Almost complete Neovibe

[Crawf]

Hi,I finally decided to have a go at the Neovibe so i etched and bored the board and now have it populated apart from the Voltage regulator and still have to make the light shield,what i was wondering was would these items be ok in it's constuction,first the dual pot
http://www.maplin.co.uk/Module.aspx?ModuleNo=2204

and would the PSU as i have one at home be ok? it's this one from Maplins  http://www.maplin.co.uk/Module.aspx?ModuleNo=43055

A question about wiring the 2.1 PSU input, it say's in PDF "do not ground either wire" on this type of Jack:-  http://www.banzaieffects.com/Lumberg-NEB-J-21C-pr-17604.html      do i just miss out the ground lug on the jack and wire the other two lugs?

Sorry if the answers are obvious to some but i did search the forum but the amount of Neovibe threads are so many "a needle in a haystack" came to mind,of course once it's powered up my problems might be just beginning 
thanks Crawford.

[R.G.]

Hi,I finally decided to have a go at the Neovibe so i etched and bored the board and now have it populated apart from the Voltage regulator and still have to make the light shield,what i was wondering was would these items be ok in it's constuction,first the dual pot

The 100K log can be made to work. The taper is backwards from what you really need.

and would the PSU as i have one at home be ok? it's this one from Maplins  http://www.maplin.co.uk/Module.aspx?ModuleNo=43055

It'll be OK. Set it for 15Vac.

A question about wiring the 2.1 PSU input, it say's in PDF "do not ground either wire" on this type of Jack:-  http://www.banzaieffects.com/Lumberg-NEB-J-21C-pr-17604.html      do i just miss out the ground lug on the jack and wire the other two lugs?

No. The jack as shown has no ground lug. There is one lug that connects to the center of the plug, another to the outside sleeve of the plug. The third lug is connected to the outside-sleeve lug by an internal switch when there is no plug inserted. You will only connect the center and outside sleeve lugs. Be sure that neither of the  wires from the jack comes into contact with the grounded case or signal ground. 

[Crawf]

Thanks R.G. i can carry on and finish it now and hopefully i'll post back with  a working vibe,Crawford. 

[Crawf]

Hi,as promised i said i would post back once i had completed the pedal,so once i installed the Voltage regulator i powered it up loose without a box and,nothing, so i checked the solder connections for bridges and loose connections and i found two in complete copper traces and two loose components and a lifted trace which was my fault,once these were fixed i have now a pulsing lamp but no sound except when i touch the output jack so i put the jacks and the switch in a box and left the board and pots lying loose,adjusted the trimmer for the lamp brightness,covered the lamp and LDR's temporarily and ............................voila vibing sounds,        couldn't believe it but was relieved as i didn't relish the debug.

I did discover a bad connection on the volume pot so that will be replaced and the i can't seem to get it to slow right down but i'm using a dual linear pot instead of log, would this give me less control over the speed? other than that i'm happy that i got a result,i welcome any thoughts on the speed issue in case its more than just the pot that needs changed,cheers Crawford. 

[R.G.]

If you used a linear speed pot, it should give the same maximum and minimum speeds as a tapered one, but the speed variation will be all bunched up at one end of the pot rotation.

In theory, the larger the pot resistance, the wider the range of speeds; however this is limited by the internal resistors on the board, 4.7K in series with the pots and 220K in parallel with them. You might try a pair of 220K resistors to replace the pot temporarily and see if your unit still oscillates. If it does, you can probably use a 250K pot and get wider speed range.

[Crawf]

You might try a pair of 220K resistors to replace the pot temporarily and see if your unit still oscillates.

Could you explain how i would do this,do i remove the pot from the wires and attach the resistors?

If it does, you can probably use a 250K pot and get wider speed range.

Would this also be a dual pot?

Sorry if i'm not quite grasping this

[R.G.]

Could you explain how i would do this,do i remove the pot from the wires and attach the resistors?

Would this also be a dual pot?

Yes, and yes. No need for the red face - you're new at this, no reason you should already know it.

[Crawf]

Thanks R.G. it's just that as much as i try i find electronics very hard to understand i only still have a basic grasp of schematics and suchlike,what i have learned so far is to etch, bore and populate my own boards and have successfully made numerous pedals(which have been gigged) including the  CE-2 Chorus from  tonepad and 3 easyvibes in a row and everyone fired up first time which tells me my soldering skills must be passable but when what might be a simple debug to some usually gets me stumped so when i asked about attaching the resistors to the wires and you said yes i thought "damn" i'm really still not sure even how to do that although if i could see what to do then that would be differant,so i'm afraid i'm a "paint by numbers" pedal builder,is a quick sketch too much to ask or is there something on the web i could use as a reference? thanks again, Crawford.

