solved: Creative Lab T3000 2.1 sound

[ttx450]

Hi everyone.. first post here.  I am newer to elc, have some past experiences, been getting involved as a hobby, to learn how to repair more and just learn.  Been mostly playing with older electronics.

The unit in question is close to 30yrs old.  It was taken out by some stray lightening voltage surge.  I played with it about a year ago a bit, but have not had much luck yet.  Its really to learn, but it does have better sound then the unit I currently use for my computer.  So if I get it working ++

Unit is dead, acts like its in stand by.  I dont know much about IC's, I posted up some values I got off the ICs.  Maybe someone has some experiences with this.

All measurements where from a analog scope so not real accurate, but should be close enough.

Appreciate any guidance.  thks


4556AD JRC dual OP AMP

1-6v
2-6v
3-6v
4-0v
5-6v
6-6v
7-6v
8-12v

MC4558CN cannot read manf, think it ST dual op amp

1-6v
2-6v
3-6v
4-0
5-6v
6-6v
7-6v
8-12v

# 1   M51132L mits dual vol balance

1-12v
2-4v
3-12v
4-0
5-0
6-0
7-4v

# 2   M51132L mits dual vol balance

1-12v
2-4v
3-12v
4-0
5-0
6-0
7-4v

TDA7379 stmicro audio pwr amp

1-0
2-0
3-18v
4-0
5-0
6-0
7-0
8-0
9-0
10-0
11-0
12-0
13-18v
14-0
15-0

[Audiorepair]

TDA7379  pin 7 should be high, your readings show this amp is in Standby.

The datasheet (page 4)  shows a capacitor on pin 7, it might be that this is faulty, pulling the pin down.

https://datasheet.octopart.com/E-TDA7379-STMicroelectronics-datasheet-14137126.pdf

[ttx450]

TDA7379  pin 7 should be high, your readings show this amp is in Standby.

The datasheet (page 4)  shows a capacitor on pin 7, it might be that this is faulty, pulling the pin down.

https://datasheet.octopart.com/E-TDA7379-STMicroelectronics-datasheet-14137126.pdf

Hi,

I replaced the TDA7379 last year with a new one, and no luck.  I still have the old one.

I am hesitant to do much without understanding.  Does it take 1.5v to take out of standby & 3.5v is over limit?  What sends a signal to pin 7?  thks

[Audiorepair]

I think that says that 1.5v takes it out of standby, but should that voltage subsequently fall to below 3.5v, it will go back into standby.

If your standby pin is constantly on zero volts, well that then is your problem.

The capacitor on pin 7 is the most likely suspect.

[CharlotteSwiss]

that capacitor that you see on the right of the TDA has a black head; is it just a marker mark or some problem?

[ttx450]

that capacitor that you see on the right of the TDA has a black head; is it just a marker mark or some problem?

hi, no I marked those last year when I pulled them and was testing.  so many elctro cap in a audio board. 

I pulled the two by the signal input,and tested the esr getting 11ohm- 1uf. Esr charts are all over the place.   its high, both read the same.. to fail on awake from stand-by seems they have to be open or shorted, but dont know.

I pulled many components and tested last year.. kind of lost track.  I might pull all the elc caps one by one and make a map.  hate to waste that much time if it is something simple that I might be over looking.

[Audiorepair]

If you wanted a quick and dirty solution and this to be all over, and don't mind some possible thumps on power up and down,  :

Cut the standby pin 7.
Solder a wire from pin 7 now in the air to either pin 3 (VCC) or ground.

I'm actually a little confused now from the datasheet whether standby on/off is VCC/ground, but one of them is sure to work.


Edit:
And, you could bodge in a resistor and capacitor as per the datasheet test circuit to give a standby delay time.
This would stop the power on thump, but not the power off one, if there was one.

[CharlotteSwiss]

i repaired a couple of times a similar fixture, audio power amplifer was STA540 (quite similar to your board), that also had st-by pin 7; if you have st-by 0V (assuming you pressed ON), the amplifier will not be able to turn on (the one repaired by me turned on above 2.4v, and worked at about 8v)
Check the track that arrives at pin 7, somewhere you have the problem.
But the DC power supply to the card is correct?

