Rat turbo not distorting.

[geezer15]

Hi,

I bought this pedal as faulty and hope to get it working and add a couple of mods ie rat - turbo switch.

Now first things first. I am getting a clean sound out of the pedal -there is no change in sound on or off. The switch is working and the signal is bypassing the circuit when its off. When on the led lights, the volume and tone control work but there is no change in sound when I turn the distortion knob.

I have used an audio probe and get a signal in and out of the chip. Surely the signal out of the chip should be distorted?- it isn't. Thinking the chip must be faulty, I have replaced it (and fitted a socket). There is no change- still not distorted.

I am at a loss as to where else to look. Any suggestions much appreciated.

Thanks

Pete H

[Earthscum]

Just ran into this in another thread: Check your pot. I think it's bad, may have got smoked. If not that, then read through the debugging thread and post voltages here. (you have a DMM, right?). I have a strong feeling it's the pot, or a bad joint associated with the pot. Might check real close for bad solder joints.

[geezer15]

Thanks for yor assistance- I haven't removed the pot to test but in situ it appears to be working correctly 92.2k - 0.
The chip pin voltages are 1- 8.41, 2 8.31, 3- 8.33, 4- 8.85, 5- 0, 6- 8.23, 7- 8.86, 8- 8.38
the diodes (led's) are difficult to read/get to but 8.85 and 0 seems about right.

heres a schematic- http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Thanks
Pete

[petemoore]

1- 8.41  erk
2 8.31,  ''  ''
3- 8.33, ''  ''
4- 8.85,    Connect this pin to ground
5- 0,
6- 8.23,
7- 8.86,
8- 8.38
  See if that helps

[Earthscum]

Actually, pull that diode you replaced and retest your voltages, if you will, and repost here.

If voltages go back to something that appears normal, try putting that diode back in, but backwards from the direction you had it (also, test it to make sure it's not conducting backwards, i.e. burnt out). Then you can throw two sets of voltages up and give us an idea of the circumstances.

Also, this is a stock unit (I assume), so just make sure your #4 pin has good solder joint. Does it appear that the IC has been replaced? If so, make sure it was put in correctly, of course.

...

I just remembered several years ago that one of my buddies showed me his brand new pedal that had a diode clipped like you mention. He asked me if I knew why it was like that. At the time, I really had no clue about electronics except the most basic. Now, I believe this may be a factory thing. If your worker put the polarity protection diode in backwards, you can just clip it, send it out the door, and hope nobody hooks up power backwards to it. That saves a couple from the recycle heap. Basically, taking a pickle out of each jar to save a ton in the long run. easy fix, unit works. Probably considered to be like the spleen, unit works just fine without it.

[geezer15]

Mmm..

I haven't replaced any diodes- just the chip cos I thought the fault was with the old one. Other than that yes the pedal is stock.
Pin 4 goes to ground
I have taken another set of readings but I don't know what is 'more normal' i'm afraid. I suspect I may have shorted the power jack lead against one of the jacks (its just a bare wire) when I took the first readings but I'm not sure its just a thought, when I look now, as I've noticed how easy it is to do that.

OK readings V2
1- 7.94
2- 4.32
3 3.91
4- 0
5- 0
6- 4.32
7- 8.57
8- 4.41

thanks

[ashcat_lt]

 I suspect the resistors+caps which make the "bottom" of the voltage divider are somehow not hitting ground the way they should.

[geezer15]

Got it!

whilst looking for the 47uF electrolytic cap and the two 33k resistors suggested above (I never did none of the 6 electrolytic caps have that value on them and I cant see 3 orange bands on any resistor never mind 2) I found that 1 leg on each of the 4.7uf and 2.2 uf electrolytic caps that run to ground had no solder on them. Came from the factory that way and this is the supposed better built USA pedal rather than the Chinese (I think) Built rat 2. I bought it from a company selling it as sub. looks like they couldnt find it either so I don't feel so bad. Not sure why they didn't send it back to proco themselves though. Maybe they had it in stock too long.

Anyway I can only think I hadn't noticed before as there are a couple of 'empty holes' on the board where there are no componants and these looked the same. Pushed the legs in a blob of solder and away she goes.

OK now I shall look at doing the mods (mightier mouse and reutz mod).

Thanks for your help one and all

[Earthscum]

glad ya got it working! That thought occurred to me, but seeing as how there's 2 caps and 2 resistors to ground, what's the chances of BOTH being bad joints. CRAZY!

If you would've left the 2.2 unsoldered, ya would've had a Reutz modded Rat 

[ashcat_lt]

With the pot not shorted it was the only way you weren't getting meaningful gain.  Is a bit amazing that both caps were loose.  I'm just surprised I actually got it right!

[ode2no1]

i did the ruetz mod to my turbo rat but also replaced one of the clipping led's with a 1n914 and it sounds amazing. might want to give it a shot. so now it's a hybrid between a rat and turbo rat but with lower gain and a nice round tone. i like it as a light overdrive and a ballsy distortion.