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Tinker
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Posted: 14 January 2018 at 7:38pm | IP Logged Quote Tinker

Ha, apparently none of you bothered to check this schematic! There is a glaring error on the above drawing, which I copied from warpspeed's sketch, unfortunately.
Can you spot it?

So, please disregard the above schematic, I'll attach the corrected one below.

Madness, sorry, can't do PDF. Irfanview, which I use to convert the original bitmap, refuses to save in .pdf format.
What's wrong with the .gif file anyway? Can't you just print it out?

A couple of other items relating to the component designations warpspeed posted. I did a *very* thorough check by comparing my schematic to the PCB tracks and found the following:

T3, ECB should be flipped to read BCE if this transistor is mounted on top of the PCB as per silk screen.

RV1 & RV2, label the pot leg opposite the silkscreen A & V as cw (clockwise) to get the pot rotation correct if the plug in extension wires are used.






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Warpspeed
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Posted: 14 January 2018 at 8:23pm | IP Logged Quote Warpspeed

Well this is something I have never seen before, its quite unique.

Klaus is quite right, but would you believe the 2SD882 data sheet I was using is wrong.

They have numbered their pins backwards, 321 instead of the usual 123.
If you cannot believe a data sheet, what can you believe ?
http://www.st.com/content/ccc/resource/technical/document/datasheet/94/f8/66/07/d9/c8/40/55/CD00062867.pdf/files/CD00062 867.pdf/jcr:content/translations/en.CD00062867.pdf



I looked at this circuit for a long time, printed out the transistor data sheets and tried to reverse engineer the whole thing. So I just assumed the data sheet had the right connections.

As for the safe operating area of the 2SD1047 output transistor, see Figure 2 in the data sheet:
http://www.st.com/content/ccc/resource/technical/document/datasheet/b3/86/80/4e/89/45/4b/6d/DM00026462.pdf/files/DM00026 462.pdf/jcr:content/translations/en.DM00026462.pdf

Thirty volts and three amps takes us right up to the maximum for dc operation.
Its not a safe design.
It has its toes hanging right over the abyss.


Edited by Warpspeed on 14 January 2018 at 8:42pm


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Madness
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Posted: 14 January 2018 at 8:49pm | IP Logged Quote Madness

Klaus to create a PDF normally you print to a PDF printer driver which makes the file. Later versions of windows have this built in, just print the document and select Microsoft Print to PDF, if you are using some other operating system there will be a similar procedure.

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Tinker
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Posted: 14 January 2018 at 10:48pm | IP Logged Quote Tinker

Tony, I looked up that datasheet too but see nothing wrong there with the pins.
Perhaps the confusion lies with the transistor orientation, it has the heat sink surface toward the PCB edge, not facing in as the datasheet picture shows.

Gary, perhaps you are not familiar with the Express PCB schematic program I use to draw this.
It lets me print to my printer and does that automatically as soon as I hit the 'print' button. There is no file I could access (AFAIK)ready for me with that process.

The only way I can save the document other than a .sch file is exporting it as a bitmap.

Edited by Tinker on 14 January 2018 at 10:50pm


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Revlac
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Posted: 14 January 2018 at 10:58pm | IP Logged Quote Revlac

That ST data sheet is different from the NEC data sheet?
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Warpspeed
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Posted: 15 January 2018 at 6:56am | IP Logged Quote Warpspeed

Revlac wrote:
That ST data sheet is different from the NEC data sheet?

Yes, other data sheets have the pins going the normal way with one on the left, and three on the right.
http://www.alldatasheet.com/datasheet-pdf/pdf/77279/NEC/2SD882.html




Edited by Warpspeed on 15 January 2018 at 7:08am


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