Common cap voltages?

[large_ghostman]

I have some equipment for DNA sequencing and the PSU keeps going down, it was originally used in a lab with a isolated supply from some kind of huge offline unit (sort of like a large UPS). After fixing the PSU so many times I decided to take a bit of a deeper look, the main smoothing caps appear to be 220V.
What are the common voltages for caps in psu's that are mains powered?

I dont understand why the caps are 220V rated when the UK is higher? Is it likely the caps keep blowing because they are seeing a consistantly higher Voltage 220V? too make things worse how are the Voltages measured? By this I mean is 220V RMS? I am trying to figure if the caps are too low rated and if I should replace them. Its always the same 4 caps that go after 2-3 months, I have used decent brands and tried more than 1 brand. I havnt yet tried a higher rated cap

 

[4pyros]

LG, Smoothing caps to me are on the DC output side of the power supply.
Is this your case? and what is the output voltage?

 

[large_ghostman]

LG, Smoothing caps to me are on the DC output side of the power supply.
Is this your case? and what is the output voltage?

DOH DOH DOH

You are correct! How did this snippet of information not penetrate my brain?? I was utterly convinced I was right! I have been on this path for a week now and not once did the penny drop! How utterly stupid of me, the most NOOB of NOOB errors! Excuse me while I go hit myself around the head. So now I know that DC smoothing caps are on the erm DC side and sitting at 24V, I am back to square 1. I cannot believe I got caught out so easily! I read your reply and it slowly sunk in really painfully lol

 

[4pyros]

My best guess right off the top of my head is it may have a bad rectifyer and is sending to much ribble to the DC caps?

 

[large_ghostman]

My best guess right off the top of my head is it may have a bad rectifyer and is sending to much ribble to the DC caps?

I do not wish to talk about it

 

[KeepItSimpleStupid]

LG:

It may be a ripple problem. Not all caps are designed for filtering SMPS power supplies. Can you point to a datasheet of the caps that are in there? But first, lets find caps suitable.

If you can find a ONEAC power conditioner cheap, have at it. It's nothing but a transformer, but it does wonders. ebay has them at a fraction of the cost of a new one.

 

[KeepItSimpleStupid]

See: **broken link removed**

You may find smaller caps in parallel will be beneficial - see the article.

 

[large_ghostman]

LG:

It may be a ripple problem. Not all caps are designed for filtering SMPS power supplies. Can you point to a datasheet of the caps that are in there? But first, lets find caps suitable.

If you can find a ONEAC power conditioner cheap, have at it. It's nothing but a transformer, but it does wonders. ebay has them at a fraction of the cost of a new one.

They all seem to be 120V. I cant find a datasheet at the moment I will need to open it up again and check what caps I put in, no idea whats up with it as I checked on a scope and ripple was tiny. Having said that we do get spikes here that are pretty bad, I think its because we are literately surrounded by giant wind farms!

One day I will get off grid and have nice clean power (yeah yeah yeah)

 

[KeepItSimpleStupid]

It might be tine, but it's a high frequency. Some electrolytics are a little slow.

ZNR's across the caps will protect the caps. Post a pic. Spacing, radial, axial and max physical size. Ripple freq would help too and I'll what I can select.

 

[large_ghostman]

I will take it apart after school tomorrow as I am only in for the morning, I have most the day booked for my project but need to get this machine working so I can use it. I also need to finish the stupid Art project and get it handed in, my soldering station is playing up, sometimes it goes cold for no reason, maybe its a broken wire in the iron lead. I have spare elements if that is playing up, its the type you can change the bit. It started playing up after changing a tip.

 

[Mikebits]

I have some equipment for DNA sequencing and the PSU keeps going down, it was originally used in a lab with a isolated supply from some kind of huge offline unit (sort of like a large UPS). After fixing the PSU so many times I decided to take a bit of a deeper look, the main smoothing caps appear to be 220V.
What are the common voltages for caps in psu's that are mains powered?

I dont understand why the caps are 220V rated when the UK is higher? Is it likely the caps keep blowing because they are seeing a consistantly higher Voltage 220V? too make things worse how are the Voltages measured? By this I mean is 220V RMS? I am trying to figure if the caps are too low rated and if I should replace them. Its always the same 4 caps that go after 2-3 months, I have used decent brands and tried more than 1 brand. I havnt yet tried a higher rated cap

Is that for some Gel electrophoresis setup? It has been awhile since I did that in school. I can't remember, what kinda current runs through the buffer? Is it possible you just have a poorly made power supply? Do you have the model number for the supply?

 

[large_ghostman]

Is that for some Gel electrophoresis setup? It has been awhile since I did that in school. I can't remember, what kinda current runs through the buffer? Is it possible you just have a poorly made power supply? Do you have the model number for the supply?

Its a won hung low! Its a similar machine to this one (not exact model but they are almost identical) https://1.bp.blogspot.com/-JukQ360in2c/T7ncBnp3gZI/AAAAAAAAAds/Cs2hKemJaU0/s1600/seq1.png

I think you know who was correct and the rectifier is leaking like a bucket with no bottom in.

And yes its a real PITA to get to the power board!! So far only 6 screws left over and 2 plastic thingies from somewhere deep inside that I think they just put in to make it rattle a bit

 

[strantor]

The thought of you playing with DNA scares me a bit.

 

[large_ghostman]

The thought of you playing with DNA scares me a bit.

Then I wont tell you what the bacterium is . If its any consolation my mum shares your concerns.