FAAC 826 MPS controller board

[zhv]

Hello!
Recently my sliding gate operator failed electronically (reason: water in photodetectors). I took the controller out of the operator and turned it upside down on my bench. I see some SMD components are burnt, but I can´t get any replacements for them because no one can recognize them. It looks like diode with a circular notch in one end and text LT807 in the upper line and S1M in the lower line. The arrow represents the notch.

    |----------------|
|---|      LT807     |---|
|   |<               |   |
|---|        S1M     |---|
    |----------------|

I am sorry for my english. It is not my native language.

 

[Resqueline]

Googling it seems like an S1M could be an ordinary 1A 1000V rectifier diode (SMA case).
Your english seems pretty perfect to me btw..

 

[zhv]

Those seemed to be the right diodes. Ordered 6 to replace the burnt ones. But now a bit more difficult problem (actually the culprit of this whole mess). In one of the photocells there is a burnt component in TO-220 package. Only readable markings are SEC on the first line, faint numbers 704 in the second line and in near the middle pin TIP. Looks like a voltage regulator but i´m not shure. Accesessory voltage in 826 MPS is 24 volts.

 

[Resqueline]

SEC is the maker; not important. 704 is probably the date code. TIP is a transistor series, ordinary or Darlington depending on the subsequent 3 digits.

 

[zhv]

The part with the three digits has "conveniently" melted away. Is there any way to identify the proper transistor replacement. Also, the leg on the right has also broken off.

 

[Resqueline]

If we can get a diagram of the circuit immediately surrounding the transistor we should be able to guesstimate what kind of transistor will do the job.
We can probably assist you in making a diagram if you can provide us with real clear shots of both sides of the PCB. Does it have double-sided tracks?

 

[zhv]

Some pictures. Some of them have heavy lens distortion because I had to use a magnifying glass. The yellow arrow points to the location of the transistor legs. The bottom row of big solder points is a screw type terminal with 5 connectors which pinout is unknown. Fortunately it only has one layer.

 

[Resqueline]

The pictures were better than we're used to but still the poor lighting made the PCB tracks hard to read, despite trying to enhance them, so it took some time.
The power circuit is as attached. The placement of the TIP means that it has to be a PNP, and the 12kΩ base resistor means that it has to be a Darlington.
Any of these TO-220 PNP Darlingtons should work: TIP105/ 106/ 107/ 115/ 116/ 117/ 125/ 126/ 127/ 135/ 136/ 137/ 145/ 146/ 147.
I'm sure you have noticed that you'll have to replace C3. There may be other damages too of course.