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Detach output devices from heatsink
Detach output devices from heatsink
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Old 28th September 2021, 08:46 AM   #11
Mark Tillotson is offline Mark Tillotson
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Originally Posted by A Jedi View Post
What is their purpose?
To add impedance at high frequency to prevent unwanted oscillations.
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Old 28th September 2021, 09:25 AM   #12
MikePP is online now MikePP
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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

Last edited by MikePP; 28th September 2021 at 09:28 AM.
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Old 28th September 2021, 09:45 AM   #13
MikePP is online now MikePP
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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.

Last edited by MikePP; 28th September 2021 at 10:02 AM.
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Old 28th September 2021, 10:34 AM   #14
A Jedi is offline A Jedi  United States
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Detach output devices from heatsink
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.
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Old 28th September 2021, 10:51 AM   #15
MikePP is online now MikePP
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Originally Posted by A Jedi View Post
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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Old 28th September 2021, 03:46 PM   #16
adason is offline adason  United States
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Originally Posted by A Jedi View Post
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.
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Old 28th September 2021, 08:21 PM   #17
HighTec is offline HighTec  Croatia
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That's why I don't like silicon pads. Mica are a bit more expensive but more reliable. At least you can squeeze the OP devices without worrying that they will protrude through the pad and touch the heatsink. Besides, silicon pads deteriorate over time.
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