power supply filter should be connected to chassis?

[fala]

Hi, some power inlets have built in filters that have been composed of some cap and coils. I used to connect earth of this filter to chassis and physical earth directly and connect chassis via a high impedance connection to board ground. I lost many sensitive ICs (total values over 300$) in past few months and I didn't know why? during development there are many times that accidentally chassis and board ground become short circuit. It usually causes a visible spark suggesting a surge current. Now, I noticed that most valuable Ics that I have lost had a ground pin in addition to V+/V- pins. I suspected spikes in power supply can enter chassis via cap in power supply filter and causes a huge voltage between board ground and chassis and when accidentally chassis and board ground become short circuit a surge current causes a surge voltage over my sensitive ICs well beyond their threshold and causes them to burn. Can it be the cause why my sensitive ICs like ADCs and DACs are burnt?

 

[Js_Ong]

Hi, Fala,

have u checked the capasitor terminal and the output if your supply using voltmeter? what is the figure? and check if any component of your suppy has short circuited to the chasis. if yes, this can cause serious damage to your component.

 

[fala]

Hi Js_Ong,
There is no short circuit to chassis but line is not very clean. I can touch the chassis without being killed. Chassis and line are isolated. chassis is connected to physical earth and chassis is connected via high impedance to board ground. also earth of line filter is also connected to chassis. so if I put one hand on board's ground and another hand on chassis(physical earth) it gives me a minor shock.
Also another thing that I forgot to mention in original post is that board is connected to computer via RS232 so board ground should be connected to computer ground.