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Why do all the images show 1.00 V/ except the last one which has 2.00 V/? Is that the volts per division or something else?

If everything is actually 2V/div then these last images look pretty OK. ...

Yes, looking at the schematic again I do see what you mean.

What I see is that instead of the current coming from the summing node through the collector circuit, it appears to come from the opamp o ...

Oh, sorry, you need to turn your coupling from AC to DC so we can see what the DC offset is. This is also necessary for adjusting T3 and T4 which may explain your tri and sine wave shapes, but not th ...

I have gone through the points, and it looks as it should. C7 is the right value, and the base one the right J14 is connected to ground, and both emittrds to R15.

Also probed around U5, and con ...

3. U3b pin 7 should be a constant negative voltage (for a given frequency setting) but not too close to the negative rail voltage.

The voltage on pin7 goes from -0.51 at the highest frequen ...

I would suggest starting by checking the following:
1. 5V reference : check at U7a pin 1, C8, Q1 drain and R13 to make sure they all have the same constant voltage of approximately 5V.

Defin ...

At this point, I would personally stop taking shots in the dark and start troubleshooting specific points in the circuit to narrow down the culprit.

The decay you're seeing indicates that the expo ...

I think I'm starting to understand where the confusion might be coming from. You seem to be thinking that in the Juno the digital part controlling the ramp current is in the DCO. It's not.

The mi ...

However, I have an amateur understanding of the "why" in all of this. I can read a schematic and follow wiring diagrams, but my biggest hurdle is knowing why all this stuff works in conju ...

So what I wonder is this, why not just use a normal expo too but tune it a bit low so that the digital reset always trumps it, but that the analog expo follows the digital hard sync pretty closely? ...

The PAiA circuit you are borrowing from uses an inverting configuration. You can't simply swap the input to the non-inverting input as you've done and expect it to operate the same. Inverting and no ...

1. The low level of distortion isn't because the clip voltage is too low, it's that it is too high. Adding diodes will only exacerbate the problem, which already may be happening because you've adde ...

Schematics are often split into multiple pages. It makes it easier to read, it can get very cluttered putting everything on one page. The labels are key as PHOBoS explained. Basically every net wit ...

Well that's a bummer, but not surprising since the gate is closed by the CV going to the lowest value. Conceptually, an easy solution might be to add a small delay between U2B and Q3 to allow the hol ...

And, that was it! R21 was the problem. It was the correct value but was faulty.
Well there you go! See, you just gotta through the circuit systematically, follow the clues and narrow it down till yo ...

There's a problem in there somewhere, don't assume anything. Short, cut in a trace, bad component, something.

Check that pin 8 and the end of R16 connected to it are the same voltage. Check that ...

Sounds like a problem with the feedback resistor R16.

Pin 8 should be amplifying the voltage at pin 10 by a factor of 3.

Pins 9 and 10 should be the same voltage as long as they are within about ...

Well that sounds better. The small blips at pin 3 are expected. They should be much larger out of pin 1. Might be a bad connection around pins 2 and 3 or the components connected to them if pin 1 i ...

Looks like you caught my post before I edited it. I got a couple wires crossed so it wasn't totally accurate. Embarassed

Anyway, ya, I think we need to be looking at the U4 area.

You're essential ...

The saturation voltage is the maximum voltage the op amp can put out. With a 12V supply it will max out at about 10.5V. With a 9V supply it will be less, about 7.5V.

The comparator threshold in the ...

Oh ya, tough to do with the naked eye.

I use one of those lamps with the magnifying glass in it. The lab I used to work in had microscopes. Then there are those head band magnifiers which I haven ...

Ngh!

After doing more and more troubleshooting and exchanging components to see if anything was borked, I now have something entirely different and no oscillation from the 555 at all:

Check IC3 ...

I use a flux pen. Put on the pads, place the component, a little dab of solder on a clean iron tip, just touch the tip to the pad and edge of component and the solder wicks right in.

