wfco power converter 8855 in camper

[tonytiger]

hi,im trying to fix my converter unit that has no 12vdc or 120vac
when i plug 120vac on it directly,there is no 12vdc coming out and vise vesa....
now i check most all fuses,resistors,capacitors,ect... the thing i notice i have no voltage on my 2 big capacitors on the 120vac....there is no diagram for this board on net that i could find.all help or info would be appreciated.

[budm]

Re: wfco power converter 8855 in camper

Is there remote on/off control to turn the unit on/off?

[R_J]

Re: wfco power converter 8855 in camper

You have the bridge rectifier disconnected, that's why you don't have any DC on the main filters, I don't see it mounted to the heatsink, once you connect it, if you still don't have dc on the main caps, your fuse is open.
From the specs, WF-8855E converter/charger, this is just a 120 volt input to 12 volt output converter, not the other way around

[budm]

Re: wfco power converter 8855 in camper

Looking at the board layout, RJ is correct about the bridge rectifier is not shown not connected; the two White wires should go to the two ~ pins of the bridge, the Red wire should go to the + of the bridge and Black wire should go to the - of the bridge.

[stj]

Re: wfco power converter 8855 in camper

resolder and check those cooking resistors too.
and once it works, shift the fan sideways to blow across the heatsink more.

[R_J]

Re: wfco power converter 8855 in camper

The bridge should be mounted to the heatsink, If I had to pick a cap to replace I would start with the one next to the 2 large ceramic resistors

[budm]

Re: wfco power converter 8855 in camper

So someone else worked on this unit and removed the bridge rectifier?

[tonytiger]

Re: wfco power converter 8855 in camper

hi guys sorry for delay,i received my bridge retifier today and installed it...but now i have 3.1 vdc when plug in(ac)and when i disconect my ac power i have 14.3vdc for a brift moment,any ideal what i could check next.thank you.

[R_J]

Re: wfco power converter 8855 in camper

What do you have for a load on the 12 volt side? I believe it should operate without a load and output around 13 volts. What happened to the original bridge rectifier?
How did you check the small electrolytic capacitors? did you check ther value with a cap meter or there esr with a esr meter?
I only see one small electrolytic on the 12 volt output side.

[tonytiger]

Re: wfco power converter 8855 in camper

i put a 12 volt car battery as a load and before i tested voltage on car battery and it was 12.80 and want i connected ac power there is still 12.80 vdc no climing up...the 2 big ceramic resistor do comme hot,fan not turning on,and the big heat sink don't even warm up,stay cold.the client brought me this unit as is,even him don't remember why these wires where loose.and i did check the cap by taking them out and tested with a meter,they where less than 5 to 10% off the normal rate.and yes only one cap on 12vdc side....but i will re-do a second check in case i missed something.and thanks r.j for the pin out help you giving me,i really did not do much of this unit so i will take all the help i can.

[R_J]

Re: wfco power converter 8855 in camper

What is connected to CN2? I see that U5 is a 12C508a 8 bit microcontroller, I will guess that U6 is a 5 volt regulator ic to supply U5. Check it's voltage

[tonytiger]

Re: wfco power converter 8855 in camper

hi sorry this projet is taking me time since i don't work on it very much.but R_J i have no ideal of what was connected on cn2(client just brought it like that)i was hoping it would be a switch or something like that since i do not have voltage on u5 so i will be checking u6 tonight but don't have much hope....thanks for the help.i will take anything to finish this job.

[R_J]

Re: wfco power converter 8855 in camper

It looks like the +12 output, connects to R48 which should be the input to the U6 regulator, It shoud have +5v on its output to operate the feedback circuit.
I am guessing CN2 goes to a a status indicator somewhere, indicating the output voltage/charge status

[shadetreetrader11]

Re: wfco power converter 8855 in camper

Anyone know what transistor u6 is? It's right by the 12v output lead.

[R_J]

Re: wfco power converter 8855 in camper

It is a KA431AZ reference ic