Tweet
Hello everyone, Iīm cloning the Biphase and have arrived at powering it up and tweaking the LFOīs. Phaser B on itīs
own with Generator 2 works perfectly: sinus and squared it does real slow(+-12 second cycle) to fast, with amplitude
control by way of R127.
The problem is Generator 1. Either with A and B or just A, the Rate-pot has one small turn spot halfway where it
goes from superfast to hyper in a few degrees, resulting in a strobe on the effect-pcb. Generator 1 is pretty
different from 2 and I havenīt come up with anything obvious doing a signal trace from start to finish. The actual
LFO(either square or sinus) seems to be 213 A and B but the rate pot does virtually nothing there. Also, LFO trimpot
adjustment R126 and amplitude trimpot adjustment R128 donīt do anything. 212A looks like a log amp, 212B a non-
amplifying inverter and 215 A a buffer.
I looked at the original schematics and they look the same except for R68 which on the original says 20k, but the 1
may have faded.. Testing this made no difference though.
This is the famous page where many a Mutron-fan resided for hours and hours: Patrocheīs blog: MU-TRON Biphase MUSITRONIC - Plans et Clonage - Le blog de crazy-patroche.over-blog.com , where you
can find all the schematics. Relevant here is the "Schema de Controle" and then the bottom part of it.
Also here a simplified version with just the(in my humble amateur idea) relevant part(no pedal control), and the pcb
as I printed and mounted it. Components were all checked and everything so far looks physically ok on the pcb.
Iīm studying up on building LFOīs but so far I havenīt been able to figure out where the problem lies here, and I
would appreciate your opinions and knowledge,
Many thanks in advance, Bram.
own with Generator 2 works perfectly: sinus and squared it does real slow(+-12 second cycle) to fast, with amplitude
control by way of R127.
The problem is Generator 1. Either with A and B or just A, the Rate-pot has one small turn spot halfway where it
goes from superfast to hyper in a few degrees, resulting in a strobe on the effect-pcb. Generator 1 is pretty
different from 2 and I havenīt come up with anything obvious doing a signal trace from start to finish. The actual
LFO(either square or sinus) seems to be 213 A and B but the rate pot does virtually nothing there. Also, LFO trimpot
adjustment R126 and amplitude trimpot adjustment R128 donīt do anything. 212A looks like a log amp, 212B a non-
amplifying inverter and 215 A a buffer.
I looked at the original schematics and they look the same except for R68 which on the original says 20k, but the 1
may have faded.. Testing this made no difference though.
This is the famous page where many a Mutron-fan resided for hours and hours: Patrocheīs blog: MU-TRON Biphase MUSITRONIC - Plans et Clonage - Le blog de crazy-patroche.over-blog.com , where you
can find all the schematics. Relevant here is the "Schema de Controle" and then the bottom part of it.
Also here a simplified version with just the(in my humble amateur idea) relevant part(no pedal control), and the pcb
as I printed and mounted it. Components were all checked and everything so far looks physically ok on the pcb.
Iīm studying up on building LFOīs but so far I havenīt been able to figure out where the problem lies here, and I
would appreciate your opinions and knowledge,
Many thanks in advance, Bram.
Attached Files
Comment