated power supply (i.e. the 12V, 5V, and 3.3V rails are all regulated together). If you lower the voltage on one of these rails, the voltage on the other rails will fall proportionately. So it may not be possible to adjust the voltages to exactly the way you'd like them to be.

IMO you should try the power supply first with a load (an old P4 motherboard would be good) and if the voltages are still too high for your tastes, then adjust. But again, IMO, your voltages are pretty good. If anything, the 5VSB is the most important. Make sure it is well within spec.

[LDSisHere]

Re: Looking for advice on an Ultra 550 high voltage and other mods

I have a Ultra LS500 that blew up the 5vsb two transistor circuit. I tried to repair it, and it blew out again. They are so tricky to fix when they blow! So I added a Viper 22A circuit to replace the two transistor circuit. The old saying, if it ain't broke, don't fix it might apply in your case, but here are the schematics of what I did.

I am still trying to compare the 5VSB circuit on my supply with what you found on the LS500 but it is not an easy task to say the least. Trying to figure out the component layout in relation to the traces is tedious and frustrating. I am just glad this power supply does not have any SMD.

The cap choices you made are good.

Thanks for confirming this, I was concerned this may have been a problem.

IMO you should try the power supply first with a load (an old P4 motherboard would be good) and if the voltages are still too high for your tastes, then adjust. But again, IMO, your voltages are pretty good. If anything, the 5VSB is the most important. Make sure it is well within spec.

I was thinking that the voltage may sag some under a real load and bring the numbers down closer to the middle of the ATX specification but I have not had a chance to try it yet. I am not going to make any voltage adjustments until after I use it on a real load. The 5VSB is almost perfect, but I still may do the mod suggested by Everell for this circuit just for the experience.

But most importantly: this is a group-regulated power supply (i.e. the 12V, 5V, and 3.3V rails are all regulated together). If you lower the voltage on one of these rails, the voltage on the other rails will fall proportionately. So it may not be possible to adjust the voltages to exactly the way you'd like them to be.

I was wondering how the 12V OVP board played into this regulation? (attached picture) Is 12V regulated separately or is it just monitored closer? The only potentiometers that I saw in this supply are on the 12V OVP board that you see in the picture. Power supplies are way more complex than I ever gave them credit for in the past.

Thanks for taking the time to assist me in endeavor,

Lloyd

[Logistics]

Re: Looking for advice on an Ultra 550 high voltage and other mods

A cousin of mine recently, gave my parents a system containing one of these supplies. I can't get past how the inductors are pressed right up against the heatsinks, and the caps raised up off the PCB because they can't fit otherwise. Blech! It has a few of the medium sized caps beginning to blow on the secondary side so I'm just gonna look for something else. Just seems like a bad design layout.

[brethin]

Re: Looking for advice on an Ultra 550 high voltage and other mods

A cousin of mine recently, gave my parents a system containing one of these supplies. I can't get past how the inductors are pressed right up against the heatsinks, and the caps raised up off the PCB because they can't fit otherwise. Blech! It has a few of the medium sized caps beginning to blow on the secondary side so I'm just gonna look for something else. Just seems like a bad design layout.

Nice I love when people revive 6+ year old threads from the dead!

[momaka]

Re: Looking for advice on an Ultra 550 high voltage and other mods

Nice I love when people revive 6+ year old threads from the dead!

Eh... if the post is relevant, I don't see why not.
In this case, I have to agree with Logistics that these Ultra PSUs, which appear to be based on an outdated YoungYear half-bridge design with terrible layout, are indeed hardly worth fixing/upgrading.

[everell]

Re: Looking for advice on an Ultra 550 high voltage and other mods

I think reviving old threads is great....a great review of some of the things we have done in the past. What I think is not great is tossing some of these grand old power supplies which are fantastic tools for learning. I guess what I am saying is that I don't know it all....yet!