tremolo "Der Puls" from Musikding troubleshooting

[stupid.the.cat]

Hey,

I'm new to the DIY world. I've tried to assemble a "Der Puls" tremolo kit from Musikding. The soldering went pretty well, the joints look neat (that's what an experienced friend told me at least). Since I don't know much about how electronics really work, i just followed the schematics and the wiring instructions, very carefully that is.

Still there is a bug somewhere. The bypass works, the led works when I switch it on, but instead of a tremolo i just get the normal guitar signal, a bit quieter than the bypass. One of the potis does nothing (rate), the other increases/decreases the volume (depth).

With my limited knowledge I still tried tyo figure out what went wrong and I started comparing the schematics with the pcb (see links below!). A couple things puzzled me:

1) The connection of R18 to R13 and P2a seems to be missing. It looks like R18 goes straight to C8 and P2b.

2) P1a seems ok, but doesn't P1b have to go into the D3 hole on top of the pcb?

3) P1c is missing on the schematics.

4) It looks like P2b and P2c are switched on the pcb, relative to the schematics.

5) C4 has a polarity on the schematics, but the delivered capacitor hasn't. The value is the same though.

That's it, thanks very much in advance for helping an eager amateur!

Cheers, Philipp

http://diy.musikding.de/wp-content/uploads/2015/03/pulsarschalt_errata.pdf

http://diy.musikding.de/wp-content/uploads/2015/03/pulswire.pdf

[antonis]

So Philipp, instead of wellcome you want us to verify the PCB and then to debug your actual build...
(and you don't even take in mind that it's mid Friday in a mid upgrading forum..)


(just kidding.. - emoticons inactive)
Wellcome... :beer: :beer:

[antonis]

So...
After a quick check according to your observations, the PCB labeling is surely wrong..

I leave to another guy with better vision skills to verify if it's only labeling mistakes (i.e. Rx instead of Ry e.t.c.) or there are trace/wiring mistakes..


P.S.
Maybe it's a good exercise for the weekend - see you on Monday..

[samhay]

Sounds like the LFO (low frequency oscillator) is not working. Check you have the transistors and electrolytic capacitors in the correct way round.

[hd]

Hi everyone,
Like stupid.the.cat, I'm a newbie and I'm beginning with the "Der Puls" tremolo kit from Musikding.
First of all, please excuse my bad English, I'm doing my best to make myself clear.
The problem I have isn't the same than stupid.the.cat but I've prefered to post in this thread than create a new one. Correct me if I'm wrong.
About stupid.the.cat questions, he left the same message on the Musikding forum and Klauss from Musikding answered this (google traduction from german):
"Hello Philipp,

1) which complies with R18 and R13, as is the plan a mistake, the board agrees, however. I will correct!
2) P1b is D2, D2 and D3 are connected to the circuit board.
3) P1c is D2
4) is in the wiring diagram but already correct
5) That's right, the 1uF has no polarity

You should first check your cabling times, whether because everything is going according to wiring diagram. Then the installation direction of the ICs, the electrolytic capacitors and the transistors."
http://musikding.rocks/wbb/index.php/Thread/418006-Der-Puls-Musikding/.
stupid.the.cat, if you could please give a better traduction, that would be very nice!

What I understand : there are mistakes on the schematic but not on the pcb and everything should work!

So, I've tried to follow the "DEBUGGING - What to do when it doesn't work". I've checked 3 times wire, soldered joint, ... and can't find where the problem comes from...
I'm not very familiar with the electronic meter, I tried to do my best, so excuse me if there is some incoherent information... Ask me for better or more, I'll try!

1.What does it do, not do, and sound like? 
The bypass work fine. When switch on, the led works but there's no sound except some interferences (something like "tac, tac-tac, tac, tac-tac, ...")
2.Name of the circuit =
Der Puls, from http://www.musikding.de http://diy.musikding.de/?p=649&lang=en
3.Source of the circuit (URL of schematic or project) =
Schematic: http://diy.musikding.de/wp-content/uploads/2015/03/pulsarschalt_errata.pdf 
and wiring  http://diy.musikding.de/wp-content/uploads/2015/03/pulswire.pdf
4.Any modifications to the circuit?
No
5.Any parts substitutions?
No.
6.Positive ground to negative ground conversion?
No
7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage?
=> 8,61
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead =
Voltage at the circuit board end of the black battery lead =

Here, I don't understand what I have to do exactly... with the black meter lead on output jack and re meter lead on "+9V" on circuit board: 8,36


Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1
C = 0
0,39< B <0,55 (can't stabilize...)
E = 0

Q2
3,1< C <6,9 (can't stabilize...)
-1,4< B<0,15
E= 0

IC1 (or U1)
5,7<P1<5,95
5,45<P2<5,6
P3=4,6
P4=0
P5=0
P6=3,2
P7=3,19
P8=0

D1
A (anode, the non-band end) =8,3
K (cathode, the banded end) =6,78


In advance, thanks for your help!

