KLEE CALIBRATION QUESTION

[jaskah]

i recently finished a klee synthcube kit. everything is working in the bring-up procedure. i'm now trying to go through the calibration process.

trying to calibrate the offset zero, and following the manual with my multimeter set to volts and ground attached to j10 and the positive lead to pin 1 of u8, i'm only getting 12 volts reading, no matter how much i turn the r42 pot. i assume i must be doing something wrong.

perhaps a standard multimeter is not the right tool for this sort of calibration. what have the rest of you used?

many thanks for any help.

[blue hell]

I'm assuming page 8 in the file em_klee-PCP_Schematics as found on the page https://electro-music.com/forum/topic-24821.html

I did not look it up .. i'm guessing that the supply voltage is a a symetrical +12, 0, -12 Volt supply.

When this is correct .. we can go on with:

1 - There I do find pin 1 of on U8 (TL074 also it is TP501 there,a test point). Pin 1 is an output - this means that a standard voltmeter should be fine [and also that there --may-- be a build issue - but it may also be something else].

2 - I find J10 there as well which you used for ground, but I did not see which pin of that connector you are using.

When you are using pin 1 the expected readout value should be 12 volt ... you should be using ground which is on pin 2 or 3 of J10 - the build docs should say which one, but if it does not - i'd pick Agnd on pin 2 (because U8 is an analog component).

3 - When you are using J11's pin 2 or 3 ... then probably something is not connected well, or something is broken. You can start by having a good look at all connections of R42, J8 and R17

4 - you can measure on pin 2 of U8 and twist R42 a bit - the voltage should vary

Ok, best to first check all this I guess - and good luck - the Klee is fun

[jaskah]

thanks for your reply.

[blue hell]

Do you have a link to the manual then .. as this is very odd

[blue hell]

Ok, i'm reading page 110 in the issue 5 build doc .. it says :

-- Clip the negative (ground) lead of the DVM to analog ground. A good place to
connect it would be somewhere on the analog ground system of the panel – say the ground lug of one of the programming pots.

[an image here]

-- Register A Voltage Offset Zero Trim
• Touch the tip of the positive DVM lead to pin 1 of U8.
• While observing the DVM, adjust R42 for 0V on the DVM. Get as close to
absolutely zero volts as possible.

[jaskah]

exactly

[blue hell]

I tried to explain where the negative terminal of the meter should go, to pin 2 of J11 - or to analog ground - you did not say where that one went and if that one was to pin 1 of J11 your measurements could make sense.

To make that clear I numbered the sections I wrote, such that what is in one section belongs together. So, where section 2 is about J11 I did not mean pin2 of U8.

anyway and never mind i'm unsuitable to help you I guess - sorry.

[jaskah]

thanks again for your reply.

i've attached a photo of the klee analog board to show which pin i'm attaching the ground terminal of my multimeter to at j10 (i've circled this in red). if this is incorrect then which would be the correct pin?

sorry for the confusion and thanks again for your help.

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[blue hell]

I'm sorry .. where i said J11 in one of my last posts that was meant to say J10 ... and then I felt a sudden urge to make a copious amount of chocolate mouse


Anyway, you are using a wrong ground reference, you are using pin4 on J10, or the -12V as a reference where you should use ground as a reference. This was what I was affraid of, and what I was trying to explain.

Ok, again :

The ground to use is on pin 2 of J10. So move that current connection for the black meter terminal two positions up (in that image you posted).

It is (as one of the two connections there labeled as gnd) AGnd, and it is pin 2 on J10. AGnd stands for analog ground.

Then try your calibration again - and when you still can not set the voltage to zero on pin 1 of U8, there is something else wrong too.

In fact, where you were measuring 12V that was with respect to the negative supply voltage, and so in fact, in respect to ground, it was 0 Volts. It is customary to measure voltages with respect to ground, and ground is not the most negative supply voltage in a dual (or multiple) supplied contraption - but it is the reference - and in cas of the analog ground the reference for analog signals.

The other ground is the reference for digital signals. Nominaly they are the same, but the digital one is dirtier usually and could add unwanted signals to the analog bits of the circuit.

[jaskah]

thanks much again for your help.

i have now managed to calibrate everything correctly and the klee seems to be working as it should.

the only issue now is the range led has stopped working. the actual range functions as stated in the bring-up procedure are operating correctly, so i'm not sure what went wrong here. at some point i'll just go ahead and replace the led.

[blue hell]

Good - what is the range LED btw?

[jaskah]

thanks for your reply.

[blue hell]

[jaskah]

i'm attaching a photo of the front panel with the led i'm referring to circled in red.
thanks

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[blue hell]

So .. it has no refdes (like D25 or whatever it is ...) and it is not in the schematics?

Where it is on the panel - without any text - tels me nothing, It does not exist

[jaskah]

yes, i see what you mean. even in the bom for the front panel, there is no reference designator for these led's.

for what it's worth, i'm attaching another photo with the position of this particular led on the pcb.

thanks

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[blue hell]

Ah, so it is not the electro-music klee but an undocumented unofficial modification by synthcube .. there is some bla bla in their build manual but it does not say what it is and how it works ... or even why it is there

They bloody should provide schematics.. but i can not find it.

Anyway, 1k seems a bit low .. is all i can say . amounting to over 10mA worst case .. depending on how it actually is connected ..

Old fashioned leds could handle that, not sure about the modern high efficiency thingies .. the led's data sheet will have to tell .. but eh .. probably undocumented what it is eh .. so impossible to look it up then

[jaskah]

in case you're interested, here's the mouser link to the led's being used:

https://mou.sr/3EcSY7U

and are the attached schematics the ones you were looking at?

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[blue hell]

Ah, ok 25mA max for the LED - when there really is 1kOhm in series (which i read somewhere) it should not break.

And the attached docs look pretty much like the original ones from here - so yes, I saw them - and no, I could not find a range LED on it.