Little Wing Schematics

[Milnoque]

I am planning to build Geezers "Little Wing Reverb". As part of the process I drew up the schematic and layout in AutoCad. I find this helps me learn a little more about the circuit. I'm hoping someone will review my work and let me know if I got it right.

[Jack_Hester]

Very nice CAD work.  Are you using the export function to save your CAD files to .pdf?  I've only exported to different graphics formats, and the resolution is very low.  I like the resolution of your drawings.  Also, what version of ACAD do you use?  I have '05.  Thanks for posting.

Jack

[Milnoque]

Thanks for the compliment

I'm on AutoCad LT 2010.

Yes that was just an export.

[Milnoque]

I just noticed that I drew the main filter caps upside down in the layout. I'll fix that tomorrow.

[overtone]

Nice.
I like the quality of your work. I use AutoCad to get my own layouts right too.
One question on the layout: are you going to take the layout further to reflect the actual sizes of your larger components (to give you a check that it all fits in the intended chassis) or is your intention just to have a general layout?
Best,
tony

[Jack_Hester]

Well, checking my ACAD '05, I find there is no PDF selection in the export function.  Might have known.  I have another, DraftSight, that reads DWG files.  I'll see if it can export to PDF.  Keep up the good work.

Jack

[Milnoque]

I'd like to go ahead and get the device proportions in the ballpark without getting too anal about it. All this work will apply to every layout I do later. If someone can suggest where I should use carbon comp resistors to best effect I'd like to distinguish the resistor types. I'd also like to come up with some kind of color code for the wire and the connections in the tubes. You can't make any sense of the 6bm8 without it. I don't yet know how to think about that. I've been reading (I haven't figured out how to use the search efficiently) but there's alot of conflicting viewpoints. Feel free to weigh in here.

But first and foremost, do I have the info right on the drawings?

[Milnoque]

Well, checking my ACAD '05, I find there is no PDF selection in the export function.  Might have known.  I have another, DraftSight, that reads DWG files.  I'll see if it can export to PDF.  Keep up the good work.

Jack

When I was running 2003 I used a free download I found. I think it was this: http://deskpdf.en.softonic.com/
When the trial timed out it just added a watermark on my prints that wasn't obtrusive.

[overtone]

I get a pdf output through the plot window, I select pdf instead of a plotter or printer.

I'd like to go ahead and get the device proportions in the ballpark without getting too anal about it...

I think you have good tolerances on the layout. I do not worry about the smaller components, but for larger caps - especially when you put them on the board as I do - then I find AutoCad really comes in it's own.

Wiring: There are no fixed conventions as far as I know for wiring colors, but mostly you will see:
B+: red
Plate / Anode: blue
Cathode: yellow
after that you see variations.
I use green for g1 grid wires, white for g2 screens, black for grounds and twist two different colors for the heaters.

On resistors: have you read these two below links yet?
http://www.geofex.com/article_folders/carbon_comp/carboncomp.htm
http://www.aikenamps.com/ResistorNoise.htm

[Milnoque]

Thanks for the links Overtone. The first one was right on point. I'll have to chew on the Aiken one for a while.

Thanks for the wire color suggestion

[andrew_k]

Very nice. I have a Little Wing PI+power amp section built up that I use for testing preamp designs, I should actually try the Little Wing pre in it one day!

Don't know if it's any help, but here are some parts I drew to 1:1 scale a couple years back - http://leftjustified.net/resources/parts.svg  I use them in inkscape to roughly plot builds and boards. Not highly detailed, but all sizes are right as I had the parts in front of me to measure.

[svejkist]

I am planning to build Geezers "Little Wing Reverb". As part of the process I drew up the schematic and layout in AutoCad. I find this helps me learn a little more about the circuit. I'm hoping someone will review my work and let me know if I got it right.

I think C12 is supposed to go from the SPDT tail switch on the PI to pin 1 (triode grid), rather than to pin 9 (triode plate) as is shown on the schematic PDF. No?

[Ed_Chambley]

Well, checking my ACAD '05, I find there is no PDF selection in the export function.  Might have known.  I have another, DraftSight, that reads DWG files.  I'll see if it can export to PDF.  Keep up the good work.

Jack

Jack, you should be able to print to pdf.  There are a lot of virtual print drivers that provide a Print to PDF option.  I use Adobe PDF driver as it retains editable vector whereas some simply rasterize everything which is fine for a nice preview.

[Jack_Hester]

Jack, you should be able to print to pdf.  There are a lot of virtual print drivers that provide a Print to PDF option.  I use Adobe PDF driver as it retains editable vector whereas some simply rasterize everything which is fine for a nice preview.

I've been using DeskPDF as my PDF print driver, for a number of years.  Along with a lot of others, just to compare.  I like DeskPDF, but like all the others, it doesn't print to exact scale, like printing directly to my Epson Workforce.  The PDF is smaller, maybe 90 to 95% of original size. 

I just thought that it would be nice to have a built-in driver that would plot my drawings to the actual scale.  I have experimented with DeskPDF, and increased the size a bit when saving.  It got close at 103 to 105%, but I don't want to do that every time.  I can plot directly to the Epson and it's dead nuts on, when putting a ruler on the page. 

Jack

[sluckey]

I use Adobe Acrobat Pro v9. It prints my Visio drawings at exact scale if you tell it to do so.

[Jack_Hester]

I'm thinking that my issue is the scaling, when the file is plotted/saved.  And, I haven't found a way to adjust that in DeskPDF.  Only when I print it.  I'll go back and look into the driver setup.  Haven't been there in a while.

Jack

[Ed_Chambley]

Sometimes your driver is set to allow for margins and/or fit to size.  Removing these and printing to actual size will usually do the trick.  I have been using Adobe Acrobat Pro and the PDF printer it installs.  The default setting will reduce the output, but if you uncheck fit to page and insure it is printing 100% it works great.


So it is probably a driver setting.  What I like about the Adobe PDF printer is it does not convert images to raster so I can still open and edit.

[DummyLoad]

on the layout in the title block - should the following:

7 Watt Push/Pull 6GM8 Amplifier

actually be:

7 Watt Push/Pull 6BM8 Amplifier

thanks,


--pete

[svejkist]

Also, I would expect the junction of the two 220Ks between the PI couplers to be grounded.

[HotBluePlates]

I think C12 is supposed to go from the SPDT tail switch on the PI to pin 1 (triode grid), rather than to pin 9 (triode plate) as is shown on the schematic PDF. No?

Yes. It's drawn correctly on the layout but not on the schematic.

Also, I would expect the junction of the two 220Ks between the PI couplers to be grounded.

Correct. This is not properly drawn on either the schematic or layout. There should be a ground connection from the junction of those resistors.