carlibration problem / note out of tune

[975262801]

Hi,
I have build a few x0xb0x for my friends. I found a common problem on all x0xb0x. The notes goes out of tune on the second day after I done the carlibration. Why? All note is in tune after carlibration. I have not touch anything. Next day when I switch it on again, the note is always goes out of tune. All note shift about one note up or down. Anyone know what cause this problem?

Regards,
phil

[isak]

maybe its cold

just kidding, really dont know man, good luck finding the problem and please let us know what was the problem

cheers,
Isak E.

[guest]

if you retune it
does it stay in tune after that

does your kit have the r100 thermistors in it

can you bring it back into tune
with the tune knob on the front

[975262801]

if you retune it
does it stay in tune after that

does your kit have the r100 thermistors in it

can you bring it back into tune
with the tune knob on the front

Some does and some doesn't.
The one which can be retune, I can easily tune the TM4 back to the right tune(or tune knob at the front). It is weird. I have not touch the x0xb0x at all after the carlibration. Next day woke up in the morning and use a tuner to test the C1 C2 C3 C4, they either goes one note higher or lower. It becomes D1 D2 D3 D4. I know the themistor is sensative to temperature, but it affect the note that much?
However, this is not the worse case. I have some x0xb0x goes out of tune and I am not able to put it back to the right tune. It is very strange. It was 100% working and carlibrate without any problem after I finish all the soldering. All note stay at the right tune. Next day I recheck them, all notes are out of tune. Even I turn TM5 to the max. I am not able to get a exact one octave. Something like C1 to B1 is all I can get for each octave. I never get the octave from C1 to C2 then C3 and C4 in one octave range. It's like the octave range got narrow or somethng. This is so weird. I have a few x0xb0x have the same problem like this. I am sure I use correct resistors/caps/diode/transistor. Soldering on each joint is fine too. There is not many parts in the VCO section. Have u got any idea what cause this strange problem. All these x0xb0x has one common problem, they are all in the right tune when I first finish the soldering and the problem always comes up on the second day when I try to recheck the tune.

[975262801]

If this tune problem happen at the very beinging. It could be soldering wrong resistor or caps, but this is not the case. All x0xb0x are carlibrate correct at the right tune. Then I tune it off and havn't touch it until next moring just to re-assure the tuning is correct, and then the note is either goes one note off or gone crazy with a totally wrong narrow octave range.

[isak]

Did you self source the kits or bought them from a dealer?
If from a dealer...who?

[guest]

if you have an accurate voltmeter
tune the x0x up
and measure the cv out for a few notes
c1 c2 c3 etc

then when it goes out of tuen again
measure the cv out for those notes again

there are three possible problems
1. your components are not very stable or the tempco resistor is busted
2. your cv is drifting most likely from 5.333v drifting
3. something is overheating inside

[antto]

i'm not an expert at all
but my nose tells me something on the board is still hot when you first callibrate.. and cools down the next day

i had such experience when i desoldered C29 and soldered it backwards.. the first audio sample i recorded after soldering had nothing in common with another recording i did a bunch of hours later (without touching any knobs in the mean time..)

[975262801]

I self source most of the part myself. I am sure all resistor / IC / capicitor / diode is fine. The only parts I am not sure if it cause the problem is the 1k thermistor and the 2sc1583. The 2sc1583 is some used old parts.
The thermistor is very sensative to temperature. It is acceptable if it goes one note out of tune next day, because I can retune with the tuning knob on the front panel. However, some x0xb0x is seriously off tune with a narrow range. It can not re-tune to one octave even I turn the TM5 to the max. Guess what, I switch on the x0xb0x today and it works fine now. It is so strange. I have two x0xb0x have the same problem. Sometimes goes out of tune with narrow range and sometimes it goes back to normal tune. I agree with you that may be one of the part is unstable in the VCO section. May be sesative to heat or something. Any suggestion which component will cause this problem? There is not many parts on the VCO section. I don't think this problem is caused by resistor / caps / IC.

[guest]

where did you get the thermistors from
and what is the part number

check the cv out just to make sure

[975262801]

I bought it from Willzyx Music .
KOA themistors.
PN: LT1/4LT52R102J3100

I have tried the x0xb0x with this drifting problem this morning. The tune has the same problem again. It was working yesterday.
C1 C2 C3 C4 C5 becomes A1 G F# F F today. This is so strange.

[975262801]

After I switch on the machine for more than 30 mins, I try to test the tune again. This time, it is kind of back to normal. It is one note off tune. I need to turn the tuning knob at the front panel quite a fair bit to adjust it back to the middle C , but the carlibration is not perfect. What I get on the tuner on each octave is C# C (+20) C (-20) B (+50) C (-50) . This is totally not usable for making music.

[guest]

measure the cv out
just to make sure its the vco
and if the cv doesnt drift
replace the thermistor
its broken

[975262801]

1k themistor connects to Q26, the working one is 5.32V and other end is 5.33V. Non working one is 5.25V and 5.32V.

[975262801]

For working unit, the dc reading of pin 7 of IC 11 is :
C d e F g a b c
2.01 2.17 2.33 2.43 2.59 2.75 2.91 3

For the non -working unit, just when I try to test it, it goes back to normal again, so I am not able to check the voltage when it is at the "out of tune status". However, I have check the voltage when it is with the correct tune.
2 2.16 2.33 2.41 2.57 2.77 2.94 3.02

Not much difference with the working unit when it is working. I have no idea why it goes out of tune sometimes.......