[slacker]

I don't know if your board is exactly the same as the GGG one but if you look at there wiring diagram here http://www.generalguitargadgets.com/pdf/neovibeupdate.pdf you'll see one of the outer lugs of both of the pots connect to point C and then the wipers connect to point E and D. What RG meant was disconnect the pots and put one 220k resistor from Point C to D and another from point C to E. That will be roughly the same as a 250k pot set to maximum resistance.

Hope the makes sense.

[Crawf]

Hi Slacker,yes it does make sense so i tried it and it makes the lamp pulse very slowly so if i use a 250k pot like R.G. suggested i would have a better range of speed,as it is with the 100k dual log connected back i can only get the fastest rate.
I'm not quite sure what i'm hearing is perfect but i still have to make the light shield and box it up so i'll check out some clips posted on this site,thanks again Crawford.

[Crawf]

Hi Again,well i tried a 250 pot and the unit vibed at full speed but still came to a dead stop when only just turning down the pot a fraction, but it stopped working completly so i replaced Q11 12 and 13 and it started vibing again so i took some voltage readings

                                        C        B           E 
the first readings gave Q1 14.98  1.37      .92
                                  Q2 4.08    2.14      1.52
                                  Q3 11.38  4.10      3.45

thinking these first three didn't look right i replaced the transistors and got these  (Q4 to Q13 were the same before the change of Q1-Q3)
      C                          B          E
Q1  0.63                    .06       0.00       (Q1-Q12 2n3904)
Q2   .09                     .63       .07
Q3 14.97                   .09       0.00
Q4 14.98                    4.8       4.34
Q5 11.31                   4.34      3.69
Q6 14.98                    4.63      4.17
Q7 11.47                   4.17      3.52
Q8 14.98                   4.71      4.25
Q9 11.40                   4.25      3.57
Q10 14.98                 5.98      5.42
Q11 no reading        11.18    13.06
Q12 no reading         13.05    12.39
Q13 19.94                   5.71      5.13     (MPSA 18)

R13 4.8       Voltage Reg 14.99     
R18 11.3      D Bridge + in 9.9
R32 5.98      D Bridge + out no reading
R34 5.42
R40 11.3
Q11 and Q12 collector does show a reading if i set my meter to higher range, i get 23.6 for both collector legs.

My PSU is a 15Vac set to 15v

Unfortunately my board is suffering from some repairs due to traces lifting during replacing some parts so i have bought a board from GGG which i intend to socket all transistors and also have bought some parts from smallbear, so if this one is irrepairable i'll start again.

Hope these make sense and is enough info,Crawford.

 

[Crawf]

Anybody out there with thoughts on the voltage readings especially R.G. if you are around
I presume Q1,Q2 and Q3 have problems due to the readings i'm getting probably due to desoldering and resoldering,cheers.

[R.G.]

Anybody out there with thoughts on the voltage readings especially R.G. if you are around
I presume Q1,Q2 and Q3 have problems due to the readings i'm getting probably due to desoldering and resoldering,cheers.

Just back in off the road.

Yes, Q1, 2, and 3 are now nonfunctional, probably as a result of the soldering. You can try fixing it, as you don't lose anything except the time and possibly frustration.

It is likely that the LFO is stopping as a result of low gain in Q11/Q12. If you have another MPSA18, put it in for Q11.

[Crawf]

Thanks R.G. Managed to fix a broken trace and now get these readings for Q1-Q3 everything else was the same as before, inserted another MPSA18 for Q11 and Q12 but still can only get it pulsate at a fast rate,is there anything else i can double check e.g other cap and resistor values at specific points on the board or a component i could have damaged due to overheating?.
I'll check again my components against the parts list just in case! thanks, Crawford.



  C                          B          E

Q1  2.13                1.35       0.93     (Q1-Q12 2n3904)
Q2   4.12               2.13       1.52
Q3 11.36               4.12       3.47
Q4 14.98                    4.8       4.34
Q5 11.31                   4.34      3.69
Q6 14.98                    4.63      4.17
Q7 11.47                   4.17      3.52
Q8 14.98                   4.71      4.25
Q9 11.40                   4.25      3.57
Q10 14.98                 5.98      5.42
Q11 no reading        11.35    13.35   MPSA18
Q12 no reading         13.31    12.65
Q13 19.94                   5.71      5.13     (MPSA 18)

R13 4.8       Voltage Reg 14.99     
R18 11.3      D Bridge + in 9.9
R32 5.98      D Bridge + out no reading
R34 5.42
R40 11.3

[R.G.]

You're very close to having it working now.

