TR8060 clone TR808

AFAIK the majority of TR-808's do this.

There's a capacitor that *should* charge then discharge when triggered - it controls the VCA for the clap noise, aka reverb.

However, as you've noticed it often needs several triggers before it starts opening up the VCA.

When people were building the MB808, it was first assumed it was a pcb problem until people realized it was the original circuit that had a fault.

In regards to the MB808, Moogah wrote:

i've been tracing this problem on one of the units I have here, and what I've found is exactly what Etaoin describes (except I think he meant C76, which is the 47n green cap near the 2 1M resistors). Watching this cap on the scope, the thing that really bugs me is that the voltage settles to -10mV (?!) and I can't figure out why it's able to settle to a point below ground.. and we know from basic transistor theory that the 945 which creates the envelope here won't turn on until the voltage is above 60mV. When I worked out the RC time constant equation for this it made perfect sense that the cap needed a bit of "pre-charging" before there would be any appreciable envelope voltage above the 60mV cutoff point. My thoughts about this are: either the transistor should be biased closer to the 60mV turn on point, or there is a problem with the ground plane in this area which is causing the voltage to be lower than it should be....

Perhaps this problem is solved easily by reducing the 1M resistor which the trigger pulse comes in through, this would allow the cap to charge faster without affecting the discharge rate (I think..)

C144 is only backwards on the schematics and not in production 808's.