TAPLFO Multiplier Issue

[YouAre]

I recently breadboarded a TAPLFO tempo clock as stock (seen here http://electricdruid.net/images/lfo/TapClock.gif ), and the clock would often oscillate at twice what I tap. I know it was twice because I tapped along to a metronome and noticed the LED would blink twice as fast. To test this theory, I tapped on every other beat and the light would stay in time. I replaced the resistor for pin 11 (multiplier pin) with a potentiometer setup identical to the tempo pin. The potentiometer had no effect on the tempo of the LED.

I swapped out the chip (I have a few), crystal, caps, pots. I also checked that the rails were running at 5v (~4.92v), and even moved the entire circuit to a different half of the breadboard. All to no avail.

Finally, I built the Tap Trem project on Taylor's PCB, and the clock works just fine. I've been in contact with both Taylor, and Tom Wiltshire regarding this issue. I'd like to get this working on a breadboard for future prototyping of projects. I'd also like to find out what the problem is before I try to perf this sucker, and then run into the same problem. That would likely cause a brain hemorrhage.

Do any of you have thoughts on what the problem could be or similar experiences?

Thanks for all your help!

[YouAre]

Ok after having spoken with Taylor and Tom again, we're still perplexed. I'm thinking that if any of you guys have a layout (that's one sided) I can reference that against my breadboard layout to see what's going on.

It can be any layout using the taplfo utilizing any of the features. I'd really appreciate it!

Thanks!

[Hides-His-Eyes]

Poor layout could lead to interference "triggering" the tap...

[Taylor]

My experience is that, with such a decisive issue, the problem is rarely the subtle or obscure problems we hope for. It's usually that something was just wired up wrong. Have you rebuilt it on your breadboard and verified that you had wired it properly, but that it's not working?

My PCB follows the schem in Tom's datasheet pretty closely, but the schem for my board can be viewed directly here:

http://musicpcb.com/pcbs/tap-tempo-tremolo/

As frustrating as it is, I think it's unlikely that the physical layout would cause the issue that everything works except the multiplier knob. I think it's more likely that either it was wired up weird, or you had a jumper to ground that you didn't notice, etc.

[Hides-His-Eyes]

If it was half I'd just say 'multiplier' was shorted, but twice requires ~2.5/6 Vss at the pin; that's a weird number to be stuck at.

[Taylor]

True. YouAre, did you measure the voltage at pin 11 when it was misbehaving?

[YouAre]

Poor layout could lead to interference "triggering" the tap...

That's what I'm thinking. It's why I was hoping there's a single sided layout out there that I can try.

If it was half I'd just say 'multiplier' was shorted, but twice requires ~2.5/6 Vss at the pin; that's a weird number to be stuck at.

True. YouAre, did you measure the voltage at pin 11 when it was misbehaving?

Heh, I set it to 5v with a 10k resistor to the rails, which should theoretically default it to 1x (as per the instructions in the datasheet). Then I replaced it with a pot, and set the voltage to 1volt, which shooooould be the 1x multiplier. This was measured at the middle lug of the waveform pot. I really doubt the voltage would be different at pin 11

And Taylor, I consulted your schematic from the Tap Trem instructions. I've done a lot of debugging over the past 2 weeks, and was hoping to try a layout to get a different perspective.

Thanks again for all the support guys.

[Valoosj]

I have a one-sided layout, but I'm in Peru and London till the 18th ... You could always make your own based on the pics of mine in the other topic on the trem?

[.Mike]

I did a verified single-sided layout for the VCLFO, which is very similar to the TAPLFO and could easily be modified since they are so similar. Link

If I have a chance, I will try to breadboard a TAPLFO circuit this weekend.

Mike

[YouAre]

I have a one-sided layout, but I'm in Peru and London till the 18th ... You could always make your own based on the pics of mine in the other topic on the trem?

Peru AND London? Luuucky! I'll look it up. Thanks! Which topic is it? The "design a tap tempo trem," or Taylors "build the...?"

I did a verified single-sided layout for the VCLFO, which is very similar to the TAPLFO and could easily be modified since they are so similar. Link

If I have a chance, I will try to breadboard a TAPLFO circuit this weekend.

Mike

I'll check it out, thank you! And thank you so much for breadboarding it!

[.Mike]

OK, it is on my breadboard exactly as shown, with the exception of using 680R for the LED current limiting resistors, since those are what I had handy.

I was unable to reproduce any of the speed doubling that you experienced-- my LED flashed in time with the taps.

I can take photos... make a sketch... take voltages... record a video...

What would help you...?

