Help with a heater, Pelonis HC-451 Please

Kahoona

Super Member
Hi
A friend of mine has three Pelonis Ceramic Disc heaters which he loves. Pelonis no longer will repair them. All three will only work in a very low output. They have been repaired for this problem before. They should put out the required amount of heat to warm the area up to the selected temp and then lower the output to maintain it. They were a very good heater in their day, close to $150 then. He wants me to fix one of them. I said I'd try but this is not a simple 3 way switch and rheostat. Here is what I know:

The heat sensor does change impedance when the temperature changes.
The rotary function switch seems to work properly.
The fan spins.
The heating element puts out low heat, weather it puts out high I am not sure. I suspect the element is good since it is not a simple 2 speed but a variable one.

Here is what I suspect:
I suspect the variable resistor connected to the temperature dial among other things.
I wonder it there are other problems on the board.

Should I?:
Change out the VR or since half of the cost of a Mouser order is postage, just repopulate the entire board as I would do with an Amp power supply that age?

Can anyone tell me where to get a schematic or any kind of service manual?
Has anyone fixed one of these or have any suggestions? I am out of my element here but this is for a good friend and also a bit of a grudge match.

Photos and instruction manual attached.

Thanks in advance
Kahoona
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This is the part that I would change first, knowing nothing but having to start somewhere. It has 104 stamped on the topside. It is 12mm long and 6mm wide. The lugs are 10mm and 5 mm apart. Has to be 1 turn. It looks like a big trimmer resistor but I can't find anything to match with a resistance of 104 except one with a minimum of 300! Any ideas?
 

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Before changing anything, I'd consider re-pointing ALL the connections as well as clean the controls, and see if that helps. Same thing you'd do for an old stereo really, but in this case, we're talking regular exposure to extreme hot/cold cycles.

Did the same thing with a controller board that had gone intermittent on my oil furnace. Been working like a champ for several years since the fix.
 
This is the part that I would change first, knowing nothing but having to start somewhere. It has 104 stamped on the topside. It is 12mm long and 6mm wide. The lugs are 10mm and 5 mm apart. Has to be 1 turn. It looks like a big trimmer resistor but I can't find anything to match with a resistance of 104 except one with a minimum of 300! Any ideas?
I would ohm out the pots. Do not see much else to go bad. Dexoit the controls.
 
Thanks for the input. I tried both after reading your suggestions but no joy. After testing the various components that I could and eliminating them I am left with the big old chip on the board which I cannot find a replacement for. I think that is why Pelonis stopped repairing them. I was able to make it into a simple 3 level heater without thermostatic control. It works well this way and that was his second choice. I have a 25ohm pair of discs, a 55 ohm pair and then both at once (which I called "overdrive" and painted that switch red). Can't win em all bit I can have fun with them.
 
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