neovibe

[no one ever]

...that's why i ordered all metal films for this project...

[newperson]

Yea,
I tested 10-20 resistors to find the closest vaule for each one.  I will move on the the metal films for all other stuff. 

[newperson]

With some more fiddling around I found that what I was doing was injecting some voltage into the base of Q1.  I found that I could use my probes to touch any of the 15+ volt line with one probe and at the same time touch the Q1 base and it would charge it up to work for a min.  What could be causing it to drain when I put my meter on it to read the voltage?

I really do not know why it does this because I have no idea how the transformer works other than the base stopping or allowing V to flow through it.

Is it possible that I have used the wrong type of tranformers?  I used mouser part number 512- 2N3904_D10Z.  Or what value do I need to replace to allow Q1 base to see more voltage.  Am I on the right track?  What number reading should I get for these transistors in my meter?  They have all been around 128. 

Paul.

[no one ever]

R.G... q13 and c18 are unlabeled on your schematic...

what is pad B for?

[newperson]

Just in case R.G did not see the results he asked for,

R1: 19.05K          Paper says: 22K
R2: 21.8K            Paper says: 22K
R3: 33.6K*  reads 46.2 out of circuit. Replaced with 46.1.  Now reads 33.5K in board     Paper says: 47K
R4: 1.2M             Paper says: 1.2M
R5: 98.8K            Paper says: 100K
R6: 6.78K            Paper says: 6.8K
R7: 1.103M* reads 1.202M out.  Now reads 1.19M back in.        Paper says:  1.2M
R8: 1.195K          Paper says: 1.2 K
R9: 3.28K            Paper says: 3.3K
R10: 46.8K          Paper says: 47K
R11: 4.7K            Paper says: 4.7K

Q1base to Q2 E: runs right over 2M
Q1 base to ground runs up over 2M, but seems to be right over 2M

Took Q1 out.  Reads 129.  Replaced with another Q1 with 128 reading.
New Replaced Q1 base to Q2 E: reads 1.98M
New Replaced Q1 to ground reads 1.97M

Do not see where the R4/R5 junction is but:
Top of R5 is 13.44V
Bottom of R5 is 15.61V

Top of R4 starts around .3 then runs down to 0V
Bottom of R4 runs down to 0 also.

Tested the effect again and got the same no input signal passing until it touch Q1 base to R5.  Then the effected input signal fades out like before.

Does this help any?
Paul.

[no one ever]

check your pcb/transistor pads for shorts? if it's not in a box, then i do believe you should ground the output jack too. if it were in a case then the output ground would be supplied by the enclosure connecting the two jacks.

[R.G.]

With some more fiddling around I found that what I was doing was injecting some voltage into the base of Q1.  I found that I could use my probes to touch any of the 15+ volt line with one probe and at the same time touch the Q1 base and it would charge it up to work for a min.  What could be causing it to drain when I put my meter on it to read the voltage?

Excellent! You've learned that a meter actually conducts a little electricity from the circuit you put it on. The meter itself looks like a resistor of between 1M and 10M to the circuit. The bias resistor that's supposed to bias Q1 is 1.2M, so the meter itself can easily change what you're trying to measure. A beginner just reads a meter. An educated debugger knows that the meter changes things itself.

What's happening there is that your meter is allowing some current to flow into the base while it's connected to +15 and Q1 base. That lets things work for a minute. When you touch the base and ground, it bleeds any charge away and Q1 is turned off.

Is it possible that I have used the wrong type of tranformers?  I used mouser part number 512- 2N3904_D10Z.  Or what value do I need to replace to allow Q1 base to see more voltage.  Am I on the right track?  What number reading should I get for these transistors in my meter?  They have all been around 128.

They're transistors, and no, you didn't get the wrong ones. Those should work fine. That's not the problem.

Q1base to Q2 E: runs right over 2M
Q1 base to ground runs up over 2M, but seems to be right over 2M
Took Q1 out.  Reads 129.  Replaced with another Q1 with 128 reading.
New Replaced Q1 base to Q2 E: reads 1.98M
New Replaced Q1 to ground reads 1.97M

But this is. You can see from the schematic that there is a resistor between Q2 emitter and Q1 base, and it's supposed to be 1.2M. You're measuring well over that. It is impossible for you to measure over 2M across that resistor unless either the resistor is bad or there's an open connection on one end. If your measurements are correct, the base of Q1 is effectively open, and that would account for all the symptoms you describe.

Check the circuit board and soldering very carefully around Q1, Q2, and the resistors connected to them. I think you'll find an open circuit.

Top of R5 is 13.44V
Bottom of R5 is 15.61V

Top of R4 starts around .3 then runs down to 0V
Bottom of R4 runs down to 0 also.

That makes me think that R4 is open on one end or the other. Again, check the PCB and soldering.

q13 and c18 are unlabeled on your schematic...

Yep. Bummer. I'll have to fix that.

what is pad B for?

It's a second input. The original univibe had one, so I put one on too.

[no one ever]

excellent post, R.G.! (as usual  )

what is pad B for?

It's a second input. The original univibe had one, so I put one on too.

what for, might i ask?

[R.G.]

what for, might i ask?

I haven't a clue. Perhaps it would be useful for setups other than guitar as we use it today.

There were several conjectures about how people would use musical equipment that proved wrong. The most notable example is the old Thomas Vox guitar amplifiers, which had preamp channels for lead, rhythm, and bass guitars all in the same amp. They thought that a band would buy one amp and all play through it, I think. That sounds so strange today that it's hard to believe.

I think the second input on the univibe must stem from something like that - an idea about how equipment would be used that turned out to be wrong.

