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Projects => General Questions => Topic started by: darrenw6000 on March 17, 2017, 10:33:18 PM

Title: pork barrel MN3207 MN3007
Post by: darrenw6000 on March 17, 2017, 10:33:18 PM
with the extra pins that are on the board, normal pinout of an MN3007 is that pin 1 is ground and in this circuit the added pins would send voltage to pin 1.
Title: Re: pork barrel MN3207 MN3007
Post by: madbean on March 17, 2017, 10:41:44 PM
That's because it is a negative ground circuit. MN3007 were designed for positive ground. When you use +dc you have to flip power and ground on the BBD. Check out the CE-2 schem and you will see the same thing.

http://www.hobby-hour.com/electronics/s/schematics/boss-ce2-chorus-schematic.gif
Title: Re: pork barrel MN3207 MN3007
Post by: darrenw6000 on March 17, 2017, 10:58:16 PM
so the mn3207 is for standard negative ground circuits
Title: Re: pork barrel MN3207 MN3007
Post by: madbean on March 18, 2017, 12:38:40 AM
Correct. In general, the MN320x is the lower-voltage negative ground version of its MN300x counter-part. Both can be used for negative ground circuits, however.
Title: Re: pork barrel MN3207 MN3007
Post by: darrenw6000 on March 18, 2017, 08:25:41 AM
Also in that schematic there appears to be N channel JFET(Q9) is that just something to do with how Boss did the LED switching?
Also on there looks like the output is coming from pin 1 of IC1 but on the pork barrel schematic its coming from pin 7,
Title: Re: pork barrel MN3207 MN3007
Post by: somnif on March 18, 2017, 10:18:03 AM
Quote from: darrenw6000 on March 18, 2017, 08:25:41 AM
Also in that schematic there appears to be N channel JFET(Q9) is that just something to do with how Boss did the LED switching?
Also on there looks like the output is coming from pin 1 of IC1 but on the pork barrel schematic its coming from pin 7,

Correct on the boss-style switching. http://www.geofex.com/Article_Folders/bosstech.pdf  I've always presumed they went with this set up due to the cost of mechanical switches (saving a few cents a box adds up I suppose) but maybe those wacky Roland engineers had some other logic in mind.