Hearthrob tremolo clipping

[composition4]

Hi,

I recently built markm's Hearthrob tremolo and it's a fantastic sound for such a simple circuit.

The only problem is that it clips (distorts) on anything harder than a medium-loudness guitar strum.  My pickups aren't really high output, and I'm not running anything in front of the pedal. I've tried putting a buffer before/after, no difference.

I tried swapping the 2n5088 transistors with higher (2n5088) and lower (2n4401) HFEs, but no difference to the clipping!

Does anyone else have this problem, or any ideas on how to fix it?

Thanks,
Jonathan

[John Lyons]

Do you have an audio probe?
This way you can trace the circuit to see where the clipping starts.

John

[composition4]

Thanks John,

I ran out of time troubleshooting, but yes I do have an audio probe.. I'll have to wait until the weekend (work getting in the way of my life, such a shame) to get a chance to rip it apart and have a poke around.  I'll report back here on the weekend with results!

Thanks,
Jonathan

[composition4]

Okay so I had a few minutes to have a play around, and found out some strange things...

If I flick the "rate" switch (the one that shifts the range of the rate pot) and play the guitar... it has NO trem and is very fuzzy (like an underbiased transistor) for a few seconds, then gradually gets less fuzzy and the trem increases. Then after a few seconds, it stabilises - unfortunately it still clips/fuzzes though.

Strangely enough, sometimes it seems to distort more than other times...

I haven't had a chance to take it apart yet to audio-probe it, but I though the above info may be a clue?

Thanks
Jonathan

Oh and by the way the battery is fresh too, I checked that first!

[John Lyons]

Sounds like possibly a bad cap.
Check the polarity of the electroytic caps.
It's probably a layout issue.

john

[markm]

My thoughts are that C1 in the layout may be bad or oriented incorrectly.

http://www.aronnelson.com/gallery/main.php/v/MarkMs-Gallery/album15/album76/Hearthrob_Tremolo_LAYOUT.gif.html

[John Lyons]

I meant "Layout" meaning a mis-placed part polarity wise.
Assuming you built on mark board..it's verified.

Very curious that you popped up here Mark...

john

[composition4]

Actually I built it on vero using layout here - http://www.diystompboxes.com/smfforum/index.php?topic=64672.0

Which is apparently verified.  I checked the caps, all oriented correctly. I replaced C1, but clipping still there.

Umm.. what else?  The pedal is fine on bypass, so it's definitely the board..  no solder bridges or the like.  I pulled out the transistors one at a time, but it made no difference to clipping (well, except Q1 which cut the sound off completely when taken out).

I poked around with the audio probe, but unfortunately I'm not exactly sure of how this circuit works so I couldn't "follow" the signal through to find out where it's clipping..

Thanks again for your help so far, I'm open to any suggestions

Jonathan

[composition4]

Oh and one more thing, the clipping didn't seem so bad at first (in fact I only noticed it when playing quite hard), but now (a week or so later) it seems to be getting worse and worse? So much so that even playing the guitar at a moderate hardness now will cause lots of distortion...

As I mentioned before it's definitely not that battery, have tried 3 different ones ranging from 9.0 - 10v

Thanks
Jonathan

[gez]

Schematic (not layout - meaningless things) and voltage readings?

[markm]

Very curious that you popped up here Mark...

john

I'm 'round from time to time John just not as much as before.
I had some heavy personal crap go-down last fall and now I'm on the upswing.
It's good to see y'all again though!!

[John Lyons]

Ok, Mark, at any rate it's good to see you back.
Hopefully things are smoothing out.
Take care.
john

Jonathan
Reflow all of the solder connections and check the board with a magifier.
Make sure there are no solder bridges or tiny wire hairs bridging pads/parts.
If all the caps and components are in right then it's a wiring issue most likely.
Give some voltages for the EBC of each transistor as well.

john