Hi - here's how to check the opto... http://huebnerie.de/blog/2013/07/polysix-photocoupler-myths/
"This leads to an eady way to check whether a tuning problem is related to the photocoupler circuit at all: measure the voltage on pin 7 of IC18. Within regulation it should be somewhat between -2 and -6 volts, -3 are more normal.
When the loop breaks open due to failure of the photocoupler or related parts, it will be stuck on the maximum negative output, something around -13 volts. There must always be a small current through the LED, otherwise the loop does not work and the TUNE HIGH preset has no effect!"
For the older daughterboard version it's pin 6 on IC18 as it's an 071 instead of an 072...."This leads to an eady way to check whether a tuning problem is related to the photocoupler circuit at all: measure the voltage on pin 7 of IC18. Within regulation it should be somewhat between -2 and -6 volts, -3 are more normal.
When the loop breaks open due to failure of the photocoupler or related parts, it will be stuck on the maximum negative output, something around -13 volts. There must always be a small current through the LED, otherwise the loop does not work and the TUNE HIGH preset has no effect!"
On Wed, Sep 20, 2017 at 3:44 PM, mr gham mrgham@yahoo.com [PolySix] <PolySix@yahoogroups.com> wrote:
Hi Tony,
This is a new 366
Envoyé depuis Yahoo Mail pour iPhoneLe mercredi, septembre 20, 2017, 4:28 PM, Tony McAdam swamp.gigs@googlemail.com [PolySix] <PolySix@yahoogroups.com> a écrit :
What version 366 board is it ? Sounds like an optocoupler problem...