WOPL 400 4/ powerups went well, one PEM not so much

silver_face

silver_face

Journeyman
Joined
Feb 18, 2018
Messages
216
Location
Southern Indiana
Tagline
---6 and 7 days work week, no end in sight
I did not get one PEM soldered correctly on the back of the left board. PEM is in the board straight, but the solder must have been a cold solder.
I did the first powerup, went well. Got to the point, it's time to install to second row of transistors. The top screw on the XQ5 location on the left
board got stuck in the PEM about 3/4 way through and I could not move it.

So I try to back the screw out and the PEM broke lose from the board. AW-Oh, now what?
I did not want to take the boards back out of the chassis, if the PEM broke lose all the way from the board I could have.

So, I got my soldering iron out and soldered the PEM from the front side of the board, got it too were the PEM would not spin,
while I now was able to back the transistor screw out. As far as I can tell, the nylon bushing is still good and not melted.

I finished installing the transistor with the screw still not wanting to go all the way in, so I used washers on the screw.

Went on to finish all four powerups.
 

Attachments

  • IMG_20190401_152923.jpg
    IMG_20190401_152923.jpg
    827.2 KB · Views: 37
  • IMG_20190401_153239.jpg
    IMG_20190401_153239.jpg
    1.4 MB · Views: 36
My powerup's went as:

L board
+83.7
-83.6
output/ground
0.0

R board
+83.7
-83.5
output/ground
0.0
 
Looks like more than 1 cold solder joint.

I have at times, ran a 6-32 tape through each pem after soldering them in.
 
Great idea, I will locate a 6-32 tap. I don't like the washers under the screw head.
 
Yes tap it out you will be good to go, you might want to reflow those solder joints I like to get the solder to flow to the topside of each component as well to assure good solid contact especially on multi layer boards, this will assure way better trouble free performance down the road... just my 2 cents
 
Ray has an excellent point. For through hole components you want a good solder joint on both sides of the board.
 
Thanks roccus and NavLinear for pointing out the solder joint on both sides of the boards need solder, makes sense.
I will do that tomorrow. I will do all my boards in the future that way with through holes.
 
For those who may be interested I got these from Navlinear. They make a good job to hold the Pems flat to the board. Dennis may still have these. I leave the little Kapton seal over the treaded hole till soldering is finished
 

Attachments

  • 4FA139D0-DDED-4B99-893C-6DEAD3B84633.jpeg
    4FA139D0-DDED-4B99-893C-6DEAD3B84633.jpeg
    1.4 MB · Views: 24
  • B96BFFFC-7C80-4FE7-8843-E0D535E7ED07.jpeg
    B96BFFFC-7C80-4FE7-8843-E0D535E7ED07.jpeg
    2.3 MB · Views: 26
silver_face said:
Thanks roccus and NavLinear for pointing out the solder joint on both sides of the boards need solder, makes sense.
I will do that tomorrow. I will do all my boards in the future that way with through holes.
Click to expand...


Are you going to try and do that in place, or remove the boards???
 
If you are using the PEM holders...... You better crank up the heat on your iron. a screw running through the pem will wick A LOT OF HEAT away from the joint. I don't use them.
 
you don't need to try to solder BOTH sides. With the CORRECT amount of heat and the application of flux, the solder will flow and get to both sides.
 
WOPL Sniffer said:
HUH??? what screws and washers???
Click to expand...

In the pic, I show one output with a screw that has washers under the screw head to hold the output transistor down,
because the screw stopped short of going through the pem. This is the one I have to re-tap and fix, and check all the other pem's.
Just the one is troublesome. Also do some solder work on the other components where there is no solder on the printed side.
So, I'm pulling the outputs and boards back out to fix what I missed the first time. With this said, I already had this powered up
through all four stages of powerups with I thought was good results. Just want to make sure all is well for the next 40 years of
amp life.
 

Attachments

  • IMG_20190401_153239.jpg
    IMG_20190401_153239.jpg
    1.4 MB · Views: 6
silver_face said:
In the pic, I show one output with a screw that has washers under the screw head to hold the output transistor down,
because the screw stopped short of going through the pem. This is the one I have to re-tap and fix, and check all the other pem's.
Just the one is troublesome. Also do some solder work on the other components where there is no solder on the printed side.
So, I'm pulling the outputs and boards back out to fix what I missed the first time. With this said, I already had this powered up
through all four stages of powerups with I thought was good results. Just want to make sure all is well for the next 40 years of
amp life.
Click to expand...

Well, I guess I made that a lot longer answer than it should have been, sorry bout that, Perry...……...
 
Last edited:
It was about a year ago when I did these boards, if my memory is correct, I had my solder iron set at 750 degrees.
Maybe flux and solder flow was wrong.
 

Attachments

  • IMG_20180226_015417.jpg
    IMG_20180226_015417.jpg
    1 MB · Views: 7
You must log in or register to reply here.
Back
Top