Russian Small Stone Lag Issue

[drummer4gc]

Hey everyone,

I'm trying to debug a Small Stone that I have (Russian black box). When first kicked on, there is a volume drop, but no phasing. Then, the volume kicks back up, still no phasing. Finally, the phaser kicks in and sounds wonderful. The time that this whole process takes is dependent on the setting of the rate pot - maybe a 15-20 second process at min, just about instant at max. It only happens once - I can turn it off and on, and it will work properly until I disconnect and reconnect the battery.

I'm assuming this has got to be related to an old capacitor charging too slowly, but I tried changing out the electrolytics (albeit with approximate values, 22ufs for 33s) to no avail. I'd be happy to post voltages, but I'm assuming you would need to see the numbers during the lagtime - let me know which pins would be helpful to see and I'd be happy to oblige.

Schematic for reference:



Thanks for your help!
Matt

[drummer4gc]

bump. just need to know which voltages (and when - during phasing or before phasing starts) would be helpful for the debug and I'm happy to post them!

[PRR]

Does not make sense. The LFO runs all the time, even when bypass/effect is in bypass.

[drummer4gc]

I bet that if I plugged the pedal in and connected to power, waited a minute, then played, it would work fine. It seems like it needs to "warm up", but after that it runs fine. And since the lfo is always running, it shouldn't need to be kicked on to warm up. Ill test tonight.

However, this warmup phenomenon is real, and real confusing. With an audio probe, I get ticking/heart beating from pin 8 (I think) of ic5, but it doesn't start immediately - just like the effect. Any ideas why it seems to need some warm up time?

It appears not to be just me either, have a look - http://www.harmonycentral.com/t5/Effects-Pedals-Multi-Effects-and/Small-stone-VS-Phase-90/td-p/18881030

Thanks!

[PRR]

The only likely long-charge part is the 33uF at the bottom.

IMHO, a 60 second warmup isn't a fatal flaw. Had several hi-fis that took 30 seconds to make any sound, several minutes to stabilize. Computers take 20 seconds to 5 minutes to boot-up.

[drummer4gc]

Ok, weird - I plugged it in last night and let it sit for about 60 seconds to "warm up". If the LFO was lagging for whatever reason, this should have given it time to warm up and get started, but still, when I engaged the effect, there was a delay until the phasing kicked in. Why would this issue be dependent on having a guitar signal routed through the circuit??

[idy]

This is the least ancient thread dealing with the black box russian small stone so... I found that the bypass also grounds out the lfo. The two pole footswitch is thus (leaving the input of the circuit always attached to the input jack) choosing between bypass and effect out and either grounding the LED or the lfo. Presume there was a ticking or swishing in bypass w/o this.

Maybe this explains the "lag" issue: a cap needs to charge up to get the lfo going after bypasss. The one I'm working on does not have this problem...

[Mark Hammer]

Every now and then, there will be a thread started by someone who would like to save the battery by turning the power off with the footswitch when they hit bypass.  Naturally, the answer is always the same: engaging the effect may impose a minimum wait time for the circuit to be fully powered up.  This thread sounds like one of those cases.

[drummer4gc]

Wish I could remember how this resolved, but I really don't remember. It wasn't modified by me to switch power on and off with the bypass switch. Strange though - I've got a Russian big muff on the bench currently that doesn't like to play nice until about 5 seconds after stomping on the first time after power is supplied, then it's great.

[idy]

The stock switching does not turn power off to the circuit when bypassed, it just grounds out the lfo. The circuit remains powered up but the lfo is defeated in bypass. Univibe had something like this, with no bypass at all, just a "cancel" switch to turn the lfo off.