about 6 years ago my son and i built a diy univibe each. the both worked buy his was better than mine. my one was not very loud. i didnt bother about it till a couple of months ago. i had taken a few parts from it for other pedals. i put the parts back, but there was no sound. i took all the transistors capacitors out and measured them. they all seem alright. i measured all the resistors in circuit and they all read the same as my sons working one. i took his board out of his and tried it in my enclosure and it worked so it is something on my board thats not working. it is only the sound not working as the lights flash. i cant think of anything else to check. anybody any ideas.
Welcome.
6 years ago. Wow.
Help us to help you please show us the schematic you are working from.
Go here
https://www.diystompboxes.com/smfforum/index.php?topic=29816.0
Report back with some more information to aid debugging.
Looks like the lfo is working if the bulb is flashing.
Do you own an audio probe? Worth a search if you don't and it might come in handy later on.
Could be a multitude of things, curious that yours was never as loud as your sons too.
Let's see what we can find. Respect to anyone who can build a univibe.
(https://i.postimg.cc/xJhvkbW3/Univibe-layout-flipped-horizontally.png) (https://postimg.cc/xJhvkbW3)
kipper4 thanks for the reply here is the layout i used. i hope it is ok to use it.
Post a few photos of the board. Also, do you have a multimeter and do you know how to do an audio probe test?
marcus - munky i have got a multi meter. here are some photos.
(https://i.postimg.cc/BtJ4SkwY/IMG-0001.jpg) (https://postimg.cc/BtJ4SkwY)
(https://i.postimg.cc/B85kRQsq/IMG-0002.jpg) (https://postimg.cc/B85kRQsq)
(https://i.postimg.cc/5Y0gpx2K/IMG-0065.jpg) (https://postimg.cc/5Y0gpx2K)
(https://i.postimg.cc/njg4kB5M/IMG-0076.jpg) (https://postimg.cc/njg4kB5M)
Nice pics, and very nice looking board. This seems to be a clone of the original univibe board. Post a photo of the trace side, maybe we spot something you didn't.
Also, which transistors did you used? And how are you powering it?
Since you have a multimeter, be ready to measure voltages of all the transistors but Q11, Q12 and Q13, since they're part of the lfo and we know they're working. Connect the black probe to ground and use the red probe to measure the voltages on each leg of the transistors. But first let us know the transistors used and how are you powering the circuit, maybe you don't need to do those measurements.
transistors are all 2n5088 excepy the first one which is a silver bc109. i am powering it with 15v wall power supply. i am not sure of the order of the transistors. do they start with the silver as Q1 then go up the left then along the top then the ones in the middle.
The layout you posted have them marked as Q1, Q2... until Q13.
I can't clearly see on your photos, but are the transistor legs twisted or something like that? Could you post a close-up photo of the transistors and how their legs are getting into the board?
the base and collector pins are twisted.
Yep, that's how they need to be connected. So, we'll really need the voltage measurements of all transistors (but the 3 from the lfo).
i will do these as base collector emmiter Q1 1.109 1.566 .621 Q2 1.567 1.626 1.629 Q3 1.484 1.310 1.313 Q4 1.624 1.586 1.534 Q5 1.534 1.881 1.404 Q6 1.628 1.587 1.549 Q7 1.549 1.888 1.431 Q8 1.627 1.586 1.544 Q9 1.544 1.878 1.429 Q10 1.725 1.585 0000 Q11 1.616 1.517 1.452 Q12 1.448 1.517 1.441 Q13 754 753 107 i have done all 13.
Your voltages are very low. I mean, Q1 is somewhat near what you should expect. On the collector, you should expect around 5V for Q2, 10.5V for Q3, 15V for Q4, Q6, Q8 and Q10, and 11.5V for Q5, Q7 and Q9.
The power supply part of the circuit is on the bottom right side of the board. Check voltages on power input (the one connected to D3) and at each + lug of those big caps (1000uF and the 2 220uF). All voltages again with the black probe connected to ground of the circuit.
i tested the transistors in diode mode with no mains power was that right.
No, you need to check their
voltages, with the power plugged in.