I used 25C since that most likely matches the situation of sitting there testing out your new circuit with the chassis open and putting your finger on it to see if it's getting hot. But ya, at some p ...

hmm 40C actually seems pretty low with 2W dissipation and such a small heatsink.
Oh! I was using the 7.5 C/W quoted in the mouser page. I just looked at the data sheet and that value is with forced ...

Author	Message
Topic: Yusynth VCO problem tracking at low frequencies
gdavis Replies: 34 Views: 22214	Posted: Sun Mar 11, 2018 2:46 pm Subject: Yusynth VCO problem tracking at low frequencies Forum: DIY Hardware and Software » YuSynth
gdavis Replies: 34 Views: 22214	Why do all the images show 1.00 V/ except the last one which has 2.00 V/? Is that the volts per division or something else? If everything is actually 2V/div then these last images look pretty OK. ...
Topic: How does current source in polivoks filter work?
gdavis Replies: 12 Views: 12384	Posted: Fri Mar 09, 2018 6:58 pm Subject: How does current source in polivoks filter work? Forum: DIY Hardware and Software
gdavis Replies: 12 Views: 12384	Yes, looking at the schematic again I do see what you mean. What I see is that instead of the current coming from the summing node through the collector circuit, it appears to come from the opamp o ...
Topic: Yusynth VCO problem tracking at low frequencies
gdavis Replies: 34 Views: 22214	Posted: Fri Mar 09, 2018 6:13 pm Subject: Yusynth VCO problem tracking at low frequencies Forum: DIY Hardware and Software » YuSynth
gdavis Replies: 34 Views: 22214	Oh, sorry, you need to turn your coupling from AC to DC so we can see what the DC offset is. This is also necessary for adjusting T3 and T4 which may explain your tri and sine wave shapes, but not th ...
Topic: Yusynth VCO problem tracking at low frequencies
gdavis Replies: 34 Views: 22214	Posted: Fri Mar 09, 2018 11:16 am Subject: Yusynth VCO problem tracking at low frequencies Forum: DIY Hardware and Software » YuSynth
gdavis Replies: 34 Views: 22214	I have gone through the points, and it looks as it should. C7 is the right value, and the base one the right J14 is connected to ground, and both emittrds to R15. Also probed around U5, and con ...
Topic: Yusynth VCO problem tracking at low frequencies
gdavis Replies: 34 Views: 22214	Posted: Thu Mar 08, 2018 9:48 pm Subject: Yusynth VCO problem tracking at low frequencies Forum: DIY Hardware and Software » YuSynth
gdavis Replies: 34 Views: 22214	3. U3b pin 7 should be a constant negative voltage (for a given frequency setting) but not too close to the negative rail voltage. The voltage on pin7 goes from -0.51 at the highest frequen ...
Topic: Yusynth VCO problem tracking at low frequencies
gdavis Replies: 34 Views: 22214	Posted: Thu Mar 08, 2018 8:48 pm Subject: Yusynth VCO problem tracking at low frequencies Forum: DIY Hardware and Software » YuSynth
gdavis Replies: 34 Views: 22214	I would suggest starting by checking the following: 1. 5V reference : check at U7a pin 1, C8, Q1 drain and R13 to make sure they all have the same constant voltage of approximately 5V. Defin ...
Topic: Yusynth VCO problem tracking at low frequencies
gdavis Replies: 34 Views: 22214	Posted: Sun Mar 04, 2018 11:27 am Subject: Yusynth VCO problem tracking at low frequencies Forum: DIY Hardware and Software » YuSynth
gdavis Replies: 34 Views: 22214	At this point, I would personally stop taking shots in the dark and start troubleshooting specific points in the circuit to narrow down the culprit. The decay you're seeing indicates that the expo ...
Topic: DCO has hard reset on normal analog expo VCO?
gdavis Replies: 5 Views: 3618	Posted: Fri Dec 08, 2017 8:16 pm Subject: DCO has hard reset on normal analog expo VCO? Forum: DIY Hardware and Software
