Hello!
I'm troubleshooting a Crumar Trilogy that shows a problem related to the oscillators board.
Here's the link to download the full service manual, the oscillators board is at page 5, DWG1.
https://synth.ewancolsell.com/home/crumar-trilogy
The circuit is fairly simple, two master oscillators (IC3, IC2) drive two top octave generators (IC11, IC10).
You can individually tune the oscillators and when you slightly detune one of the two you have a pleasant phasing effect.
The problem occurs when you synchronize the oscillators, manually with the tune knobs or automatically pushing the "Sync" button and only "master oscillator 1" drives both TOGs
When the "Sync" is pushed the waves from IC10 and IC11 stuck out of phase by a certain degree, it depends to the moment you sync the oscillators.
Here's a small video of the oscilloscope showing this.
The oscilloscope and audio signals are taken from the synth's "Organ" output.
The problem is related to all the keyboard keys, but they are affected differently depending to the moment you activate the "sync".
I've monitored the master clock at pin 2 of IC10 and IC11 with a dual trace oscilloscope and they are of course perfectly in-phase when the sync is activated.
So, what's going on here, in your opinion?
I'm troubleshooting a Crumar Trilogy that shows a problem related to the oscillators board.
Here's the link to download the full service manual, the oscillators board is at page 5, DWG1.
https://synth.ewancolsell.com/home/crumar-trilogy
The circuit is fairly simple, two master oscillators (IC3, IC2) drive two top octave generators (IC11, IC10).
You can individually tune the oscillators and when you slightly detune one of the two you have a pleasant phasing effect.
The problem occurs when you synchronize the oscillators, manually with the tune knobs or automatically pushing the "Sync" button and only "master oscillator 1" drives both TOGs
When the "Sync" is pushed the waves from IC10 and IC11 stuck out of phase by a certain degree, it depends to the moment you sync the oscillators.
Here's a small video of the oscilloscope showing this.
The oscilloscope and audio signals are taken from the synth's "Organ" output.
The problem is related to all the keyboard keys, but they are affected differently depending to the moment you activate the "sync".
I've monitored the master clock at pin 2 of IC10 and IC11 with a dual trace oscilloscope and they are of course perfectly in-phase when the sync is activated.
So, what's going on here, in your opinion?
Statistics: Posted by Stevefuzz72 — Fri Aug 09, 2024 12:07 am — Replies 2 — Views 81