Keysight DSO-X 2004A dead

[Campus]

Hi,

my Keysight was in storage for about a year and now I wanted to start using it again but it's completely dead  . No life sign whatsoever. Does it make sense to investigate this further or is this just too old to have any chance of being successful (especially for me without any power supply experience)?

Kind Regards

[Pinkus]

Does the fan of the power supply start up (will be audible) and does any LED light up?

[Campus]

Nothing, no fan no led, as if no power cable is connected.

[mikeselectricstuff]

Likely to be an easy fix if it's the power supply. Most common fault on SMPSUs is startup supply cap - look for a small low-voltage electrolytic on the mains side of the supply and replace it.
 

[HighVoltage]

Yes, most likely the power supply.

I had a different Keysight scope with a bad power supply and it turned out to be an overheated and open power resistor.

You can power the scope with a lab power supply, to see if the rest of the scope is working.

[Campus]

The caps look fine to me but I found a badly burned resistor (?) on the back:

[Campus]

Yes, most likely the power supply.

I had a different Keysight scope with a bad power supply and it turned out to be an overheated and open power resistor.

You can power the scope with a lab power supply, to see if the rest of the scope is working.

Can you point me to a post where to connect it to a lab power supply? The mainboard seems to have quite a lot of connections to the power supply and I couldn't find any repair manual so far.

[HighVoltage]

Go to 10:00 in this video:

[HighVoltage]

The mainboard seems to have quite a lot of connections to the power supply and I couldn't find any repair manual so far.

It is a simple 2 wire hookup with a 12V power supply as you can see in the video above.

Just make sure to connect the polarity correctly!!!!

[Campus]

I have now successfully tested the device with just a plain 12V connection to the line board. 

Looks like the MOSFET mentioned in the video is also damaged in my case although it looks like new. The drain connected resistor is so damaged that I can not even recognize the print anymore. In my case it was colored in blue. Any idea what I need to be aware of when getting a replacement for this kind of resistor?

[Bud]

Mosfets get damaged by storing the equipment in closet? 
Moisture ingression perhaps?

[Campus]

I am confused about this as well. It was definitely working when I put the device into the original box and it was stored in a heated/dry office environment. It also made no sound when I tried to run it yesterday so I am a bit clueless what happened.

[kripton2035]

main capacitor went dry during storage. at first power up, it caused inrush current that burned fuse, resistor and mosfet (and may be diode too)

[Campus]

Thanks for the explanation. I will try to find replacements for these parts to replace them. I am still a bit puzzled why the cap looks perfectly fine and does not have slightest bulge or fluid around it. I also measured it to still have 85um capacity with my DMM.

[kripton2035]

you must also measure the esr of the cap. a big cap can have too high esr and not bulging at all.


it can also be another cap on the board that went high esr and made the current go too high in certain parts of the circuit.
measuring the esr of all polarized caps on the board could be a good thing.

[CapLeaker]

I ran into the same problem with my Agilent DSO-X 2012. I wrote about it in badcaps here: https://www.badcaps.net/forum/showthread.php?t=97854
I even was able to come up with who made that PSU. It’s not made by Agilent. All it took to repair  was a mini fuse and a new main filter cap that I got out of my parts bin.

[Campus]

I inspected the power supply under the microscope and several regions look quite bad. Even the metal housing of the supply has some burned areas. I am a bit afraid that I am not competent enough to measure all the components to make a good and solid (long-term) fix. So I will go for one of the available replacement power supplies which are mentioned in another thread for the same kind of issue on similar devices.

[CapLeaker]

Check the pads of the main filter cap for a short. Take the 420V main filter cap out and measure it’s pads to see if there is still a short, if you don’t see any check the output for a short. Stick temporary a 420V 100 something uF in, replace the mini fuse and try it.
Look at the bright side… I mean you can’t break stuff that’s already broken. I was kind of surprised to find that the actual PSU isn't made by Agilent at all. The only problem might be to find the correct size cap.
In the other thread I posted the pdf for the replacement PSU. See it as a cheap learning opportunity.
Btw… my scope is still working fine with the parts out of the junk bin.

[Campus]

Good idea I will try to fix it just to learn a bit more how to do these kind of things. Thanks for the positive input.

[HighVoltage]

In the other thread I posted the pdf for the replacement PSU.

Please post the PDF here as well, since I can not look at it without an account there.

[kripton2035]

In the other thread I posted the pdf for the replacement PSU.

[voltsandjolts]

Hmm, note self: never design-in Cherokee International (China) Power Supply Ltd.

[CapLeaker]

In the other thread I posted the pdf for the replacement PSU.

I've been over there for many years now, been lurking here for many years too, but never had made an account until the other day. Kripton2035 already copied the pdf here, thanks bud!
I did notice that for some reason on 10 year old Agilent Oscilloscopes, the PSU goes poof.  Just a shame to throw the whole thing out, because of a $1 cap and 50 cent fuse. I had bought some licenses for extra features on my scope. Agilent charged me a lot more than $1.50! Only to find out at the end that they are cost cutting by putting general available 3rd party PSU's in there. Made me think twice after that.

[wraper]

I've been over there for many years now, been lurking here for many years too, but never had made an account until the other day. Kripton2035 already copied the pdf here, thanks bud!
I did notice that for some reason on 10 year old Agilent Oscilloscopes, the PSU goes poof.  Just a shame to throw the whole thing out, because of a $1 cap and 50 cent fuse. I had bought some licenses for extra features on my scope. Agilent charged me a lot more than $1.50! Only to find out at the end that they are cost cutting by putting general available 3rd party PSU's in there. Made me think twice after that.

What makes you think that custom made PSU would necessarily be any better? Also by it's looks its a decent PSU with good components used.

Agilent charged me a lot more than $1.50!

Do you expect them fixing 10 yo oscilloscope for $1.5? Not to say nothing prevents you changing those parts yourself. Nor Keysight will repair that PSU, they will simply change it.

[HighVoltage]

I did notice that for some reason on 10 year old Agilent Oscilloscopes, the PSU goes poof.  Just a shame to throw the whole thing out, because of a $1 cap and 50 cent fuse.

Actually this is how some of us get 10 year old scopes cheap and fix them easily.