aussie amp DC offsets

[ngquan]

Hi guys, just looking for some  advise here. I have posted in diyaudio but not much responses. I have 2 HPA Nx 200 modules  which i have recently decided to retap into middle of heat sink to ensure adequate cooling. It was working fine previously. The problem now is one channel showing Dc off set of 0.44V when installed in chassis ,the othe channel Dc off set is 14 mV. The module them selves tested fine with power supply showing Dc offset on both 14mV s. I am wondering the higher Dc offsets when installed in chassis was due to PSU issue or grounding issue?. I have try to establish a better grounding but it is not making much difference.

Quan

[Rumour]

Hi ngquan,

 

I am a new member and just came across your post. Strange problem. Something else must have changed when you moved the modules.

 

If you remove the modules from the heatsink do they measure ok?

Is the mica washer under the transistors still properly intact?

Is the screw that holds the transistors touching anything else?........is there a plastic insulating washer around the screw?  

I would look at the heat sink and see if it is touching anything else that it shouldn't be.

 

Is there some sort of inductive effect happening........if you remove the modules and they measure ok then try moving them closer to the new heatsink position and see if the readings change slightly.

 

Hope the above helps.

[Listener]

ng.

 

Why not give Anthony a call at Aussie Amps.

 

He has always been kind enough to answer my questions....even when they were mindnumbingly stupid!

 

Steven.

 

Oh and I have no idea what is causing the problem, but Mr Rumour may have some good ideas there.

[hochopeper]

From memory this question was posted in Anthony's support forum on diyA also and I think the units were going to be sent back to Anthony or some of the solder joins reflowed by ng, I can't remember seeing a final outcome though ...