tremulus problems

[1878]

Hello.

I bought a Tremulus Lune PCB from Tonepad. I've populated it and completed all the offboard wiring, but all I get when I switch it on is a pronounced THUMP THUMP THUMP !! The speed LED doesn't work either. I thought I may have wired the LED wrong, so I tried a new LED and it still doesn't work !?!?

I get a signal in bypass, but nothing when it's switched on. Just the thumping. Any ideas ??

Thanks.

I forgot to mention, I could only get a low noise TL072. It's called a TL072IP (low noise) on the bag it came in. Would this have any adverse affects ??

[Krinor]

That op amp should be fine. Low noise is after all what you want isn't it ?

You did put the op amp and the transistors on sockets didn't you ? Always a smart move since then you don't need to be afraid of overheating them while soldering. And also you don't need to worry about the hassle involved in removing them if you happen to orient them the wrong way...

As everyone else would say: "Check and re check your soldering carefully". I built mine on a PCB from Tonepad too, and with all due respect I have to say that this PCB was not the best I've worked on. It was very easy to ruin the traces - which I was unlucky enough to do... I didn't even notice that one of the traces had been accidentally cut until I had finished the whole thing. I found the problem using a magnifying glass in the end. It had cracked loose from the heat of re flowing of a joint. Of course yours might be from an entirely different batch, so this might not be important, but I just thought I'd draw attention to it - just in case. Thoroughly check every trace and soldering joint. Maybe even re flow some joints ? Check the orientation on op amps and transistors. Once you spot the problem it's probably something easy like a bad ground connection or something like that.

Good luck.

[1878]

Thanks for the reply.

Just gone over everything and I can't see any mistakes. I'll get my makeshift probe on it tomorrow and see what's what. I'm wondering if there's a vactrol problem to be honest. I had the same trouble when I built the Uglyface, so I'll check that out first.

Thanks again.

[FuzzAldrin]

I have mine working now, and have the same problem (I think)

It thumps as the LFO is cycling when I turn it on.
On fuzzcentral he says:

"The first thing that I noticed was a loud "popping" as the LFO cycled. After looking through the Commonsound tweaking guide for the Tremulus Lune (available on the Tremulus Lune page of the Commonsound site...see the links below in the 'Project Files' section below) and following the directions therein, I soldered a 0.001µF capacitor across the trimpot and added a 100µF capacitor from V+ to ground. These two simple additions to the circuit completely solved the problem, leaving me with the best tremolo on the planet!"

Im gonna try this out.

[1878]

Unfortunately, I have no guitar signal coming through at all, just the thump. I was too busy to have a look at it today, but I'm hoping I can get an hour or two with it tomorrow.

[1878]

I've just re-soldered everything and checked the polarity of the caps, etc. All seems good. I've been over it with a makeshift tester and it seems there's no signal getting in whatsoever. Checked the input jack and 3PDT and they're fine too. I removed the Vactrol (homemade) and soldered in a new LED and LDR so I could see if the LED was getting power... no.

The thumping is still there when it's switched on, as is the signal in bypass. The traces on the PCB are covered with a white plastic, so I can't tell if any of them are broken, but I've just ordered myself a multimeter, so I'm hoping that can tell me more when it arrives. Saying that, I've never used one before so I'll probably use it wrong and get a load of false readings 

I'll get back when I've investigated more.

Thanks everyone.

[Mick Bailey]

Can you post some pics?

[Barcode80]

this sounds like you might have the in and out jacks connected backward. this would mean in bypass signal would pass, because direction is irrelevant. but if you reverse the in and out jacks, you will get similar problems. double check that.

[1878]

Thanks again for the replies.

I've checked the input/output jacks and they're connected correctly. I made that mistake once before (and subsequently felt incredibly stupid !!) on a different build and I swore never to make it again... I still checked to make sure though 

I only ever build pedals with a 9v jack, so I replaced the stereo input jack with a mono. I must've done something wrong initially because even though there's no change in signal, the 'speed' LED now lights, but doesn't pulse. The 'status' LED has worked all along. Does this give anyone anymore clues ??

