Digicabi dry cabinet

[Sausage]

My Drybox red light is on and not blinking but the lowest rh I get is 58%.

I'm guessing the peltier is working but it's a power supply problem. Are these suitable, for a first round of troubleshooting?

https://sg.shp.ee/iRDXa4n

My next guess would be the power brick.

 

[one eye jack]

I replaced the 22uf capacitor and it worked for awhile but ultimately I think it is the power supply. You can try replacing the transistors or replace it with a small 5V switch mode supply or even a linear supply. Good luck.

My Drybox red light is on and not blinking but the lowest rh I get is 58%.

I'm guessing the peltier is working but it's a power supply problem. Are these suitable, for a first round of troubleshooting?

https://sg.shp.ee/iRDXa4n

My next guess would be the power brick.

 

[Sausage]

I replaced the 22uf capacitor and it worked for awhile but ultimately I think it is the power supply. You can try replacing the transistors or replace it with a small 5V switch mode supply or even a linear supply. Good luck.

When you say power supply, do you mean thr power brick? Or the components on the PCB?

 

[one eye jack]

The 22uf capacitor is in the power supply PCB. There is a medium power transistor on heatsink and 2 smaller to92 type transistors. If you do not know how to trouble shoot the power PCB ( long PCB ) then easy way is to replace with another switch mode power supply with output of 5 volts. See post#3 for more photos.

 

[Sausage]

The 22uf capacitor is in the power supply PCB. There is a medium power transistor on heatsink and 2 smaller to92 type transistors. If you do not know how to trouble shoot the power PCB ( long PCB ) then easy way is to replace with another switch mode power supply with output of 5 volts. See post#3 for more photos.


View attachment 118005

Thank you!

 

[Sausage]

I've opened mine but I have totally no idea how to take the big PCB out. There don't seem to be any screws holding it down, so how do I take it out of the box?

 

[one eye jack]

I've opened mine but I have totally no idea how to take the big PCB out. There don't seem to be any screws holding it down, so how do I take it out of the box?

I just discovered another similar model drycab and it has a different PCB where the older design described here. Manufacturer has saved costs so everything is on the tiny pcb under the cover of the humidity adjustment knob.

To remove the cover just gently use fingers to push up the cover . If it does not wiggle free then use a flat screwdriver to pry it at the holes in the side. When you push the cover off do not use force as the knob has a green LED which is connected via a white connector on the PCB. So is the peltier unit and the power supply to the IEC power connector. Well a picture is worth a thousand words.

Note the arrows pointing to the 22uf 400v electrolytic capacitor and the power connector.

Note the torn wire of the green led. This is the result of not making sure or pushing aside the wire to make way for the knob to attach the adjustment knob on the PCB. Also take note that the knob can only be inserted when the half moon shape is a aligned to the control knob/handle .

This is the outside part of the other side showing there is no power PCB of the older design inside. Access via 3 screws and same for the power connector side.


If you are interested to know how a switchmode supply work this video explains in a layman way.
For more detail understanding of electronic circuitry watch other videos but be wary that you are dealing with mains 230 volts ac current which can be dangerous to a human. You have been warned. Take note that the MOSFET or switch transistor is not used here but a BUT 12 AF which to my understanding is a SCR switch. ( Silicon controlled rectifier )

 

[Sausage]

Thank you, I just need a new power supply board (to replace the big PCB), can we get any 240v to 5v ones off the shelf?

 

[one eye jack]

Thank you, I just need a new power supply board (to replace the big PCB), can we get any 240v to 5v ones off the shelf?

Yes, look at Lazada or shopee or taoboa. I think you have to deal with the connectors as these power supply do not have connectors. You can buy from Sim lim tower and crimp yourself or solder them permanently to the PCB. The power supply should be small size since current consumption is low.

 

[Sausage]

Thank you.. 5v is ok? Not 3.3v?
Also do I get a 700mA one or 2A one?

Anyway those switching power supplies I see on lazada all use a transformer instead of the hlk-pm voltage regulator.

 

[one eye jack]

Thank you.. 5v is ok? Not 3.3v?
Also do I get a 700mA one or 2A one?

Anyway those switching power supplies I see on lazada all use a transformer instead of the hlk-pm voltage regulator.

Get the 5V 700ma. one. See how it goes. Take note that input designed for 220Vac. so output voltage can be higher but generally switchmode supply design for variable input voltage like 110 - 240vac. No mention of shipping cost. Take care that it is insulated from the metal parts as it does not have a metal casing. Try blutack or foam double sided tape.

https://www.lazada.sg/products/ac-dc-33v5v12v-precision-buck-converter-ac-220v-to-5v-dc-step-down-transformer-power-supply-module-1a-12w-i2610147059.html

 

[Sausage]

Ok, so I managed to get hold of a 5v 700mA power supply board from Lazada and wired it up:

https://www.lazada.sg/products/ac-d...2=1187001226&sub_id3=106658&sub_id6=CPI_EXLAZ

I'm surprised that nowadays the power boards are so tiny compared to 10 years ago.

Anyway, it worked, and at max setting the water drops form within 1 minute. However I was playing around with a smart home power monitoring plug to see the power consumption and this is what I observd.

At minimal setting on the dial, the green LED is off but the red LED is on. At this state, there is 0mA power consumption and 0W power usage.

