400 S2 - Wopl In Progress

7

74sdta

Journeyman
Joined
Sep 2, 2023
Messages
112
Here goes my adventure into the WOPL world. This is my 400 S2 that I have had for 20+ years and pulled it out of storage to get it singing again. It elected itself as the first convert since I could not get the right channel bias down where it needed to be.

Initial look;
Front.jpg
Xfmr.jpg
Inside.jpg
 
Looking at the photos, it appears the amp was mounted in a rack, and the matching rack handles were removed. Hopefully you still have them. The good thing is whoever installed the amp in the rack didn’t butcher the front panel.

The driver board is in pretty good shape, given its age there’s no scorching on the left side of the board where the power supply is located. The 7.5 K 2 watt resistors on the driver board are failure prone. When they open up, the amp goes DC on the output, If you intend to keep this driver board at a minimum replace those two resistors

There are a couple capacitors on the display boards that tend to open up. The lowest cost solution is to replace all the electrolytic capacitors on the boards. The alternative is upgrade to the white oak display boards.
 
It is a clean sample. As far as I know, I am the second owner of this 400 S2, 2000 S2 pre, 5100 S2 tuner and 7000 S2 tape deck (have the original sales receipt from when my uncle purchased the gear). All of it was mounted in a rack and unfortunately, all handles are missing.

Add'l pics of backside;
Trans1.jpgTrans2.jpgInOut.jpg
 
Yes, this unit did not have that nasty crap.

As of now, the unit has been blown apart and the xfmr, p-straps are set aside. The heatsinks have been prepped and sit on the bench with the WO chassis.

I have not melted any solder in a looooog time, so I thought I would start with the WO LED boards as a warm-up. Completed boards;
LEDBd Front.jpg
LEDBd Back.jpg

Now off to see if my station is up to the backplane PEM nut work.
 
Update - not much progress since dogs were occupying garage due to weather. Ordered misc. parts and cleaned up both ends of transformer.
xfmrcaps.jpg

Started backplane work today. Review from the pros - does this look good?

pemshot.jpg
 
74sdta said:
Update - not much progress since dogs were occupying garage due to weather. Ordered misc. parts and cleaned up both ends of transformer.
View attachment 79643

Started backplane work today. Review from the pros - does this look good?

View attachment 79644
Click to expand...
I can’t really tell, but you want the solder on the PEM nuts all the way around, make it look like a metal pimple with a concave sloping side. This takes a lot of heat and a lot of solder.
 
74sdta said:
Update - not much progress since dogs were occupying garage due to weather. Ordered misc. parts and cleaned up both ends of transformer.
View attachment 79643

Started backplane work today. Review from the pros - does this look good?

View attachment 79644
Click to expand...
I agree with the guys, a little blurry but those two that are in focus look like they are not soldered on the back side, is this right? LOTS of heat and solder as this is a HIGH POWER connection.
 
Thanks for the better view but again, maybe it is a shadow or some flux but these areas look a little suspect

1706454115171.png

But let's see what the real experts have to say...
 
Shadows are playing tricks in the picture. I double checked those under magnification and had my daughters check (better eyes) after explaining the end goal to them.

Thank again!
 
Pulpmillguy said:
I agree with the guys, a little blurry but those two that are in focus look like they are not soldered on the back side, is this right? LOTS of heat and solder as this is a HIGH POWER connection.
Click to expand...
It’s also a high stress area- they hold both the transistors and the heatsinks in place, the heatsinks often become a “grab point” when you go to lift it. That being said, be careful with transistor installation, overtightening can pierce the silpads giving rise to a short circuit. A delicate balance…
 
MarkWComer said:
It’s also a high stress area- they hold both the transistors and the heatsinks in place, the heatsinks often become a “grab point” when you go to lift it. That being said, be careful with transistor installation, overtightening can pierce the silpads giving rise to a short circuit. A delicate balance…
Click to expand...
3-4 inch pounds recommended...
 
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