700b #2 Clean Slate

[Vintage 700b]

The weather here has been -15° to -19° (below zero!) without the wind chill, so it has been a good time to make some progress on PL 700b #2. I finished the boards about 2 weeks ago, and have the chassis stripped, and ready. A new slate, this stage always feels great. The heat sinks were caked with thermal paste, that is honestly my least favorite job on the build. I did not find any colored round tag with the original assembler’s name, and this amp appears to have never been touched from original build, and was filthy (cat hair, dust, 45 years of filth) so it took a while to get everything cleaned up. Looking forward to assembly and testing. The label on the main board has "ASSY" C and the M.D. says 209 .
It’s a wonderful addiction!!!!! Thanks guys!

 

[laatsch55]

Good man!!

 

[Vintage 700b]

Thanks Lee, now the fun begins. I made a fixture for reworking the heat sinks to match the chassis, with the first 700b,
will use that on custom fitting this set with the chassis/backplanes. I do the work in a Bridgeport, and it works slick.
Easy to deburr the holes for the SHCS's, so the Sil-Pads don't cut.
Then just about everything new, it's such a rewarding build!

 

[laatsch55]

Bridgeport makes it repeatable for sure...

 

[J!m]

Perpendicular and concentric at the very least.

 

[Vintage 700b]

I mentioned the other day that I did not find a colored round tag on this 700b when I tore it down.
I made a new ground strap and fit it up, grabbed the old caps for orientation when I soldered the transformer leads to it
and remembered the one capacitor has "CB" initialed on it. Is this the original builder's initials? I have a lot of PL equipment
and it all seems to have a red, green, blue or yellow paper tag on one of the interior walls. Just curious if you guys recognize
"CB"?
Making good progress, got the backplanes in, tweaking the heat sinks in the shop, and the new bridge rectifier wired up.
Steady as she goes.

 

[laatsch55]

CB does not ring a bell...

 

[laatsch55]

Love your take on a BABB....

 

[Vintage 700b]

Put one like that in my last 700, good for another 45 years!

 

[laatsch55]

Yep, love the shape and application bud!!

 

[Vintage 700b]

Here are a few pictures of my original mockup in 700b. BABB was just too big, and extra screw at the bottom was unnecessary. I trimmed that down and set the prototype for future builds. Screw heads are soldered in place on backside. These shots are of my first 700b. Obviously, I was still tweaking wiring, and in various stages of assembly.

 

[laatsch55]

How did we miss an important development like that. A new twist on a BABB?? Hell yeah!!

 

[Vintage 700b]

Had a very productive day today, if it could go right....it did! I got all of the transistors installed, Backplanes and Main board tested, initial adjustments made on the new 700b, and will hopefully finish up the front panel, input wiring, and DC Protect board tomorrow. Wires are all run and tested for the front panel light board, and I have removed the Zobel Network from the relay board. That wiring for the relay board is all run and checked out as well. I am sharing a few pictures. The quality of Joe's boards honestly sets the standard! It is such a pleasure building these amps.......and then that WOPL'd sound....speaks for itself! So today was more or less the birthday of another WOPL'd 700b.
I set the bias at .360/.360, DC Offset is 0.000 L and 0.001 on the R. My line AC was 126v today. I use one mulltimeter on my Variac and another for testing. In the one picture you can see the "dim: bulb, 126v in and .360 bias. DBT is an antique I rebuilt over 40 years ago! It was old then.
Fun Stuff!

 

[George S.]

Love your Vac-U-Tronic tester with the glass fuse, extremely cool! Congratulations on your build, nicely done!

 

[Vintage 700b]

Yep, tested vacuum motors for many years, and has been steady as my DBT with only a few updates for over 40 .

 

[Gepetto]

Very nice work on the 700B. And I love your Vac-U-Tronic tester too. So cool I had to look up a YouTube video on it.

 

[Vintage 700b]

Thank You Joe,
It's an oldy but a goody and if I need to check the suction on an Electrolux, or vintage Kirby it's dual purpose.
! Looking forward to finishing up this 700B. I said earlier that the quality of the design, and components makes this such a pleasure to build. I have had a 700B in my life since 1978 and it has never sounded as incredible as it does after the full WOPL treatment. I hear things on familiar albums (many I have owned for over 50 years) that I have never heard before. That continues to put a smile on my face as I listen to new music, and savor the collection. Thank You!

 

[laatsch55]

Excellent!! Dig the DBT too!! Love that WOPL sound!!

 

[Vintage 700b]

Tomorrow another WOPL 700B will be born!!! (Officially)

 

[laatsch55]

Not just born, but a quality restart on life!!