Maxon Ibanez CS 505 Chorus Stereo - Distortion on wet channel - HELP

[Astuck]

Hi folks,
I'm trying to repair a Maxon CS505 : the dry channel is OK but the wet channel has a slight distortion mixed with the chorus signal.
I'm using both outputs so 1st jack is dry only while the 2nd jack is wet only.

I've changed all IC but still distortion, same with FET switching transistors : light distortion.
Polarised capacitors have been changed too. BIAS and CLOCK trims are checked and OK.

The CS505 has surely been repaired once, the 78L12 was replaced with 78L15 with a 2.7v zener diode in serie on 78L15 out to get a Vcc=12vdc I presume.
I switched it back to 78L12 and I replaced the 2.7v zener with 1N4148 diode, the ICs receive 11vdc and 5.5vdc after the voltage divider.
Still distortion...

I'll try tomorrow without the 1N4148 and check again.
If anyone have an idea, any help will be appreciated.
Thanks, cheers.

[Astuck]

Hi,
So the problem was the regulator and the diode !
Everything's back to the original drawing and the distortion is gone 78L12 is all the CS505 wants !
BDD MN3007 had 11v and that was just wrong.

The last problem is the LED, it blows after 5min ON... 3rd change for it and still the same thing.
LED is powered by the 2x9v batteries then 5,1k and switching FET.

Cheers

[DrAlx]

The MN3007 will handle a 15V supply.  My guess is that whoever changed the regulator didn't trim the bias pot for the BBD to cope with the higher supply voltage, which is why the delayed signal was distorted.

Bias trimmer location is in the service manua:l http://www.tonehome.de/ibanez-effects/0-series-ts-808/cs-505-chorus/

[Astuck]

Hi DrAlx,
Thanks for your advices !
I tried to re-bias the pot but nothing changed, only dead spot out of bias and no sound.
Cheers

[Astuck]

So it was the 5k1 a litlle low, changed to 15k and it works fine !

My LED is a violet ultrabright 1100mcD and is bright at 1mA.