Danger Maytag Oven Broiler Malfunction 7601P175-60

[@outtakontroll3334]

not the only one, i had a friend with the same problem, fixed that one by also replacing the relays. weak design point, i think they are just undersized for the current draw and eventually fuse stuck.

[@john_Jean-Marc_JMP5184]

Wow, that's scary. We really need to stay alert to this kind of potential danger, that's for sure. I don't suppose the oven was equipped with an automatic shut-off system? Although perhaps it wouldn't have worked due to the faulty relay. I'd be curious to know. Thanks again for the video.

[@sfaires]

This would not happen if the spot on the board marked DLB at 8:41 actually had a Double Line Break relay which opens L2 when the oven is switched off. (See the terminals Line 2 and Line 2 load.) The broil would still come on continuously but only when the oven was on, so less of a safety hazard. I believe the DLB relay is required in Canada as I have never seen an oven control board here without one.

[@NicksElectronicRepair]

Yeah we recently started seeing that on newer oven boards

[@jackipiegg]

7:12 Do you use lead-free solder to increase the melting temp for heating devices?

[@NicksElectronicRepair]

No, we use leaded as it will have a stronger bond between the component and PCB and be less likely to crack or fail over time. The issue is not that the component gets hot. The temperatures don't get above 80C near the components, the issue is the thermal cycles and difference in temperature between the unit being off and on. So if this oven was operating between absolute 0 and 0 Celsius aka freezing, you would still get cracked solder joints. The problem is the thermal expansion and contraction between the low temp when the unit is off and the high temp when the unit is on. The molecules of the PCB expand and contract at different rates than the solder and the leg of the component. This different rate of expansion and contraction is what stresses the joints and over time causes the cracks. The bigger the difference between the lowest and highest temp the more expansion and contraction you get and thus the more likely you are to get a cracked joint. This is why the items that get the hotter get the more cracked joints because the off state of the oven brings all components to the same temp aka room temp and the parts that get the hottest get the highest amount of expansion and contraction stress. Does that make sense?

[@KeithHanlan]

That's a terrible failure mode. It would be very interesting to dismantle the relay to understand why it failed closed. There should be a spring to return the switch to its open position, no? Did it break? Did the contacts fuse due to arcing? How does its design compare with other relays designed for a similar application? Thank you for sharing your experience!

[@NicksElectronicRepair]

We have seen a few more like that come in recently actually

[@brianperkins6121]

Is there a thermal fuse in the either broil or bake element circuit of the oven goes over temp due to a relay with welded closed contacts ?

[@NicksElectronicRepair]

No I don't believe so