Mike

[Hides-His-Eyes]

Poor layout could lead to interference "triggering" the tap...

That's what I'm thinking. It's why I was hoping there's a single sided layout out there that I can try.

If it was half I'd just say 'multiplier' was shorted, but twice requires ~2.5/6 Vss at the pin; that's a weird number to be stuck at.

True. YouAre, did you measure the voltage at pin 11 when it was misbehaving?

Heh, I set it to 5v with a 10k resistor to the rails, which should theoretically default it to 1x (as per the instructions in the datasheet). Then I replaced it with a pot, and set the voltage to 1volt, which shooooould be the 1x multiplier. This was measured at the middle lug of the waveform pot. I really doubt the voltage would be different at pin 11

And Taylor, I consulted your schematic from the Tap Trem instructions. I've done a lot of debugging over the past 2 weeks, and was hoping to try a layout to get a different perspective.

Thanks again for all the support guys.

You're debugging. Check it.

[YouAre]

OK, it is on my breadboard exactly as shown, with the exception of using 680R for the LED current limiting resistors, since those are what I had handy.

I was unable to reproduce any of the speed doubling that you experienced-- my LED flashed in time with the taps.

I can take photos... make a sketch... take voltages... record a video...

What would help you...?

Mike

Wow, Mike you're awesome.

A photo or a sketch would be amazing! Thank you so much! I'll try rebuilding mine tonight based on that.

You're debugging. Check it.

Good point. Will do.

[Valoosj]

I have a one-sided layout, but I'm in Peru and London till the 18th ... You could always make your own based on the pics of mine in the other topic on the trem?

Peru AND London? Luuucky! I'll look it up. Thanks! Which topic is it? The "design a tap tempo trem," or Taylors "build the...?"

I did a verified single-sided layout for the VCLFO, which is very similar to the TAPLFO and could easily be modified since they are so similar. Link

If I have a chance, I will try to breadboard a TAPLFO circuit this weekend.

Mike

I'll check it out, thank you! And thank you so much for breadboarding it!

Build the tap t ... by Taylor

[.Mike]

Breadboard equivalent:



Voltages
1   4.95
2   0.91
3   1.58
4   4.89
5   .15 - 4.82
6   0
7   0 - 4.72
8   4.9
9   2.47
10   4.9
11   4.9
12   0
13   0
14   0

I hope this helps! Let me know if there is anything else that you think might help.

Mike

[YouAre]

I hope this helps! Let me know if there is anything else that you think might help.

Mike

Mike,

I was thinking of driving to Cali (from Jersey) this summer for a little graduation trip before working in the real world. I may have to make a 900 mile detour to go to Georgia to buy you a drink.

So I followed your breadboard exactly and....it works! Guess what it was....

PIN 8!!!!!!!

In the datasheet for the clock source ( http://electricdruid.net/images/lfo/TapClock.gif ) it shows that pin 8 is tied to the rails via a 10k resistor. In my datasheet however, it's just floating and not connected to anything...In Taylor's Schematic, and all the links on the Electric Druid show tying pin 8 to 5v, but my datasheet has pin 8 connected to nothing...It WOULD be my like that I get an old datasheet. Haha

So wow. Yeah. Turns out I'm not entirely incompetent, just using old instructions   

Thanks again for everything guys!

[.Mike]

Sweeeet! I'm glad you got it working.

I kind of felt that I needed to pay forward the help that Tom gave me when I was working on my VCLFO tremolo.

I was getting a stutter in the square wave every twelve flashes. I just couldn't figure it out, and nobody here had used Tom's LFO as I was using it. Tom was nice enough to help me through it. He knew the answer right away-- and quickly had me up and running (I had pin 11 S&H Rate tied to +5 when it should have been 0).

My tremolo went on to be the datasheet tremolo, and subsequently the base for Taylor's awesome tap tempo tremolo project, so I'm like seeing other people using Tom's LFOs.

Have fun!

Mike

[Taylor]

Ah, how frustrating for you! But glad it got sorted. Tom changed pin 8 into a "next multiplier" switch in early 2010, so you must have the pre-TAPLFO2 datasheet from 2009.

[YouAre]

Ah, how frustrating for you! But glad it got sorted. Tom changed pin 8 into a "next multiplier" switch in early 2010, so you must have the pre-TAPLFO2 datasheet from 2009.

It's strange. The top of the Datasheet says TapLFO2, and the next multiplier is labeled on it...so I'm just going to take solace in the fact that....I was setting it up right! It was the datasheet that was wrong   

[Taylor]

That's the spirit!