First, check the values of every component in the LFO circuit - that's all the parts connected around Q11 and Q12. Yes, again. Sorry. It could be a resistor where you're reading the color code wrong. I am slightly colorblind to shades of red and if I'm not careful, I mix up  1k and 10k resistors for example because the shades of red and orange vary a bit. Use a meter if you have to.

Next: verify whether the circuit can oscillate slowly by replacing the speed pot with two 220K resistors, as you did before. Does the light now pulse very slowly?

If it does the problem is with your speed pot, not the circuit board. Use your ohmmeter to verify that the resistance changes smoothly on both sections as you turn the pot.

[Crawf]

Thanks R.G.

First, check the values of every component in the LFO circuit - that's all the parts connected around Q11 and Q12. Yes, again. Sorry. It could be a resistor where you're reading the color code wrong. I am slightly colorblind to shades of red and if I'm not careful, I mix up  1k and 10k resistors for example because the shades of red and orange vary a bit. Use a meter if you have to.

Yes i'm sure all is correct but i'll check again.

Next: verify whether the circuit can oscillate slowly by replacing the speed pot with two 220K resistors, as you did before. Does the light now pulse very slowly?

Yes it does but it's almost inaudible through an amp with the 220k resistors but visible so i hooked up two 47k resistors the same way and got  a faster pulsing which i could hear when i played the guitar,almost a Troweresque speed.

[/quote]
If it does the problem is with your speed pot, not the circuit board. Use your ohmmeter to verify that the resistance changes smoothly on both sections as you turn the pot.[/quote]

The pot seems to reduce or increase the reading smoothly according to my meter plus this is the 3rd pot i've tried and they all do the same thing,could it be my wiring? "with the dual log pot correct way up as in the layout pad C goes to top lug 3,pad D goes to bot lug 3,pad D goes to bot lug 2 and bot lugs 2 and 1 are connected to top lugs 1 and 2"

The unit is vibing,how good is subjective, maybe my choice of LDR's could be better and how i've rigged the light shield but it does work apart from the speed control.
Thanks for your patience,you must get fed up going over the same old ground,maybe a book dedicated to this pedal and it's debugging would be good
cheers,Crawford.   

[R.G.]

The pot seems to reduce or increase the reading smoothly according to my meter plus this is the 3rd pot i've tried and they all do the same thing,could it be my wiring?

If they all act that way and all change smoothly to a meter, yes, it's probably wiring.

"with the dual log pot correct way up as in the layout pad C goes to top lug 3,pad D goes to bot lug 3,pad D goes to bot lug 2 and bot lugs 2 and 1 are connected to top lugs 1 and 2"

I don't like the numbering of pot leads. I've seen people vigorously defend numbering in both directions. So I always hold out for either "clockwise" or "hot/cold" designations. These can be determined with a meter no matter what the physical setup of the pot. You put your meter (-) lead on the wiper and turn the shaft fully clockwise. The lug which is lowest resistance to the wiper is the "CW" or "hot" lug. The other one is the CCW (counter clockwise) or "cold" lug. Completely unambiguous and easy to verify.

In the Neovibe, you're trying to get two resistors that both are large resistance at full counterclockwise, and small resistance at full clockwise. So
(1) Identify the CW lugs on each section of the pot.
(2) connect a wire from one CW lug to pad D.
(3) connect another wire from the other CW lug to pad E
(4) strip an extra long section of one end of a third wire bare; connect that to BOTH wipers, jumpering the wipers together with the bare section.
(5) run the other end of this third wire to pad C.

Yes, I know the diagram shows the third wire connecting the CCW lugs too. It doesn't matter. You can leave the CCW lugs open, or short them together, or short them AND the wipers together. All the same to this circuit.

Clear? Or did I muddy it up further?

[Crawf]

Clear? Or did I muddy it up further?
[/quote]

Hello again R.G. Your explanation was as clear as a bell and the pot is now working as it should,i can slow it down and speed it up till i'm blue in the face!!!!!!! I just need to choose which light shield to make.

Seriously though, i can't thank you enough for your time and patience in resolving these issues,
As i had said before i have bought a board from GGG and some parts from smallbear so although my own is working i'll build another as a backup.

Thanks again, Crawford.

[Crawf]

Hello again,Since my last post  i have built another Neovibe with a GGG board but this time with the LDR's facing up the way and although i havn't made the light shield or boxed it up it certainly sounds promising( to try it i placed a small mirror over the lamp and covered the board with a cardboard box)

What i was wondering was, although i'm using a 15vac adapter can i use an 18vdc adapter without removing any parts from the board e.g diode bridge or will it run happily with either? thanks, Crawford.

[R.G.]

Should work with either one.