Be careful installing N72s in CH02 chassis!

[tpryan]

Do not allow any live metal bits to make contact with the chassis, even for a second! We've had a number of assembled N72s come back in recent weeks, all with R49 burned open. What is almost certainly happening is that the heatsink of Q6 or some other energized lead is shorting against the chassis. You must make sure there is some clearance between the heat sink and the chassis! Allowing any contact will kill your module and possibly damage PC board traces.

[Squier]

How do you fix this? When you screw it in, it's too tight.

[tpryan]

Just move the Q6 heatsink away from the edge of the board. Make sure the U1 heatsink isn't touching the output transformer. Make sure all the leads are trimmed properly. It really isn't difficult.

[jason baliban]

I am starting to mount these into the chassis but i am seeing where there is a problem.

Even when the heat sink from Q6 is mounted as far from the edge of the board as possible, some of the heat sinks flare out at the top.

In this case, should we bend the heat sink to ensure there is no prob?

Also, is there anything else we can do like apply an insulator on the actual chassis at this contact point?

jB

[tpryan]

By all means, straighten up the tines on the heatsink if need be. We haven't found a need for an extra insulator.

[jason baliban]

Great!

For the cautious like myself, can you recommend anything for insulation....just for safety sake:) Will thick paper even do the trick?

jB

[jason baliban]

Are the two transformer bodies considered LIVE? There seems to be no way to prevent the body of the output transformer from touching the bottom of the chassis and the input transformer from touching the top of the chassis.

jB

[tpryan]

Are the two transformer bodies considered LIVE?

No, the transformer cases are connected to chassis ground.

[deasym@me.com]

I replaced r49 but what else is there to do in order to fix the pre. I already bent the q6 heat since away from the chassis so it won't happen again. But, what do I need to do to get this thing working again?
Thanks for any assistance,
Marshall

[fat0wl]

I had to replace R49 because of the issue with the heat sink touching the chassis. (Not to be rude, but I really wish there was some warning of this in the kit.)

I have a decent amount of experience with soldering but I'm afraid I might be stuck on this... any advice? I could try jumpering somewhere. I am a bit worried my board is starting to get messy and once these problems start compounding it gets over my head.