BossAreaForum

Let's use this thread to collect some helpful information for all the people who want to calibrate their vintage effects (non-BOSS). For some units there are no service manuals or schematics around. And some don't have labelled components on the boards, making it quite difficult to find out what is what.

The two units I begin with have already been posted in other parts of the forum, but I'd like to gather everything in this topic.

KORG FK-1 V-C-F

There is no service manual around, in the internet only this same lo-fi photograph of the schematics can be found, that I uploaded a copy of here:
KORG V-C-F schematics

The big 10kΩ trimpot adjusts the main voltage for the circuit and should be set to 15.0 V.
The two 1kΩ trimpots seem to adjust the intensity of the "Expand" function of the lowpass and highpass filter.
The 100kΩ trimpot that is sitting right next to the one 1kΩ trimpot sets the high-pass filter frequency, the other 100kΩ trimpot is for the low-pass filter.

Pearl AD-33 Analog Delay

AVR1: Feedback Channel I
AVR2: Feedback Channel II
AVR3: BBD Bias (not 100% sure)
AVR4: Clock Cancel (not 100% sure)
AVR5: Clock Frequency
AVR6: Filter

Aria AD-10 Analog Delay

The trimpot labelled "1" in this picture adjusts the longest, "2" the shortest possible delay time.
The other two trimpots are supposedly for bias and feedback (I didn't touch them).

Pepe wrote: ↑

Sat May 10, 2025 12:39 pm

Pearl AD-33 Analog Delay

AVR1: Feedback Channel I
AVR2: Feedback Channel II
AVR3: BBD Bias (not 100% sure)
AVR4: Clock Cancel (not 100% sure)
AVR5: Clock Frequency
AVR6: Filter

Thank you!