Products > Test Equipment

Inside the new Korad KA3305P linear PSU

<< < (29/34) > >>

Scottjd:
I have 2 of these, one has a low power and barely spinning fannthat turns in after it powers up about 1 minute(but output power is off).
The other, the fan stays off until I use the output and have a load on it, as it heats up the fan spins, depending on the temperature regulates how fast the fan spins. The difference between the units could be the locations of the sensor for the temp, or even how much thermal compound is applied?
Or maybe it’s a calibration thing, and at what room temp it was calibrated at?
It could also be some fans start to spin with less current then others, but both units might be putting out the same starting up current and voltage? Or one fan has slightly smother bearing then the other?

Yes, it is some PWN depending on the temp of the unit under load that speeds the fan up. I think the cap might give it that extra lush to keep it in a low spin on the cold start. But this might also depend on how stable the temp of room/house is?

I don’t recall seeing any variable resistor to adjust this for the fan.

I would try this with my units, but they are lacked and ready to move. Also even when I get my new place and the lab unpacked I might not have both of them anymore. I’m working with some local schools to give away some of the extra stuff I don’t need like 3 Korda PSU, and q Rigol DP832. I think I can afford to give up 2 of the Korads and put them to good use with the high schools engineering class or robotics club.
Also less stuff I need to move, or out in storage until I buy a new place.
Scott

willumpie82:
I just received my Korad KA3305P (unfortunately received a Tenma rebrand with "safety" binding posts instead of screw terminals)
It seems that they still install the factory broken fans, although PWM controlled it makes an annoying rateling noise. Like it should I took it apart before turning it on, All the wiring was nicely tucked and secured but found the mains switch kinda loose (screws not completely fastened) I removed the handle to make it stack better with my other equipment, with it's 10ish kg it is not so portable after all.

willumpie82:
I wanted to fix that fan buzzing, but apperantly it is not caused directly by the fan, the PWM control makes the fan hummm. I installed a new-ish fan and the problem retains. When I was at it I also took the effort of cleaning up the heat compound mess it came with.

there are ceramic isolators between the powertrannies and the heatsink, because of the fan retaining method used you have to disassemble the complete heatsink because a big cap is in the way of one of the screws. the fan itself has to be modified to fit in the slot of the heatsink.

below some pitures I took in the process

Scottjd:
The only way to get the fan to stop under normal powered on and no load would be to use a fan that spends easier, and used less power. It’s the fan trying to spin at the minimum powers being delivered and not enough to get it started. Or maybe if the room was slightly colder with the ambient temperature it could be at a stop. When the fan stutters, if you spin it a little it will probably maintain a slow speed.
I didn’t realize you were going to replace the fan or I would have mentioned that before.

On some of the units you can adjust the output power of the contact on 5V rail in the back left (or right) corner with a variable resistor. You can measure the output from the posts with a load and inline meter, then turn it down a little if you dint use this 5 volt rail. Or maybe turn it down so you can still use it, but instead of it delivering 3 amps you might only get 2 Amps.
By turning this down it doesn’t work as hard or heat up as much with a 5 volt rail that is constantly on and not being used. This should allow the idle temperature to be lower, and as a result the thermal triggered fan PWN will put out less hopefully resulting in the fan not trying to start getting in the stutter.
So if you don’t use the 5 volt rail, this could be an option for you?
Hope this helps,
Scott

Pnoxi:
Power supply Tenma 72-2630 (Korad KA3303D ?) at a good price! 95.92€ + VAT

https://sk.farnell.com/tenma/72-2630/power-supply-bench-0-30v-5v/dp/2478798

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod