please check my ROG Peppermill vero layout

[jamiefbolton]

could somebody help double check this before I make it. Instead of a 50k trim on the J201 I've used a voltage divider i've seen on the MuAmp. Just making sure this is okay?



schematic here http://runoffgroove.com/peppermill.html

thanks
jamie

[Kearns892]

Jamie,

I noticed a few things about your layout:

1) You added a 1M resistor from input to ground that is not in the schematic, was this intentional?

2) I don't think you have applied the voltage divider properly here, and, as far as I understand, a voltage divider is not called for at all in this situation. Currently you have no resistance between the power source and the Drain of the JFET, the voltage divider then connects the Drain, and some additional voltage, to the Source, neither of which is called for by the 50k trim. The trimpot is wired as a variable resistor, all that needs to be done to sub for it is simply replace the trim pot with a single fixed resistor going from +9v to the J201 Drain. You should build the rest of the circuit then use some alligator clips, a 50k pot, and a multimeter to select the fixed resistor.

Thats all I saw, but I just gave it a glance over.
Let me know if I need to elaborate. I hope this helps.

[jamiefbolton]

Thanks for the help!

I added the 1M as a pull down resistor. Is this okay?

I see what you are saying about the voltage divider. I'll do what you said and figure it out that way. I just don't want to mess with a trim pot on vero layout. I have one already wired up on an old perf layout. I'll check the trim pot there and see what i come up with.

Can someone else verify this new info too? Just in case..


thanks
jamie

[jamiefbolton]

ok here is a new layout. i've removed the voltage divider and only used a single resistor (value TBD) from the 9+ to the J201 Drain.

[Kearns892]

Can't see the new layout.

[jamiefbolton]

sorry about that....let try this again..

[jamiefbolton]

ok, so i got a working layout hopefully. but i am getting weird voltages on the drains of both the J201 and BS170.

i ended up using resistors in series or parallel  to get the voltages close to correct. is this quasi-normal? in the last peppermill i built, the voltages to the BS170 were correct using the 4.7k from the 9+, but this time things were different. i'm sure the layout was close to the same and i didn't make a layout error, but nevertheless the voltages were off.

i ended up using a fixed resistor of 18.3k to the the j201 voltages at 4.49

so this is what i ended up with. ROG calls for voltages at Drain

BS170          J201
5.62             4.52

i ended up with

BS170        J201
5.79           4.49

this is as close as i could get. will this be okay? stuff will still sound right?