power is not stable. (solved,replaced 78L05 with KIA78S06P)

[isak]

Hi guys

i have a friend x0x here and it seems like when i turn it on the power is not stable, in the my RME mixer i can see the level meter is jumping even where is no sound.
video clip : (there is no sound from the x0x in the video clip)
http://www.youtube.com/watch?v=ZoNujqJFqqo

when i play a regular C2 note its warbling but only when the power is not stable!
sound clip :
http://www.sendspace.com/file/jw03vm

the problem is randomly coming and going, its not permanent.

ic23 is : C358C
ic21 is : 78L05
other then that all seems to be ok.

what do u think guys?

ohhh...and when the power is ok and stable i cant tune it , when we fix the power issues we go to the tuning stuff, i think its more then just tuning.

[guest]

is this x0x completely built

what value resistors are on the leds
how many milliamps is the powersupply

what sort of package is the 78L05 in
is it a big TO-220 package
or the small TO-92

usually the 78L05 is the smaller 5v regulator
only rated for 100mA
so it could be cutting out

does it happen in all modes
is it periodic at all
does it happen more at startup
if you shake the box does it happen more

there might be a bad connection on a cable someplace
that is shorting to ground or periodically coming unconnected
causing jumps in the audio output

does the audio out have the same jumpy output with no sound
on both the mixout and the headphone out

[isak]

Hi Guest, going out for a tour with me again ?

is this x0x completely built

yes.

what value resistors are on the leds

please guest give me resistors numbers, i dont know what leds are sorry.

how many milliamps is the powersupply

9VAC , 400mA.

what sort of package is the 78L05 in
is it a big TO-220 package
or the small TO-92

it looks like a small transistor.

usually the 78L05 is the smaller 5v regulator
only rated for 100mA
so it could be cutting out

yes it is.

does it happen in all modes

yes.

is it periodic at all

well, i'm not sure...it comes and goes, sometimes when i turn the x0x its ok, no problem, sometimes turn it on and its there.

does it happen more at startup

sometimes.

if you shake the box does it happen more

didnt shake it so i cant tell.

does the audio out have the same jumpy output with no sound

yes, the video u see is with no sound from the x0x, i think its something that have to do with the power, coz it controls also on the notes.

on both the mixout and the headphone out

i'll have to wait until it come back and then i'll check from the headphones output.

[guest]

the leds are the blinking lights in the digital section
and they have resistors to limit the current through them
they are probably all the same value
so r244 or r262 or r203 or r208 should do

you will want to replace the 78L05 with a 78M05
even if the circuit draws less than 100mA
which it probably does
the 78M05 can handle the heat better
is the 78L05 getting hot at all

[isak]

so i did understand u! sorry, i was thinking to my self why the hell he is talking about the leds..?
u think there is connection between the non stable power to the leds?
r244=9.97k
r262=10.04k
r203=10k
r208=9.82k

is the 78L05 getting hot at all

yes it is getting hot, i have a replacement here.. its KIA78S06P, 6V, 150mA regulator.
replace 78L05 with KIA78S06P?

[guest]

no that will hurt the microcontroller
you will need a 78M05 or 7805
be sure its in the larger TO-220 package
they are very common
if there is a local electronics store
they should have one in stock

the led resistors are good

[isak]

u mean the one that looks like iC20? this large?
it wont fit, its to big.

[guest]

im sorry
i was assuming ic20 becuase you said 78L05

the 78L06 is fine for ic21
that is what it should be

what is the voltage across c3 and c5

[guest]

and by 78l06
i mean the KIA78S06P is good

[isak]

ok, instead of ic21that should be 78L06..its 78L05 small size (transistor shape).
do i need to change it to KIA78S06P?

c3=15.9v
c5=17.14v

[guest]

yes
you should change it

those voltages are really high on the capacitors as well
do you have another powersupply you could try

what is the voltage on c8
it shouldnt be above 25v

[isak]

do you have another powersupply you could try

yes i have, 9VAC , 600mA.

C8 is 30V

with the 9VAC ,600mA.. C8 is 29.2V.

[guest]

you can try the other powersupply
but measure the voltage on c8 after you plug it in
and use whichever one is lower
ic23 can handle 36v
but it will probably start getting a bit warm

c8 might be having trouble with the high voltage
so either get a higher rated capacitor
or a powersupply that is lower in power
the latter is the better solution

[isak]

but measure the voltage on c8 after you plug it in

29.2V

ic23 can handle 36v

IC23 here is C358C dont forget!!!

c8 might be having trouble with the high voltage
so either get a higher rated capacitor

u mean stay with 100uF but with a high V like 50V or 100V?

or a powersupply that is lower in power
the latter is the better solution

8VAC? 7VAC?

p.s .. ic21 78L06 is changed to KIA78S06P.

[guest]

the c358c can only handle 30v
so it might have been damaged
but is probably still ok

see if you can find a 9vac 200ma supply
it will be difficult to find an 8vac supply
the 400ma supply should be good
but there is so much variation between supplies
that it is hard to know without plugging it in