Quote from: Marcos - Munky on April 12, 2020, 08:54:58 PM
Since you have a multimeter, be ready to measure voltages of all the transistors but Q11, Q12 and Q13, since they're part of the lfo and we know they're working. Connect the black probe to ground and use the red probe to measure the voltages on each leg of the transistors.
i took the readings again with the meter in diode mode and power on. Q1 1.015 1.759 623 Q2 1.758 1.315 1.633 Q3 1.958 0000 1.316 all the other transistors read zero. the 3 large caps read zero. d3 diode reads zero.
Don't use your meter in diode mode for this. Switch it to voltage measurement. Clip the negative/black lead of your meter to circuit ground. Use the red/positive lead to test voltages.
Here's what you're looking for. For NPN bipolar transistors (all the transistors in the univibe circuit are this kind) the base will always be 0.5 to 0.7V more positive than the emitter terminal. If this is not true, then the transistor is not working as an amplifier. The collector terminal of the transistor must be more positive than the base* by one to many volts for the transistor to be working as an amplifier.
Before you get too far, re-re-re-check that all of your transistors leads are in the circuit-correct holes. When you have to twist leads (I think in this case you had to reverse base and emitter) it is easy to miss one. It's also very easy to have the two leads short together. Once you've done that, measure the voltages on the solder pads of the transistors, as it's easy for a meter lead to be mis-placed. Ask me how I know this. :)
Make us up a chart of the transistors by number, and the voltages on each of the terminals. For this test, the DC power should be on, and there should be no signal. I've done a lot of troubleshooting on the univibe circuit, and I can often spot what part is wrong from these voltages.
*[This is generally true, and true for all of the ones in the univibe. There are a few exceptions, but don't confuse yourself with the exceptions until you understand transistors better.]
base collector emitter Q1 .065 .638 .001 Q2 .636 .077 .072 Q3 15.56 .001 .001 Q4 5.00 15.56 4.57 Q5 4.57 11.49 3.95 Q6 4.92 15.56 4.49 Q7 4.49 11.60 3.87 Q8 5.24 15.56 5.29 Q9 4.82 11.45 4.20 Q10 6.30 15.56 5.79 Q11 920 18.56 9.90 Q12 9.40 18.56 9.90 Q13 2.993 12.94 2.358 diode d3 19.30 big capacitors 18.56 17.04 15.56
Even without a chart as asked by R.G., I can see some things that clearly are wrong.
Around 15.5V at the end of the power suply. That's ok. Lfo working. Q4 up to Q10 have voltages very close to the expected values, we cay say those are ok.
Q1 voltage is very low. You should expect around 2V on the collector. The same goes for Q2, you should expect around 5V on the collector. Q3 is pretty odd, you should have around 10V on the collector (you have zero), 5V on the base (you have 15V!) and 4.5V on the emitter (you have zero).
So basically recheck all those resistors on the left side of the board. Check the layout you posted, they're all in orange. Visually check if they have the correct values. Check Q3 to see if the legs are at the correct places and if they aren't shorting together. Do the voltage measurements again for Q3.
marcus munky i measured q1 q2 and q3 again Q1 base000 collector 14.40 emitter 66 Q2 the same as the last time i read it Q3 base 000 collector 14.40 emitter 66
So something is clearly wrong around those transistors. Check the resistors I said, you may have replaced a few of them for wrong value ones.
i changed Q2 transistor and a 220k resistor at the bottom of the board. the transistor now reads. base .638 collector 3.75 emitter 1.515 the resistor was a 220k one. it was reading 47k in circuit, the new one is readung 72 in circuit. there still is no sound. i read all the resistors on the left side of the board, they are all reading the same as in my sons working clone univibe.
You shoudn't measure resistors in a circuit, because they interact with other parts and you'll get the wrong reading.
Check the resistors for their color codes.
I can't clearly see from the photos you posted, but the 3,3K resistor should be orange-orange-red. I can clearly see orange-orange, but can't see the other color.
Also, what exactly did you removed from the board?
the colour of the 3.3k resistor is orange orange red. it reads 2.9k in circuit. i am checking my resistor readings with my sons working clone univibe. all the resistors are the right value.
Marcos is giving you solid advice. You cannot reliably read resistances in circuit. The parallel parts affect the reading. He's also correct - the first three transistors form a preamp and phase splitter. Yours is hosed.
