Be aware: Yihua YH-305D bench PSU

[razvitm]

schematic of a 305D ... any mod suggestions?

i have a power source just like this one, but i don't know where the wires from the knobs go. 2 voltage and 2 current knobes. where do i connect them? can someone please draw the wires on the schematic please?

[LEDAero]

Honestly not sure if it was from the drop or not...

It was.

[alex27riva]

Since the volts reading is stable it suggests the output current is also stable but the meter is faulted, likely the IC itself in the module.

To confirm this, attach a good ammeter to the output and adjust the current.  You should see the good ammeter read linearly as you adjust up and down while the PSU ammeter reads all over the place.  Short circuit the output, and the CC LED should light, a final note that the current module is working by testing the short circuit protection.

If the above works, then its easiest to replace the ammeter module rather than repairing it.

Hi, how can i fix this problem?

Same problem again, maybe the cold weather?

[Shock]

As mentioned an intermittent/dry solder joint or problematic connector. Capacitors failing with high ESR can be the cause of cold failures as the colder they are the higher the ESR.

[bob808]

I have the Zhaoxin RXN-305D variant.
Has anyone added a sense wire circuit into these power supplies?

[bitseeker]

bob808, can you attach some more pics of the PCBs at higher resolution?

[GigaJoe]

Wonderful ..... 30 VAC ( 5 ??) between ground and a negative or positive output, regardless PS on or off ... Just fry my circuit, detached just a positive and left a negative wire, touch by soldering tip  (it grounded) .... oops ... 

[GigaJoe]

Finally, look inside,  The problem with 30V AC on output , was due to power switch disconnect a ground wire, not a hot wire , so the hot wire over transformer and so induced that 30V on output. Changing wire on power socket solved it ...

[bitseeker]

Wow, that was a nasty one. Good thing you found and fixed the source.

[minicowman]

You showed the better part of a schematic for one of the Chinese power supplies (305D).. Some of it was cut off.  Just wondering if I could get a look at the rest of the schematic. Or, if there is more documentation on this.. What you had posted is the most I had found on these to date.  Thanks.

[henryinsydney]

Thanks a lot for the schematics! This is really close to my WEP 305D if not the same board. I was about to reverse engineer it but there are about 80 components on the board (single sided, though), still an onerous job.
Mine just stopped putting out any voltage/current and even said so on the LEDs.. no matter what the dials were set to.