runoffgroove cabsim don't work

[Lucas Grijande]

Hi, can anyone help me? please!!! I've been make it last night but don't work...I use bf245 instead the mpf102,the voltage in the drain of 2 transistors are 4.5v as is especified at runoffgroove and the only that he tell is...nothing! :oops:  :cry:  all the conections are as in the eschematic...the -9 lug goes to  ground?

Thanks

[Joep]

Did you checked the pinouts of the MPF102 and BF245? They are NOT pincompatible.

What's the -9 lug? I don't see it in the schem....

Bye,

Joep

[Lucas Grijande]

The -9v is the black cable in the battery...i don't know where it goes but i'm supossing that it goes to ground.

The mpf102 pins are d s g (i think) and bf245 pins are g s d...yes?

It loock's simple but i've been tested all and i don't know what is hapens...

I'm very confused now...

[Paul Marossy]

Normally, the black wire on the battery clip would be connected to ground.
As long as your pins on the JFET are connected properly, it should work. Did you double check all of your connections against the schematic? Perhaps you didn't connect something that shoul have been or something is connected where it shouldn't be...

[Lucas Grijande]

Thanks paul, i'd re-chec ked the conections against the schematic but i cant see where is the problem... :cry:  i'm thinking about make another and put this throw the window!!! :twisted:

[Paul Marossy]

I've been guilty of those same feelings myself.  :wink:
Or maybe you could building it again. There have been a few circuits that I built which didn't work the first time, but worked great the second time around...

Sometimes putting it away for a week and coming back to it works well. Then mistakes sometimes jump out at you!

[Jered]

Hi are you building this on perf, breadboard, PCB? Test it after each stage. The capacitor/resistor connected to the drain of the first fet is where you shoud listen for soun to see if its working. Get it working then build the next stage and listen again, and so on....chances are you might be making the same mistake in each stage...which will cause you to start tearing your hair out in frustration because it seems hopeless.
 Let us know how it goes.
 Jered

[Paul Marossy]

Duh. Of course! Using an audio probe can be a very handy tool for troubleshooting. If you haven't already built one, you need to.  

Here is how I built mine:
http://www.diyguitarist.com/PDF_Files/DIY-AudioTester.pdf

Hope you figure it out.

[Joep]

Are you using BF245A's? B and C might not work....

[Lucas Grijande]

Thanks guys, a lot!!! i'm using BF245 B...is this the problem??? if yes,what jfets can i put here? in my local shop they don't have mpf102...

I'm building this in a perfboard and i'd put 2 50k trimmers instead the drain resistors...

I'd checked all and i'm sure that the components (except jfets) are the same that are in the eschematic...but nothing.
Now i'll take it another oportunitty...tonight i'll tell you what happend!!!

Thanks

[Lucas Grijande]

I'm not a lucky man...i can't get it working...why??? The circuit seems to be ok but i'm not sure about BF245B's....Can anyone help me on this?

[smoguzbenjamin]

Have you checked the transistor voltages yet? They might be misbiased.

[Lucas Grijande]

Yes i had checked the transistors voltages:

Q1  drain 4.5V  source 1.5V  gate 0.0V
Q2  drain 4.5V  source 1.65V  gate 0.0V

Are this ok? help me please!!!

[B Tremblay]

Those readings look fine, they're close to the voltages from my build.  It still isn't working?

[smoguzbenjamin]

Yeah that's a little wierd. Have you traced it with an audio rpobe yet? It might not seem like it but those things are darn handy

[Chris R]

if the readings on both the fets are right.. maybe you should check the output cap and output jack wiring.

C

[Lucas Grijande]

It's working!!!!! Yuhuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu!!!!!! :lol:  :lol:
Finally it only had a bad cap (first 100n) and now is working pretty well...but when i put my bluesbreaker clone before it and push the switch the level goes down a lot!!! Any idea??? whit only the guitar all it's ok...

Thanks to all you!!!  I'm the worst on this but it is more easy with you,thanks!!! :wink:  Sometimes i can't explain it better because mi english are very poor but your help is very important for me...

[Lucas Grijande]

Another question: Can i tweak it? How? If i change the value of the bass pot to 100k?... can i get more bass? How can i "adapt" the filters to my own taste? marshall sound or other will be posible tweaking the filters?
The sound is very good but i'm a bit inquiet....

[Joep]

Yes, increasing the pot will give more bass.

[smoguzbenjamin]

but when i put my bluesbreaker clone before it and push the switch the level goes down a lot!!! Any idea???

Impedance mismatching maybe? Are you sure that the Bluesbreaker is not causing the volume drop? There are many things that could be happening here