Help me get my flipster going (w pics)

[mjwhit]

This is my first build. I have done a bit of stuff before, guitar electronics etc but nothing like this.

Working on a flipster.... but when i plug it in i just get a bit of noise(reasonably quiet), no guitar input, but for some reason when i touch the strings on my bass the noise will change.
EDIT=after some tinkering, I have very low output.
Is it possible i put a wrong value capacitor somewere and its blocking these frequencies?

Ive double checked my layout and soldering, but now i dont know what to check now.

Could you guys give me some hints please?

Once i get it going i will add a bypass and an led, but one thing at a time.

Thanks in advance




and itl be going in here once its going

[tehfunk]

I just built one of these for a friend, it's subtle with the settings he uses on it, but he really likes it. anyway, umm, the main thing I can suggest is making an audio probe and going through the circuit, you will have a much easier time finding your mistake that way.

[cpm]

did you put the FETs the right way?

[mjwhit]

did you put the FETs the right way?

Yep  First thing i checked...

After going over everthing i now have an interesting problem. I have normal output but the gain, treble and bass pots dont seem to change anything. Im thinking its a short somewere?

[cpm]

After going over everthing i now have an interesting problem. I have normal output but the gain, treble and bass pots dont seem to change anything. Im thinking its a short somewere?

Gain should be noticeable as it a standard volume btween stages. Going down to 0 its grounded thus silencing the next stages.Check your grounds then.

Your tone pots look like they are linear (i see 1MB). They are supposed to be log (or reverse log?). A linear pot only makes a change in a small part of the full travel.

[mjwhit]

O.k ive checked the grounding. I think the pots arent getting any power at all, but somehow the output is getting the clean original signal? The gain was working for a while, but as soon as i got proper signal out, it stopped working. 

[anchovie]

What bias voltages have you set the trimpots to provide?

[mjwhit]

.8 volts. I know its ment to be around 4-5 but if i change the pots i dont get any signal...


I think im doing it right. when you mean bias voltage you mean one voltimeter probe goes to ground and the other goes to the outout of the pots?

[tehfunk]

.8 volts. I know its ment to be around 4-5 but if i change the pots i dont get any signal...


I think im doing it right. when you mean bias voltage you mean one voltimeter probe goes to ground and the other goes to the outout of the pots?

that's probably what's causing your problems, in this case, the bias voltage (which should be at least 4-5 volts) is the voltage measured with one probe to ground and the other one at the drain of the jfet. You need to adjust the trimpots so that every jfet biases to at least 4-5 volts. the one i built for my friend, I set to 6.5 volts to get some more headroom because he liked that better, but i was using j201's, i'm not sure what you're using.

[mjwhit]

O.k so I think I found the problem!

Something to do with the power supply. My battery was running low so i thought id install an adapter plug instead of replacing the battery. I think the problem was i had attempted to wire up the stereo input jack as a switch and must have done something wrong. I thought i was getting power but aparrently not.

So now the bass/treble and everything is going.

Problem now is that i cant get it to break up, even at full gain its still clean signal. Its also noticably, but not drasticly quieter.
Is this because i used MPF106's?

The only three JFET's available to me are MPF102's MPF106's or 2N5484. What would be your recomendation?
Thanks guys!

[tehfunk]

O.k so I think I found the problem!

Something to do with the power supply. My battery was running low so i thought id install an adapter plug instead of replacing the battery. I think the problem was i had attempted to wire up the stereo input jack as a switch and must have done something wrong. I thought i was getting power but aparrently not.

So now the bass/treble and everything is going.

Problem now is that i cant get it to break up, even at full gain its still clean signal. Its also noticably, but not drasticly quieter.
Is this because i used MPF106's?

The only three JFET's available to me are MPF102's MPF106's or 2N5484. What would be your recomendation?
Thanks guys!

well the break up point is managed by where you bias the transistors, did you bias them to 4.5 volts, you should get a reasonable amount of break up if you did?

[cpm]

With MPF102 there is little breakup if anything. I did mine with a combination of J201, MPF102 andd BF245A

To increase gain you can try lowering resistor values on FET sources, or adding a bypass cap on some more stage, like the 22u in parallel with source resistor.

[Jarno]

Mine also hasn't got a tremendous amount of gain, I used a J201 (high gain) in first position and MPF102's in the rest, I think I'll change the second one to J201 as well.

[cpm]

well, what i actually did is replace teh first stage with a compressor (opto/ldr type), kind of subtle just to push the filpster into tube-like crunchy overdrive

[mjwhit]

was your guys output louder or quieter than the input? mine is disturbingly quieter even at max controls.