Your power supply is giving you about 15.5VDC for power to the preamp and phase stages. The way the preamp works is that Q3 has to turn out equal-and-opposite signals at collector and emitter. It does this with approximately equal collector and emitter resistances. They are set up so that ideally, the collector will be sitting at 3/4 of the power supply, and the emitter will be at 1/4 of the power supply. This is approximate, but I would expect about 4V on the emitter and ~11V on the collector.
With 4V on the emitter of Q3, the emitter of Q1 is held at 1.2/(1.2+3.9)= 0.235 times the 4V, or about 1V. The base of Q1 then has to be 0.5V or so above that. So the actual base of Q1 has to be at about 1.4-1.5V. It's using very, very little base current, which it gets through that 1.2M resistor to the emitter of Q2.
The voltage drop across that resistor is unknown without knowing the hfe of Q1, but since Q1 can't conduct more than 15V/1.3M = 12uA, the base current can't be much more than 1/100 of that, or about 120nA. That, through is about 0.14V.
So Q2's emitter needs to sit at 1.4 + 0.14 = 1.54 to 1.64V. This, through the 6800 ohm emitter resistor, is 227uA roughly. That much current has to flow through the 47K collector resistor. That's 10.665V, which is down from the 15V power supply or 4.33V.
We're nearly back to where we started - with 4V on the Q3 emitter. We have come back to the base of Q3 being at 4.33V. That's 0.33V above Q3's emitter. It really ought to be 0.5V; however, its >>really, really<< close, and it's close enough to be auto-corrected by the circuit itself. So the estimations of circuit voltages seem to be reasonable. Actual circuits do seem to work this way (by measurement). The voltage on the base of Q1 is hard to measure accurately because the impedances are so high there that a meter will load it down and it will measure low. But the other voltages on Q1, Q2, and Q3 do in fact measure this way.
This long wandering ramble through how it works is just to say - yep, something is very wrong in the preamp. Since there are only three transistors there and a few capacitors, it might make sense to just clip out all three transistors, remove the electro caps; then check the resistor values >visually<, replace any wrong values, and then put in new transistors and caps, carefully watching polarity.
RG i have changed Q1 and Q2 i will change Q3. I was taking resistor readings from another working univibe to see if mine were the same. if they have to come out i will take them out.
RG the last reading i gave for Q3 was collector 11.05 base 3.77 emitter 3.51 is that within spec.
Well, there isn't any specification for this thing, but that's certainly better than the first ones.
So what are your voltages now?
Q1 base .009 collector 1.327 emitter 14.40 Q2 base 2.108 collector 3.73 emitter 1.523
Measure Q1 again. You can't have 14V at the emitter. Emitter voltage should be lower than collector voltage.
Think about this: if you check the univibe schematic (or any npn transistor circuit), you have the collector connected to the power supply voltage via a resistor, while the emitter is connected to ground via another resistor. So the collector is more close to the maximum voltage, while the emitter is more close of the zero voltage. So a working circuit will have the collector voltage higher than the emitter voltage.
you are right it is 14.40 on the collector.
OK. Q1 has 14+ volts on the collector. The schematic shows Q2 base wired directly to the collector of Q1. How can they have different voltages?
Verify Q1 outline package type..
It might be TO-39(A) with case tab pointing Collector (instead of Emitter..)
(although its size seems to be TO-18 but you never know..)
(https://i.imgur.com/9nV9siS.gif)
Quote from: Marcos - Munky on April 14, 2020, 02:16:42 PM
Also, what exactly did you removed from the board?
:icon_rolleyes:
antonis it is a bc 109 it has it written on the side. i also checked the pins with a peak dca55 transistor meter. the tab is emitter middle leg is base and third leg is collector.
marcos - munky when i built it about 6 years ago i left it till a couple of months ago. when i opened it there were parts missing. i must of used them for other pedals. i replaced the parts which were the diodes and a 10uf capacitor. i cant remember if there were anymore. last weekend i took all the capacitors and transisters out one by one and tested them with an atlas esr meter and a peak dca55 transistor meter.
Quote from: plen on April 15, 2020, 01:00:50 PM
antonis it is a bc 109 it has it written on the side. i also checked the pins with a peak dca55 transistor meter. the tab is emitter middle leg is base and third leg is collector.
