EcoQuest Fresh Air II air purifier repair

I have purchased some junk EcoQuest Fresh Air air purifiers to repair.  I fixed one by replacing the capacitors in the power supply.  I like these air purifiers because they feature an Ozone maker, and Ionizer a UV light (to kill germs) and a normal air filter too!

I have two of these air purifiers that I cannot fix.  They come in two versions.  Version one has a 12 volt switching power supply in the lower left corner.  Then there are three Triacs in the middle that turn power on to the devices.  Then there is a 5 volt regulator over on the right side that powers the logic circuits.  On mine the IC for the 12 volt power supply blew up.  I tried taking a 12 volt AC adapter and powering it up that way.  The green LED comes on indicating that the 5 volt power supply is working.  However the LCD powers up but remains blank.

I labeled the parts in this picture.

My other air purifier is a version two device.  It uses a telephone cord or a SATA cable to connect the LCD Display.  The power supply in the front left corner only puts out about 2 volts and gets very hot. In this model the switching power supply makes 8 VDC, 12 VDC and 40 VDC.  The test points for these are located just above the power supply transformer that is covered in metal in the picture below.

This is a close up showing the power supply test points.

Once again I used an AC adapter to provide 12 volts and 8 volts but it would not power up even then.  However the AC adapter was not loaded down indicating that the switching power supply is at fault.

Does anyone have schematics or anything that would help me in fixing these?

Here is the Viper53 schematic thanks to a commentator:

Here is a link to the documents:

https://ecoquestfreshair.com/upload/iblock/9cf/FreshAir_DofC_10-08-04.pdf

See more on EcoQuest repairs at: https://bobdavis321.blogspot.com/search?q=ecoquest

EcoQuest Fresh Air II air purifier repair 3

 Once again I am fixing one of my two Fresh AIr by ecoQuest air filters.  This time it struggles to turn on.  I was taking longer and longer to start up making multiple attempts but then failing and trying again.  It acted like a bad capacitor and the 8 volt power was at 5 volts so I tried a 220uF 16 volt capacitor from the 8 volts to ground.  It made no difference.  Then I moved the positive lead to the 12 volt power supply and it WORKED!

These pictures show where I soldered in the capacitor.  It need a little glue under it as well.

EcoQuest Fresh Air II air purifier repair 2

I found myself once again doing some EcoQuest Fresh Air II air purifier repairs.  One of ours quit making ozone.  I opened it up but could not find the problem.  After looking at it several times and getting ready to salvage parts and toss it, I then discovered that R11 was toast.  Checking the FET, a 10N20L showed that it was shorted!

I disconnected the 10N20L by clipping the leads and it was still shorted.  R11 was toast and there was no way to find out its value.  Unfortunatly I threw out my spare board! Oops.

I could not find a 10N20 but did find a IRF630 that has similar specs and used that.  The drain is connected by the case but the replacement will not solder to the board so you will need to run a small jumper wire.  A 4.7 ohm one watt resistor will work for R11 as it was a current limiter resistor (I think).

  So it has been up and running for a couple of hours now with no problems.