Johnson JM-150 amp PCBs

[Andy S.]

OK, hope you all are doing fine today. I'm hangin' in there.

Got a question for ya. I have a Johnson Millennium Stereo 150 (JM-150) amp that has a leaky Power supply cap. This has double sided soldered pcbs. Usually , a good soldering iron and a solder sucker bulb and I'm on my way. But for some reason, unknown to me, I can't seem to get this thing loose from the board.

I've gotten the solder nice and fluid like, sucked it up, but there always seems to be a big glob left. And even if I heat it up then try to pull the cap from the other side, it doesn't budge. Solder wick doesn't help. All that's done is stick to the solder site!!

So, any recommendations on how to extract the solder and pull the part?


Thanks in advance,

Andy

[Enzo]

The large copper traces are sucking the heat away faster than your iron can replace it.

I use a desoldering station, but even then, on some big stuff I find myself adding heat with my regular iron to get the juices flowing.

I hate wick.

But if removing the solder isn't working, try extracting the part from the solder. In fact, first resolder the part. Having solder all around the legs of the cap will allow heat to travel more easily. Get a small screwdriver under the edge of the cap next to one leg. Now heat that leg until the solder melts, and gently lift the cap a little. Between board flex, flex in the bottom end of the cap, you ought to be able to raise that side a little bit. Don't force it, we don't want to rip the traces off the board or snap the board. Just get a millimeter or two. Now go to the other side and get that side up a mm or two. Alternate side to side gaining a little space each time. Once there is a little space, then each following try will be easier to move. If you cannot get under the thing to start, try pressing the side of the cap as a way of making vertical pressure on the underside.

Once the part is finally worried out, THEN clean the solder from the holes.

[Rob Mercure]

Hey Andy,

If you get where to the point where you simply can't get the thing apart see if "Mike" - can't remember his last name at the moment - is still doing repairs at Buddy Roger's Music. I managed their electronics shop in for a while early in this decade and Mike as a part time tech whose day job was industrial electronics. Hell of a tech and much better than me at "real" electronics - just not as focused on guitar amplification. If anyone one in the city can get that cap out Mike can. Tell him Rob sent you and said "hi."

Rob

PS: What's the "perfect" name for Cinty band? "Jeezle Pete." Oh, do you play corn hole with your sister in the back yard? <grin>

[Andy S.]

Enzo said:

Now heat that leg until the solder melts, and gently lift the cap a little. Between board flex, flex in the bottom end of the cap, you ought to be able to raise that side a little bit. Don't force it, we don't want to rip the traces off the board or snap the board. Just get a millimeter or two. Now go to the other side and get that side up a mm or two. Alternate side to side gaining a little space each time. Once there is a little space, then each following try will be easier to move.

Whoa!! Penetrating glimpses of the obvious on MY part!! I hadn't even noticed that HUGE trace on the component side! Geez! Yeh, that would suck some heat away, alright! I really gotta start working on these things earlier in the evening!

I moved up to my 75 watt gun and added a touch more solder as suggested. Then gently pulled each side as Enzo said. Got it out finally.

Thanks again!

Andy