CAREFUL: Problem with the shunt regulator board

[arveedub]

The heat sinks over the MJE5731 transistors on the shunt regulator boards can potentially short IA to OA or IB to OB. They did for me. Luckily noticed this as I was constructing the board & not after I had powered on the amp.

To fix this I cut the corners off the heat sinks with a dremel. Be careful as this problem might not show up at build time. Down the road you could jostle a heat sink & create the short.

The image on page 24 of the manual clearly shows how easily this could happen.

 

[Paul Joppa]

That's a bummer - thanks for noticing and posting! I did check this very carefully against the drawing when I designed the board; I guess the heat sinks are not as identical as I had expected.

There will be a (minor) revision of the board coming out in the next few months; I've moved those pads slightly in response to this post. Meanwhile we'll look into retrofits; probably a bit of insulating tape will do the job.

 

[Grainger49]

The picture looks kind of scary.  I hadn't noticed that.  Will tape slide under the heat sinks if they are already soldered down (well the regulators are soldered down)?

 

[Scratch_P]

Two workarounds I've found that work for me on this subject are:

A).  Do not shove the the 5731's all the way in to the board (insert til they stop and then raise 1/8" or so before soldering).  Fully install heat sink.

B).  Install the 5731's all the way onto the board and do not slide the heat sink on fully.  The heat sink still has plenty of grab, and seems to function just fine.

Hope this helps.

Shawn