domingo, 23 de julio de 2017

Microwave Oven Daewoo

A Daewoo Microwave Oven
In a previous page I have reviewed in some detail a microwave oven (Teka MW170).
I have found at home the electrical parts of another microwave oven, whose origin I do not remember, likely recollected from some street. It seems of the Daewoo brand.

I will review here the electrical parts, referring to the previous page for the common elements.

Wiring Diagram
The wiring diagram that I have prepared from the parts and the circuit is this one:

The diagram is incomplete as the timer/power motors are missing, but the connectors are there.


Parts
Power Source
While the Teka 170 had just a fuse, this one has a filter unit for high frequencies.
The board is labelled DWLF-M13 SS.

The fuse is rated 15 A at 250 V.
R1 is 1.5 Mohm
C1 is a film capacitor from Pilkor, box shaped, PCX2 335M MKP, with 100 nF, tolerance class M.
C2 and C3 are labelled "NW 222 MX1Y2", ceramic capacitors for interference filtering (X1Y2), 2.2 nF and tolerance class M.
No clue about L1...

Switches
S1, S3: from Gersun, GSM V1603A2, 16 A at 250 VAC, SPST NO,
S2: from Starion, SZM V16-FA-61, 16 A at 250 VAC, SPDT.
S4: from Starion, SZM V16-FA-63, 16 A at 250 VAC, SPST NO.

Thermal Swiches
Labelled:
- TH1: NT101 KTE, N1CO 90 5331
- TH2: NT101 KTE, N65 75 5324.
I have no information on where they were installed. From the wiring diagram it seems TH2 is on on the magnetron, the other in the oven's food compartment.


Turn-table Motor
Synchronous motor from GPS Corp. 5-6 rpm, 3-2.5 W, 220-240 V. Model ST-16 MN73MQAD.
Daewoo sees to use them frequently (f.eg. here).



Fan Motor
Moor shaded pole, with no references.
The motor was covered in grease, so either the ventilation was crappy, or the users of the oven were doing heavy cooking.

(Sorry, the plate was under the grease! Manufactured by Daewoo Electronics Corp. Label: "MV10CA, M02, 230 V 50 Hz,  0.28 A max, Z.P. B Class").
The motor runs an axial fan (on the Teka it was a centrifugal fan). Impeller diam. 11 cm.

Timer and Power Switch
The mechanism (motor) activating he timer is not in the parts that I have, just the geared switch and selector. 
One of the switches (TIM1) is normally off, and is set on when the time selector is moved from its zero position.
The function of the other switch (POW1) is unclear.




Transformer Feed
The power supply to the transformer is regulated by a small board, whose main element is a relay.
The board is labelled as "DWSR 1".

The relay, from Texcell, is model KH, contact arrangement 11 (form A, SPST-NO), termination TMP (for PCB), E-24H. Specifications are likely similar to these ones
It is unclear to me the operation of this relay. The model seems out of manufacture, and I have not found direct references to it. As per one catalog from Texcell for similar relays,  the schematics would be:

Based on this, the scheme of the regulating relay would be:
 
Transformer, Capacitor and Magnetron
The transformer is from Daewoo Electronics Copr., with no indication of ratings (230 V, 5 Hz, Class 220, R1S80).



The HV capacitor has a capacity of 0.98 uF, rated at 2100 V, with an internal resistor of 10 Mohm.
The diode is marked "C1 01" (o, perhaps, "1010").
The fuse is marked as: " 5 kV, 550 mA".


Finally, the magnetros is from Daewoo, 2M218 50323AN JF.











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