Tib

[duck_arse]

hello and welcome, hd.

your IC1 pin8 should be battery voltage, 8V61. you'll need to find out why it isn't. on your pcb diagram, pin one has the little black triangle, then number anti-clockwise, so pin8 is opposite pin 1. it seems your oscillator is working, though.

[hd]

Hi duck_arse, thanks a lot for your answer!
So, I've removed and replace the IC1, now voltages are:
IC1
P1=3,60
P2=3,61
P3=4,01
P4=0
P5=0
P6=8,05
P7=8,05
P8=8,41

Battery is now 8,5.
This is quiet a difference. (But P8 should be at 8,5?)

I should have misplaced the IC in the socket. Sorry
(I've checked this several times before... It seems the IC doesn't fit very well in the socket. Do you think that could be a problem? I've ckecked the connection between the IC and the socket and everything is fine).

So now:
1.What does it do, not do, and sound like? 
The bypass work fine. When switch on, the led works but the sound is very low (with amp volume at max) and very bad: there's a kind of tremolo "pulse" effect but very poor and the guitar sound (except the tremolo effect) is very poor too...

I'm getting closer!!

Thanks again for your help.
Tib

[duck_arse]

hd - sockets are ok for expensive parts, parts you wanna maybe swap, and those builders just starting out. some use them for all forever; they are allowed. there are a couple of people have been driven nuts by a faulty build, only to find the IC socket is causing all their trouble. some are worse than others. rant over.

8V41 is close enough for jazz. I'd be guessing it's now down to a wiring error. if you search for "audio probe" on this very forum, you can knock up a tool you'll find very useful. go to it.

[hd]

Hi duck_arse and thanks a lot for your answer!
I'll do an audio probe as soon as possible. I've found the wiki page guide to make one!
I actually don't have a ".1uF capacitor", I only have a 47nF or a 1uF.
Can I use one of these two or do I have to get a .1uF?
A huge thanks once again!

[antonis]

@hd: If you have 2 X 47nF, wire them in parallel and you're more than OK...

If you use a 47nF in place of 100nF you actually double the signal and feedback cut-off frequency (low) which varies from 33Hz to 53Hz..
At 70Hz you'll be OK (for guitar signal) but at 112Hz maybe you'll have some problems with first frets of low E string..

Maybe an oversizing of R2, R3 and R4 should correct this "problem"...

[stupid.the.cat]

Hey everybody,

I'm not online too often (too much distraction...), so I don't reply very quickly...

Thanks for posting in this conversation hd! Everything is helpful at the moment to get a deeper understanding of what might and might not be wrong.

Will re-solder all the wires today and hope for better results...

[duck_arse]

...... and while I'm having a rant .....

So, I've removed and replace the IC1, now voltages are:
IC1
P1=3,60
P2=3,61
P3=4,01
P4=0
P5=0
P6=8,05
P7=8,05
P8=8,41

this. the IC1b in this project is wired as a voltage follower, in that the output (pin 7) follows whatever voltage is applied to the input (pin 5). MANY people doing layouts of projects needing/using a single op-amp stage will use a dual instead, because it makes the layout easier, or something. then they have half an IC, and don't use it, and terminate it incorrectly, as indicated by yer voltages.

the datasheet says the TL07x input won't tolerate/go to ground. that means the output can do -whatever-. and it has, in this case (and the opposite of what might be expected). datasheet also says not input not to V+. the layout means fixing the voltage at pin 5 (it could have been used to buffer the R8//R9 junction) is major surgery.

it may not be a problem ever, but it is wrong, and this is a rant. now [/over]

[hd]

Hi everyone,
And thanks to all of you for your active participation.
@antonis: what "problem" would be corrected by oversizing R2, R3 and R4: the audio probe one or the der pulse pedal one?!
@duck_arse: my english skills don't let me totally understand your "rant"...! I got that there's a layout problem but the pedal could deal with it.
@stupid.the.cat: it's good to hear from you! Please keep giving us news about your debugging affair!
Now I need to get some materials and find some time to make the audio probe and do tests. I'll come back to you as soon as possible!

[antonis]

@antonis: what "problem" would be corrected by oversizing R2, R3 and R4: the audio probe one or the der pulse pedal one?!

None of them..

The "problem" may arise with the 100nF -> 47nF replacement..
(resistors oversizing is nedded for the new RC product compensation..)

edit: I refer to tremolo input circuit because I thought that you didn't have the 100nF input capacitor..

[hd]

@antonis: Thanks for the clarification!
You're right, I have one 100nF... but just one, and it's in the circuit! I need another one for the audio probe.
I'll come back as soon as possible!