Hello members,
I’m a total beginner, and this is my very first project.
I’m trying to repair an Aroma rice cooker model ARC-2000A
The rice cooker turns on fine but it won’t heat up or cook anything.
Upon dissembling it, I noticed a burnt spot around R103.
Can you please help me identify the Resistor’s value and role in this?
I appreciate any help I can get.
my future repair projects will include music keyboards and drum machines.

 

Can you measure the reistance of R103 (in circuit will be fune)?

 

It looks like a voltage dropper to feed the Zener and a regulator, so probably around 100 to 500 ohms, 3W,. As said measure it.

 

My first guess would be that R103 resistor is ok.
The first thing to check is the thermal fuse.

 

Thank you for the reply.
measuring the resistor’s value 63 ohms

Can you measure the reistance of R103 (in circuit will be fune)?

It looks like a voltage dropper to feed the Zener and a regulator, so probably around 100 to 500 ohms, 3W,. As said measure it.

My first guess would be that R103 resistor is ok.
The first thing to check is the thermal fuse.

 

My first guess would be that R103 resistor is ok.
The first thing to check is the thermal fuse.

I believe this the thermal fuse
measuring its resistance was 0.1 ohm

 

I believe this the thermal fuse
measuring its resistance was 0.1 ohm

The thermal fuse may be good, but one of the wire connections may have come loose.
So, just in case, check the conductivity between any terminals or suspicious wire connection points. Thermal expansion and contraction can cause deceptive problems over a period of time.

 

Ok measure the voltages at these points with a DVM Negative lead on A.

A to B
A to C
A to D
A to E
A to F

 

Ok measure the voltages at these points with a DVM Negative lead on A.

A to B
A to C
A to D
A to E
A to F

View attachment 223834

like I said I’m a total beginner and I’m learning as I go.
I used a fluke 87V
set on AC ~V
measuring unit in V
negative on A
measured voltage A to B/C/D/E/F showed 1.78~1.8 around those values

 

Ok try again on DC ..

 

Ok try again on DC ..

Thank you again for you help and patience.
here are the voltage measurements on DC
A to B 12.15 V
A to C 8.3 V
A to D 5.01 V
A to E 0 V
A to F 0 V

 

Looks like the supply is low, check the Zener diodes at F, zd102, zd103, they go in series with the 7805 regulator ground pin.

 

Looks like the supply is low, check the Zener diodes at F, zd102, zd103, they go in series with the 7805 regulator ground pin.

Thank you again for the help.
I measured the Zener diodes at F and both had a 505 K ohms both directions.

 

Test the Zeners on Diode test on the DVM, it should read 0.7V one way only.

Black lead to Cathode.

 

Test the Zeners on Diode test on the DVM, it should read 0.7V one way only.

Black lead to Cathode.

Ok, I just tried that
on diode mode. Black lead to cathode
It reads 0.688 V for both diodes

 

This is what I think it looks like, the two transistors short out the Zeners to turn off the relay, so can you get the number of the two transistors Q111 and Q112, and check if there is no shorts across the Q111 C/E.

Something switches on Q112 and that turns off Q111.

Feel Free to edit the circuit diagram if it's wrong.

 

This is what I think it looks like, the two transistors short out the Zeners to turn off the relay, so can you get the number of the two transistors Q111 and Q112, and check if there is no shorts across the Q111 C/E.

Something switches on Q112 and that turns off Q111.

Feel Free to edit the circuit diagram if it's wrong.

View attachment 223855

Here is a close up of the transistors and I tried to take a better pc of the board.

 

Yes So Q111 is a Npn and Q112 is a PNP.

So when it's powered up, can you measure the voltages at the B,E,C at both transistors with the DVM on DC Negative lead on test point A.

You should be getting at lest 15 to 20V on test points A and B from the bridge rectifier output, Zd101 maybe faulty.

 

Yes So Q111 is a Npn and Q112 is a PNP.

So when it's powered up, can you measure the voltages at the B,E,C at both transistors with the DVM on DC Negative lead on test point A.

You should be getting at lest 15 to 20V on test points A and B from the bridge rectifier output, Zd101 maybe faulty.

What I’ve tried, I got 0 V for the Q111 and 5 V for the Q112 and when testing zd101 I get OL no reading
im not sure if I’m helping in this troubleshooting.
thanks again.
let me know if the readings make sense.
and we I can continue more testing tomorrow.

 

Just looked at the PCB tracks, and the relay coil is in series with the two Zeners Zd102 Zd103 not parallel.

One test you could do is to short out B/E Q111 , and measure the voltage across points A and E, it should make the relay click in.