Thanks.

[Barcode80]

if you can post some up close pics of your build, we may be able to give more info.

[1878]

I'll try and sort some pics out tomorrow, but I'm not too sure how they'd help because you can't see the traces due to the plastic covering.

I'm seriously fu**ed off with this build !! I thought PCB's were gonna be so much easier ?!?! It seems like a waste of time and money at the moment, because after checking it over for what seems like the 100th time, I still can't see anything wrong. I've even changed some components (ic's and polarised caps) in the hope one of them was knackered.

Does anyone know of a perfboard layout for the lune ?? I seem to be more successful with that.

[oskar]

Patience!

1. Wait for the multimeter to come.
2. Post voltages.

[1878]

Yes... patience.

And breathe...

The multimeter came today, so I'll check and post findings when I get home from work tomorrow. It's probably gonna be something completely stupid that one of you will spot straight away.

Thanks again.

[1878]

What are the most relevant measurements you would need to spot a problem ?? I've measured and recorded all the pins on the ic's as well as the polarised caps and LED/LDR.

Thanks.

I've also (and this might be where the problem lies) performed these mods as found on tonepad.com...

There has been a couple of changes to the schematic since this project was posted, those are:

In the Audio path:
Change the two 47k resistors to 220k.
Change trimpot to a 10k, you may want to use a panel mounted pot for easier adjustment instead. (I did)
Add a 330pF capacitor across opamp pins 6 and 7.

In the LFO:
Change 100ohm resistor to 2k7.
Change the 100uF cap to a 10uF.

Symmetry mod parts (two diodes and 500k pot) need to be wired offboard in this layout.

[oskar]

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Follow the template in this link.

[Mick Bailey]

Because your LED doesn't flash I'm wondering if there isn't any isolation between the LED/LDR combo. Possibly a short in this area, either tracks bridged by unetched copper, or a solder bridge allowing the pulsed DC that should be modulating the LED appearing directly across the LDR. Just a guess, though.

I've just checked my own circuit and regardless of the control settings I get just a few millivolts DC across the LDR (actually 0.004v) so you could check this as an indication.

FWIW, I etched a PCB from the layout on Fuzz Central and this worked fine first time. I think it's worthwhile finding out why your particular build is presenting problems rather than rebuilding on perfboard or vero. You may even end up with different problems if you take this route.

The component changes won't stop the pedal from working if you use the values suggested.

[1878]

The LDR voltages were very low. I'll write them up properly tomorrow. I made a bit of a rushed job of it and I want to check them again to make sure. I must admit, at first glance, everything looks ok. I know it's not though !?!?

I removed my homemade Vactrol and replaced it with an LED and LDR so I could see if the LED lit up, it doesn't, but it seems to be getting power. It's a mystery at the moment, but I'm thinking it's something really simple. It's annoying me so much because as soon as this pedal is finished, so is my pedalboard !!

[1878]

These are the verified measurements for the ic's:

TL072

1 - 0.15     8 - 9.10
2 - 0.58     7 - 1.77
3 - 0.58     6 - 0.59
4 - 0.01     5 - 0.57

4558

1 - 8.20     8 - 9.20
2 - 8.20     7 - 8.43
3 - 9.06     6 - 9.06
4 - 0.00     5 - 9.06

The LED and the corresponding LDR measurements:

LED                  LDR

Pos - 4.20        0.19
Neg - 8.20       0.94

Just realised I soldered the Vactrol LED incorrectly. It's now lit, but doesn't pulse.

I hope someone can glean some info from these. I haven't got time to measure the rest of the componants at the moment.

[oskar]

-Check Vb ( schematic top/ left ) It should be 4.5V

[1878]

I'm working from the layout at tonepad.com...

http://www.tonepad.com/getFile.asp?id=84

Where's Vb on that ?? Actually, what's Vb ?? I'm still pretty much a beginner at all this.