Electronics > Repair

DC Power Supply TM5020E

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Sello:
Hi Kindly help I have a problem with my power supply doesn't show on the screen no output voltage also the fan does not run the board does not show anything burnt the components seems to be fine no shows to blown but i do not receive any voltage on the output can i get some advice on how to go about finding the fault or what may be the fault causing the power supply not to have an output.

_rushin_or_draggin_:
The simplest thing to check first would be the fuse. There might be one where the cable plugs in at the back. If not, it should be somewhere inside (but I am betting on the plug). Since so many things seems to not be working, that typically points to a single failure point. Also, check to see if you're getting voltage to and from the regulators. The fan is most likely connected directly to one of the regulators. It looks like maybe 4 are mounted on the heatsink.

Update with your findings and we'll see where that leads us!

Sello:
I have checked the fuse is working fine also i get voltage from the regulators but on the transformer the secondary side i get a very small voltage

Swake:
The displays are coming on and read 0 volt, do I understand that correctly?

There is what I think is a klixon on the heatsink (see pic). It is a thermal fuse that resets itself. It should only switch when the temperature is higher than specified, but these sometimes stop working entirely. Could you check the type (read what is written on it) and measure if it is open of closed?

Power supplies in the same form factor and case are very common and have been made in many versions for many brands including Farnell. If someone could share a schematic of a similar unit that would be very helpful.

Warning: This is a switched mode power supply. Be very careful poking around in it as there are lethal voltages in that thing a bit everywhere.

Andy Watson:

--- Quote from: Swake on December 23, 2024, 01:27:42 pm --- If someone could share a schematic of a similar unit that would be very helpful.

--- End quote ---
Appears to be a re-badged Mastech. See first few replies of this post:
https://www.eevblog.com/forum/repair/mastech-hy5020e-50v-20a-bench-supply-economical-to-repair/

Or perhaps the OP could post the circuit that he has on his laptop!

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