SAD1024 clock noise help

[puretube]

Intensity-pot does not directly connect to the +supply of IC12 (in the schemo)...

[four_corners]

Intensity-pot does not directly connect to the +supply of IC12 (in the schemo)...

Oops, you are correct, I was looking at the backside of the board of course. so Intensity pot is connected to IC12 pin 1.

If I want to use an electrolytic cap, would I put positive to Pin 1, negative to ground?

[puretube]

Don`t use elcos!

[four_corners]

Don`t use elcos!

Haha ok I won’t!

Think I’ll monitor pin 1 on IC12 to see what’s going on with and without the cap.

[puretube]

Don`t use elcos!

Haha ok I won’t!)

Think I’ll monitor pin1 on IC12 to see what’s going on with and without the cap.

Upon my request in reply #12 you already said in reply #15 that you don`t see "pips/ticks" there, on the scope.
Although you also already stated a clean output there, it`d be more interesting to observe pin7 of IC12 which is where the voltage from pin1 goes to after it has travelled through the Intensity-pot and R103 into pin6 and being smoothed/integrated/filtered by C51.
(And maybe gathered some "dirt" on its way there).

Maybe C51 is the candidate for replacement. 25V or 40V working voltage doesn`t hurt! Nowadays they`re almost all of the same small or even smaller size ...

[four_corners]

Don`t use elcos!

Haha ok I won’t!)

Think I’ll monitor pin1 on IC12 to see what’s going on with and without the cap.

Upon my request in reply #12 you already said in reply #15 that you don`t see "pips/ticks" there, on the scope.
Although you also already stated a clean output there, it`d be more interesting to observe pin7 of IC12 which is where the voltage from pin1 goes to after it has travelled through the Intensity-pot and R103 into pin6 and being smoothed/integrated/filtered by C51.
(And maybe gathered some "dirt" on its way there).

Maybe C51 is the candidate for replacement. 25V or 40V working voltage doesn`t hurt! Nowadays they`re almost all of the same small or even smaller size ...

Well I think I fried the CD4013, lol. Fingers crossed that I didn't fry the  sad1024.

Basically, I went to calibrate the V3 and V4 once and for all, and mixed up that fact the TP6 and TP7 are on pin 12 and 13, not on pin 6 and 7. So probe is clipped on pin 7, probe slips and shorts between pin 6 and pin 7, and flanger fully cuts out.

So pin6, Set 1, was shorted to ground.

Of course pin 6 on the 4013 connects directly to the sad1024 on pin 7, meaning pin 7 was also shorted to ground, and pin 7 is the voltage supply.

Shorting the sad1024 voltage to ground wouldn't kill it, it would just cut off the supply, correct?

I'm still getting the sine wave out of IC12 pin 1, meaning either the 4013, Q18, or Q19 is dead.

Should have a new 4013 here next week. Schematic says "Motorola only" but I just ordered a CD4013, so we will see.


____

I replaced C51 a few days ago with a higher voltage electro, but it didn't help.

Also, the scope image I posted were a mistake, those came from IC11 not IC12. I need to check pin 7 again to see if it is a clean signal.

[puretube]

    Ouch!

Q20 first.  :'(

I replaced C51 a few days ago with a higher voltage electro, but it didn't help.

Ooops - yes, sorry, I forgot.

[four_corners]

Q20 first.  :'(

I had ordered some C945's with my CD4013 order, but maybe I have a transistor already that I could drop in. I need to see if anything is a suitable replacement.

[four_corners]

Looks like I can just use a 3904, but the C945 has the collector in the middle, so I'll need to do some leg twisting on the 3904

[four_corners]

Don`t use elcos!

Haha ok I won’t!)

Think I’ll monitor pin1 on IC12 to see what’s going on with and without the cap.

Upon my request in reply #12 you already said in reply #15 that you don`t see "pips/ticks" there, on the scope.
Although you also already stated a clean output there, it`d be more interesting to observe pin7 of IC12 which is where the voltage from pin1 goes to after it has travelled through the Intensity-pot and R103 into pin6 and being smoothed/integrated/filtered by C51.
(And maybe gathered some "dirt" on its way there).

Maybe C51 is the candidate for replacement. 25V or 40V working voltage doesn`t hurt! Nowadays they`re almost all of the same small or even smaller size ...

Woohoo, back in business, was just Q20 as you suspected.

Here is IC12 pin7, looks like a noisy sine wave.

[puretube]

Congrats - looks good!
The noise-hash is just a sign of the HF BBD-sampling.
The LFO-signal looks absolutely tick-free.
At which settings of the Intensity and Manual pots was the pic taken?
Try/watch all combinations of settings (preferably with constant Speed-rate),
to see whether some ticking-spikes appear ...

[four_corners]

Congrats - looks good!
The noise-hash is just a sign of the HF BBD-sampling.
The LFO-signal looks absolutely tick-free.
At which settings of the Intensity and Manual pots was the pic taken?
Try/watch all combinations of settings (preferably with constant Speed-rate),
to see whether some ticking-spikes appear ...

This was with Intensity at 10, and im not sure about Manual.

So my capacitor from ground to IC12 pin 1 makes the pin 1 waveform (which feeds into the Intensity pot, VR3 and VR4) go from this...



to this...



Audio wise, it goes from ticking, to more like a static noise floor sound.

[puretube]

not what we want.

Have you done the VR3 & VR4 adj. procedure (without that cap), since you repaired Q20?
Or was that already done when you fried it?

[four_corners]

not what we want.

Have you done the VR3 & VR4 adj. procedure (without that cap), since you repaired Q20?
Or was that already done when you fried it?

Well, long story short, it isn't working again, haha.

