1222 Tuner VCO Module

[Moseley]

Hello,

First full module build and hitting some roadblocks.

I am not getting any lights from the screen or the LEDs and also no sound from any outputs. Is it possible to get sound without the LEDs and screen lighting up?

I damaged the pcb board when de soldering the connector that holds the bank of 8 1/4 jacks. I did a quick fix on the copper and do have continuity between the CV pin and the cv control potentiometer but wondering if that could have impacted something else?

I have worked my way through a bunch of the trouble shooting info on the site but still no joy. As this is my first module I have a few questions.

I bought a few 1W and 2W resistors when I sourced components that I used in this build, will that be causing any issues? I read online that in most cases it will not but wondering on what you guys think or have encountered.

TL072CN is reading -10.67V at pin 4 but pin 8 is reading -0.61V
TL074CN is reading -10.67V at pin 11 but pin 4 is reading -0.61V

CEM3340 is reading 0V at pin 14 which I think should be reading something!

I am not getting continuity between pin 14 on the 3340 and -12V from the power header, presume I should be though.

The Arduino is read - 0.22V at the VIN pin which should be more?

I have tried to check resistor values but when I use my multi meter the values are different to what they should be on the meter, I got the same component out of my resistor box though and tested it and it reads as it should. If I have plugged the module in will the resistor values change or something? This part really confuses me. I just plugged the module in and the values are sort of close but still not on, do the capacitors or the circuit itself effect these?

I have also swapped out the TL072 and TL074 chips for different ones but I don’t have a different 3340 chip to try, could the chip be damaged? But I should still get voltage still surely when I test the actual pcb part of the board?

I am basically stuck and hoping I have missed something basic that someone on here can spot!

All help is much appreciated!!!

[analogoutput]

Looks like you’re not getting +12 V power. Make sure your power supply’s +12 V rail is working. Then with power off, check continuity from power header pins 9–10 (pins on the opposite end from the red stripe) to one end of R40. Then check continuity from other end of R40 to + terminal of C8 and to TL072 pin 8, TL074 pin 1, 3340 pin 16, and Arduino VIN pin L7805 pin 1. Also check to make sure there is NO continuity from any of those points to ground (middle 6 pins of the power header).

Also, before you make a regrettable mistake, put a piece of tape over the link header or stick an extra IDC connector in it or something to prevent accidentally plugging a power cable into it!

Checking resistances in circuit is problematic — you’re sensitive to all components connecting to those two points, not just the one resistor you’re interested in. That can lead to a lower (sometimes much lower) reading than the actual value of the resistor — though not higher, so if you read something too high that’s an indication something is wrong. But lower might be fine.

@Moseley

I am not getting continuity between pin 14 on the 3340 and -12V from the power header, presume I should be though.

Pin 14 certainly should NOT be connected to -12 V! Anyway your -12 V rail looks, well, not so bad. Not so great either, 10.67 V is too low, but it’s a lot better than -0.61 V so start with the +12 V rail.

[lookmumnocomputer]

hey so yes like @analogoutput says, if no light on the Arduino itself you may not be getting +12v. first thing to do to see any sign of life is the power light turns on on the Arduino

I dont immediately see an issue but there is a broken track on one of the connectors to the jack board, it shouldn’t be the problem thats making it all not work but you’d need to get a bit of wire to make a connection between the two points where the broken track is going, its easy just use your finger to see where the track leads

[Willi359]

As Sam and analogoutput said havin’ the Arduino running is a good sign. there even is an intro animation on the display when the unit powers up. These parts represent the tuning aspect of the whole thing. it is possible to get audible output without them.

[Bpbby]

Hi, next time you try to power it, remove all the chips. Even the arduino. You can then test all the connections safely. It is fine to take it slow

@Willi359 what animations ??? I dont have any…

[Willi359]

mine runs trough all segments, LEDs and note letters… part of the code i used, maybe an improved version… i recognize the avatar from around here

I was realy happy when i saw it for the first time… YES!

[Moseley]

Ok amazing!

Gonna do this when home again.

Yep you are right the power supply is not giving out +12 or 5!

So maybe it’s working perfectly! Looking at the supply now

[Moseley]

@analogoutput

Then with power off, check continuity from power header pins 9–10 (pins on the opposite end from the red stripe) to one end of R40. Then check continuity from other end of R40 to + terminal of C8 and to TL072 pin 8, TL074 pin 1, 3340 pin 16, and Arduino VIN pin. Also check to make sure there is NO continuity from any of those points to ground (middle 6 pins of the power header).

So I have continuity for all of these except the VIN on the arduino, what does this mean in reality? I also don’t have continuity on the 3340 on pin 16 but actually on pin 18?!?

[Bpbby]

Hmmmm 3340 only has 16 pins. Which is plenty…

Not having continuity would mean that you have no direct connection. As you are using a PCB from Sam it is not possible, so my best guess is that you have a bad connection, cold joint, etc…

[analogoutput]

My mistake, the Arduino is powered by an external 5V regulator so no continuity to 12 V is correct.

So your VCO may be fine, but in need of a working power supply.

[Moseley]

Ah yes indeed, one pin diagram I found said 18 pins!

[Moseley]

Ok great!!!

Fingers crossed I plug in the new supply and it works!!!

That’s for the help though team, as always, you all rule!

[analogoutput]

That’d be the CEM3345.

[devicex]

and as a side note cover that extra extension socket before you accidentally plug the power lead into it ! a few of us have learned the hard way
good luck with the finish on your build . there are a few fixes that can be found on the threads related to the 1222 tuner VCO module .

[Moseley]

Nice one, yep covered it up as you are the second to suggest it so the danger seems real!!

Fixes you say? Will have to read through again and see what they are, any you have done yourself?

[heckseven]

The danger is very real. I have plugged into the wrong socket twice.

[ChristianBloch]

@lookmumnocomputer

put a 20M resistor (I didn’t have one so used 2 10M’s) between the two solder points circled in red.

what this does is it also sends the voltage going to the PWM pin on the 3340 to the pitch input too! just enough to counteract the pitch drop.

…

anyway! let me know if anyone dares trying this! I’m gunna continue testing it.

I can confirm that this “dodgy” fix works . I implemented it standard on the Eurorack version.

[analogoutput]

Interesting. Above @stmllr reported needing 6.6M instead of 20M to cancel out the pitch shift, and when I tried it on breadboard I found I needed 4.7M. So it seemed to me the basic idea was sound but the resistor value needed varied. Now it sounds like you’re saying 20M worked for all your VCOs. Hm.

Anyway, I used a regulated -5 V in my design and that eliminated the problem for me. Not practical for a 1222 retrofit though.

[Moseley]

New power supply came AND IT WORKS!!!

is it normal that Triangle wave is much lower in volume than the square though?

Haven’t calibrated yet but the lights are on and I have sound!!!

[analogoutput]

Yes.

1222 Tuner VCO Module

Yeah, pulse is +Vcc minus voltage drop over the output transistor (which depends on current, but is nominally +Vcc−1.5V), while triangle output is fixed at +Vcc/3 (so 4 V with a 12 V supply) and any non-trivial load will affect the tuning (so you really want a buffer on that one). Ramp/sawtooth is +Vcc×2/3 (8 V), with more internal buffering. (there may be an argument for turning triangle or ramp into PWM outside the chip to make things more stable, cf the AS3340-HYB variant discussed here, but…

Triangle amplitude is 0 to 4 V, ramp is 0 to 8 V, and pulse is 0 to 10.5 V. The 1222 just buffers those and sends them to the output jacks. There are other 3340 designs that equalize the amplitudes and center them on zero.