Repairing Hobart Champ 2060 control board

Hello,
My machinist friend asked me if I can repair this board for him. I am capable of testing, sourcing and replacing individual parts but I am working
blind. All I have is a dead control board containing bunch of LF347 op amps, their accompanying discrete components, some driver transistors and one IXYS power transistor which I was told that is what usually blows. I tested this transistor independently by driving it with a signal generator and it the scope tells me that it is ok. I do not have the schematic and the entire board is covered in thick layer of conformal coating which makes it very difficult to determine the fault. Does anyone know what normally goes bad with these boards?
Machine - Hobart Champ 2060 Board #198203
--

Boris Mohar



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sounds like that you need to put a very sharp needle point on your leads.
I would rather test that transistor with base/emitter/collector measurements as gains or losses can fool you even though you know what level that you are inputting to the transistor.
b

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.