M422, no power light

[richdell]

I unplugged my working heater last spring. I just plugged it in and nothing happen, no lights, nothing. I took the covers off, found power getting to the circuit board and the transformer is warm. What can I do now?
Thanks in advance

[HayZee518]

check the motherboard fuses. replace them with the exact amperages.

[richdell]

I pulled and checked the 2 amp & 10 amp fuses, and they are good. Still no lights

[38Super]

I'm just lurking in the background to see what answers you get. I tried to turn my 441 on about 15 minutes ago and get nothing. My garage took a lightning strike this past summer, so I'll go looking for the fuses you mentioned and see what they look like.

[richdell]

Have you found out anything yet? Nobody seems to have any ideas, other then fuses. My heater was unplugged all summer, so it's a bigger mystery. I have tracked down someone who does service, so I may have to "bite the bullet" and get help. Good luck.

[38Super]

It looks like I got away easy. My 10A fuse was fine - the 2A fuse was blown. A new fuse and I'm back in business. This is the first time I've ever even removed the grille, so I'm afraid I have no suggestions for you.

[adnadeau]

If you have a multimeter, you could check the DC voltages on the circuit board. Connect the negative lead to point EP and check the +5 and +12 test points for voltage. If one or both of those is bad, then you can try to troubleshoot further, buy a new board on E-Bay or from a dealer, or send the board out for repair. There is a link somewhere on this forum to an outfit that claims to repair them.
The lightning strike could have destroyed a whole lot of stuff; just plugging it back in after a summer of inactivity is another issue.

[richdell]

Thanks for the information. I checked the voltages and got 2.04 at the 5v point and 13.8 at the 12v point. Oddly, (I think) it makes no difference if the power switch is off or on.

[adnadeau]

The circuit board is hot all the time as long as the AC cord is plugged in. The ON/OFF switch just activates some of the circuitry. The 12V reading is okay; the 2 volts instead of 5 volts is not; there's a short somewhere. Visually check the big electrolytic capacitors to the right of the transformer. Look for any deformation on the top and for any kind of crud underneath them. One may have gone bad when the board was unplugged. You can remove parts downstream from the 5V supply to try to isolate the short. Also, Mathis electronics fixes Monitor circuit boards for $100 according to their web site.

[richdell]

I have contacted Mathis Electronics and will send the board to them tomorrow.
I'll post back here when the board is fixed, wish me luck!

Thanks much for your help