[newperson]

Hi again,

Thanks for all the help R.G. and no one ever.  I looked and looked for a bad joint and could not find one.  But with the information about what pin is the bias for the transistor I started to mess around with it.  I found if I put in a 470K resistor instead of the 1.2M for R4 it (fixed) my problem.  Now the Q1 base to ground read 1.114M where you said it should read 1.2M.  Do you think this is close enough?  How could I be getting close to the correct reading now?  Did this really fix the problem or just put duct tape on it? What should the correct (E B C)Voltage read for Q1-Q4?

Also, could I use the other input by just adding another input jack to it?  Would I need to change any parts?  Would it change the signal of the first thing(guitar) plugged in?  I know that when I plug in two guitars into an amp it cuts the first signal down somewhat. 

Now if you think the problem is fixed, I have to box it up and play with the phase mix like the other posts suggest.  Right now it is really deep and cutting out the signal almost with the depth pot turned all the way up.  You can still hear the thump of the light with the guitar turned all the way down.  Perhaps the LDRs are too close to the bulb?  I would like to hear a bit more phase and less tremolo. 

How is it designed to sound?  How does other people's sound?

No one ever, I would use a transistor holder for Q12.  I had to replace this one about five times.  It would keep blowing when I probed around, and also when I would switch back and forth between using an A.C adapter and a D.C adapter.  It seems you have to change the trimmer pot the opp. way when you switch from A.C to D.C.  I put a holder in for Q13 but it never blew.  I thought that this one was the one that should blow?

Is there a way to get a slower phase out of it?

I ending up using a 18VDC wall wart.  I also tried a 16VAC wall wart, but it liked to blow Q12.  I am guessing I did not try hard enough to find the sweet spot on the trimmer though.


So I learned a bit about biasing transistors and a bit about my meter with this build so far.
Thank you again,
-Paul.

[no one ever]

Thanks a lot Paul.. Although I'm not sure if my assistance was quite on the same level as R.G.'s.

Thanks for the tips... What transistors did you use in particular spots? All 2n5088's or all 5088's with a 3904 for q13 (Lamp driver, i assume)? I'm thinking of subbing darlington transistors in place of the discrete pairs.

Where did you get your 18vdc adapter? I'm hard pressed to find one at the moment.



One final question, before I start building this thing and inevitably post my non-working vibe's voltages. Can the Univibe circuit (not including lamp cct) run on more than 15v? Could I use a 7818 instead of 7815? Or am I just necessitating higher voltage caps and increasing the potential for blown transistors. I guess I'm just following the example of boutique producers that boast of their 18v vibes, but I'm still curious.

[no one ever]

Oh, and before I forget, for anyone that's interested, on the parts sheet, the part #'s for the transistors are noted as being 512-(tran type). Mouser has seemingly branched off of this, creating different suffixes to that formula for what I assume are similar but just ever-so-slightly different transistors. If anyone doesn't want to take a risk and order one with the shortest suffix available, just enter part # 610-(tran type). I think these ones even come with pre-bent leads, something I love. Also, lower noise metal film resistors can be substituted in place of the carbons for (IIRC) $.03 more for each resistor by using the 271-(value) part # instead of the 291 system. And finally, for an exact replica of the gigantic knobs used by boutique-ers, the part # is 450-2039.

[R.G.]

with the information about what pin is the bias for the transistor I started to mess around with it.  I found if I put in a 470K resistor instead of the 1.2M for R4 it (fixed) my problem.  Now the Q1 base to ground read 1.114M where you said it should read 1.2M.  Do you think this is close enough?

It's close enough by one good measurement - it works. However, it does beg the question...

How could I be getting close to the correct reading now?  Did this really fix the problem or just put duct tape on it?

... how come you get 1.1M between two points that should only be separated by a 470K resistor? I would say you're using duct tape. Are you doing your resistance measurements with the power off? It should be for resistance measurements.

I messed you up a bit. I meant the junction of R5 and R7 where I said R5 and R4 in my post. R5 and R4 don't connect. Sorry.

What should the correct (E B C)Voltage read for Q1-Q4?

Here's Q1 - Q3.

Q1C, Q2B = 2.28
Q1B = 1.6
Q1E = 1.05
Q2C, Q3B = 4.58
Q2E = 1.64
Q3C = 11.92
Q3E = 3.92

Those assume that the power supply is 16.00V.

Also, could I use the other input by just adding another input jack to it?  Would I need to change any parts?

It would work, no parts changes needed.

Would it change the signal of the first thing(guitar) plugged in?  I know that when I plug in two guitars into an amp it cuts the first signal down somewhat.

It would indeed cut the signals a bit.

Now if you think the problem is fixed, I have to box it up and play with the phase mix like the other posts suggest.  Right now it is really deep and cutting out the signal almost with the depth pot turned all the way up.  You can still hear the thump of the light with the guitar turned all the way down.  Perhaps the LDRs are too close to the bulb?  I would like to hear a bit more phase and less tremolo.

Yes, play with LDRs and positioning.

Is there a way to get a slower phase out of it?

Increase the 3 LFO caps from 1uF to 2.2 uF; should slow it down by about 2:1.

Can the Univibe circuit (not including lamp cct) run on more than 15v? Could I use a 7818 instead of 7815? Or am I just necessitating higher voltage caps and increasing the potential for blown transistors. I guess I'm just following the example of boutique producers that boast of their 18v vibes, but I'm still curious.

You can use a 7818, it will run just fine. The original was unregulated, and ran somewhere between 15V and 20V depending on the components.  Higher voltages does increase the potential (sorry...  ) for blowing the lamp driver, but that's about it. Frankly, I've never heard much difference in the sound depending on the signal chain voltage supply level. The signal chain circuits don't change their operation much between 15V and 18V. You could probably run the signal chain on voltages up to 24V if you use 35V caps. Again, I would not expect much change in sound, if any.