Power supply blowing fuses in Zebra 2746e thermal printer.

[Toasty]

Re: Power supply blowing fuses in Zebra 2746e thermal printer.

Excellent!

Take some notes of voltage readings when you can, to compare against if you have another problem. Please post them here to help others.

So, it did need to be connected to printer in order to work. Perhaps you can figure out what was connected (jumpered) so you can run it on the bench in stand-alone mode.

Cheers!

Toast

[lucky13]

Re: Power supply blowing fuses in Zebra 2746e thermal printer.

torin3 sure has a lot of determination!

Congrats on job well done.

[Gianni]

Re: Power supply blowing fuses in Zebra 2746e thermal printer.

@ torin3: I'm glad you succeeded, you have earned experience and this thread can be useful for other people. Very nice job

@ Toasty: about your posts number 41 and 44 I had posted number 13 . I'm really curios to know how this PSU starts because usually the controller is on primary side starting from mains through resistor or auxiliary PSU or self-power.
In this PSU i don't think T2 is feeding TL494, it is connected to Q3 and Q4 to drive the power transistor.
D23-D24-C26 are connected to the big transformer so they can feed TL494 only if TL494 is driving the power transistor.

I have a doubt about IC3, the triac: if I'm not wrong it is connected to the toroid placed between input bridge and a red ceramic cap C10. In post 24 I wrote "So IC3 it is a triac, probably it is part of a crowbar to blow the input fuse for input overvoltage protection" but now looking better at the tracks I think I was wrong: it is possible it is part of start up circuit but I can't follow tracks and component connection to understand how it can work.
It would be interesting to remove it (IC3) and check if the PSU can start, if IC3 is only part of the input crowbar it does not block the PSU if removed.

Ciao
Gianni

[torin3]

Re: Power supply blowing fuses in Zebra 2746e thermal printer.

Well, unfortunately, I'm not going to be able to touch it for a while. I got transferred from IT to the shop floor in the hand-op department (where I've been helping out part-time for a few months). I'm not supposed to do any computer related stuff until further notice. Should only be temporary. Business is picking up, but they don't want to bring people back just yet until they are sure they can support them. But they need more hands than they have, and I'm 'movable'.

[lightninguk]

Re: Power supply blowing fuses in Zebra 2746e thermal printer.

Hello all

I'm new to this site . I also have a problem with the same power supply board. The fuse has blown. I have found 2 components burnt out. Can't read any information from them, they are toast. . They are sited next to the QC Capacitor. Any body know what the comonents are on MOV1 & MOV 2 ??

Many thanks

Steve

[lightninguk]

Re: Power supply blowing fuses in Zebra 2746e thermal printer.

Hello again

I've found out a little more information. I think there Metal Oxide Varisters.

Can just about make out.

V07K
140

Regards

Steve

[Toasty]

Re: Power supply blowing fuses in Zebra 2746e thermal printer.

Here's the datasheet. Google is your friend.

[lightninguk]

Re: Power supply blowing fuses in Zebra 2746e thermal printer.

Many thanks

Steve

[sebr]

Re: Power supply blowing fuses in Zebra 2746e thermal printer.

I also got a dead printer with this PSU on my desk. After checking the suspicious components I could not find any fault. So resoldering the whole PSU did the job.
But I am thinking of replacing both primary caps in advance. This seems to be arare case where promary caps fail sooner than any other caps on this board. At least the blown components lead me to this conclusion, or?