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Post by guest » Wed Aug 02, 2017 6:14 pm

is it a crowdsupply x0x-heart? or did you make your own board?

it sounds like U1 is busted, or not soldered correctly. this could be due to a bad part, or it could be due to a short in the powersupply section. turn off the power, and measure the resistance to ground on either side of D1. if there is a short on the cathode side of D1, then it might not be U1.
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Post by nicdro » Thu Aug 03, 2017 9:45 am

guest wrote:is it a crowdsupply x0x-heart? or did you make your own board?

it sounds like U1 is busted, or not soldered correctly. this could be due to a bad part, or it could be due to a short in the powersupply section. turn off the power, and measure the resistance to ground on either side of D1. if there is a short on the cathode side of D1, then it might not be U1.
The board is from a pusherman run.
I have no continuity on any side of D1 to GND.
Whats odd is i have continuity from R90 (pin 7) to GND.

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Post by guest » Thu Aug 03, 2017 10:38 am

i dont know anything about those boards. do you have a picture? maybe i can spot something amiss.

the input voltage to U1 should be 5V, and the output 15V (measure on C2). if it is not, then either the output is getting shorted, or there is a problem with U1 or its associated circuitry. you can either lift R1 or U2, and this will disengage the remaining circuit. if you still dont get 15V on C2, then you probably need to replace U1. if you want to make sure, you can measure the voltages on U1: Vin, EN = 5V, GND = 0V, LX = square wave @ 15V, FB = 1.2V. its possible the diode or inductor, or maybe a trace is bad, but U1 is more likely than any of those.
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Post by nicdro » Thu Aug 03, 2017 10:54 am

guest wrote:i dont know anything about those boards. do you have a picture? maybe i can spot something amiss.

the input voltage to U1 should be 5V, and the output 15V (measure on C2). if it is not, then either the output is getting shorted, or there is a problem with U1 or its associated circuitry. you can either lift R1 or U2, and this will disengage the remaining circuit. if you still dont get 15V on C2, then you probably need to replace U1. if you want to make sure, you can measure the voltages on U1: Vin, EN = 5V, GND = 0V, LX = square wave @ 15V, FB = 1.2V. its possible the diode or inductor, or maybe a trace is bad, but U1 is more likely than any of those.
thanks for the reply!
I separated the power section from the rest of the board to exclude any issues on other parts and sections of the pcb.
i get following voltages of u1 (ncp1406snt1g) i replaced minutes ago:
CE: +4,93V
FB: +0,044V
VDD: +4,93V
LX: +4,90V
The conductor has a resistance of 11ohm (which is ok as the specs say max 55ohm).
Here are some pics of this mess (i damaged a pin (but the voltages were given the same before and after that) - so there is a resistor leg replacing a trace ;))
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Image

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Post by guest » Thu Aug 03, 2017 11:04 am

did you solder up the board yourself?

double check the values of R2,R3, and R4. then check continuity to the pins of U1 and their associated components. for example, FB to R4, GND to GND, etc. this will check the solder joints of U1. then verify that none of the pins are shorting to each other (except EN to VDD and LX through L1) do a diode check on D1.

i noticed your pcb drawing above has +12V written on the U1 input. only 5V should be applied.
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Post by nicdro » Thu Aug 03, 2017 11:10 am

guest wrote:did you solder up the board yourself?

double check the values of R2,R3, and R4. then check continuity to the pins of U1 and their associated components. for example, FB to R4, GND to GND, etc. this will check the solder joints of U1. then verify that none of the pins are shorting to each other (except EN to VDD and LX through L1) do a diode check on D1.

i noticed your pcb drawing above has +12V written on the U1 input. only 5V should be applied.
Yes I did it by myself.
I get continuity between L1 and EN/VDD as the Inductor has no resistance - that is what makes me curious...
R2, R3, and R4 are correct values. The Diode says (B3N on it and the DMM says 0,00024V - i dont know if it is the right one?! May i replace it with MMBD4148 ones?).

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Post by guest » Thu Aug 03, 2017 11:32 am

you can try swapping it with an 1N4148, it wont hurt anything, although it might not last under heavy load.

the thing that makes me suspicious of R2,3,4 is that they should be acting as a ~1:10 voltage divider, so 5V in should make ~500mV out, but its 44mV. a leakage into U1 would also account for this, but that would imply that U1 is busted.
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Post by nicdro » Thu Aug 03, 2017 11:36 am

guest wrote:you can try swapping it with an 1N4148, it wont hurt anything, although it might not last under heavy load.

the thing that makes me suspicious of R2,3,4 is that they should be acting as a ~1:10 voltage divider, so 5V in should make ~500mV out, but its 44mV. a leakage into U1 would also account for this, but that would imply that U1 is busted.
now i have 0,39V on FB perhaps i mismetered the first time.
I desoldered and resoldered the diode. It is my third U1 so i think this one might be fine.
Is it correct to have continuity on both the inductor pins?

