Tap Tempo Tremolo Again

[Guybrush]

Hey all

I'm having a second go at building MusicPCB's Tap Tempo Tremolo after screwing my first attempt up beyond repair.

Just hooked it up to my test rig and surprise surprise, it doesn't work. Sound in bypass but nothing when the effect is engaged.

I got my audio probe out connected it to the out lead on my test rig and started poking around. I found that I get tremolo at pin 7 of the TL072 chip, which turns to clean signal when I switch the effect off. Great news!

My question is, can I just run a wire with a 1uf electro cap from the underside of pin 7 to the top right lug (using Madbeads standard wiring diagram) of my 3pdt and just forget the out wire from the board? Surely this is all that is happening while it's on my test rig?

Hope that makes sense.

Thanks in advance.

[jkokura]

I think it sorta makes sense, but I'd suggest you work a little bit longer and find out why your signal isn't getting to the output. I don't have a schem in front of me just this moment, but methinks it shouldn't be too hard to trace the problem down if you know your LFO is working.

Jacob

[Guybrush]

Cheers for the reply Jacob.

Ok, so I have traced the dry signal path with my audio probe using the below image that Guitarmageddon kindly drew for last time I tried building this.



With the effect engaged I get clean signal up to point 4. At point 5 (pin 2 of the IC) it goes dead. I've reflowed the solder joint to pin 2 of the IC socket but still no luck.

Here is the schematic:



Thanks again for your help.

[jkokura]

Okay. So if you're losing signal at the entry point on the IC, there are couple potential problems.

1. Proper power is not getting to the IC.
2. You have a solder bridge with any of the various parts that all connect to the joint in question
3. The IC is bad (happens less than %1 of the time)

What voltages are you getting on that IC?

Jacob

[Guybrush]

Hey Jacob.

I lost my temper with it and just soldered the out lead to the IC. It's working but there's some horrendous ticking in certain settings. That'll teach me for not being patient!

Thanks for your help.

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[midwayfair]

Hey Jacob.

I lost my temper with it and just soldered the out lead to the IC. It's working but there's some horrendous ticking in certain settings. That'll teach me for not being patient!

Thanks for your help.

Sent from my HTC One using Tapatalk

check that the 330pF cap is actually connected to the op amp. If it isn't, you'll hear ticking.

[Guybrush]

I took the cap out and the ticking wasn't affected one way or the other. I tried loads of different caps up to 1uF but there was no difference at all.

There's obviously something wrong and my stupid 'fix' has no doubt confused matters.

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[Guybrush]

Sorry to drag up an old thread but I've decided to stop being lazy and try and fix this properly. Can anyone help?

Voltages from the ICs are as fikkoes:

TapLFO

1- 5.03
2- 2.18
3- 2.00
4- 5.02
5- DMM doesn't settle. Ranges from 2.19 to 2.61
6- 01.9mv
7- DMM doesn't settle. Ranges from 2.03 to 2.96
8- 5.02
9- 5.03
10- 5.03
11- 00.5mv
12- 2.24
13- 5.03
14- 0.01mv

TL072

1- 4.52
2- 4.52
3- 4.49
4- 0.05mv
5- 4.49
6- 4.52
7- 4.53
8- 9.06

Does anyone know of these look right?

[Guitarmageddon]

TL072 voltages look fine. Try swapping the chip (and double check it's orientation)
Look for shorts to ground at points 8 and up too. (DMM set to continuity)
Sent you a Pm too.

[bcalla]

If you read the build thread on DIYSB, you'll see that ticking is a common problem with the TTT.  I'd break this into 2 separate problems.  Get the tremolo to your output, then work on the ticking.

[Guybrush]

Cheers guys. I don't have a replacement chip at the moment but will get a couple orderd today.

I can't spot any solder bridges that could be causing a short.

There are definitely (at least) 2 issues to iron out. I think the best course of action is to get some output and then tackle the ticking. I know some ticking is to be expected but I'm sure the amount I'm getting is not normal. Here are some photos that will hopefully help.





Thanks again

[Guitarmageddon]

Everyone of these I've built ticked at first. Worry about that latter.
You said you'd wired the output direct to the IC, where did you connect it?
Is it the same ic you used for your first build? I'd certainly try another.
I see you've got the gain control as an external pot. Does any signal reach it?

[Guybrush]

Pretty sure it is a new IC. I was getting signal with lots of ticking when I connected the output to lug 7 of the chip. This bodge fix has now been undone and I'm back to not getting any sound when the effect is engaged.

I've just hooked it back up to my test rig and gone over it with my audio probe. I am getting perfect tremolo with only very minor ticking (in extreme settings) when I touch the probe to the below indicated point on the external gain knob. The pad is connected to lug 1 of the pot.



I guess I coud do the same thing I did before and solder the output to the pot lug (instead of the IC lug) but it'd be good to know why it isn't working as intended.

Thanks

[bcalla]

Have you tried posting in the "Building the tap tempo tremolo" thread at DIYSB?  Taylor monitors that thread & helps people troubleshoot.

[Guybrush]

Yep. I drew a blank over there I'm afraid.

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