gdavis Replies: 5 Views: 3618	I think I'm starting to understand where the confusion might be coming from. You seem to be thinking that in the Juno the digital part controlling the ramp current is in the DCO. It's not. The mi ...
Topic: General DIY Questions
gdavis Replies: 7 Views: 4036	Posted: Wed Dec 06, 2017 9:53 pm Subject: Re: General DIY Questions Forum: DIY Hardware and Software
gdavis Replies: 7 Views: 4036	However, I have an amateur understanding of the "why" in all of this. I can read a schematic and follow wiring diagrams, but my biggest hurdle is knowing why all this stuff works in conju ...
Topic: DCO has hard reset on normal analog expo VCO?
gdavis Replies: 5 Views: 3618	Posted: Wed Dec 06, 2017 8:57 pm Subject: Re: DCO has hard reset on normal analog expo VCO? Forum: DIY Hardware and Software
gdavis Replies: 5 Views: 3618	So what I wonder is this, why not just use a normal expo too but tune it a bit low so that the digital reset always trumps it, but that the analog expo follows the digital hard sync pretty closely? ...
Topic: Help with voltage-controlled distortion circuit design
gdavis Replies: 4 Views: 8348	Posted: Mon Oct 02, 2017 7:31 pm Subject: Help with voltage-controlled distortion circuit design Forum: DIY Hardware and Software » Musical Interfaces
gdavis Replies: 4 Views: 8348	The PAiA circuit you are borrowing from uses an inverting configuration. You can't simply swap the input to the non-inverting input as you've done and expect it to operate the same. Inverting and no ...
Topic: Help with voltage-controlled distortion circuit design
gdavis Replies: 4 Views: 8348	Posted: Sat Sep 30, 2017 12:24 pm Subject: Help with voltage-controlled distortion circuit design Forum: DIY Hardware and Software » Musical Interfaces
gdavis Replies: 4 Views: 8348	1. The low level of distortion isn't because the clip voltage is too low, it's that it is too high. Adding diodes will only exacerbate the problem, which already may be happening because you've adde ...
Topic: LM358 exponential VCO help
gdavis Replies: 5 Views: 7619	Posted: Tue Sep 26, 2017 8:24 pm Subject: LM358 exponential VCO help Forum: DIY Hardware and Software » Developers' Corner
gdavis Replies: 5 Views: 7619	Schematics are often split into multiple pages. It makes it easier to read, it can get very cluttered putting everything on one page. The labels are key as PHOBoS explained. Basically every net wit ...
Topic: Single Buss 1V/Oct Troubleshooting
gdavis Replies: 17 Views: 11902	Posted: Mon Sep 04, 2017 8:36 pm Subject: Single Buss 1V/Oct Troubleshooting Forum: DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
gdavis Replies: 17 Views: 11902	Well that's a bummer, but not surprising since the gate is closed by the CV going to the lowest value. Conceptually, an easy solution might be to add a small delay between U2B and Q3 to allow the hol ...
Topic: Single Buss 1V/Oct Troubleshooting
gdavis Replies: 17 Views: 11902	Posted: Mon Sep 04, 2017 7:56 pm Subject: Single Buss 1V/Oct Troubleshooting Forum: DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
gdavis Replies: 17 Views: 11902	And, that was it! R21 was the problem. It was the correct value but was faulty. Well there you go! See, you just gotta through the circuit systematically, follow the clues and narrow it down till yo ...
Topic: Single Buss 1V/Oct Troubleshooting
gdavis Replies: 17 Views: 11902	Posted: Mon Sep 04, 2017 5:33 pm Subject: Single Buss 1V/Oct Troubleshooting Forum: DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
gdavis Replies: 17 Views: 11902	There's a problem in there somewhere, don't assume anything. Short, cut in a trace, bad component, something. Check that pin 8 and the end of R16 connected to it are the same voltage. Check that ...
Topic: Single Buss 1V/Oct Troubleshooting
