ASM-1 osc.sync issue

[Magnus Danielson]

From: e <edgarfov at zahav.net.il>
Subject: ASM-1 osc.sync issue
Date: Tue, 22 Feb 2000 00:06:51 +0200

> Hi all

Hi!

> i have tested the asm1 oscilators sync in's
> And i'v found out it aint working
> 
> The schematics shows:     sync in-----> 100pf cap ---> so on.
> i overide the cap to see what happends and the sync worked somehow
> Maybe the results are abit extreme. saw tooth shown to be without
> its tooth.
> 
> |``\  (example of single cycle with this kind of sync_without100pf cap)
> 
> In the asm text was written that 100pf cap was tested and worked fine
> Any insight about this situation is welcome!

The time constant of that RC filter is

tc = R*C = (20k//10k) * 100p = 667 ns

Maybe this timeconstant is a bit too low, so that slow slope waveforms will
not make it thru this 1-pole highpass filter. I'd try stomping in a higher
capacitance - maybe even go to the extent of 1 nF or so ;)

After all, the sync input isn't exactly the high precission part of that VCO.

Any opinions guys?

Cheers,
Magnus