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Help identifying component on 858D rework clone KSD858DP

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rsumner:
I'm new to the forum and just starting my journey into hobby electronics, so please excuse any of my ignorance in advance  :)

I bought a cheap 858D hot air station clone from Amazon about a month ago.  After using it a couple of times, I noticed the gun was no longer blowing air.  I got a new air gun unit from the seller on Amazon only to find the same problem.  The handheld will heat-up. but will quickly start to melt the plastic because it is blowing now air.

I had a look at the circuit board and noticed I had a fried component.  I looked at schematics online of other 858D clones, but none seem to match my layout. It seems to the CN manufacturer has switched to nearly 100% SMD components.  The identifier on the board is KSD858DP-F/C REV D with a date marking of 2021-05-27. 

Can anyone help me identify the 6-pin SMD chip marked "U1" in the picture so I can replace it?  In addition, I need the size of the cap at C17 and the resistor right above it in the pick, which is R30. 

I think I'm going to need to replace most of the resistors near this chip because R2 reads as a 1.003k resistor, but it's reading 3.5k. 

bob91343:
I don't see any U1.

rsumner:
It's in the 3rd pic to the left of the C7 cap.

TheBay:
I can't believe a company is still making these clones with a removable handpiece, they are so dangerous as they have live mains voltage at the din socket.  :palm:

rsumner:
@TheBay, oh, they're definitely dangerous.  The chip that is blown on my board is clearly involved in temp control of the heating element and fan control (both of which are contained in the hand piece).  What's crazy is that the fan control is completely broken in my case, but the heating element will still stay on.  If I were to leave it unattended, the hand piece would likely catch fire, but would definitely melt the entire casing of the hand piece. 

I've already replaced the air station with something more reliable, but interested in seeing if I can get this unit running as a backup.

My problem is the component that's in the U1 position on the circuit board is too badly damaged for me to determine what it was. Looking at the reverse engineered schematics for the 858 (https://blog.enbewe.de/posts/images/858D/858D_Schematic-big.png), I was thinking it was the SOT-223 package format of the 2N3904 transistor, which would be a PZT3904.

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