When I went to adjust VR3 and VR4, I was able to get the upper range to 1MHz (Manual at 10), but couldn't get it anywhere close to 100kHz when Manual was at zero, the lowest I could get it was 500kHz. I noticed the higher the resistance, the lower I could get it when Manual was at zero, so I desoldered VR3 and VR4 and put new 500k trimmers instead of the 220k trimmers.

Turn it back on.... no effect again.

When desoldering the original trimmers, a couple pads lifted, but I made sure after soldering the new ones that the lifted pads showed continuity to the parts before/after each pin (which is easier as the wiper on each is connected to one of the lugs).

I'm still getting a clean waveform from IC12 pin 1 and pin 7, and speed and intensity still change that waveform. The only thing I can think of is I may have overheated the pads on the trimmers when desoldering, which may have fried Q19. Annoyingly, it is some weird C1583 5 pin transistor. It seems basically like 2 matched transistors with their emitters tied in the middle, base pins on 1 and 5, collector on 2 and 4. EDIT: Looks like the PMP4201 can be used on an adapter board in place of C1583. Not sure if I can test the transistor while in the circuit though.

No need to respond until I at least figure this out.

[amptramp]

If you have a 5-pin differential amp transistor pair, you can sometimes substitute an op amp input stage and take the output from the compensation / centering pins.  An LM318 or a 5534 has this provision but you have to figure out how to eliminate any effect from the rest of the op amp.

[four_corners]

If you have a 5-pin differential amp transistor pair, you can sometimes substitute an op amp input stage and take the output from the compensation / centering pins.  An LM318 or a 5534 has this provision but you have to figure out how to eliminate any effect from the rest of the op amp.

Thanks, I'll look into that.


I think I figured out why the flanger died on me. I somehow managed to mess up the CD4013. After trying to follow sine ways all around this circuit, I figured out I am no longer getting the same signal out of pin 12 and 13 on the CD4013. Pin 12 is correct, but pin 13 is just noise, so obviously something is going wrong there. They are both derived from the same Data Input and Clock Input, so it must be something within the chip that has crapped out I assume. Have some 4013s getting here on Tuesday, so I'll try then.

If that doesn’t fix it I’ll move to the transistors.

[puretube]

Let`s hope it`s the 4013`s outputs, but not the BBD`s clock-inputs that mess up ... 

[anotherjim]

With noise present on an output pin, it's likely the 4013 output has disconnected.
The note that it has to be a Motorola suggests something is different about them. There was a time when there were many versions of these logic parts that had specifications particular to the manufacturer. Now there are far fewer choices and the Moto isn't one of them. You may find the clock waveform even less square with a modern replacement, especially at the highest clock frequency. We will hope it's not a problem.

If it came to it, the dual transistor could be replaced with a little adapter board with a pair of matched hfe NPNs like 2N3904 stuck face to face. I don't think this application really requires perfectly matched tracking between the two transistors as it does in a VCO pitch CV converter.

[four_corners]

With noise present on an output pin, it's likely the 4013 output has disconnected.
The note that it has to be a Motorola suggests something is different about them. There was a time when there were many versions of these logic parts that had specifications particular to the manufacturer. Now there are far fewer choices and the Moto isn't one of them. You may find the clock waveform even less square with a modern replacement, especially at the highest clock frequency. We will hope it's not a problem.

If it came to it, the dual transistor could be replaced with a little adapter board with a pair of matched hfe NPNs like 2N3904 stuck face to face. I don't think this application really requires perfectly matched tracking between the two transistors as it does in a VCO pitch CV converter.

Thanks for the info about both the 4013 and dual transistor. Sounds like if I try the CD4013 and the flanging comes back but is weird, I can then just find a NOS Motorola one online. Same with the transistors (I actually found an Oshpark board that takes an SMD dual transistor and breaks it out into the correct pin out as this specific dual transistor).

[four_corners]

With noise present on an output pin, it's likely the 4013 output has disconnected.
The note that it has to be a Motorola suggests something is different about them. There was a time when there were many versions of these logic parts that had specifications particular to the manufacturer. Now there are far fewer choices and the Moto isn't one of them. You may find the clock waveform even less square with a modern replacement, especially at the highest clock frequency. We will hope it's not a problem.

If it came to it, the dual transistor could be replaced with a little adapter board with a pair of matched hfe NPNs like 2N3904 stuck face to face. I don't think this application really requires perfectly matched tracking between the two transistors as it does in a VCO pitch CV converter.

Well, put in a new CD4013 and still the same issue, no flanging at all.

I tried replacing some of the C945 transistors with no help.

I didn't have any A733, and 2SA1015 seemed close enough so I tried one of those, but no luck either. Should I try to get real A733's or should the 2SA1015 be okay?

_______

So the last 2 main things to try would be the dual transistor, and then the SAD1024 bbd.

As a test for the time being, could I just breadboard a couple 2N3904's and put temporary leads to the solder points? Basically if they don't match at all, would the effect still work, just wouldn't be sort of "calibrated" correctly? I also have some KSC1845 that seem like they could work, and they also have center Collector, so I just would have to solder the emitters together.

The other option is buy a $150-250 pedal to grab a SAD1024 (obviously don't want to do this unless I definitely have to. Is there any way to test that it is the SAD1024 (specifically pin 10, which currently is the only obvious issue I see, as it isn't receiving a clean signal from IC13 of the 4013).

_______

Unfortunately it is just getting worse and worse, as this PCB is becoming a brittle mess, haha. The traces lift soo quickly and break off, as if I'm using a welder instead of a soldering iron. I've had to bend numerous leads to solder past failed pads, but I always check continuity between components. That being said, this could be something very small and annoying. I've built tons of pedals, a Buchla Easel, and many polysynths, so I'm not a total novice, but that doesnt mean I didn't make a mistake.