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Old 3rd December 2007, 08:18 AM   #1
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Default Help with Schematic

Hi Folks,

Need a little help with this schematic. Simple question I believe.

Concerning the power supply caps as circled in the schematic - Although not marked on the circuit diagram, I presume that these are electrolytic caps with the positive side closest to the choke?

Can anyone just confirm this for me. I have asked a similar question abut this schematic - it just seems a little sloppy (by that I mean non-precise) to me but I can't find any other.

I have just had the chassis made and am hoping to post a completed amp within the next month or so. I am making a stereo version of the mark 3 from the ground up - probably should have made a couple of monoblocks, did not really appreciate how much this thing was going to weigh!

Cheers,

Rob
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Old 3rd December 2007, 09:00 AM   #2
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You are right in saying they are electros. The schemnatic is clear in that that is a standard symbol for an electro with the curved line representing the cathode.

Shoog
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Old 3rd December 2007, 09:06 AM   #3
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Hey thanks Shoog,

That's what I thought but (and here's my point about the sloppy schematic) they have used that symbol for all of the caps, including the non-polarized ones!

Thanks for the help,

Rob
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Old 3rd December 2007, 02:34 PM   #4
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Quote:
they have used that symbol for all of the caps, including the non-polarized ones!
Not only that, but 50 uF caps for the negative bias supply are shown with the + symbol in the correct place, but the curved line in the wrong place.

Oh, well. Hopefully they had good assembly drawings when they built these, and not just the schematic.
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Old 4th December 2007, 12:14 PM   #5
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Hi Robert,

Well I think that a lot of the guts of the amp was built onto a preassembled circuit board, so that obviously made the schematic a little less critical. However, 50 years down the track and I am building this from the circuit diagram alone, so little inaccuracies have the potential to mess things up for me. Thanks for the help.

Rob
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Old 4th December 2007, 08:51 PM   #6
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Rob,

Your assumption is correct. As a matter of fact I just finished rebuilding my Mark IIIs from scratch. Please take a look in my project.

Norm
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Old 4th December 2007, 10:48 PM   #7
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Here is the inside pic of my amp
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Old 4th December 2007, 10:48 PM   #8
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and here is the outside.
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Old 5th December 2007, 04:58 AM   #9
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Hey beautufil work Truenorth,

How does it sound?

As mentioned, I should have mine finished within a couple of weeks and will post some photo's.

Cheers,

Rob
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Old 5th December 2007, 07:15 AM   #10
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Hey Rob,

My sounds darn good. Couple of pointers in case you don't know it already:
1] For the power supply caps (which you circled) try to stick to the values or close to the values shown. Larger capacitance doesn't do any good with the tubes... those caps (single or multiple of) should be rated higher than 600VDC.
2] the .25uF coupling caps depending on the type does alter the sound of the amp. I ended up with jensen oil/paper caps for smoothness.

Please post your amp when you are done.

Cheers,

Norm
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