Far as I know it’s always been the case that some chips have half circle notches, some have indented circles at the pin 1 end… and some have half circle notches at the pin 1 end and indented circles at the other end.
It’s stupid, but it’s always been stupid.
What is always true is if the label text is right side up, pin 1 is lower left.
My systems work on ±12V and have reversed the polarity numerous times (I screw up a lot) and have never had let the smoke out our fried the chips. I use TL072, TL074, LM358, and LM324. Never fried a one. I did have a electrolytic capacitor explode once. You have to be very careful with those as they are little grenades when the go pop!
The only half moon markers I have seen are on Texas Instruments chips. Most other chips have just a little nipple, dot, or inlaid circle at pin one. Those pictured are quite typical.
As a practice, I test for continuity and shorts before applying power on a new board. I can never emphasize the importance of a good quality bench meter for testing. If you are working on a lot of boards, for the money you can’t beat the Siglent SDM3045X. If you are on a tighter budget (I have this as a backup) you should have the OWON XDM1241. The handheld DMMs are OK but I found the bench DMMs have many more hidden features that I have found very helpful.
An old analog oscilloscope is extremely useful as well. I practically stole one on ebay years ago. While it isn’t tightly calibrated it is so useful to be sure waveshapes are correct and levels are decent.
I’m finally trying to calibrate this thing and I’m running into what I think is a problem, perhaps not? Let’s see what you all think.
I’m using my Mutable Instruments module tester. I’ve got it calibrated and sending a 2 octave arp to the 1v/oct input of the polymorph VCO (it alternates between 1v and 3v every 5 seconds. I’ve verified this via multimeter). I can see the VCO responding to the voltage change, but it’s at only 3Hz at the low end (with the octave switch at its lowest notch and both tuning knobs set to 12 o’clock). Certainly this has to be far too low, but none of the trimmers on the VCO seem to significantly affect this value. Am I just being stupid or having the wrong expectations?
I haven’t finished my Polymorph VCO yet, as I am still hunting for the final components, but I would like to suggest:
measure the resistance with a multimeter between the soldered pins of the trim potentiometers several times while changing the trim in the mean time, to make sure they are working. If not:
reflowing the solder of the trim potentiometers.
I recently had a similar problem with a trim pot in a DIY attenuverter module I was building, where the trim pot had no effect. With the two steps above, I was able to fix the issue.
3Hz at 1V does seem a bit low, it should be in the audible range. There’s no trimmers for the offset (the freq at 0V), as that what the tuning pots set. The trimmers only set the scaling of the 1V/oct input and the octave switch. I’d recommend you check the component values and solder joints of the components surrounding the exponential converter input. Can you get it to scale correctly? Eg does your 1-3V arp produce 3-12Hz? That might provide some clues.
Yeah it scales appropriately as far as I can tell
Getting the right ranges from the tune knobs as well? Coarse should be about an octave, fine and a full step
Yeah the tune knobs have a very wide range as well.
Can you check the values of the scaling resistors and the timing cap?
R59 measures at 22k and I have a 392j63 capacitor off the TCAP pin @ c20. RV14 is a 5k trimmer. I’ll see if i can get an accurate reading on that cap.
I pulled the cap and it reads high (between 4.3 and 5 nf. I’ll swap it out and report back.
EDIT: That cap must have been damaged when I removed it from the board to test. After replacing it with a known good/tested cap I’m back to seeing the same behavior. 2 octave arp alternates between ~3-12ish Hz
What about R26?
20 chars
AHA. Only 118k
It has the correct (270k) resistor code on it, it’s just low (or reading low in-situ). Will swap it.
Another false alarm. Resistance tested fine once it was removed
I’ll test mine later, see what freq it gives me at 0V
Seems like your measurements are right! I have two assembled units here, both read ~1.7Hz at 0V. I know there’s no standard for what freq 0V should correspond to, but 1.7Hz maybe isn’t the most useful. I will add a bias resistor to next versions. If you’d like to clutz it yourself, a 39k resistor between VREF+ (pin 23) and IEXPFR (pin 7) should place the 0V point around 20Hz.
youre the best. Thanks
This works much better now. Thanks again. I’ve got everything calibrated as well as I can now. There only seems to be one lingering problem, which is that the sub waveform will switch from triangle to saw just fine, but there seems to be no audible difference between the saw and square at all.
Do you have a scope available to look at it? What kind of switch did you use for it?
I do. I’ll scope it when I get home
I double checked and it’s a SP3T. I remember the switch costing like $6 too LOL