OK but then you have to explain what R.G. asked you:
Quote from: R.G. on April 14, 2020, 11:19:41 PM
Q1 has 14+ volts on the collector. The schematic shows Q2 base wired directly to the collector of Q1. How can they have different voltages?
antonis i cant check that at the moment as i have taken the three transistors and capacitors out of the board to read them. i dont know if anyone wants to check any of them.
after taking the capacitors and transistors out to read them and read the the resistors there was a 47k resistor next to the ldrs cover which was reading 4.5 i took it out and put it back in, then it read 47k. after soldering everything back in and trying the univibe i now get sound. the effect is very weak.
OK, so it's better. From your description, I think you corrected a bad solder joint.
In any case, what are the transistor voltages now?
I'm harping on this because it's a deadly effective way to find problems.
RG my power supply is not working. i am using a different 19v power supply. i dont know if it will give the wrong readings. Q1 base 1.299 collector 2.093 emitter 920 Q2 base 2.097 collector 3.72 emmiter 1.503 Q3 base 3.72 collector 11.14 emmiter 3.102 i took them out of circuit and read them with a peak dca55. i dont know if the readings are any good for you.
Quote from: plen on April 16, 2020, 09:54:32 PM
RG my power supply is not working. i am using a different 19v power supply. i dont know if it will give the wrong readings.
It's OK. I can look at the critical things, adjusting for what 19V on the power supply might mean. As an aside, the absolute power supply voltage doesn't matter a whole lot for the univibe circuit, as long as it's within 15-20V. When I did my univibe update/clone boards, I put in 7815 or 7818 voltage regulator chips for the low impedance more than for a fixed power supply voltage.
QuoteQ1 base 1.299 collector 2.093 emitter 920
Base is 1.299, emitter is 0.92, difference is 0.36, base more positive. This is probably OK. We'll see later in this note that it really is OK. The first transistor of the univibe has a quirk that the meter's resistance makes it look lower than it should be.
The collector is higher than the base, so this thing is probably working as an amplifier.
QuoteQ2 base 2.097 collector 3.72 emmiter 1.503
Base is 2.097-1.503 = 0.594V higher than the base. This is good - it's a normal voltage for an NPN base-emitter in active operation. The collector is higher than the base, so this transistor is operating as an amplifier.
Even better, the collector of Q1 and the base of Q2 are showing the same voltage (within measurement tolerance) so the circuit actuals match what we expect from the schematic.
QuoteQ3 base 3.72 collector 11.14 emmiter 3.102
Again, base higher than emitter by one silicon diode drop (0.5-0.7V) so this transistor is active. The collector is higher than the base, so it's in the amplifying region of operation.
The only criticism I have of this one is that the emitter is at 3.102V, but you show the collector at 11.14V. This is suspicious, and especially so since you're seeing not-much-effect. Here's why.
The emitter voltage of 3.102 is flowing through a 3.9K resistor and a 1.2K resistor. That's a total of 5.1K ohms. Ohm's Law tells us that 3.102V through a 5100 ohm resistor is 608uA of current. This is the sum of the collector current and base current. The base current is 1/50 to 1/100 of this. For this quick and dirty purpose, we can assume the base current is 6uA, and call the collector current 602uA.
This current has to flow through the collector resistor. This resistor is 4700 ohms, so the voltage across it is 602uA*4700 ohms, or 2.892V. This has to be subtracted from the power supply voltage of 19V. I would expect the collector to be at 19-2.892 = 16.17V. Instead, it's five volts lower.
So something is wrong here. Either the power supply that is actually getting to this transistor is down at about 14V, or something else is siphoning off current, not the transistor as it should be.
This matches the complaint of poor effect. If the signals at collector and emitter of Q3 are not equal and opposite reasonably, then you don't get much effect.
If I were doing this, at this point I would:
1. measure the voltage at both ends of the 4700 ohm collector resistor. You would expect the collector end to be 11V, per your measurements. The other is probably 14V. If it's really 19V, then the "4700 ohm" collector resistor can't really be 4700 ohms.
2. remove the two 1uF capacitors, one from collector of q3 and one from the emitter; measure the DC voltage on base, collector, and emitter of Q3 again, as well as the power supply at the top of the 4700 resistor.
Something is still hosed in this, and it could account for your problems now.
Quotei took them out of circuit and read them with a peak dca55. i dont know if the readings are any good for you.
19VDC power supply is going through a diode drop and a couple R-C filter stages, before it feeds the Q3 collector resistor.
