I ordered the cheapest white 2 digit CC display I saw on Ali. I tried to be sensible and go through datasheets, but half the sellers didn't have any, and those that did didn't seem to match up to my dead display. I decided that I was overthinking things, did what the manufacturers probably did, and went for the cheapest. I put one in, and it's been working fine ever since.
The five beeps are because you've taken the water tank out and the unit can detect it's missing. That got me at first too, then I realised it was a good sign and meant that the MCU was still working. It's astonishing...
CG2
Member
Last Activity: 10-27-2024, 05:26 AM
Joined: 11-13-2022
Location: Brighton
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The display is marked MLS-4201ASC1-B7 5-DY 2242. Searching for that gives no results. There is a 4201AS 2 digit 7 segment display which is the right size (0.4 in) but it is red rather than white. It is CC and comes in two types. Type I has pins 5 and 10 as the cathodes, type II pins 4 and 5. There is no suggestion of how they are marked to differentiate them.
Trying to test the broken one with a multimeter wasn't helpful. Using a bench supply suggests that it is common cathode, with the cathodes being pins 3 and 8. I've ordered some of the cheapest likely candidates from Aliexpress...Leave a comment:
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CN16 isn't used on this model.
But I've worked it out, and it's a pretty obscure fault. It was related to the display, though not as I expected. I buzzed out all the connections from the TM1638 just trying to understand it better. There was a short between two pins which both went to the 7 segment display. I took the display off and the short went away. I powered the board up on my workbench with the temp sensors connected, the water level shorted and a 12k resistor in place of the humidity sensor. Pressed the power button and a couplr LEDs lit up and the relays clicked on. I'm surprised...Leave a comment:
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My first thought was bad caps on the power supply, so I pulled the CD6 and CD7 to check ESR, but they were fine. I then pulled CD2 as that looked the most likely to be in a hot spot, but again it was fine.Didn't have the flux i8mmediately to hand when I put them back, but they worked OK, so reworking went on the list of things to do later.
I've put in a 12K resistor instead of the humidity sensor, but still nothing so that may well be OK.
Next thought was maybe the TM1638 display driver chip wasn't working. There must be a reason the display is not showing anything and...Leave a comment:
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I don't think it's ever getting to the point of triggering the relay. I'm not hearing any clicks. According to the manual:
But my display is blank. Pressing any of the buttons just lights up one of the decimal points on the 7-segment display. I don't think I've ever seen a segment light up.
The temperature sensor is driven by a solid 5v dc. It shows a resistance of 4.5k which drops to 4.2K when I touch it. That all seems fine.
The supply for the humidity sensor is more complicated. It is a square wave of +5V / -5V at a frequency of about 1KHz....Leave a comment:
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Too late to edit, but it looks like that was a red herring. I'm getting a rock solid 5 volts across the pins where the water level connector plugs in. Leaving the sensor unplugged gives the 5 beeps at start up. Shorting the pins together to mimic the switch being triggered gets rid of that, but the dehumidifier still doesn't start up. Now there's still nothing on the display but no beeps to give a clue as to what is happening. I'm puzzled.Leave a comment:
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Meaco Arete One / Deye Dehumidifier not working
I've got a dehumidifier that has stopped working. Plug it in, press the power switch, and it beeps 5 times. Nothing showing in the display (which is just two 7 segment displays) apart from the two decimal points flashing. The model is a MeacoDry Arete One 18L, which seems to be a rebadged Deye (all the boards are marked Deye). Here's what I've got so far (details in case anyone else in future should need them).
Starting with the power board. Mains power comes in at the red connector top left. The compressor is powered by the orange connector to the right of that and is switched by... -
Check the resistances of the blanket and compare it with the good one before you turn to the controller. Some blankets have a sense wire in addition to the heating one, and if that is damaged the controller responds by effectively committing suicide. The blown resistors may be a symptom of a dead blanket.Leave a comment:
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Is it that hard to test diacs? It looks OK and isn't shorted. My "test" was to connect it up to one of those cheap component testers which said "defect device" The triac checked out OK on the same bit of kit. Those little diacs cost virtually nothing anyway, so I've ordered some, but might try changing just the potentiometer and see what happens.Leave a comment:
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Thanks. The triac checks out OK, but it looks as if the diac went instead. The potentiometer is gone as well, but they seem to be available cheaply on aliexpress [url]https://www.aliexpress.com/item/1005005632064132.html[/url] The wiring on this is scarily thin. I'm guessing that someone stuck in a couple of 60W bulbs and that killed it.https://Thanks. The triac checks out... scarily thin.Leave a comment:
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LED uplighter dimmer burnt resistor
I've got a 240v LED uplighter which isn't working. Pulling it apart shows a clearly burnt resistor on the circuit board, and I'm hoping some of you will have suggestions on what to replace it with. First, here are some photos. Power comes in, through the fuse and choke, then through the big blue variable resistor labelled B500K (ignore the similar blue component at the bottom - it's a simple switch for an attached reading lamp). It then passes through the burnt resistor (or at least did once), through diac DB1 and the unburned 30 ohm resistor to the gate of the triac.Now I assume there's a simple... -
A small correction to my post #7 above. The inductor is 1mh (or as the datasheet prefers to say 1000 uh). If anyone wasted their time googling for a 1H that would fit the allotted space, I apologise.Leave a comment:
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Re: Hotel Chocolat Velvetiser dead
Thanks for your help. Post has been a bit slow due to the holiday weekend, but it finally arrived and everything is working again. It's interesting to see another approach to EMI noise suppression. I did wonder why there was no filtering on the input as you usually find on these small SM power supplies.
