My Weller WES51 has served me nicely however it just started to act up. It works for a bit then quits. The board has several test points on it but I can't seem to find a schematic or service manual for this device to trouble shoot it properly.

So far I've - Tested all points to satisfaction as per the owners manual (required resistances etc.), taken the iron apart and checked for loose/broken wires, tested the transformer output at 24V and confirmed a steady 5V voltage regulator output on the board. If I disconnect the iron and test the output pins for the required 24V I get a fluctuating voltage which I would presume is temp regulation at work but the darn thing won't heat up. Would a bad tip cause this effect? It's a weekend and I can't get a new tip until Monday.

I'd hate to scrap it without a fight.

 

Try something simple, like replacing the heater element. That is the part that suffers the most thermal stress and might easily become intermittent.

 

Thanks for the input I'll be doing that but I'm thinking something else is going on here. I get no reaction out of the unit at all now and the voltage regulator isn't putting anything out. Ordered a Hakko FX-888D this morning. I hear good things about it ... If I ignore the funky look and no auto shutoff feature. Soon as I find time I'll dive into this some more.

 

check the resistance of the heater, by unpluging the iron from the base unit and probing at the plug, it will be a 4 pin terminal,one pair is the element and the other pair is the thermocouple.

 

I've checked all the pins as per the manual and got the proper values. I went out and bought a Hakko 888D. I'll need it to repair this one anyway. I promptly messed up the temperature settings and now have to re calibrate the Hakko. Oh well, I wanted a tip thermometer anyway. Not my week.