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Post by nicdro » Thu Aug 03, 2017 11:45 am

AND to be sure:
R4 10k
R3 47k
R2 100k
C6 1nF

Datasheet of u1 says 1,3M, 110k and 68pF.

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Post by guest » Thu Aug 03, 2017 11:50 am

yes, those are correct values, and .39V makes sense.
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Post by guest » Thu Aug 03, 2017 11:51 am

also, continuity to where from both sides of inductor? i would also remove R1 until U1 is shown to be working.
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Post by guest » Thu Aug 03, 2017 11:54 am

it looks like there could be short to ground in the pcb on C4. its hard to tell from the picture. if U1 is good, then the only reason it would not be producing 15V is that its drawing too much current someplace (or bad component, but it sounds like youve checked all of them).
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Post by nicdro » Thu Aug 03, 2017 12:00 pm

C4 has no continuity to gnd.
I removed R1 and no change at all :(

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Post by guest » Thu Aug 03, 2017 12:04 pm

disconnect whatever youre using to supply 5V to the circuit, and verify that its 5V. then measure the current flowing into the x0x-heart from the 5V. with R1 disconnected it shouldnt be more than a few milliamps or so.
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Post by nicdro » Thu Aug 03, 2017 12:18 pm

The voltage comes from modular tester and is def. 5V (4.89 to be accurate).
I get 250mA and it drops. I dont know if I measure correctly (never done before).

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Post by guest » Thu Aug 03, 2017 12:24 pm

some meters require moving the probe to a different hole in the meter. it might start really high for a brief second, but should drop down to a few milliamps really quick. another way to test, is to put a 100ohm resistor in series with the x0x-heart, and measure the voltage drop across that resistor. it should be a few hundred millivots tops.
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Post by nicdro » Thu Aug 03, 2017 12:36 pm

guest wrote:some meters require moving the probe to a different hole in the meter. it might start really high for a brief second, but should drop down to a few milliamps really quick. another way to test, is to put a 100ohm resistor in series with the x0x-heart, and measure the voltage drop across that resistor. it should be a few hundred millivots tops.
ok this why i did. and i put one probe to gnd the other to one pin of R1. I t droppped to a much lower value though but not really quick.
I will leave it for today and continue tomorrow with a fresh brain!
thanks for helping me out!

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Post by guest » Thu Aug 03, 2017 12:43 pm

measure the current at the input to the x0xheart; so from your 5V module tester output to the input of U1. when your meter is in current mode, you have to put the meter in series. connect the ground of the x0xheart to the ground of the 5V supply. but, do not connect the +5V line as you would normally. instead, place the red probe on 5V, and the black probe at the input of U1. in this way, the meter makes the electrical connection, and the current flows through the meter, and the meter can then display the value. be sure to remove R1 for this test (or at least make a measurement with it out, you can also measure with it in).
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Post by gruebleengourd » Thu Aug 03, 2017 2:37 pm

Just want to say that I spent a lot of time the last couple weeks with my xox-heart/pacemaker, a colin fraser souped up tb303, a cyclone tt303, and a syntecno teebee.

All are great and special, but my xox-heart, once adjusted to it's sweet spot had something really great going on with the sound. It may have something to do with the output amp, as I've swapped in an opa2228, and it took careful adjustments of the output levels to get it just right.
but Wow.

big up to guest!!!! :sb:

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Post by guest » Thu Aug 03, 2017 9:49 pm

thanks, thats great to hear. the output amp allows for a distortion which is different, and more pronounced than the original, but can also do very clean. and the filter uses matched transistors throughout, which i think also makes a difference.
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Post by nicdro » Fri Aug 04, 2017 12:50 am


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Post by nicdro » Fri Aug 04, 2017 12:57 am

So i had 500mA and then a little smoke.
I measured at the CE/PIN1 of U1.
I'll replace it.

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Post by guest » Fri Aug 04, 2017 4:02 am

those are not exactly the same, but you could make the TA part work if you had to. they have similar specifications, but different footprints. it should fit on the old footprint, though.

so why do you think it started to smoke this time? it wasnt smoking before when connected to the powersupply. and what part smoked? 500mA at 5V requires a 10ohm load, which makes me think there is a short some place around U1. did you accidently touch the FB pin with 5V? did you remove R1?
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Post by nicdro » Fri Aug 04, 2017 4:21 am

guest wrote:those are not exactly the same, but you could make the TA part work if you had to. they have similar specifications, but different footprints. it should fit on the old footprint, though.

so why do you think it started to smoke this time? it wasnt smoking before when connected to the powersupply. and what part smoked? 500mA at 5V requires a 10ohm load, which makes me think there is a short some place around U1. did you accidently touch the FB pin with 5V? did you remove R1?
i dont know what exactly smoked.
R1 wasnt placed. I replaced U1 and no changes at all. I ordered new inductors and NCPs perhaps the batch i got is not good. I triple checked everything for bridges. Is it normal that i have continuity on these two pins when the inductor is in place?
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Post by guest » Fri Aug 04, 2017 4:30 am

yes, those pins will short through the inductor. but, you might want to remove the inductor and make sure there is no short with it out.
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