60 lines
2.6 KiB
Markdown
60 lines
2.6 KiB
Markdown
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---
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title: "Saike 858D Rework Station - Original Schematic"
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date: 2018-06-22T14:50:00+02:00
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author: eNBeWe
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type: post
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categories:
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- Allgemein
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- Bastelkram
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tags:
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- 858D
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- DIY
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- Arduino
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---
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Recently, [I posted the teardown]({{<relref "2018-06-20-Reverse-Engineer-a-Saike-858D.md">}}) of my Saike 858D SMD rework station.
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Now it is time to really reverse engineer the main PCB.
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Some of the parts are similar to other "flavors" of the 858D, but some seem to be different.
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<!--more-->
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## Approach
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My process of reverse engineering can be seen in the following picture (click for large version).
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[](/posts/images/858D/Reverse-Engineering-big.jpg)
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I started with a picture of the copper side of the PCB which I flipped horizontally,
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so this view is kind of an "X-Ray" view through the front side of the PCB.
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Then I started with marking most of the copper traces in different colors.
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Most of the colors are just randomly chosen, but the yellow area is the +5V VCC line and the 0V areas are marked blue.
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Afterwards I added all the components on a second layer. Due to the mirrored back side graphics,
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I can match the position to the image of the front side of the PCB and still read parts numbers.
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Lastly, I added all part references and as much part information as possible, i.e. part names, pin names, etc.
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I took the values from resistors from their marking visible on the images. However I am not entirely sure
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that all values are correct, because at some places I have the nagging feeling that the values are not matching my expectations.
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## Schematics
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I rebuilt the schematics of the PCB in KiCad. Here is the complete schematic in all it's glory.
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[](/posts/images/858D/858D_Schematic-big.png)
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Let's go through the parts one by one.
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### Mains connection and Heater driver
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[](/posts/images/858D/858D_Schematic_Mains_Heater-big.png)
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The left part of the schematic is about as simple as possible.
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The mains power is bridged over to the connector for the transformer.
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The only notable part is a big suppression capacitor (0.1uF 275V) by Tenta.
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The right part of the schematic is the heater control circuit.
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The microcontroller can control the NPN-transistor Q1 through the limiting resistor R4.
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This pulls down the cathode potential and activates the optocoupler U2 which is a MOC3041.
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The MOC3041 is a triac driver and that it does. It contains a zero-crossing detection
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circuit and controls the triac U1, which in my device is a BTA16.
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