It's a positive air system not AC as such, it blows air into the house at very low adjustable speed and runs at about 16w. It is majorly effective at reducing (read completely eliminating) condensation in the colder months, something that plagues UK houses especially older ones like mine.
It's a 24v Power supply. The MP4558 takes that as input and pretty much puts 24v (about 22.8) out as output. it then goes through a tiny SMC voltage regulator that brings that down to 3.3v to power the PIC MCU etc. I don't know why the 24v supply doesn't go straight to the 3.3v regulator or have...
silentrunning
Member
Last Activity: 12-14-2023, 04:57 PM
Joined: 12-11-2023
Location: Polegate
-
Thanks for the advice. The board did look a right mess under the microscope so I gave a good clean with IPA and a toothbrush and it's WORKING!!!!!!! Thanks Pete for the suggestion.
Blimey, what a journey! Harp - I did try everything you suggested apart from the ice cube trick - cost of living on the UK has gone through the roof so the refrigerator is a thing of the past for me! Nothing I did identified the temp sensitive component. Heating the back side of the board with the thermistor on it did nothing.
I'm guessing it was one or more of the components associated with...Leave a comment:
-
Here's another view
[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"image.png","data-attachmentid":3161608}[/ATTACH]Here's another view
[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"image.png","data-attachmentid":3161608}[/ATTACH]...Leave a comment:
-
That's beyond my pay grade! I'm just a beginner when it comes to this game. I've beginning to think it maybe a voltage regulator issue. I've identified this chip as a voltage regulator and the two resistors in the middle right as a voltage divider that sets the output voltage. I've noticed the output voltage is only about 0.9volts when the board is failing to start. Does the resistor with no markings look dodgy to anyone, I'm not familiar enough at the moment with failed components. It seems weird to have no markings. According to the data sheet of the chip it would need to be about 32k to give...
Leave a comment:
-
I replaced the 3 big caps and put the thermistor all to no avail so the bin is beckoning for this board!...Leave a comment:
-
NOPE!!!!! Spoke to soon. Same problem. So looks like something else is the issue!Leave a comment:
-
Well I have had a lot of fun deciphering what the board does and learnt a shed load of stuff!
I was looking at buying a replacement thermistor but did a quick calculation with something I've never heard of called the Steinhart-hart equation (thermistor characteristic equation) plugging in details from a data sheet that seemed to match some of the resistance measurements I've been taking and figured I could replace it with a 5k resistor which would be the value of thermistor at about 20c when the unit should most definitely be running - and actually was if I gave the board the hair...Leave a comment:
-
Struggling to get a decent picture. Is this any better?. I removed the thermistor and resoldered it. It was 14k - both ways(!) - whilst off the board. Still the same behaviour....Leave a comment:
-
Not sure if this means anything but when I measure the resistance of the thyrmister I get 7.5k one way but 9k when the leads are reversed ! What's that all about?Leave a comment:
-
Cool. I've been looking at the pwm fan signal that it generates with an oscilloscope with the possibility of making my own control board if I can't get this one to behave. What should I look out for regarding oscillscope readings for the caps. If I remove them I'll probably just put new ones in?Leave a comment:
-
Yep tried em all but couldn't get any consistent behaviour. Do you think replacing the three big caps is worth a shot?Leave a comment:
-
And only warm air will do the trick. Air from an unheated fan does nothing...Leave a comment:
-
Done that but to no effect. I can't pin down any one component that when warned brings the unit on....Leave a comment:
-
Here's a link to the unit
[url]https://www.nuaire.co.uk/residential-commercial-industrial-nuaire-products/nuaire-drimaster-positive-input-ventilation-systems[/url]
I've tried warming just separate component's and areas of the board but with no consistency. I've tried a separate power supply with no change. The MCU is a [B]PIC18F24K20
The caps look ok but I'm a newby to electronics.[/B]
https://Here's a link to the unit<br...-systems[/url]Leave a comment:
-
Oo forgot to say it has no markings on it. It's resistance is about 8k at about 16cLeave a comment:
-
Yes indeedy I thought it might be so I've been reading up on them.
The unit is actually a positive air flow fan that simply blows air into the house so no evaporator or anything like that. Could the ntc be being used for some other purpose, it is connected to one of the pins of the MCU via a tiny capacitor or two with the other end I think going to ground. Having said that given it's location on the back of the board I guess it's ambient temp it's after.
Measuring it's resistance I can see that change as I heat it up slightly.
I have resoldered it but with...Leave a comment:
-
Thanks. I'll give that a go. Any idea where I might find information about that little blue thing?...Leave a comment:
-
Picture of PCB attached. Many thanks....
Leave a comment:
-
Circuit board starts only when warm air passes over it.
I have an air con appliance that doesn't always start when power is applied. I have removed the small control board which is separate from and supplied by a 24v power supply (that works fine) and inspected it for any obvious failed components but can see none. I have discovered that the board will start if I wave a hair dryer over it for a few seconds. The board appears to have no temperature sensors or sensitive components on it. Can anyone suggest what the most likely candidate for a failure mode of this form.
Many thanks.
John... -
Hi all.
I'm a retired software engineer getting into electronics and no doubt will need some advice before to long!
JohnLeave a comment:
No activity results to display
Leave a comment: