Korad KA3005P Repair and Warning

[Terabyte2007]

Just finished the repair on my Korad KA3005P. Turned it on just a bit ago and set the output to 5V and enabled it and **poof**! My device I was powering smoked! The displayed voltage read 0.000 when turned on and 5.000V when turned off. Grabbed my DMM and checked the output, 19 Volts! WTF. When I enabled the output regardless of how I set the voltage it was 19 volts! Cracked it open, poked around a bit and found a cracked or cold solder joint on the output terminal PCB. There is a small red/black set of wires that presumably go back to the control PCB that monitor voltage at the terminals. Well, they were not sensing the voltage when the output was switched on and apparently when this happens the unit forces 19V on the output! Cleaned and re-soldered the connector and she works again! Beware of this, if for some reason the sense lines get disconnected or you have a bad connection the unit will source 19V upon enabling the output regardless of what you have set on the control panel.

Just an FYI...

[Andreas]

Perhaps it would be worth to spend a 100 Ohms resistor on the PCB between output and sense line. Just in case the sense line gets loose.

With best regards

Andreas

[HighVoltage]

After I watched this #315 episode of Dave's review in 2012, I knew I would never buy one of those Korad KA3005P

[Yansi]

Also note Dave's followup :-)

tps://www.youtube.com/watch?v=_HrvuHSywms


I have two of those supplies at home, both redone a little bit. I've got rid off those crap heatsink parodies, replaced them with a proper heatsink and also slowed the fan down a bit.

Now the supply does not overheat, it is not loud at all and the heatsinking  efficiency was improved by a good deal.

[Terabyte2007]

Yeah, I saw those videos before. Luckily, this is not my main power source, but a backup/utility PSU I use for testing motors, fans, and the occasional charging. Just happened to use it on a 5V circuit that had no OV protection and as Murphy would have it, Poof! I think I will add some additional protection and a few other mods could not hurt also.

[Yansi]

What type of transistors do you have in your supply? (That ones which had blown)

[Terabyte2007]

What type of transistors do you have in your supply? (That ones which had blown)

It wasn't the transistors internal to the supply, it was the 5V circuit I was testing. It appears the Korad has no shutdown protection nor does the OVP work if something happens to the set of sense wires that go from the input terminal PCB back to the control PCB. A cold solder joint, broken connector or wire and the output goes to a fixed 19V regardless of what you have set on your controls. So essentially, the 5V circuit I was testing went up in smoke because of this issue with the cracked solder joint on the terminal input PCB board. I will be adding some mods to add a bit of protection to the unit which should have been thought of by Korad.