Garage system

Hi-Fi discussion
Post Reply
Nobeone
Posts: 984
Joined: Sun Mar 29, 2020 8:32 am

Re: Garage system

Post by Nobeone »

I agree with Mark, don't try and fit a component in a through hole filled with solder.

I would:

a) wet the tip of the iron and apply to one leg, melt the solder, use the solder sucker to remove as much as you can
b) repeat on the other leg
c) using a wetted tip of the iron heat one leg until the remaining solder melts, wriggle the component from the other side of the PCB, you can gently push with a soldering iron tip on the leg to poke it back through, swap to the other leg, bit by bit you will extract the legs. Sometimes they come out easily, sometimes they will need "inching" out, "mm-ing" more like. Want you don't want to do is apply pressure to the pad with the iron, on older PCBs they will lift (not a big deal, push them flat with the iron, glue them back if you need to) or tear (ugly but not an electrical problem, but you will be sad!).
d) clean up the holes ready for the new component, sometimes easiest by putting more solder on and sucking it all back off! Or use desoldering wick.

The hard to remove components will be where to production operative or robot PCB stuffer got a nice tight grip on the legs and bent them almost flush to the PCB leaving little wriggle room. As Mark says, a more destructive approach by snipping legs from above and just desoldering the snipped leg works but leaves you no option to refit if you later want to.

Oh, and the main 6800uF power caps, those snap in beasts will be hard to get out, you will need to be brave, really heat up the joint and get the solder melted, both legs at once if you can, lay the iron right across the legs, and grab the capacitor and wriggle and heat and wriggle. You may need more solder rather then less to get good thermal contact with the iron. When they do come out be careful of splashing solder. Eye protection is not a bad call for this job! I burned myself badly after slipping with an iron in my first few days at Naim, I think desoldering PSU caps from Naits! The women (for they mostly were) in the wiring area of production had hysterics laughing at me or jumped to my aid with freezer spray in near equal measure, so take care! I can still see the scar...
Last edited by Nobeone on Fri Jun 19, 2020 6:26 am, edited 1 time in total.
Nobeone
Posts: 984
Joined: Sun Mar 29, 2020 8:32 am

Re: Garage system

Post by Nobeone »

Next thing I have just remembered, the pre amp PSU axial 3300uF cap will have a ferrite bead super glued to the PCB so each leg goes through a ferrite bead I think. You want to keep these on the PCB, so if they get removed as you remove the cap, refit them with the new cap, solder the cap down, then with the PCB the right way up, position the ferrite bead against the PCB so the leg goes through the middle and put a drop if super glue down to hold it. Don't glue then solder, the fumes are right nasty ... solder then glue!

All the caps are polarised so they all need to go back in the same orientation. You have plenty of photos to help you. Shout if you are unsure on any.
hifiaf
Posts: 1527
Joined: Tue Apr 28, 2020 12:49 am
Contact:

Re: Garage system

Post by hifiaf »

I'm very glad I asked -- this is all very, very helpful. Thanks, Will and Mark. I'm especially glad I didn't tug on the leads from the light panel!

I'm now a little afraid of the big snap-in caps! I'll be extra careful -- but also bold! -- and wear eye protection. They "snap in" by a clockwise motion, I expect, so as I desolder I'll need to twist counterclockwise and lift at once? No going one leg at a time on them, I bet. I notice the Kemet replacements are a little bigger than the Rubycon originals, but there should be space.

This has been such a fun project to this point. I just hope I don't mess up all your good work, Will, with shoddy desoldering.

I'll get to it all this evening.
User avatar
YNWaN
Site Admin
Posts: 6809
Joined: Wed Apr 27, 2011 2:02 pm

Re: Garage system

Post by YNWaN »

It wasn’t for a Nait but when I built my D.C. blocker I soldered in a whole bunch of large snap in caps and then decided I wanted bigger ones - they weren’t all that difficult to remove. On those I did remove the majority of the solder first with the sucker. :).
Mark
Nobeone
Posts: 984
Joined: Sun Mar 29, 2020 8:32 am

Re: Garage system

Post by Nobeone »

I think if you remove the solder you will see what the existing Rubycons legs are like from the bit that pokes through the PCB, some have twists on the snap in legs, some just have straight "fins" that are a tight fit, can't remember and not sure in this case but I do remember I had a hell of job getting some out on some PCBs when I was given the first week task of reclaiming expensive components from boards that failed test. Not sure why, they never went back into the production chain, perhaps for employee builds, but then we always seemed to find a way to make a good unit ;) maybe a test for the new boy ...

Let us hope I have over exagerated the issue and it is a snip as Mark suggests, just trying to arm you with an understanding of potential problems rather than saying they will defo be a big issue
Nobeone
Posts: 984
Joined: Sun Mar 29, 2020 8:32 am

Re: Garage system

Post by Nobeone »

Yes the Kemets are bigger, they should fit, they should be the same size as the factory specials Naim use for service.
User avatar
YNWaN
Site Admin
Posts: 6809
Joined: Wed Apr 27, 2011 2:02 pm

Re: Garage system

Post by YNWaN »

Nobeone wrote: Tue Jun 16, 2020 3:50 pmLet us hope I have over exagerated the issue and it is a snip as Mark suggests, just trying to arm you with an understanding of potential problems rather than saying they will defo be a big issue
Ah well, I didn’t mean to suggest it was a breeze - but it wasn’t as hard as I feared it would be :).
Mark
hifiaf
Posts: 1527
Joined: Tue Apr 28, 2020 12:49 am
Contact:

Re: Garage system

Post by hifiaf »

Well, the PCB is out!

Image

Not a trivial matter -- lots of twisting and careful maneuvering, a fuse holder to remove from the PCB, a ground wire... and most annoyingly, oddly sized nuts holding the PCB to the standoffs. My calipers have them at 5.3mm (27/128"?), just the right size to work neither in an 5 or 6mm socket. Eventually I realized you could hold them pliers and tighten from the underside.

Now time to steel myself for some desoldering... after my run, though!

The PCB traces seem a little... bubbly?

Image
hifiaf
Posts: 1527
Joined: Tue Apr 28, 2020 12:49 am
Contact:

Re: Garage system

Post by hifiaf »

Well, everything is off:

Image

I followed the excellent advice here, and it worked. I didn't realize how effective the Japanese solder sucker would be. In about 75% of cases, the sucker got ALL of the solder out, leaving me just to bend the legs straight and pull them straight out. Even the huge caps weren't much of a problem -- I think my Hakko soldering iron must be pretty powerful — on the maximum temperature, it made short work of the big caps. We'll see how things go tomorrow when I get everything back in, but I think I've left plenty of room in all the pads for the replacements. And I got almost everything out without having to take a destructive approach — most have retained their 30-year-old legs.

Here's the bottom (interesting that the board says Nait 2/3):

Image

And the top:

Image
Nobeone
Posts: 984
Joined: Sun Mar 29, 2020 8:32 am

Re: Garage system

Post by Nobeone »

Great stuff Adam! Like a pro.

I suspect all production Nait2 PCBs are /3. This is a revision number, I would expect /1 to have been the very first prototype PCB for development, this would have been modified to fix a SNAFU and made /2, and then perhaps again to make a /3. During development it is common to make mistakes and to realise although the circuit works it is impractical to make in some way!

Oh the fixings will be metric nominal 5.5 mm.

It isn't the tracks as such but the solder resist that is bubbling, nothing to worry about, probably when it went through the wave solder machine, entirely normal, my memory is they all look like that.
Post Reply