Replacing the power supply on my electronic Furnace Air Cleaner

My electronic air filter went out. I think I can fix it myself, but I thought I’d check in here to see if there’s anything I haven’t thought of.

I have the Honeywell F50F 1073. I’ve narrowed it to the power supply board. On this better picture, the white card that says “Bel-Aire” is burnt in the upper left corner, and the solder pad is detached. The yellow nearby capacitor is scorched also.

OK, first off, what is that white card? It seems like it has to have that size, but why? Is it just an inductor? Is it a fuse of some kind?

The board is mounted with a few screws and some wire connecters, so swapping it out seems pretty easy. My existing board is model # 208045 B where the “B” is hand written. This seems to be just an earlier version, 208414B, but the model # on the left side of the board matches mine.

So I think I’m all set, but am I missing anything?

And what is that white card?

The white card is a wuz-part. :smiley: Actually, if you read down the application notes, they tell you that it’s a ceramic resistor under the “Power Supply Inspection” section.

Read through all of those notes - they give some hints on common failure causes.

I don’t think the “white card” is a power resistor, regardless of what those guys say. It looks like a thick-film hybrid IC to me.

I ordered the part, and it should get here tomorrow or Wednesday. Any more guesses o what the white card is? I’ll take a voltmeter to it tonight. I haven’t even felt it, to guess what material it’s made of.

gotpasswords, do you think it gets hot, and that’s why it needs to be on the card?

When you look at the card, see if it looks like a ceramic board with components on it coated with and epoxy film. If so, it’s a hybrid.

**beowulff **- my first thought was a hybrid IC as well, but the people who sell the thing say it’s a resistor and call it R3, so I was trusting them to know. :smiley:

Wouldn’t surprise me to find that it’s actually a hybrid IC with a tapped power resistor (eg: voltage divider) incorporated into it. It does seem to have a lot of legs for a resistor.

In the last link in my OP, the black rectangle in the lower right corner has three contacts with about 18 kOhm between the two outer ones. The next rectangle to the left measures about 6.5 kOhms. The short loop from there to the next contact had 2.5 MOhms. I couldn’t measure anything from there to the next contacts to the left, on a 200 MOhm scale. The card itself feels like it’s ceramic (very very stiff). I don’t think there’s any kind of IC, just a voltage divider.

Probably used to provide the HV regulation - it provides a low voltage output that is proportional to the 30KV going to the filter. So, not a power resistor, but not really a hybrid either.