Chinook RV

I plugged in the old Magnetek 7345 to see if I can figure out the circuit. Here is a screen shot of the five large resistors in parallel (R67-R71). I may remove them to see if any of them are damaged, since they seem to be running a lot hotter than I expected. You can see that the circuit board area is damaged by heat, and there is some cracks there. Functionally, there is nothing wrong with it since it is doing fine regard to its specification, but I upgraded to a Progressive Dynamics converter for its better battery charging capability.

I would like to know if any of you see similar damage or heat issue. BTW, don't touch anything in there with your bare hand if it is powered. There are a couple large capacitors in there that can give you a nice jolt if they are not bleed off.

(The heat sink is cold. The high temperature you see in the FLIR is actually reflection of the heat from the resistors off the smooth aluminum surface.)

BTW, can anyone tell me what is the color of the bands on the five resistors? According to the schematics on the reference section, they should be 1800 ohm each, which should give a combined resistance of 360 ohm in parallel. My ohmmeter says that it is about 36 ohm, which means that each of them should be 180 ohm instead, but I can not confirm that due to the condition of the resistors.

chin_k: I finally found the old Magnetek converter and disassembled it.
R67-71 are marked brown grey brown gold which means they are 180 ohm
resistors @ +/- 5% resulting in a combined parallel resistance of 45 ohms.
My converter also shows some signs of heat dis-coloring around these
resistors.
Also, the schematic I provided shows these as 1.8 ohm and they
should be 180 ohm.

Hope this helps.

GS.

chin_k: AND I can't count !!! FIVE 180 ohm resistors in parallel will be 36 ohms.

GS.

Thank you, RLB, for the confirmation. I think I will redo the section where the five resistors are, and use it as power supply for my other hobby instead. You may want to correct the schematics on the reference section, but I think most people just get a new converter, instead of fixing it nowadays.

I don't know how to remove/replace the schematic post. If I
figure that out, I'll replace the schematics.
If I can't replace, I'll add another post in the Reference section
correcting the resistor value.

GS.

There are some other updates that I have that you maybe able to confirm and incorporate into the update schematic. I will send you a private message later and see if you want to do the changes together.

I think the forum owner can delete the post if he does not want an outdated version.