| Electronics > Repair |
| DSO-X 3024A Power Supply defect |
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| georges80:
Well, another lineage power supply bit the dust (in my msox2024a). Same old story, blew the transistor (and fuse) and the main cap has gone from 100uF to around 5uF. Rather than try to repair, I followed the path of others and replaced with a Meanwell. In my case after a bunch of research/comparing, I went with an EPP-300-12 model. Mouser had it for $58. Bought some JST 4 pin females and pins to make the S+/S- and Power-on mate and then repurposed the existing AC plug to fit on 2 of the 3 pins (of the 5 pin connector) on the Meanwell. Cut the 3 GND and 3 +12V wires and crimped each set of 3 to a ring terminal. It's a tight fit, but will fit and all go back together nicely. The Power-on signal of the EPP-300 talks properly with the scope's front panel button so all functions nicely. Thanks to contributors of this thread to steer me down the right path to repair my scope. I did power it up with +12V from my powersupply first to verify nothing nasty had happened other than the crackle pop of the original powersupply. All was good so that was a relief and I knew I just need to replace the powersupply to be back in business. cheers, george. |
| salvagedcircuitry:
You definitely made the right choice! I just don't think it's worth the hassle of repairing and troubleshooting the lineage power supply anymore, as it is really not a good design. Suitable candidates I've come across so far: Meanwell RPSG-160-12 Meanwell RPS-300-12 Meanwell RPS-400-12 Meanwell EPP-300-12 Murata PQC250-12 Bel Power ABC201-1012G ... The original replacement unit I purchased, the Meanwell RPS-160-12, did not include the remote power-on option. I goofed and purchased the wrong version. The unit I meant to purchase was the Meanwell RPSG-160-12. What a difference one letter can make! The replacement power supply needs to have a remote sense and remote power-on feature as the power switch on the oscilloscope switches the secondary side of the power supply and not the primary side. Without the remote-on feature, the oscilloscope power button does nothing. Plugging the oscilloscope in would be the on/off button, which is not ideal. All these units seem pretty decent. I'm liking the fact that the Murata unit is higher efficiency and most importantly does not have a perpendicular daughter board, like the meanwells. This should make the murata unit easier to repair, but then again, none of these units should need any attention for a long time. It doesn't look like the murata has fine adjustment on Vout, so from the datasheet it can't be set to 13v which is the output voltage of the lineage PSU. The meanwells have Vout fine adjustment. The bel power has minimal adjustment. This may not be a deal breaker as these are all 12v class power supplies and the original lineage PSU only had a +-5% voltage adjustment range and poor voltage regulation. Glad to hear you got the msox2024a back up and running! |
| rolkinas:
After reading all this I took apart mine perfectly working DSO-X 2024A to check condition of smps. I use scope not that much and bought it used couple years ago. Cap measures ok: 107uF. But those baking resistors gets surprisingly hot. Precious preprogrammed obsolescence. It seems that psu might survive longer with scope being powered on and fan running. While resistors still heats while unit is powered off. It's not funny having components near 100C in device being in standby... Just curious if new SMPSs sold as spares by Keysight have such an issue? |
| salvagedcircuitry:
--- Quote from: rolkinas on December 03, 2020, 10:09:00 pm ---After reading all this I took apart mine perfectly working DSO-X 2024A to check condition of smps. I use scope not that much and bought it used couple years ago. Cap measures ok: 107uF. But those baking resistors gets surprisingly hot. Precious preprogrammed obsolescence. It seems that psu might survive longer with scope being powered on and fan running. While resistors still heats while unit is powered off. It's not funny having components near 100C in device being in standby... --- End quote --- This is excellent information. Thanks a bunch for adding the infrared images. Makes me want to pull the OEM PSU out of my other DSOx :scared: |
| Madmanguruman:
I'm liking the fact that the Murata unit is higher efficiency and most importantly does not have a perpendicular daughter board, like the meanwells. This should make the murata unit easier to repair, but then again, none of these units should need any attention for a long time. The Murata PQC250-12 works just fine with three DSOX3014As that I've repaired - the oldest repair has had close to 1 year of constant use with no issues so far. Like with other units, the wiring harness needs to be modified to make it work but it does offer remote sense as well as remote on/off (possibly with inverted logic, but the button will still work.) I must also admit that I'm biased - I work at the Murata power supply design center where the PQC250-12 was designed and qualified. :-DD |
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