unicab aka the sizzling kettle

[makisushi]

Any idea what could cause this kind of noise? Sometimes the pedal works fine, sometimes it start doing this weird noise... I tried to change the ICs, reflow, change power supply, clean the pcb with isopropyl alcohol, but no differences. It seems to get worst the longer the pedal is powered on.

 

[makisushi]

Soaked (99% alcohol) and cleaned with a toothbrush. Cold result, waiting for the pop to comes back. There's so much crap on the PCB, I don't know if you can see in the picture. I don't know what happened beside using aliexpress flux.


IC1 (BOTTOM)

1. 4.38
2. 4.38
3. 1.15
4. 0
5. 4.39
6. 4.39
7. 4.49
8. 8.73

IC2 (TOP)

1. 4.37
2. 4.38
3. 4
4. 0
5. 4.38
6 4.39
7 4.38
8. 8.73

IC3 (MID)

1. 4.38
2. 4.38
3. 4.14
4. 0
5. 1.72
6. 4.39
7. 4.38
8. 8.73

 

[makisushi]

well, I must leave but so far no noise after the cleanup...

 

[Nostradoomus]

Something is amiss at pin 3 of IC1, it should be around 4-4.5 like the others. It will read a bit lower if you don’t have a meter with a 10M impedance, but not that low.

Also pin 5 of IC3 but it probably varies with the size control.

 

[makisushi]

Something is amiss at pin 3 of IC1, it should be around 4-4.5 like the others. It will read a bit lower if you don’t have a meter with a 10M impedance, but not that low.

Also pin 5 of IC3 but it probably varies with the size control.

Pin 5 of ic3 seems to max out at 3.33. pin 3 of ic1: what could cause that ? Non inverted input 1 so is it the chip itself that could be bad ? R3 is 10k than the cap . Could something "drain" the power ?

 

[makisushi]

i've swap the tl072 of IC1 and i still have the same voltage. I also noticed on that post that IC2 and IC3 have double the voltage on some pins.

R

Thread 'Unicab no sound'

Jan 15, 2024

Just finished Unicab, no sound. I checked all the resistor color codes, seem right. Then I removed the switch, jacks go in direct. Still nothing. Measured 9v at the rails pin 4 and 8 on all 3 TL072s.

What do I check next?

• Rpschultz13
• Replies: 16
• Forum: Troubleshooting

IC3 middle
1: 8.6
2: 8.6
3: 8.6
4: ground
5: 4.5
6: 4.6
7: 4.6
8: 9.2

IC2 top
1: 8.6
2: 8.6
3: 4.8
4: 5.3
5: 4.6
6: 4.6
7: 5.5
8: 9.2