gdavis Replies: 17 Views: 11902	Posted: Mon Sep 04, 2017 1:52 pm Subject: Single Buss 1V/Oct Troubleshooting Forum: DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
gdavis Replies: 17 Views: 11902	Sounds like a problem with the feedback resistor R16. Pin 8 should be amplifying the voltage at pin 10 by a factor of 3. Pins 9 and 10 should be the same voltage as long as they are within about ...
Topic: Single Buss 1V/Oct Troubleshooting
gdavis Replies: 17 Views: 11902	Posted: Sun Sep 03, 2017 6:52 pm Subject: Single Buss 1V/Oct Troubleshooting Forum: DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
gdavis Replies: 17 Views: 11902	Well that sounds better. The small blips at pin 3 are expected. They should be much larger out of pin 1. Might be a bad connection around pins 2 and 3 or the components connected to them if pin 1 i ...
Topic: Single Buss 1V/Oct Troubleshooting
gdavis Replies: 17 Views: 11902	Posted: Sun Sep 03, 2017 3:44 pm Subject: Single Buss 1V/Oct Troubleshooting Forum: DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
gdavis Replies: 17 Views: 11902	Looks like you caught my post before I edited it. I got a couple wires crossed so it wasn't totally accurate. Anyway, ya, I think we need to be looking at the U4 area. You're essential ...
Topic: Single Buss 1V/Oct Troubleshooting
gdavis Replies: 17 Views: 11902	Posted: Sun Sep 03, 2017 3:00 pm Subject: Single Buss 1V/Oct Troubleshooting Forum: DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
gdavis Replies: 17 Views: 11902	The saturation voltage is the maximum voltage the op amp can put out. With a 12V supply it will max out at about 10.5V. With a 9V supply it will be less, about 7.5V. The comparator threshold in the ...
Topic: PHOBoS in SMD land
gdavis Replies: 61 Views: 60202	Posted: Sun Sep 03, 2017 1:20 pm Subject: PHOBoS in SMD land Forum: DIY Hardware and Software » Stickney Synthyards
gdavis Replies: 61 Views: 60202	Oh ya, tough to do with the naked eye. I use one of those lamps with the magnifying glass in it. The lab I used to work in had microscopes. Then there are those head band magnifiers which I haven ...
Topic: The VCO-555
gdavis Replies: 479 Views: 591649	Posted: Wed Aug 30, 2017 8:34 pm Subject: The VCO-555 Forum: DIY Hardware and Software » Thomas Henry designs
gdavis Replies: 479 Views: 591649	Ngh! After doing more and more troubleshooting and exchanging components to see if anything was borked, I now have something entirely different and no oscillation from the 555 at all: Check IC3 ...
Topic: PHOBoS in SMD land
gdavis Replies: 61 Views: 60202	Posted: Sun Aug 27, 2017 5:41 pm Subject: PHOBoS in SMD land Forum: DIY Hardware and Software » Stickney Synthyards
gdavis Replies: 61 Views: 60202	I use a flux pen. Put on the pads, place the component, a little dab of solder on a clean iron tip, just touch the tip to the pad and edge of component and the solder wicks right in.
Topic: Voltage Regulator Overheating - Heat Sink Needs?
gdavis Replies: 10 Views: 16243	Posted: Sun Aug 13, 2017 2:28 pm Subject: Voltage Regulator Overheating - Heat Sink Needs? Forum: DIY Hardware and Software » Circuit Bending
gdavis Replies: 10 Views: 16243	I used 25C since that most likely matches the situation of sitting there testing out your new circuit with the chassis open and putting your finger on it to see if it's getting hot. But ya, at some p ...
Topic: Voltage Regulator Overheating - Heat Sink Needs?
gdavis Replies: 10 Views: 16243	Posted: Sun Aug 13, 2017 1:16 pm Subject: Voltage Regulator Overheating - Heat Sink Needs? Forum: DIY Hardware and Software » Circuit Bending
gdavis Replies: 10 Views: 16243	hmm 40C actually seems pretty low with 2W dissipation and such a small heatsink. Oh! I was using the 7.5 C/W quoted in the mouser page. I just looked at the data sheet and that value is with forced ...