[ttx450]

i repaired a couple of times a similar fixture, audio power amplifer was STA540 (quite similar to your board), that also had st-by pin 7; if you have st-by 0V (assuming you pressed ON), the amplifier will not be able to turn on (the one repaired by me turned on above 2.4v, and worked at about 8v)
Check the track that arrives at pin 7, somewhere you have the problem.
But the DC power supply to the card is correct?

hi. thks for advice.. for pwr I get 18v in and about the same little less out on board. 

it is very hard to trace tracks, what makes this worse all the jumpers all over the place (close to 30).  will try to back track. looked long and hard for a schematic

edit-should say, one of my post say 18v on 2 legs on TDA

[CharlotteSwiss]

I see those fine cables: does it by chance have a remote control with power button? checked the continuity of all those cables? the one repaired by me had a problem on a broken cable ..
Here in the Alps it's bedtime, night ;-)

[ttx450]

I see those fine cables: does it by chance have a remote control with power button? checked the continuity of all those cables? the one repaired by me had a problem on a broken cable ..
Here in the Alps it's bedtime, night ;-)

thks.. abt the same time here. 

yes, it does have a remote pwr on vol control switch, with LED indicator.  I suspected that being a problem, being in the past dog chewed on wires.. lol.. I checked the wires many times.  Will recheck.  thks 

when the house was hit by lightening (side lateral hit), everything worked fine until then. many elc items were taken out, including the pc that this was plugged into. 

[CharlotteSwiss]

I don't see the on / off button on the remote; can the ignition be done remotely?
In the one repaired by me it was the st-by cable that went from the remote to the board to be interrupted; to solve I used the one of the led to do first

my wolf dog doesn't just gnaw the cables, he opens the devices in two 

[ttx450]

I don't see the on / off button on the remote; can the ignition be done remotely?
In the one repaired by me it was the st-by cable that went from the remote to the board to be interrupted; to solve I used the one of the led to do first

my wolf dog doesn't just gnaw the cables, he opens the devices in two 

hi, the on & off on vol pot, I guess you call that a gained switch..  the other pot is bass subwoofer control. 

[ttx450]

when checking cable for remote control thing..  I was checking the cable for resistance and continuity.   started getting some weird readings and possible shorts that did not make a lot of sense.  I further inspected the cabling and found more teeth puncher marks and cut open the cable.  well I noticed wires punctured along with grd shielding pushed into the wire a path to grd. 

I need to look very close at the cabling and cut open and repair were needed.  some resistances values were not making sense, to high and some wires seem shorted.  hope I did not spend all this time over complicating things..  we'll see far from finish.. 

[ttx450]

I don't see the on / off button on the remote; can the ignition be done remotely?
In the one repaired by me it was the st-by cable that went from the remote to the board to be interrupted; to solve I used the one of the led to do first

my wolf dog doesn't just gnaw the cables, he opens the devices in two 

hi, the on & off on vol pot, I guess you call that a gained switch..  the other pot is bass subwoofer control.

OMG, isolated that in-prego wire that had the GRD punched into it.. it WORKS..  re-checked shorts, resistances in all cable wiring and all good.   the led lights up!  thanks char..  I spent many hours on this.  now need to repackage.  the cable had a dentition in it, not obvious cut..  when I cut it open, the shielding was pushed into one of the wires...    thks

[CharlotteSwiss]

I think that cable is in bad shape; but it would be enough for you to start checking the st-by signal that is activated when you switch from off to on; in case you could make the connection with a piece of flying wire to see if the amplifier starts up then.
after all, if you have no voltage on pin 7, you must first investigate the st-by path

[ttx450]

my wolf dog doesn't just gnaw the cables, he opens the devices in two 

I had one female rott,I would not trust her with the oven (not stove top) running by herself..  she was smart enough to open the door..

[CharlotteSwiss]

I wrote the above message together with your last one, better if you have solved it; after all those thin cables were the first thing to check, as you didn't even have st-by
I would evaluate the entire replacement of the cable

 

[ttx450]

I think that cable is in bad shape; but it would be enough for you to start checking the st-by signal that is activated when you switch from off to on; in case you could make the connection with a piece of flying wire to see if the amplifier starts up then.
after all, if you have no voltage on pin 7, you must first investigate the st-by path

works as of now.. plugged into my computer and all 3 channels work with vol and base control.. thks

[CharlotteSwiss]

my wolf dog doesn't just gnaw the cables, he opens the devices in two 

I had one female rott,I would not trust her with the oven (not stove top) running by herself..  she was smart enough to open the door..

dog stuff; they always invent one to arrive in the evening
 

[CharlotteSwiss]

works as of now.. plugged into my computer and all 3 channels work with vol and base control.. thks

very well, until the dog plays with the lead again 

[ttx450]

works as of now.. plugged into my computer and all 3 channels work with vol and base control.. thks

very well, until the dog plays with the lead again 

tooks this apart 1.5-2 yrs ago, hope to get it back together.. 

[CharlotteSwiss]

you have to stand guard; when the dog bites the cable, zacc on the ears   
good night 

[ttx450]

was not easy to take apart.. see in photo.    this unit sounds very good.. will be replacing my workbench sound system was my gaming machine audio

[ttx450]

package