Maybe so. Depends on where he spiced in this other power supply, I guess.
Quote from: R.G. on April 18, 2020, 05:43:44 PM
Maybe so. Depends on where he spiced in this other power supply, I guess.
Yeah I made assumptions.
Me too. Let's see if plen will tell us the voltages on the collectors of the phase transistors. That tells us the voltage getting through to the preamp.
rg is that Q6 and Q7
Q6 and Q7 should do fine. The pairs of Q4/5, Q6/7, and Q8/9 all have one of the collectors tied to the power supply voltage. Yours were all biased OK as I remember, so any one of those pairs will do the trick of telling us what the actual power supply voltage leading to the Q1/2/3 preamp devices.
Q6 14.76 Q7 11.00
Check your voltages again. Before you said the voltages are 15.6V for Q6 and 11.6V or Q7. Are you sure you checked the collector and not the emitter?
Quote from: plen on April 13, 2020, 07:00:46 PM
base collector emitter Q1 .065 .638 .001 Q2 .636 .077 .072 Q3 15.56 .001 .001 Q4 5.00 15.56 4.57 Q5 4.57 11.49 3.95 Q6 4.92 15.56 4.49 Q7 4.49 11.60 3.87 Q8 5.24 15.56 5.29 Q9 4.82 11.45 4.20 Q10 6.30 15.56 5.79 Q11 920 18.56 9.90 Q12 9.40 18.56 9.90 Q13 2.993 12.94 2.358 diode d3 19.30 big capacitors 18.56 17.04 15.56
marcus - munky i have edited my last post. Q6 14.76 Q7 11.00 my power supply is broken. i have been using different ones that i have laying around. maybe this is why i am getting different readings. i have sent away for a 15vdc 1a power supply i hope that helps.
The thing is if you keep changing the power supply each time you do voltage measurements, we can't know for sure what's really happening.
marcos sometimes if i change a resistor or something i will try different power supplys to see if the univibe will work. different power supply do different things to the univibe. some times i forget to put the same power supply back although most of the time it is the same one. the last readings i gave you i read the wrong pin. most times im asked for readings it is 3am or 4am and i dont have a clear head.
thanks.
As Marcos notes, quit changing the power supply when you feed us info. Or at least always include all transistor pin voltages from all of them when you send us voltages. It messes up our reasoning and we can't help you.
In addition, the univibe is not terribly sensitive to power supply voltages. The basic circuit works from power supplies from about 15Vdc up to about 20Vdc. So pick one power supply in that range and use it for testing. Changing power supplies around will confuse you as well as us.
Then do the measuremens when you have a clear head, and with just only power supply. If it works with one, it should work with all of them, if the transistors are biased correctly.
See,
Quote from: R.G. on April 21, 2020, 12:09:16 PM
Q6 and Q7 should do fine. The pairs of Q4/5, Q6/7, and Q8/9 all have one of the collectors tied to the power supply voltage. Yours were all biased OK as I remember, so any one of those pairs will do the trick of telling us what the actual power supply voltage leading to the Q1/2/3 preamp devices.
RG is trying to compare the voltages on Q1/2/3 with the voltages on Q6/7, to check what should be the correct voltage on Q1/2/3. Different power supplies rated for the same voltage usually ends up giving different output voltages, and even worse, the same power supply may output different voltages based on how much current is being drawn (unless they're regulated). So if you give a reading for Q1/2/3 using one power supply and a reading for Q6/7 using a different power supply, then we can't compare them at all, and will lead us to think on "why this point have lower voltage than the other one if it was supposed to be the other way" and look for problems that doesn't exist.
marcos i mentioned the different power supplys to RG a week ago and got this reply. Quote from: plen on April 16, 2020, 09:54:32 PM
RG my power supply is not working. i am using a different 19v power supply. i dont know if it will give the wrong readings.
It's OK. I can look at the critical things, adjusting for what 19V on the power supply might mean. As an aside, the absolute power supply voltage doesn't matter a whole lot for the univibe circuit, as long as it's within 15-20V. When I did my univibe update/clone boards, I put in 7815 or 7818 voltage regulator chips for the low impedance more than for a fixed power supply voltage. the 2 univibes my son and i built 6 years ago didnt work with all the power supplys we tried them with then. so they dont work with all power supplys in the 15v to 20v region.