Neovibe Debug Help

[lonewolf]

a loud bassy hum sounds like a open ground somewhere.(like if your guitar cord is unplugged and you touch the end of it or when you plug it in you have a loud hum for a second).Q10 voltages on my neo are C=15v/B=6.0v/E=5.5v which is about the same as your Voltage the open ground could be anywhere ..you can check the in/out jacks.....one side of the volume pot goes to ground pin 1(or3)Pad L.. R6/8/38/3+ pad C..leave it OFF use the meter to dbl chk continuity

[tr1p1n]

Well pretty much, Q1&2 seemed funny, changed em out yesterday. Today (before I read your post, lonewolf, on Q10 voltages) I thought Q10s voltages were odd so I changed that transistor out anyways. Re-flowed some solder around Q10 and I don't know, The freakin thing works now  So maybe it was the transistors? or most likely I just so happen to fix the open without even realizing it? So now my question is, how can I wire up just a status led for when the power is on and maybe change to a different color when the effect is engaged? Some indication via LED would be awesome, so any help would be greatly appreciated. But lastly I'd like to personally thank Lonewolf (was here from day one, big thanks to you sir), Jdansti, R O Tiree, Jaicen_solo and twabelljr for all your advice and guidance in seeing me to the end of this. Most importantly I'd like to give a big thanks to R.G for not only having the patience and kindness to see me through, but more importantly making this available for us! So thank you everyone! Thank you R.G! Never would have made it this far without you guys. I'll keep posted on how this thing sounds now that I can finally enjoy using/tweaking it! 

[lonewolf]

thats great you have it working..now you can concentrate on getting it to sound right(if it doesnt now)..as far as led's go you can connect one directly to the 9v with a resistor to gnd..(2.8k or more) but I would suggest you may want to quit while you are ahead and just enjoy the fact that it works now..rock on..next step is to get it in a shielded box

[R O Tiree]

Result!  Well done for sticking with it, me old.  Most people would have been forgiven for giving up and throwing it in the bin.

And for your next project?

[Jdansti]

^ +1

Glad you got it going!  Good job!

[tr1p1n]

Result!  Well done for sticking with it, me old.  Most people would have been forgiven for giving up and throwing it in the bin.

And for your next project?

Fuzz face? maybe, would like to find an octavio.

As for the vibe, it sounds amazing! Already went ahead and wired up led for bypass and effect. The effect led is very bright though, anyway to tone it down? And about the speed pot any alternative wiring? anything I could do? It's only usable the last 1/4 of the way. Other than that the vibe works as intended and totally exceeds my expectations! 

[lonewolf]

you can change the resistor to make the led dimmer .....less resistance= brighter/more resistance=darker

[tr1p1n]

you can change the resistor to make the led dimmer .....less resistance= brighter/more resistance=darker

Another question....I've read a lot of people had trouble with the speed pot until they bought the one from small bear. So which one did you get that worked? Alpha Dual-Gang 24mm REVERSE Audio Taper 100K - says it for univibe clones and repairs. Plus there's this one Alpha Dual-Gang 16mm Solder Terminals 100K Rev Audio - says speed pot for neovibe and similar clones. I'm assuming the REVERSE audio taper 100k pot is the way to go?

[lonewolf]

my neo never worked right until I replaced the speed pot with the SB 24mm reverse log100k dual pot..made a huge difference...

[tr1p1n]

my neo never worked right until I replaced the speed pot with the SB 24mm reverse log100k dual pot..made a huge difference...

Thanks, went ahead and bought that one. Hopefully it clears up some of the "crowding" I get. Another question  would a 250K trimmer be fine for the wet/dry mix? Just making sure if I turn it to much one way or the other it won't ruin anything.

[lonewolf]

I used a 220k that I stole out of a sony cassette deck and it worked excellent so 250k should be ok..you wont hurt anything turning it ..just adjust it for the strongest deepest phase...if you go all the way one direction you will hear the phase that sounds like vibrato all the other way the dry signal..so somewhere in the middle you will find the sweet spot...

[tr1p1n]

I used a 220k that I stole out of a sony cassette deck and it worked excellent so 250k should be ok..you wont hurt anything turning it ..just adjust it for the strongest deepest phase...if you go all the way one direction you will hear the phase that sounds like vibrato all the other way the dry signal..so somewhere in the middle you will find the sweet spot...

The reverse pot from small bear really smoothed out the crowding and changing the 2 4.7k to 2.2k gave me sooo much more speed to work with. So now the volume and speed pots work perfect, but the depth seems to still have some trouble the first quarter turn. If its UN-fixable I can totally live with it, works amazing the last 3/4ths, but was just wondering if there is a way to get good depth at slower speeds?

