Plate Choke wires

[Adrian]

During the assembly of the hardware I came across directions concerning the plate choke wires that I would like some clarification on.
The instructions on page 17 have me cut the BLACK lead to 1" and install some heat shrink over it (not shown in photo).

Questions:
1.  Is the Plate Choke BLACK lead ever used in this application (S.E.X. 2.1)? (I can't find anywhere in the instructions where it is used, but could it be used later?)
2.  Why the heat shrink?
    Is this additional insulation?
    Should it be longer than the 1" cut black lead?

Also, the simplified schematic on page 7 shows three (3) B+ Choke connections.  One of these connections is on only one (1) channel power supply on the negative (-)  side of the 100 microfarad capacitor.  This appears to be connected directly to ground.  Is this correct, or a misprint?

 

[mcandmar]

That caught me out too, the black wire doesn't connect anywhere so the heat shrink is just to prevent it accidentally shorting out on something.  Basically cut it as short as you like, but leave enough room to get a piece of heat shrink on securely.

The 3rd B+ connection shown in the schematic is a misprint so you can ignore that.

 

[Paul Birkeland]

Man, I can't tell you how awesome it is to see builders really studying the manual.  I bet your build will turn out really well!

The plate choke in the SEX amp also does duty in the Stereomour.  For the 2A3 configuration of the Stereomour, too much current is drawn to use the whole winding (red to blue), so the tap is used.  This decreases the inductance a bit, but provides sufficient current headroom.  In the SEX amp, you will never need that current headroom, so the black lead can be snipped off.  It will have nearly the full high voltage B+ present on it, so some heatshrink is prudent here.

On the schematic, one channel of the actual amplifier is shown, and the B+ choke label here indicates a feed form the power supply.
Down at the bottom of the schematic, the power supply is shown for both channels, and there is a B+ choke label for each channel. 

Each B+ choke feed does have its own resistor/capacitor filter, so the 100uF capacitor there is correct.

-PB

 

[mcandmar]

Paul there is a 3rd "B+ choke" label that shouldn't be there on the negative side of the 100uf cap...

 

[Paul Joppa]

You are right, that's a total mistake on my part! It was on rev 1.2 and 1.3 of the circuit and none of us ever saw it. You can't see what you don't expect!

 

[Paul Birkeland]

Wow, how did we never notice that?

 

[Grainger49]

Wow, how did we never notice that?

The same way as troubleshooters looking for a bad connection.  You look at it so long you can't "see" it.  When Paully and I do a build one of reads the instruction and the other does the trouble shooting/looking. 

 

[Adrian]

Thanks for the quick responses.
As for the manuals, I read them through carefully before I start and highlight/mark stuff I want to get right and stuff I don't want to forget, etc.
Cutting off a wire on a perfectly good component without reason just didn't sit right with me so I had to ask.
I could use a detailed schematic with terminal connection numbers etc. but that's just me.  Perhaps Bottlehead handles this as proprietary information.

 

[Paul Birkeland]

We have been adding some of that as our kits progress.  I'll see if I can work that into the Smash manual. 

 

[Paul Joppa]

Yeah, usually I have the circuit drawn (and revised several times) long before there is a production layout or terminal numbers, and in the rush to production we don't go back and number the terminals. Then after the first customer questions start showing up, I'll go back and pencil the terminal numbers into my personal copy of the circuit so I can troubleshoot, because you are right - it helps a lot!