hot tubes clone help?

[joeyh1485]

I have built a hot tubes clone using the following layout, to no success i might add 

http://gaussmarkov.net/layouts/hottubes/hottubes-project.pdf        (this is a great site by the way, very helpful)

I just seem to get a high pitch squeal, i can hear some sound with my amp turned all the way up?

i have made some changes due to parts availability and they are as follows

c4= 168pf (supposed to be 180pf)
overdrive is 1meg (supposed to be 2meg)
R5 and R7 22k (supposed to be 20k)
c17 44pf (supposed to be 39pf)
i also used a tl07 and i have tried a jrc4558

i dont think any of these changes should stop the pedal working,

pin voltages are as follows

cd4049ube

1. 9.2
2. 0
3. 9.2
4. 3.7
5. 3.4
6. 3.7
7. 3.4
8. 0
9. 9.2
10. 0
11. 3.71
12. 4.08
13. 0
14. 3.72
15. 4.05
16. 0

tl07

1. 4.51
2. 4.46
3. 3.76
4. 0
5. 4.5
6. 4.59
7. 4.56
8. 9.21

Thanks in advance for any and all help with this project

regards

joe

[anchovie]

Check the grounds on your input/output jacks. If that doesn't fix it, make an audio probe and trace the signal from the input to the point where it doesn't sound right.

[Mark Hammer]

You are correct.  None of the changes you made shuold affect the pedal's functionality.

Do note that the original came with an onboard transformer and plugged into the wall.  It will work off a 9v battery - mine worked nicely with one for years...though not the same battery - but the battery won't last a long time.  Can't remember whether it squeals when the battery is low, but I know a number of pedals I've made DO..

[MikeH]

+1 on the audio probe.  Your voltages look reasonable to me.  It's likely you've got a solder bridge someplace causing unwanted noise in the audio path.  An audio probe will help you find exactly where that noise is showing up.  They are very easy to make; if you need to know how just do a search and you'll find a diagram.

[joeyh1485]

Thanks for the help guys

i have made an audio probe but i am having trouble using it, when i place it on the input signal it works fine and i get the full sound of the guitar through but when placed straight after the input cap i get nothing? also if i place it towards the end of the circuit i get the high pitched whinning noise and a very faint guuitar signal?

any ideas? are there certain points on the circuit that i need to place the probe?

sorry for all the questions again and thanks for any help in advance

regards

joe

[PRR]

> when i place it on the input signal it works fine and i get the full sound of the guitar through but when placed straight after the input cap i get nothing?

C1 looks like it is connected, but evidently isn't.

Take it out, clean and tin the leads, tin the PCB pads, and solder better.

(If C1 were connected but IC input node were grounded, you would not have "full guitar" but a very dull tone.)

[joeyh1485]

Thanks for the quick reply mate

i will do just that

although that does not explain why i get a faint signal and high pitch noise when the audio probe is places at the end of the circuit? i would of thought no guitar sound would come through at all if the input cap was not connected?

thanks again i'll keep you updated

[PRR]

> i get a faint signal and high pitch noise
> i would of thought no guitar sound would come through at all

Signals will sneak. Even through empty space.

[joeyh1485]

thanks for the help mate i think im finaly getting somewere 

you were 100% right about the input cap it was knackered when i pulled it i tested it an got 0uf  also the 4558 was knackered as well

im now up to the tone bypass area, on bypass i get nothing and with it not in bypass i get the high pitch background noise. i have changed c15 for a new cap but have not had chance to check it yet. 

dare i say im loving using this home made audio probe! its brought a whole new dimention to my pedal building so thank you anchovie for suggesting it.

i will keep you all updated with my tracing and any more ideas are more than welcome