Microwave NC door switch works on bench but not when connected

Question

LG LCRT2010ST

4 Soru Tümünü görüntüle

1Trueseeker57 @trueseeker57

İtibar: 1

Gönderildi: 29 Ara 2023

Seçenekler

Microwave NC door switch works on bench but not when connected

LG LCRT2010ST microwave door NC switch tests closed both when the door is open and when the door is closed when installed. When removed from the unit or wires disconnect the switch operates as it should ( closed when in normal position, open when depressed). Once the wires are attached, it stays closed in either position. I purchased two new switches and they both do the same thing. Tested before use and both operated correctly, when installed, both show continuity in both positions. All three test good when wires are not connected. I'm lost, why would a switch not open just because the wires are connected? Unit unplugged, capacitor discharged, no voltage on either wire.

Bu soruyu yanıtla Ben de bu sorunu yaşıyorum

Bu iyi bir soru mu?

Evet Hayır

Puan 0

Yorum Ekle

1 Cevap

jayeff @jayeff İtibar: 449,8b 11 367 1,4b · Answer 1 · 2023-12-29T22:32:09-07:00

Hi @trueseeker57

Most likely you're measuring the HV transformer primary winding when the wires are connected to the NC monitor switch.

This switch is used to short out the HV transformer in the event that the oven is operating and the door is opened by the user, shutting down the HV circuit and stopping the oven from continuing operating.

This is a safety feature designed to prevent harmful microwave radiation from escaping through an open door.

Here's the service manual for the oven.

On p.9 (of 35 pdf numbering) is the schematic diagram for the oven and on p.19/35 is the HV transformer test procedure. The HV transformer primary winding tests 0.2-0.4 Ohms, which for most DMMs (digital multimeters) appears as a short circuit.

What is the problem with the oven?

Hi @trueseeker57

Could be any of the other components in the HV circuit, i.e. transformer, capacitor, magnetron, the R2 relay on the control board or even the control board itself. The R2 relay completes the power path for the HV circuit to operate

See p.19 for how to test the HV components (the HV transformer primary appears to be OK from what you said, but this doesn't mean that the secondary winding or filament winding is OK)

See p.26 for the No microwave oscillation troubleshooting flowchart to view how to check the R2 relay.

If you do find the problem and it is a faulty part that needs to be replaced, here's a link to the parts list that is useful. Locate the wanted part in the list. This will show you the manufacturer's part number for the part. Search online for the manufacturer's part number only to find suppliers that suit you best.

Be safety aware when working in microwave ovens. The HV capacitor can store >5000V DC for months even if the power has been disconnected for this length of time. This amount of voltage can seriously injure you. The HV capacitor needs to be correctly discharged as soon as it can be accessed after the oven's cover has been removed and before commencing any further work in the oven

Hi jayeff, thanks for your answer. The microwave runs but doesn't heat the food. Both fuses are good and I replaced the diode. — 1Trueseeker57
Primary 0.5

Secondary 110

Filament 0.6

I'll get into more of it tomorrow after I do some reading in the manual. I'll post my results after 5pm tomorrow. Thank you for your time — 1Trueseeker57

LG LCRT2010ST

Microwave NC door switch works on bench but not when connected

1 Cevap

Update (12/29/23)

Yanıtını ekle