Tonepad Rat Issues

[karter2000]

Hi all,

Just completed a Tonepad Rat (La Rata), but it's not working properly.  The only mod I've done is the Ruetz mod (1k pot).  The pots seem to work as they should  (volume, filter, drive), but the sound is dark and there's no clipping regardless of what diodes I'm using.  Voltages are below:

LM308
1: 9.34
2: 8.76
3: 8.76
4: 9.20
5: 0
6: 8.86
7: 9.40
8: 9.33

2n5458
D: 9.41
G: 9.41
S: 4.33

I'm getting about 2v through the diodes, but it drops quite rapidly to 0.

Thanks,
Lyle

[GibsonGM]

 - You have a short somewhere...pin 4 is ground. Your voltages are all showing ~ supply voltage; not good!  Pin 3 should be near 1/2 supply voltage.  Check that Vb reads approx. 4.5V.   Remove IC, and check that there are no shorts between the pins in the socket....
- Is the IC in the circuit backwards?   Is that 1N4002 diode pointing the right way in the power line?

- Almost always, it's a short somewhere, a part in backwards, or 'builder error'.  Go back over everything again, Reaalllly closely, and double-triple-quad check your soldering.  Sometimes you even need a magnifying glass!

The 2V dropping to 0 indicates a short to me...check across your + and - terminals (with no battery, of course) for continuity (or measure resistance - if it is very low, it = short!).
Keep at it, you'll get it working!! 

~Mike   

[karter2000]

Hello, thank you for your reply.  It was indeed a short (next time, don't build while sick).

lt seems to work fine, but I'm not 100% crazy about the sound.  Without diodes, I'm getting lots of opamp distortion.  I know that's characteristic of Rat's, but my Vintage Rat reissue seems cleaner.  Also the drive and volume pots seem to not have much range.  The new voltages are below:

1. 9.09
2. 4.59
3. 2.23
4. 0
5. 0
6. 4.59
7. 9.21
8. 9.08

Vb is about 4.5v

2n5458:
D: 9.21
G: 1.82
S: 0

Thanks again,
Lyle