Small Clone Debug help please!

[Al Heeley]

Small clone build from the Tonepad (excellent) pcb. Guitar going thru but no chorus effect. I checked the LM358 and it pulses a LED so the clock bit seems to be ok.
Here's the voltages:
Q1(Used 2n3906 instead of 5087) 1 = E, 2=B, 3=C
1 = 5.0V
2 = 4.3
3 = 0
Q2 (2n5088)
1 = 4.9
2 = 5.4
3 = 8.4
Q3 (2n5088)
1 = 7.8
2 = 8.4
3 = 8.4    - this doesn't seem right??

[Al Heeley]

LM358
1 oscillates between 1 and 2.5V
2 = 3.8
3 = 3.8
4 = 0
5 oscillates between 1.3 and 3v
6 = 2v
7 oscillates between 0.2 and 7.1v
8 = 8.4v

MN3007
1 = 7.8v
2 = 3.8
3 = 5.5
4 = 0
5 = 0
6 = 3.8v
7 = 5.5
8 = 5.5

4558 chip
1 = 4.2
2 = 4.2
3 = 4.1
4 = 0
5 = 4.2
6 = 4.2
7 = 4.2
8 = 8.4

The 100k trim pot seems ineffective, but it does let out a tiny phthtt sound when i rotate it past the centre position!

[Al Heeley]

The 14-pin chip is a Phillips HEF4047BP - I have no idea if this is significant

[Al Heeley]

http://www.tonepad.com/buildReports.asp?projectID=8
Some of the build reports are talking about 100k depth pot, but the layout states a 10k linear. is this an error or has the circuit been modded later?

Any advice please? This layout is doing my head in

[oskar]

MN3007
1 = 7.8v
2 = 3.8
3 = 5.5
4 = 0
5 = 0
6 = 3.8v
7 = 5.5
8 = 5.5

The 100k trim pot seems ineffective, but it does let out a tiny phthtt sound when i rotate it past the centre position!

The voltages look OK-ish... You have the LFO working and sound coming through so it looks like the delay part isn't
behaving like it should. Pins 10 and 11 on the 4047 see half of the chips supply. Which I interpret as a 50% dutycycle
squarewave. Is the 150p cap properly connected? If not, the clock could be working too fast for the MN3007.

The 14-pin chip is a Phillips HEF4047BP - I have no idea if this is significant

The 4xxx series cmos chips are high speed digital stuff. I don't think it really matters which 4047 you use. I think your is
working.

Audioprobe!
Also your battery doesn't look brand new...

[Al Heeley]

rechecked the 150pF cap, its fine, also new battery tried but no difference.
The 4047 chip pin voltages are:
1 = 7.6v
2 = .5
3 = 5.9
4 = 7.7
5 = 7.7
6 = 7.7
7 = 0
8 = 0
9 = 0
10 = 3.8
11 = 3.8
12 = 0
13 = 7.6
14 = 7.7

[oskar]

Audioprobe!
Do you have signal all the way to the MN3007?

[Al Heeley]

I'll get the probe out now and check - thanks for bearing with me!

[Al Heeley]

ok, signal going into 4558 (pin 3) and out pin 1, with a bit more gain. it goes round to the trimpot but nothing emerges. nothing getting to MN3007 or to Q2. I'll put another trimpot in and see what happens.

[Al Heeley]

Nothing happening here. Does it matter if I've used 4148 diodes instead of the 1n914?

[oskar]

it goes round to the trimpot but nothing emerges. nothing getting to MN3007 or to Q2. I'll put another trimpot in and see what happens.

If the trimpot is in one of the extreme settings the signal will be all gone...
You say it reaches the trimpot (wiper), then surely it will reach the 3k3/3n3 net to the right of it.
Continue with the probe.

[Al Heeley]

OK I have signal going into 4558 pin 3 and out of pin 1.
It goes by pad A and across the 22k resistor, after the next 20k R and the 10K r the signal gets very low indeed. (pad D) - maybe the signal drop across the 20k is far bigger than I would expect? I've resoldered it and checked the value but all is ok.

From 4558 pin 1 it also flows thru the 1uF electrolytic cap up to teh 100k trimpot central wiper, but there's no signal on the trimpot 1 or 3 (1 goes to ground trace, 3 is +9v trace). Is this ok?
Signal also goes thru this 1uF e-cap, thru the 3k3 and the 10k resistors up to the Q1 emitter pin. I get no signal on B or C. Is this ok?

I'm still not detecting much of a signal getting to Q2 - so I guess theres nothing for it to amplify and pass on to the MN3007 chip?

[oskar]

OK I have signal going into 4558 pin 3 and out of pin 1.
It goes by pad A and across the 22k resistor, after the next 20k R and the 10K r the signal gets very low indeed. (pad D) - maybe the signal drop across the 20k is far bigger than I would expect? I've resoldered it and checked the value but all is ok.

That is the clean signal and it workes like it should.

From 4558 pin 1 it also flows thru the 1uF electrolytic cap up to teh 100k trimpot central wiper, but there's no signal on the trimpot 1 or 3 (1 goes to ground trace, 3 is +9v trace). Is this ok?

Yes.

I'm still not detecting much of a signal getting to Q2 - so I guess theres nothing for it to amplify and pass on to the MN3007 chip?

Yes, the problem is either the signal into that chip or it's clocked too fast.

I get no signal on B or C. Is this ok?

Yes.

[Al Heeley]

could it be a duff 3007 chip? (Hong kong ebay purchase)

[oskar]

Yes. Or the signal isn't reaching the chip or the chip is clocked too fast

Signal also goes thru this 1uF e-cap, thru the 3k3 and the 10k resistors up to the Q1 emitter pin. I get no signal on B or C. Is this ok?

The 10k resistors connects to the base of Q1 which should see a signal as should Q1 emitter.
Q1 collector is grounded and you should not get a signal here.

[Al Heeley]

is there anything other than the 150pF cap that might cause the clock to go too fast? How can i slow it? the 150pF cap has been double checked for good connection.

[oskar]

is there anything other than the 150pF cap that might cause the clock to go too fast?

I don't think so.

How can i slow it?

Put an extra cap in paralell with the 150p.

I'm not convinced though that you've got signal all the way to the MN3007. You should be able to hear it on the
junction 33k/12k before pin 3.

[Al Heeley]

Tried the extra cap in parallel to the 150pF cap, next to the pins 1 & 14 of the 4047, but no difference.

Junction 33/12k comes from the anode of the D1 diode, there's no signal coming after D1, but there's plenty before it (the cathode side fed from q1). This is where I have the 4148 diode not the recommended 1n914 type. could this be the issue? I thought the 2 types were pretty much interchangeable.

I get no audio signal on Q2 base. C reads 8.6v, b reads 5.8 and e reads 5.3v.

Appreciate the input on this, I'm getting despondant!

[Al Heeley]

heres a shot of the schematic, green trace is where i've traced audio signal to.

It all gets too faint at Q2, and signal stops at the diode after Q1.
Help!
Please!

[craigg]

i built this a while ago (with the univibe mods - worth doing once yours is debugged).  I had a few problems, and eventually started to take components off the board trying to find the problem.  Turned out that while I had socketed all the chips, one chip wasn't properly inserted in its socket.  I was still getting some sound, but obviously it wasn't working properly.  I couldn't see it because the board is so tight.  Not saying this is your problem, but...