Home Forums General Discussion Technical Questions Siemans Class 72 logic board.- Repair

I'm getting tire of sending these off to repair. Anyone have any documentation or walk through on how to repair these?

Its the same component every time.

Siemans Class 72 soft start Logic board.



Any infomation you can provice would be greatly apreciated. Looking for required parts and or other components.

look on earlier post. this is very common. the resistor is 22 ohm i believe. definitely needs resistor, capacitor is negotiable. we take ours to ECI and he charges $100 ea. we take boxes over there

just cut the blown capacitor out, i usually just scrape the board with a knife between the capacitor to clear the short, then replace the r58 resistor with same type, and your good to go. done many of them, with no problems cost 2 bucks for the resistor. i have probably repaired at least 20-30 this way and have never had a problem with the control board. the hard part is getting the rubber gooey stuff out of the way from the capacitor, i usually get a heat gun and heat it up and pull it out of the way so you can get to the capacitor. c46 is the capacitor looks like a small filter capacitor for the power supply

Well for one thing it looks like a very poorly designed circuit. It appears to be a full wave bridge rectifier circuit that has poor protection. Increase the PIV (Positive Inverse Voltage) of whatever the rectifiers are rated at. Add MOV protection to the DC and the AC. If there is any room to mount a commercial full wave bridge to metal for heat sink and solder wires on board to run to the commercial bridge. MOV's can be installed on the externally mounted bridge if possible. Make the MOV's 100 volts higher then working voltages. Inductive kick from inductive sources may be blowing rectifiers. As an example an OTIS 6164BP relay puts out 16,000 volts of inductive kick for a couple nano-seconds. This will eventually rupture silicon rectifiers and cause failure without MOV protection. (Metal Oxide Varister)

R58 20ohm 5 watt Resistor
C46 .033 MICRO FARAD 400v Capacitor

I used a company called http://www.sourceresearch.com/ Mark was my sales guy and helped me track these items down.
I'll post the part numbers tomorrow. Wanted to install on before giving part numbers.