Neovibe bulb pulse seems kinda slow?

[BubbaKahuna]

Hi all,
I'm at the point in my NV build that I'm dialing everything in before buttoning it all up and since this is my first one of these, I'm not sure what to think about the speed of the bulb's pulsing.

With the speed pot cranked, I'm only seeing about 60BPM, maybe slightly more, but well under 80BPM. From clips I've heard of other vibes both Neo and 'other', I'd think with the speed cranked wide open I should be seeing somewhere between 140 & 180BPM or even more for that really watery liquid warble effect (like in the picked chords on Soundgarden's 'Black Hole Sun').

Any components I should be looking at tweaking to wind up the speed a little? It's built to exact specsheet instructions (GGG) other than my using a trim pot for the wet-dry balance instead of a pair of resistors. I have plenty of control over the brightness of the bulb and can get it between damn near blinding abrupt pulses to not glowing and everything in between by tweaking the controls and bulb trimpot. I just can't find any setting or combination that's faster than about 60BPM. Is that as fast as this thing goes?

Now that I'm seeing that bulb pulsing on & off I'm getting really antsy to finish this thing up and get her onstage. 

Cheers,
- JJ

[R.G.]

If the 1uF NP caps in the LFO are over spec, this would slow down the top speed.

Try 1uF film, which are generally +/-10%. Electros can be as bad as +80/-20%.

[rhdwave]

Also, if you lower the values of r42 and r43 (i did to 2.2k i believe) this will increase your top speed...

[R.G.]

More importantly, lowering R42 and R43 will raise the top speed without also raising the bottom speed.

The range of speeds depends on the min to max ratio of those resistors to the maximum pot value.

The immediate temptation is to say "Ahah! I'll make R42 and R43 100 ohms and the pot a dual 1M!" Unfortunately, Mother Nature interferes, because if R42 and R43 are too low, they look like short circuits and the oscillator stops. If the pot gets too big, it looks like an open circuit when resistance is max, and the oscillator stops.

I don't know exactly where the edges of the too-little and too-large ranges are. I suspect it has to do with the actual gain of the two transistor darlington. Big current gains there would probably increase the range.

[BubbaKahuna]

Got it up to about 100BPM using 1K resistors that actually test at 985ohms.

Weird thing I've noticed is that if I touch the dual speed pot while it's flashing it increases speed a little.
I'm not touching anything else so it must be my magnetic personality that's getting it excited. 

I'm not sure I want to keep reheating my pads on these 2 resistors, but I'll try one more time at something like 400 or 500 ohms and report back what it does (or doesn't do).

I gotta say, these RTS GGG boards are tough little suckers. I've replaced the pair here 3 times and the pads haven't lifted yet.
Not like I'm living on them with my soldering iron, but they seem to take replacement of parts pretty well.

Cheers,
- JJ

[BubbaKahuna]

OK now HERE'S something interesting.

I put in apair of 560 OHM resistors and got only a slight increase in speed from the 1k I had.
I've actually gone from 4.7k to 2.2k to 1k to 560 ohm. That's quite a difference for only a slight increase in max speed.

The 'touch it and it goes faster thing' got me thinking.
I attached a test lead between the shafts of a couple of the controls and it sped up considerably, like about 50% or more.
I'm thinking I may have a ground cold solder or something so I'm going to reflow every solder joint in this thing.
If there's no difference, maybe it just wants to be screwed into a box to really work 100% for some reason.
My guess is a slightly better ground between two mystery parts somewhere in the circuit, maybe just the pots (maybe just MY pots). 

Anyway, it seems to be cranking along pretty well as long as there's something grounding the bodies/shafts of the pots so after I reflow about 200 solder joints I'm going to call it 'so far - so good'. 

Cheers,
- JJ

[BubbaKahuna]

Update:

Got it all together and it works exactly as it should. I went back to a 1.2k pair on R42/43.
It's not super fast at full speed, but fast enough for my needs.
The depth control takes it from 'not much of any effect at all' to a throbbing deep warble.
The Vibe side of it sounds really nice with the requisite 2-sided throb (my best description).
The chorus can go from nothing to seasick with a very pronounced pitch bend at the end of the sweep.

Now for the problem. Noise - and lots of it.
The effect itself sounds really great, but with that hum as loud as the guitar when not playing, it's not happening for me.
I've made sure nothing is touching anything it's not supposed to inside and made sure the polarity of my in/out jacks are correct.
I have a thick piece of plastic between the front mounted components to prevent shorting on the backs of the pots to the board.

On all amp settings, you can hear the sweep of the effect even when bypassed. 
I'm thinking it might be my power supply, but why do I hear sweeping in true bypass?

I'm using an old US Robotics modem 18VAC 20VA power supply. Too much power for a small aluminum enclosure?
I figured a modem PS would be a good choice specifically for noise issues since modems were (are) pretty suceptible to noise problems.
I also have the AC lines going from the power jack to the board inside the enclosure twisted tightly together like heater wires in a tube amp to cancel AC line noise.
All my wires are short too so the Rat-nest factor is minimized.

Any suggestions?

Cheers,
- JJ