For anyone else stumbling across this page in the future, the primary side of the power circuit is almost exactly as that on page 18 of the datasheet that lotas posted above, although a transformer has been chosen that outputs something...Leave a comment:
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Re: Hotel Chocolat Velvetiser dead
Current draw at 6.5v jumped between 5mA and 14mA as the LED flashed. Pressing the button added at most another one or two milliamps, so I don't think there are any shorts on the secondary side. The temperature sensor has a resistance of 167k at room temp, so that looks OK, and the motor is 16.5 ohms, which at 12 volts equates to about 0.75 amps, so nothing unexpected.
Now a bit of documentation for anyone else who comes to this thread in future. The relay is a Y32F-SS-112DM which is 12v switched and rated at 5 amps so operating well...Leave a comment:
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Re: Hotel Chocolat Velvetiser dead
I'm still not sure what the output voltage of the PSU is. The article I linked to in my first post suggested that the motor worked on approx. 10.5 volts, and I can't see any other power sources on the board other than this one chip. My board is slightly different, but I wouldn't be surprised if it was all running on 10.5v. My cap tester is a Peak Atlas, and it's always been reliable.
[url]https://helpfulcolin.com/repaired-dualit-milk-frother-model-dmf2/[/url]Re: Hotel Chocolat Velvetiser dead<b... not sure whatLeave a comment:
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Re: Hotel Chocolat Velvetiser dead
Thanks, that looks like the one. I think I'm on the right track, because when I soldered a couple of wires to one of the output capacitors and fed in voltage from my bench PSU, the LED started flashing slowly once I reached about 6.5 volts. I guess the flashing is an error code, probably because the temp sensor is not plugged in. Whatever it means, it shows that the MCU is not dead, and is staying awake when powered.
Now to work out exactly where the fault is. The feedback circuit for the MP020 seems idnetical to that on page 17...Leave a comment:
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Hotel Chocolat Velvetiser dead
This is a fancy milk frother, apparently almost identical to the Dualit DMF2, but sold at a big mark up as bring particularly suitable for making frothy hot chocolat. It's basically a small jug with a kettle type resistive element in the base, and in the centre of that a small motor holding a magnet which locks on to a magnet in the base of a stirrer inside the jug which spins and froths up whatever liquid is inside.
I've got one and it's not working. I've checked all the obvious things. The heater coil has continuity, as do the two thermal fuses and the motor windings. The temperature... -
Janome DC3050 Sewing Machine Pedal Resistance
OK, this is a long shot. I got this sewing machine cheap because it's end of line, ex-display, and had no pedal. The genuine pedal costs £60, while Ebay knock-offs go for around £15. So I went for the knock-off, it doesn't work, and I'm not sure whether it's the pedal or the sewing machine that has the problem.
Now this is an electronic machine, unlike the old fashioned sort where the pedal was a big resistor in series with the power to the motor. Here, the pedal is just (I think) a variable resistor fed with a 5 volt supply, and limited to a current of 5 milliamps. Assuming that... -
Re: Trying to repair an Air fryer EAF383
It's almost always the thermal fan that goes on these. That big black plastic part will come apart somehow (the nut holding on the fan may be reverse threaded). Those two white wires going through the hole to the right of the element are the ones that are connected to the fuse. When you jumped them you bypassed it.
Otherwise check for continuity across the fan windings. There's sometimes another small thermal fuse hidden in there.Last edited by CG2; 04-14-2023, 07:17 AM.Leave a comment:
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Re: Replacing UC3835A PWM controller with UC3853A
For the back story, 5 or 6 years ago I bought a job lot of 3 or 4 ATX PSUs at a salvage auction. Think Amazon returns, but they could have come from half a dozen or so different retailers. I needed one at the time, at least one worked, and a couple were dead out of the box, but otherwise brand new so they went into a cupboard and got shuffled around a bit over the years and eventually were forgotten. I stumbled across one a few months back, tested it a bit, tracked the problem down to the UC3843, bought some from Aliexpress, and...Leave a comment:
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