asm1-VCO DRIFT!!

[Magnus Danielson]

From: e <edgarfov at zahav.net.il>
Subject: asm1-VCO DRIFT!!
Date: Mon, 18 Sep 2000 01:12:22 +0200

> Hi all

Hi there...

> i have  implanted my own build
> regulator i (7815/7915) and i have notice this new disturbinese in the force 
> 
> every pot. that has + to - 15 range
> such as the FC (filter section) pot , or pwm pot. causes the vco to drift
> slightly while tweaking.
> when the turn reaches the limit suddenly a small shift in the osc, is heared.
> i scoped it , the change is measured like 30 to 40 mv shift.
> (checking the coarse tune middle leg)

I would not expect this unless the powersupply is kind of weak and is really
sensitive to change in load. The oscillator itself compensates for its direct
+15V dependence, but is not compensating for the +/- 15V dependence it has
through the pots.

> another fact is when i use my huge lab regulator , this anomaly 
> almost dissapear , at least from the hearing range.

Now, check the supply voltage (both +15V and -15V), try with both supplies,
and check if any tweaking has an abnormal change in the voltage.
I would also check if some part (on the ASM-1 and your supply) gets abnormally
hot. There is nothing on the ASM-1 that should get very hot at all.

Cheers,
Magnus