[Jaicen_solo]

There is yes, build something else!
No seriously, it's a design quirk of the univibethat the LFO amplitude drops off at low speeds.
I consider it a part of the sound, and I dont have any suggestions as to how to fix it to be honest.
At minimum depth theres no phasing, it's just the way it is as far as I know. I just set mine at 75% and leave it

[lonewolf]

did you do the output mix mod with the trimmer replacing the 2 100k resistors?..that will give you the best possible depth

[tr1p1n]

did you do the output mix mod with the trimmer replacing the 2 100k resistors?..that will give you the best possible depth

Yep, but to me, doesn't seem like it matters for the wet/dry mix. I did the bulb offset mod, SteveB's way I guess (from what I read) with R47 replaced with a 100K trimmer. Now THAT really gave me a dark orange glow and depth at slower speeds, not to mention a much darker yet brighter depth. Maybe it's the combination of the wet/dry mix and this? But the swing sounds much much better after that, still needs to be fine tuned more. But im getting there  To much fun just turning it, playing it, turning it, playing it. But god, I'd love to get it to sound like steve's vibe, getting there though (any tips would be awesome). Might give it some time before I really get down to fine tuning her, to much fun now. Looking into building a fuzz for the vibe, do you know any good fuzz face replicas?

[lonewolf]

what fuzz depends on what sound you are looking for...If you want the hendrix sound then go for roger mayer... he has a octavia that does not use a transformer..and he modded most if not all of jimi's effects as well as page/trower/beck etc...look at fuzz central as there are a lot of projects there.including the roger mayer fuzzface's...if you want something more metal/hi-gain then dr.boogey sounds real good..GGG has some great stuff also... as well as tonepad

[darlon]

hi all
didn't wanted to start a new topic so i'll write here.
got some problems with neovibe parts so i've got some questions:
I'm building neovibe right now and I have some problems with LDRs and bulb

1. I cannot find LDRs matching requirements - light resistance. can i use one of theese:
- 5K-15K
- 10lx - 20÷50 kΩ, 100lx - 4÷10 kΩ
- 20K - 60K - 100lx
- 50-90k (10lx) 10 -15k (100lx)
- 150-300k (10lx) 20-60k (100lx)

2. regarding the bulb - i cannot find one for 25mA, only 10mA and 40-50 mA - which one can i use? 10mA will die probably because of more power provided, but 40mA will be bright enough?

3. I'm planing to use BC550 as a lamp driver - will that be good choice? Hfe looks like 295... I got some 2N5088 but they will be too hot as i read. also got some bunch of 2N3904. should i use BC550 or 2N3904 will not get too much heat?

I wrote to R.G but had no reply

thanks in advance

[R.G.]

Sorry - I don't always check my messages very frequently.

1. I cannot find LDRs matching requirements - light resistance. can i use one of theese:
- 5K-15K
- 10lx - 20÷50 kΩ, 100lx - 4÷10 kΩ
- 20K - 60K - 100lx
- 50-90k (10lx) 10 -15k (100lx)
- 150-300k (10lx) 20-60k (100lx)

You can (and should) use some of them to check your work while you go looking for better ones. The Neovibe works best with very wide range LDRs. There are limiting resistors in the circuit so the resistance never goes below 4.7K nor above 220K, so you would like to get LDRs that are well outside those resistors. Of the ones you mention, the last are best. They may be fine to your ear. However, the approach I recommend is to use four of the last batch, and if listening is not great, go find some that vary between a few K in light and 1M or more dark.

2. regarding the bulb - i cannot find one for 25mA, only 10mA and 40-50 mA - which one can i use? 10mA will die probably because of more power provided, but 40mA will be bright enough?

The "25ma" is approximate. Again the rule is "buy what you can get that's close; it may be good enough, and will let you have some function while you search for the

perfect parts."
3. I'm planing to use BC550 as a lamp driver - will that be good choice? Hfe looks like 295... I got some 2N5088 but they will be too hot as i read. also got some bunch of 2N3904. should i use BC550 or 2N3904 will not get too much heat?

All of these are marginal for the lamp driver. Devices are limited in how much heat they can get out by the physical package, and all of the ones you mention have the same TO-92 package. Use the BC550, as it has a higher current limit than the 5088, but higher gain than the 3904. However, with a low power lamp driver, use the 10ma bulb.

There is a trick you can use if the lamp driver gets too hot, but the voltage across the collector-emitter never goes to nearly zero. You can put a resistor or zener in series with the bulb to soak up some of the excess power the transistor would otherwise have to dissipate. This is kind of an advanced-beginner technique, though, so for now, use the 550 and the 10ma bulb. If that's not great with your LDRs, use the parts to get it working as well as possible, and then go look for better parts.
I wrote to R.G but had no reply

thanks in advance

[R.G.]

As a general comment, the 2SC3902 looks like it would make a GREAT lamp driver. It's voltage and current ratings are much higher than needed, and it has a current gain of 150-400. And - it comes in a TO-126 case. The TO-126 is intermediate in size between the TO-92 and the TO-220, but it has an exposed metal tab to get heat out. It's much better suited to getting heat out, but not so big as the TO-220.

The neovibe board is set up so the collector-in-the-middle package of the TO-126 and TO-220 should plug right in to the alternate holes.

You can also use the 2SD1683, which is much the same as the 3902 but lower voltage, or some of the integrated darlingtons: MJE270 or TIP110 are representative.

[darlon]

R.G. Thanks!
you're the man!

unfortunately, I just bought online 12V 40mA bulb, but I'll give her a try. bought also GL5659 LDRs (dark 20M, 100lx 20K-60K)

I cannot find 2SC3902 or 2SD1683 in Poland so will have to test BC550 for now.

will post results after final assembly