Fred's "my wife thinks I'm crazy" 700B conversion

[FredR]

Had so much fun doing 400s I figured a 700B was in order. Chassis is ready. On to the backplanes.

Edit 10/12/14: This thread is for the guys (or gals?) that are interested in trying to do a WOPL mod themselves. It's doable assuming you are able to:
1) solder without mucking things up (temp controlled solder iron required)
2) be detail oriented (at least while you do this project)
3) follow instructions (Joe will tell you exactly what to do in the docs, answers emails with questions quickly)
4) take you time doing the work (if you tend to blast through projects, forget about it)
Good luck!

 

[gadget73]

Looks good so far. Are those new can caps? If so, where did you pick those up ?

 

[Northwinds]

Hey Fred! I love the 400s myself and can't wait for a 700B to be built to the max for me. I will be watching this thread and see how you build yours!

 

[FredR]

Looks good so far. Are those new can caps? If so, where did you pick those up ?

Thanks. Got them from Joe.

 

[FredR]

Hey Fred! I love the 400s myself and can't wait for a 700B to be built to the max for me. I will be watching this thread and see how you build yours!

I took some extra time to read up on past 700 threads and am glad I did. Particularly getting the star point ground right and proper routing of AC for lowest noise.

 

[Gepetto]

Had so much fun doing 400s I figured a 700B was in order. Chassis is ready. On to the backplanes.

Nice work Fred...

 

[laatsch55]

Looks good so far. Are those new can caps? If so, where did you pick those up ?

'73, we have group buys of the PS caps from time to time. Contact NavLinear . The last batch was 15kuf/160 volt for 30.00 each.

 

[FredR]

Nice work Fred...

Thanks Joe. Getting better on the meniscus thing too, but then I get a bit cocky and screw one up. Fred.

 

[laatsch55]

Thanks Joe. Getting better on the meniscus thing too, but then I get a bit cocky and screw one up. Fred.

Hard to be consistent ain't it??

 

[Gepetto]

Thanks Joe. Getting better on the meniscus thing too, but then I get a bit cocky and screw one up. Fred.

Great looking bus bar too Fred. Nicely fabricated

 

[FredR]

Thanks Joe. Must admit I've been smitten by the BABB concept. Backplanes populated and wired. Time to drop them in the chassis.

 

[Northwinds]

Moving along nicely! Loos great so far Fred!

 

[FredR]

In the first photo you'll see that I use thermal grease between the heatsinks and the chassis. Idea is to more efficiently use the mass of the chassis to keep the outputs cooler.

Also in that photo you'll see a couple tabs of duct tape on the heatsink. The 700s differ from the 8-fin 400s in that the 700 heatsinks come in 4 units of 2 fins each whereas the 400s are 2 units of 4 fins each. With the 400 this allows you to use the backplane standoffs between fins 2/3 and fins 6/7 to hold the heatsinks on the outside of the chassis and the backplanes on the inside the chassis while you wire up the backplane. Not so with the 700. Duct tape to the rescue.

Once the heatsinks are taped in place I used several screws to temporarily hold each unit down while backplane wiring occurs. See second photo. NOTE WELL: these screws must come out before powering the amp as they produce a short!

The third photo shows the backplane secured in the chassis by the temporary screws and ready for wiring. Time to fire up the soldering iron.

 

[laatsch55]

How is the fit on the standoff bushings going. Are you having to resize any holes??

 

[laatsch55]

A guy after my own heart, stainless allen heads....

 

[jbeckva]

A guy after my own heart, stainless allen heads....

Did ya provide these on your own Fred, or did they come with the kit? My last 400 kit had 'em in it (props to Joe... those make it NICE .. and easier to wrangle in tight spaces like that)

Looking real good there!

 

[laatsch55]

Joe went with stainless allen heads????????


COOLNESS!!

 

[FredR]

How is the fit on the standoff bushings going. Are you having to resize any holes??

I drilled out the heatsink holes with a letter c drill bit per Joe's docs. Checked the chassis holes for undersize and they were fine. Bushings went in smoothly.

 

[FredR]

A guy after my own heart, stainless allen heads....

Yep, Joe's providing them now. Real nice too.

 

[laatsch55]

A lot easier to hold an allen head machine screw on the wrench and do some inserting...