Gritzner output volume low
My Gritzner module has a low output. PT2399 -> pin 1 = 5.00V U1 -> TL072 pin 4 = 11.3V
U1 -> TL072 pin 8 = 11.3V
U2 -> TL072 pin 4 = 11.19V
U2 -> TL072 pin 8 = 12.5 - 12.6V
U3 -> TL082 pin 4 = 11.3V
U3 -> TL082 pin 8 = ( 1..94V and 21.16V )
Knobs @ 12 O'clock, Switches: Main, Squ, A Green is source signal, Blue is output.
73 Views
Hi Angus,
thanks for the measurements.
The PT2399 pin 1 reading of 5V looks correct, so the 5V regulator is probably working. The first thing I would like to verify is the op amp power rails, because the values you listed look unusual.
The U3 reading is especially suspicious. Pin 8 should be a stable +12 V. If you get readings like 1.94 V or 21.16 V, please double-check the pin numbering, the orientation of the TL082, and whether the measurement was made against GND or against another pin.
Please also check the PT2399 reference voltage:
pin 1: +5 V
pin 2: about +2.5 V
pins 3 and 4: GND
If pin 2 is not around 2.5 V, the PT2399 or its surrounding parts may be faulty.
Please probe the signal at these points:
1. Input jack tip
2. U1 pin 1
3. MIX pot wiper
4. U1 pin 7
5. OUT jack tip after R15
If the level is already low at U1A pin 1, the problem is before or around the input stage.
If the level is good at U1B pin 7 but low at the output jack, check R15, the OUT jack, and possible shorts to ground.
If the dry signal is fine but the delayed signal is very low, please check the PT2399 and the parts around the PT2399 filter/output section.
Also, please make sure to use an original genuine PT2399 chip. Non-original or fake PT2399s are a common cause of low level, noise, unstable delay behavior, or strange modulation problems. If possible, swap in a known-good original PT2399 and test again.
Best,
Stefan