Current Lover LFO stopping

[MadeByMike]

Hi all

After boxing up my Current Lover I've realised that from a cold turn on (and if I remove the power for more than 20 seconds or so) - the LFO will not start functioning unless I turn the Bias trim from what normally allows flanging (which is all the way towards the bottom of the board) up and then back to that extreme position.

Does anyone know what might cause this? It's extremely annoying as I love the pedal be can't be tweaking the trims every time I want it to "wake up". Is there something odd about my BIas trimmer needing to be at the extreme to allow flanging?

I've heard talk of C18 needing to be messed with, but could this cause this?

It's a really odd failure type and I would appreciate all the help/advice I can get

Thanks
M

[madbean]

I would try monitoring the dc supply with your DMM from start-up and see if your voltages are sinking somewhere...that could cause the LFO to go off like that.

[MadeByMike]

That's not the problem though - it doesn't start ok on power up and then stop after a bit - on power up the LIFO won't start unless I tweak the bias trim

[MadeByMike]

Maybe it's not the lfo not starting but that the mn3007 won't bias up until I tweak the bias pot down from its max and back up again. What does that suggest? Any readings I can take or tests I can do?

[LaceSensor]

Any chance of trying another mn3007?

[MadeByMike]

Any chance of trying another mn3007?

I've tried two that work fine in a small clone build that exhibit the same issue in my current lover

Please help!

[madbean]

I think you may need to adjust C18. Try incremental values above and below 22pF to see if this fixes the problem. Maybe 15pF, 27pF, 33pF. That's the only thing I can think of ATM, barring some kind of bad solder joint.

[MadeByMike]

I've tried that and no luck. After more investigation by checking on pin7 of the LM311 I can find that the LFO is running in the "working" and "non working" states of the pedal.

The bias setting of the trimpot when I can get flange (or when not working on power up) is giving 3.7V ish on pin3 of the MN3007. So the bias setting looks fine when the flange is occuring or otherwise.

The other MN3007 pins when it's working are:

1 - 8.6
2 - 4.2
3 - 3.7
4 - 0
5 - 0
6 - 4.2
7 - 5.6
8 - 5.6

When it's not flanging, these are the same except pins7 &8 drop to 5.2V

The LM311 voltages are alwats:

1 - 0
2 - 1 to 5V
3 - 1 to 3V
4 - 0
5 - 8.6
6 - 8.6
7 - 3 to 6V
8 - 8.6V


What I'm finding is that when I turn on the power the pedal just passes normal signal and no flange, unless I reset the trimpot by bringing it down to around 1.1V and I can hear a sort of pop or click, then I bring it back up to provide 3.6-3.8V on MN3007 pin3 and I get flange. Bias trim has 4.4V on pin3.

This is driving me nuts. Is there anything else I can check or change? The only sub I have made in the are is a 1n4001 for a 1n4007 around the clock trimmer...

[MadeByMike]

Bump?

[Scruffie]

It's probably the VCO, that section's regularly a pain with these builds.

Have you tried adjusting your clock trimmer to see if it's causing the lock ups?

You might try swapping the 1N4007 for a 1N4148 as it's a faster diode.

That or you might have a cap in backwards somewhere maybe.

[MadeByMike]

Thanks for the reply

yes I've tried setting the clock trimmer to various points in it's range but I'm not sure how this could be the issue - if you read above you'll see I can confirm the LFO/VCO is running in either the state when I'm getting no flanging or the flanging state. I still get the effect that when I start the pedal up after it being not plugged in I get only straight signal and no flange, and I have to back off the bias trim all the way and the reset it to get flanging. This only happens if the power has been removed.

I should have been more clear in that I have a 1n4001 in the VCO section in place of the specified 1n4007, but I doubt this is causing issues?

I will double check my caps (again) but I'm fairly sure that nothing is in backwards.

[LaceSensor]

check the BOM from your build pic at least I think you forgot to jumper C5

[MadeByMike]

You're absolutely right, I haven't jumped that at all - I just read the omit part of the instructions. I'll try that and report back!

Many thanks, fingers crossed!

[LaceSensor]

Well it seems that the issue is to do with power somewhat, so hopefully that fixes it.

Good luck mate.

[Scruffie]

check the BOM from your build pic at least I think you forgot to jumper C5

That'd do it 

Couldn't spot that from the voltages as it's sat at 0V anyway but yeah that would cause your issue.

Just for future reference, the 1N4001 swap for 1N4007 is fine, it's just that section has a habit of acting weird and a 1N4148 is a faster diode (yet still 0.6fV) so it can solve issues with that portion locking up and the clock not modulating properly.