Detach output devices from heatsink

What's a good way to pry these guys off without damaging them? They're stuck - I tried tapping on them left/right/forward/backward but they won't move.

Bonus question, what are the little circles on the leads?

Thanks!
 

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Try to pry off with a 1/2" utility knife AFTER desoldering.
Why do you need to remove them?


The board has a couple of long legged resistors that have started to pull up the trace on the backside of the board so I need to remove it. I thought it would be easier/faster to get the transistors off the heatsink than to desolder and solder again (this is the first amp I'm taking apart). I guess desoldering makes more sense.
 
Don't unsolder them, just tap repetively (and gently) with a punch from the side , they will eventually release
This is a NAD C370 ;) and I've done loads without damage to the washer or trannys


The ferrites are pointless really. but you don't need to unsolder them anyway if you're just replacing caps, just take the whole board off intact.


Replace the caps because they will be fubared
 
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PS: You may as well resign yourself to replacing all the (electrolytic) caps on both power output boards and the main board too (including the caps on the protection daughter board and the caps on the four pre-amp daughter boards) on this model sooner rather than later. (Leave the plastic NAD caps off these when refitting to give them more ventilation, the locating lugs will probably snap anyway.)



Pretty much 90% of them will be seriously fatigued.


It's a bread and butter job for me, but it's a good amp once done.


Note the print is easily damaged (or accidently shorted to adjacent tracks when resoldering the daughter boards back on)

You will spot the really bad caps because the sleeve colour will have changed (They all started out the same (purple-ish) colour, you'll see some of the worst affected next to heatsinks will have gone grey with the stress.
 
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MikePP you are correct - it's a 370. And yes, I'm replacing all electrolytics everywhere :) The daughter boards were a PITA. I actually did all the work with them still on the mother boards. Probably not the easiest way to do it but I did it lol.


Another trick I use to get those transistors off is use a sled bar off a cd mech , remove plate and screw (obviously), then pop the bar in the hole and again tap gently (whilst biasing it to one side with your fingers), two or three taps and the transistor will detach (washer perfectly intact))
 
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What's a good way to pry these guys off without damaging them? They're stuck - I tried tapping on them left/right/forward/backward but they won't move.

Bonus question, what are the little circles on the leads?

Thanks!

You can desolder the legs by bending them. You can test those output transistors in place on heatsink just to find out if they are good. May be they do not need to be detached.