help with a Fooldrive Please

[jkokura]

1.What does it do, not do, and sound like?

Currently it bypasses signal, and when engaged, though the LED's light up, I only get a strange hissing noise. No guitar, quiet or otherwise. Just a gentle background fffffisssssssss.

2.Name of the circuit =

Fooltone Fooldrive 2 - this is a pre mosfet iteration of a famous pedal. This version contains a compcut/none/vintage switch.

3.Source of the circuit (URL of schematic or project) =

I got the circuit from a European site. I do not have links, only what's on my hardrive. If it's cool for me to post the schem and layout I will, but there's obviously a reason this project is hard to find details on.

4.Any modifications to the circuit? Y or N

No.

5.Any parts substitutions? If yes, list them.

2x 1N4007's instead of In4005's, 2x 10uf Tant caps instead of 10uf AE caps

6.Positive ground to negative ground conversion? Y or N

I'm not sure.

7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? =>

Power supply = 9.62v

Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead = 9.62v
Voltage at the circuit board end of the black battery lead = 0

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1 = C828 on far right of pic
C = 9.62v
B = 4.56v
E = 0.72v

Q2 = C828 in middle left of pic
C= 9.62v
B= 4.36v
E= 0.54v

IC1 = JRC4558D
P1 4.79v
P2 4.89
P3 4.79v
P4 0v
P5 4.79v
P6 4.79v
P7 4.79
P8 9.62

D1 = 1N4007 at upper Middle of pic
A (anode, the non-band end) = 0
K (cathode, the banded end) = 9.62v

D2 = 1N4007 at lower middle of pic
A = 4.79v
K = 4.89v

D3= 1N914 at lower middle of pic
A = 4.89v
K = 4.79v



That's it for now folks. I'm trying to see and probe to find a problem. I think the problem is with my wiring from the switches to the board personally, so I'm analyzing that first.

If you have an suggestions or see an immediate problem with the numbers above, I appreciate all help and will strive to be all ears open also.

Jacob

[PRR]

C = 9.62v
B = 4.56v
E = 0.72v
C= 9.62v
B= 4.36v
E= 0.54v

These are incorrect. B is usually 0.6V up from E. However without a plan I can't guess if the transistors are blown, leads mixed-up, or you have some other fault.

[petemoore]

  Transistor or cap around the wrong way ?

[jkokura]

I'll check the caps and the trannies first. Thanks guys.

Pete, I love that you're always willing to make a suggestion to help, on all my "help" threads you post - thank you for that.

Also, I looked. I don't even have a schem for this - just a layout. I'll see if I can post that layout tomorrow.

Jacob

[jkokura]

Ok, I think it might be a problem with the transistors. I double checked and found a 2sc828 pinout from here: http://www.datasheet4u.com/html/C/8/2/C828_ETC.pdf.html

That PDF I downloaded said the 2sc828 pinout is ECB, but the Layout for my project is asking for a Transistor that's EBC - Could that be the problem?

So what transistor should I use now? I have limited access and would have to order some, but I have 1x 5088, 3x MPSA18 and I have 2x 2N3904's which I've used in other Tubescreamer effects. I'm fairly certain the 3904 is a EBC transistor (what I need) and the MPSA18's are CBE, meaning if I mount them 'backwards' they would have the correct pinout also.

Any ideas anyone?

Jacob

[svstee]

either the 5088 or the 3904 should work fine, they both have the pinout you need. Usually TS type circuits are not overly picky about which transistor you use anyway. 

[jkokura]

So I swapped in the 3904's, and the situation got a 'little' bit better.

Now the Q's are:

E = 9.26v
B = 1.6v
C = 1.0v

I now have less fizz, and a slight amount of guitar sound, but barely anything - the pedal is still unusable.

I'm using an audio probe, and now sound is no longer getting to the first transistor. It was before I swapped them out. I tried re-soldering a bunch of the joints between the input and that transistor, but nothing helped. Is it possible for a film cap to crap out on me when I'm swapping out a trannie? I didn't really apply that much heat, and I did so allowing all the solder joints to cool before starting another one.

Also, on another pedal I put a diode in backwards - I found the problem, but the pedal still isn't working. What's the result of having a backwards diode in - does it fry the diode? does it fry other parts around it? It's D2 in Tonpad's ross comp if you're curious.

Jacob

[petemoore]

E = 9.26v
B = 1.6v
C = 1.0v
  The order of voltage low to high looks reversed, emitter 'near' ground, base a diode drop above that, collector above base by a good bit at least.
  Either or the measurments notes got reversed.
  What does the Aud-probe have to say about this transistor input/output gain relationship ?

[jkokura]

I think I put the transistors in backwards again. I think the EBC of the 3904 is backwards to the layout, and I thought it was the same as.

What do you do with two datasheets that give opposite pinouts for the same transistor?

Jacob

[petemoore]

What do you do with two datasheets that give opposite pinouts for the same transistor?
  Hopefully detect and get rid of one.
  The Hfe meter should show some typical gain number like 300 for 3904 when it's pins are in the right way around, note the marks by the socket EBCE, four for three type of pins, by whipping the transistor around, you can get any order of pins connected without having to bend any.
  Lookin' at it's markings, most plastic NPN's are EBC, pins down.

[jkokura]

What do you do with two datasheets that give opposite pinouts for the same transistor?
  Hopefully detect and get rid of one.
  The Hfe meter should show some typical gain number like 300 for 3904 when it's pins are in the right way around, note the marks by the socket EBCE, four for three type of pins, by whipping the transistor around, you can get any order of pins connected without having to bend any.
  Lookin' at it's markings, most plastic NPN's are EBC, pins down.

Brilliant Pete, I never thought of using my DMM - I'll figure it out from that.

Jacob

[jkokura]

Now working! Glad I got it going, it sounds pretty good with the 3904's in, I'm thinking about changing them for the MPSA18's to see if it makes a difference. I also have a burr brown Op Amp to try, but I was saving that for a TS808 I'm building. the 4558 is nice in it though.

There's a huge range of sound on this project - the three settings (Compcut, None, Vintage) have a wide variety to them. Compcut is a cleaner, boost like setting. None is a pretty good all around setting, likely what I'll use the most, and sounds very tube-screamer like. The vintage setting has a bit more saturation, and sounds a little more 'lo-fi' to my ears. Could be useful in some circumstances, but I'd need to push the tone knob to 9-10.

I'm going to build a 'mosfet' version from Bean one of these days. I wanted one of the earlier iterations of this project to try first. Thanks for the help.

Jacob