When I turn to 1/4 of the circle (ie. around 25% power), it's 27mA 1.1W.
When I turn to 1/2 of the circle (ie. around 50% power), it's 38mA 4.4W.
When I turn to 3/4 of the circle (ie. around 75% power), it's 34mA 4W.
When I turn to the maximum (ie. around 100% power), it's 31mA 3.5W.

So it strikes me that it is non-linear, and the most power usage is around the 50% setting.
Anyone else getting similar results?

 

[one eye jack]

Good job done, congratulations.

 

[Sausage]

Ok, after 2 weeks of working well it spoilt again.bit is still consuming power but no drying effect. Opened it up and the peltier degraded. The wire came out of the peltier block.

Any idea what replacement I should get? Will this from shoppee do?

https://sg.shp.ee/AyKQSj6

 

[one eye jack]

Please check the specification and size of the various models that work with 5 volt supply that you already have.Ask the seller?

https://sg.shp.ee/czvWCzi

Ps you may need to buy a tube of heatsink paste to apply to the peltier mating with the heatsink.
Can get from Sim lim tower or shopee.

Fyi , peltier has 2 sides. One that gets hot and cold so you know the cold side is facing outside or into the cabinet. Connect it up and hold or touch which side is cold or hot to test.

Google the model number and look at the datasheet and look at specs at which voltage range and current that it consumes.

 

[Charles Wong]

Thank you, repaired the peltier,but now the small board with the potentiometer spoiled. The new power board lights up when powered, but the small board with the potentiometer doesn't. This one, I don't think we can buy a replacement right? Usually what spoils on this board? The transistor?

 

[one eye jack]

Thank you, repaired the peltier,but now the small board with the potentiometer spoiled. The new power board lights up when powered, but the small board with the potentiometer doesn't. This one, I don't think we can buy a replacement right? Usually what spoils on this board? The transistor?

Hi, look at my post #27 there are photos. Check if the wires connecting potentiometer is intact and most probably the 400V capacitor is bad and due for replacement.

If after replacement of capacitor worked for a short while you may need to replace the power unit with a similar one in posts #31 and #32. Good luck.

 

[Sausage]

ok what I meant was, in your post #24, I replaced the big board on the right with a small one from aliexpress, same rating. This one, when powered from the mains, lights up.

But the small board on the left does not light up anymore. So I think there's something wrong with the transistor on the left board? But I have no idea what replacement transistor to get.

The power board and peltier devices are new from aliexpress.

 

[one eye jack]

The 22uf capacitor is in the power supply PCB. There is a medium power transistor on heatsink and 2 smaller to92 type transistors. If you do not know how to trouble shoot the power PCB ( long PCB ) then easy way is to replace with another switch mode power supply with output of 5 volts. See post#3 for more photos.


View attachment 118005

@Sausage, if you have it the same PCB board as in the photo. Do a visual inspection of the board, check for corroded resistor leads as those may have steel wire instead of copper. It may have rusted through and hence broken off from body of resistor and become open circuit. If you have a multimeter do resistance test or diode test of the components if there are abnormal readings. The medium power transistor is mounted on the aluminium heatsink. You can read off the part number, use a torchlight and magnifier glass as it is small lettering. Then check if this same number part is available ,if not find an equivalent. Do if based on the part number it can be a npn or PNP device .Also if the body or encapsulation is completely in plastic or it has a metal tab usually aluminium which require a isolation material like mica sheet or other heat conductive material and associated mounting hardware like plastic bushing and washer. Also need heatsink compound ( white toothpaste like compound.)

If you cannot troubleshoot the PCB then best remedy is reinstate the assembly or seal off the hole and use moisture absorbent hungry hippo or other generic product. Of course you have to accept no control of humidity but what the hungry hippo does it job. You and use 1 or 2 containers. But you can put a standalone humidity meter digital one is better to check how much humidity after a settling down period usually in days and see if the percentage is adequate. I would suspect if 2 were used the humidity may go below the recommended reading etc. 45%.

 

[limcc]

My DB-036 digicabi bought in 2019 May just stop working. I remove the "PSU" casing to check if its dead, and it really is dead.

The fuse is blown, all capacitors, polyester and electrolytic are out of spec. The bigger yellow polyester at AC side should be 0.1uf/275VAC but measure using 100Hz frequency is 2.2nf@few KΩ! the DC side electrolytic is 100uf/16v is way out also, so as the 104J100 0.1uf/100V polyester at ~2.2nf. I replaced all of them but still the PSU didn't work. To make sure it was just the power unit side, I use a 12V AC/DC adapter with another power module with potentiometer to step down as the stock converter stated 3.6V, a PITA to find a repalcement. Fortunately, the dehumidifier unit still work.

As you can see, my model has shrink the larger SMPS to a cost saving AC/DC converter module. All other components around it were used for safety and smoothing only. As I'm gonna keep thing simple by finding a converter module replacement but the exact same model is >$33 from Aliexpress + shipping! I guess its because 3.6V is non standard voltage as other 3.3v/5v/9v/12v module is only a fraction of the cost at ~$5 a piece. I suppose 3.3V should work since it would be less than 10% lower than 3.6V. https://www.aliexpress.com/item/4001182824992.html

Problem is this module dimension is bigger and the pin spacing isn't a match on the stock. the pin is only 5mm long, unlike capacitor where I can bend the long legs to fit in the thru holes.

Like to ask for expert opinions, use wires to connect the pin to thru holes?