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mcoteca  
#1 Posted : Saturday, March 31, 2012 12:52:55 PM(UTC)
mcoteca

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So I'm about to power the Sympatico and check DC supply voltages and, afterwards, the signal path. Can I do this *without* the LM4780 installed? There's a feedback path between the LM4780 output and the THS4130 input; what should I expect at the THS4130 output if the LM4780 is not installed?

Concerning the LM4780, a previous post indicated that it should ALWAYS be powered up attached to a heat sink, even with no signal at its input, is that right?

Heat sink installation: is it important to minimize stress in the LM4780 leads by soldering them AFTER the heat sink is attached and the whole assembly screwed into the rack?

I have the Modushop.biz Pesante Dissipante chassis rack (3U P300mm) so the board assembly will need to screwed to the floor first and that means it will be difficult to access underneath the board for my initial electrical tests. Anyways, would like to basic checks without the heat sink if I may...
Russ White  
#2 Posted : Saturday, March 31, 2012 1:52:07 PM(UTC)
Russ White

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You must use the LM47080 and a heat-sink. Do not run without a heat-sink!!!

When you solder the LM4780 sill depend on you access to the HS. You can do it before or after.
mcoteca  
#3 Posted : Saturday, March 31, 2012 3:08:05 PM(UTC)
mcoteca

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So either:
1) I solder the LM4780 first and then drill the heat sink screw holes to align with the LM4780 holes;
OR
2) I install but don't solder the LM4780, drill the heat sink holes aligning them with the LM4780 holes, and THEN solder the leads.

I prefer approach 2 because the leads are still free to move up/down and sideways slightly in the PCB holes (which I assume are slightly larger than the leads) before I fix them when I solder.
Brian Donegan  
#4 Posted : Saturday, March 31, 2012 5:35:09 PM(UTC)
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Or, use a clamping bar to secure the 4780.
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