Power resistor ID needed

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Topic author
letank
Posts: 4009
Joined: Wed Oct 03, 2012 9:16 pm
Location: SF bay area

Power resistor ID needed

Post by letank »

The boiler 3 way valve is not working. The maintenance person left a note that the 3 way valve is shot, and disconnected it at the board. We still have hot water. But it seems that the controller board has some cooked power resistor(s)

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Has anyone any idea to ID the green power resistor that is visible on the lower part of the pict, I can read 470R, and 5%, and something else, but not too sure.

Image

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or is it the black cylinder? N06F

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The other issue is that the board is really tight, and there is a poor access to the molex in the back to try to wiggle it loose. I need to make some prying plastic tongs

Thank you
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (229 Kmiles... the running test lab)
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tgreese
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Re: Power resistor ID needed

Post by tgreese »

The 470R 5% component is a resistor; 470 ohms and 5% tolerance. The size will indicate the wattage rating - just use the highest wattage that will fit in the location. They are simple, and usually do not fail. It's more likely that one of the electrolytic capacitors failed, making a short to ground and overheating the resistor. The resistor showing signs of being hot does not mean it has failed... measure it.

You have a schematic? It could be something off the board that is overheating the resistor. Again, too much current through the resistor will make it hot. A power resistor failing is unlikely - more likely that another component failed on or off the board. Maybe the valve? Get the schematic.
Tim Reese
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Topic author
letank
Posts: 4009
Joined: Wed Oct 03, 2012 9:16 pm
Location: SF bay area

Re: Power resistor ID needed

Post by letank »

tgreese wrote:Get the schematic.
Thank you for the tips, system from early 1980, I can do reverse schematics.

I need to test the 3 way valve by energizing it directly with proper fuses. Of course, it is impossible to remove the 3 way valve cover because the wall is too close, unless I crack the cover which is the way to do it.
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (229 Kmiles... the running test lab)
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Tatsadasayago
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Location: Sacramento, CA

Re: Power resistor ID needed

Post by Tatsadasayago »

Looking at the heat discoloration I would say the short is on the other side of the Molex connector...
1977 Cherokee Chief - The Blair Jeep Project III
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Topic author
letank
Posts: 4009
Joined: Wed Oct 03, 2012 9:16 pm
Location: SF bay area

Re: Power resistor ID needed

Post by letank »

Tatsadasayago wrote:Looking at the heat discoloration I would say the short is on the other side of the Molex connector...
Thank you for the help, this is France and nothing is can be done, Denzel Washington said a few years ago that "In France nothing can be done" and I must agree, it took the management company 10 weeks to duplicate restricted access key... basically, with the proper cover letter it can be done in 3 days thru any authorized website...
I am working on making some plastic pry tongs to pull the board... to see what is behind it.
At least the wine is good.
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (229 Kmiles... the running test lab)
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