Hugo Holden
Veteran Member
I thought I would post this here, not because the mini-lathe is specifically a computer repair tool, but I have used mine to make spare computer parts, stand offs bushes etc. A mini lathe is such a useful electronics workshop tool for all kinds of mechanical repairs.
In any case, the information in this large article I have recently drafted is about keeping the DC motor speed controllers running.
Sieg actually created what amounts to an analog computer, with a motor control system based on OP amps and they did a really good job on them too.
It is an interesting story:
Initially they used PWM control boards. I watched over the last decade or so, these boards failing and many failed attempts to repair them posted on the net. One big part of the problem was Sieg never published a circuit functional description or any detail on how to set up the multiple pcb adjustments, leaving technicians in the dark.
Also, because the boards were surface mount types, when people attempted shotgun replacements of parts, such as the IC's, the pcb damage escalated until the board was destroyed in many cases.
In the meantime something else happened. Sieg discontinued the PWM design and moved to SCR's using phase control. This system was cheaper to make and eliminated the on board miniature power transformer and the Power Mosfet/s of the previous design. Though IMHO, they don't work quite as well at low speeds.
Now it is impossible to buy the original PWM boards, for the C1 lathe at least, for love or money. Although they were so well done they could be a target for cloning. So the design, starting out in China, could ultimately end up getting copied and cloned elsewhere.
So the idea of this article is to provide the information required to understand, repair and adjust the original PWM pcb. The general principles are the same for other models of Lathes using similar OP amp based PWM controllers. As noted in the article, to understand Sieg's servo system requires that at least 5 principles of OP amp behavior are understood.
Here is the article:
In any case, the information in this large article I have recently drafted is about keeping the DC motor speed controllers running.
Sieg actually created what amounts to an analog computer, with a motor control system based on OP amps and they did a really good job on them too.
It is an interesting story:
Initially they used PWM control boards. I watched over the last decade or so, these boards failing and many failed attempts to repair them posted on the net. One big part of the problem was Sieg never published a circuit functional description or any detail on how to set up the multiple pcb adjustments, leaving technicians in the dark.
Also, because the boards were surface mount types, when people attempted shotgun replacements of parts, such as the IC's, the pcb damage escalated until the board was destroyed in many cases.
In the meantime something else happened. Sieg discontinued the PWM design and moved to SCR's using phase control. This system was cheaper to make and eliminated the on board miniature power transformer and the Power Mosfet/s of the previous design. Though IMHO, they don't work quite as well at low speeds.
Now it is impossible to buy the original PWM boards, for the C1 lathe at least, for love or money. Although they were so well done they could be a target for cloning. So the design, starting out in China, could ultimately end up getting copied and cloned elsewhere.
So the idea of this article is to provide the information required to understand, repair and adjust the original PWM pcb. The general principles are the same for other models of Lathes using similar OP amp based PWM controllers. As noted in the article, to understand Sieg's servo system requires that at least 5 principles of OP amp behavior are understood.
Here is the article: