hello everyone, i have this speaker system(made in iran) right here with the main board and power supply on the right speaker

here are some pictures to give some info on the supply and main board and how it's back panel looks like



more information: the board has 2x 2SC5200 and 2x 2SA1943 with a L7605cv hooked to the heatsink

i have sent the speaker in for the repair 2 times only to end up with the same problem coming back up AGAIN

i dont really want to spend unnecessary money on some weak repair work out there and i'm trying out to isolate and fix the problem

the main board gets powered up completely fine without the speakers connected to the board, but as soon as the speakers get connected,they go and blast full noise on the 3 subwoofers (checked the mainboard while its happening, one of the 4 big transistors gets very hot rapidly)
i tried to wire in the woofers one by one to the system and it happens again (with wires sparking when getting connected)

can anyone give any suggestions or have any ideas to help out on this case?

 

Welcome to AAC.

Nice Speakers.
First lets do some physical test. But the PCB back into the sink properly as it were.
Use your ears for this.
Disconnect speakers. Power up the board and check if you can hear a click after a second or two.
Give around 5 seconds then power down.
Post back your hearing result.

I see that it has a digital control panel.
Need to see that PCB too.

I am skipping the full blast part for now.
but you can disconnect speakers and test the control functions without sound. Need to know that too.

By the way...What do you mean by full blast ?
Just noise or music ?

 

Use your ears for this.
Disconnect speakers. Power up the board and check if you can hear a click after a second or two.
Give around 5 seconds then power down.
Post back your hearing result.

I see that it has a digital control panel.
Need to see that PCB too.

I am skipping the full blast part for now.
but you can disconnect speakers and test the control functions without sound. Need to know that too.

By the way...What do you mean by full blast ?
Just noise or music ?

yes! i forgot to mention that i did disconnect the speakers and power up the board to hear the click sound after a bit
the click sound is pretty loud enough to be heard easily
it has a touchscreen panel on the front, it's pcb is quite hard to reach and unscrew

i'll attach a voice file of the speaker powering up with and without speakers to explain what i meant by full blast noise

 

Around time 0.05 is the relay turning on. So it means there is no DC at the output so far.
@ 0.11 that sound, Is it the sound you are referring to ?
@ 0.15 it click and comes back again. Care to explain how it happens ? Are you turning any thing on or off ?

 

It sounds like you have a shorted transistor, or maybe just turned on hard.
Leave your speakers disconnected.
When powered up, without speakers, does a transistor get hot?
Do you have both +40VDC and -40VDC supplies working?
Measure the DC voltage of each amp output to see if there is any voltage there. It should be almost 0V.
If you are getting a DC voltage there of more than say, 200mV, that is the problem that needs to be fixed before you connect the speakers again.

 

Around time 0.05 is the relay turning on. So it means there is no DC at the output so far.
@ 0.11 that sound, Is it the sound you are referring to ?
@ 0.15 it click and comes back again. Care to explain how it happens ? Are you turning any thing on or off ?

yeah that was the sound i meant, comes back on again cause i connected the speaker wires back to the board

i got it finally figured out which i'll tell in my next reply

 

It sounds like you have a shorted transistor, or maybe just turned on hard.
Leave your speakers disconnected.
When powered up, without speakers, does a transistor get hot?
Do you have both +40VDC and -40VDC supplies working?
Measure the DC voltage of each amp output to see if there is any voltage there. It should be almost 0V.
If you are getting a DC voltage there of more than say, 200mV, that is the problem that needs to be fixed before you connect the speakers again.

you are right
it was one of the 2SA1943's having a short (also getting hot) because the solder joints were melted together
i guess the repair technicians did a poor job using a cheap silicon paste for attaching them to the heatsink
otherwise,there shouldn't be any other reasons for solder joints to get that hot cause the heatsink is pretty big for 4 transistors

 

2SC5200/2SA1943 have been plagued by fakes. My guess is that the repair was done with a fake transistor.

 

One issue....!
A shorted transistor will have DC at output. The relay should not click ?

 

One issue....!
A shorted transistor will have DC at output. The relay should not click ?

i had the audio paused for the 2 parts with/without the speakers buzzing like crazy
that's why you heard the relay click

 

2SC5200/2SA1943 have been plagued by fakes. My guess is that the repair was done with a fake transistor.

is there any way to distinguish between the real ones and fakes? the ones on board and the one i got at an electronics store look exactly the same
i had my speaker repaired at two different places and each time they came back up up with the melted solders after some time (i guess? because they didn't tell me what exactly was wrong with my system)
at this point i got fed up with giving it out for repair (since it is heavy too)and decided to do it myself since i tinker with stuff all the time

 

I had a colleague who claimed he could.
My advice would be that the ones that come from reputable dealers are much more likely to be genuine.

 

The relay will not click if there is DC at the output, period.
Unless you have a faulty protection. Even then it turns on after delay
Check for DC voltage on each output at power on. You need to check at the relay contact terminals

 

The relay will not click if there is DC at the output, period.

from the 0:00 to 0:08 the speakers were not connected to the main board. that's why the relay did click
from 0:08 to the rest of the audio i had the speakers wires touch the board *after* the relay had clicked in
so that's why the clicks were heard beforehand

 

If you read through the replies, you were advised not to connect the speakers.

Measure the voltage with respect to COMMON GND at the pins of all the four output transistors.

 

from the 0:00 to 0:08 the speakers were not connected to the main board. that's why the relay did click
from 0:08 to the rest of the audio i had the speakers wires touch the board *after* the relay had clicked in
so that's why the clicks were heard beforehand

Why touching the board, why not connect at it's output connector.
Output connector will be via protection relay.

Speakers are removed to avoid noise during troubleshooting.
Let us know the details how the speaker are connected to the PCB.

 

It was my mistake tht I did not asked you that have you checked the output transistors after desoldering it.
I just assumed tht you did cause you showed a picture of them removed from sink

 

If you read through the replies, you were advised not to connect the speakers.

Measure the voltage with respect to COMMON GND at the pins of all the four output transistors.

i know i know
i only did that to show what kind of sound it makes, nothing more

checked the voltage output on all of them
they all give out stable numbers
one thing to ask here, there's a 7805cv here too which gets hot very rapidly,is it supposed to be like that?

 

Why touching the board, why not connect at it's output connector.
Output connector will be via protection relay.

Speakers are removed to avoid noise during troubleshooting.
Let us know the details how the speaker are connected to the PCB.

i'm really bad at explaining things, sorry
what i meant by touching the board was getting power exactly by the cables that were connected to the board to power the speakers

i have tested the transistors for voltage and health they are all healthy and working
i even had speakers playing music last night after i had fixed the solder joint short

 

hello everyone, i have this speaker system(made in iran) right here with the main board and power supply on the right speakerView attachment 285622

here are some pictures to give some info on the supply and main board and how it's back panel looks like
View attachment 285623View attachment 285624View attachment 285625
View attachment 285626

more information: the board has 2x 2SC5200 and 2x 2SA1943 with a L7605cv hooked to the heatsink

i have sent the speaker in for the repair 2 times only to end up with the same problem coming back up AGAIN

i dont really want to spend unnecessary money on some weak repair work out there and i'm trying out to isolate and fix the problem

the main board gets powered up completely fine without the speakers connected to the board, but as soon as the speakers get connected,they go and blast full noise on the 3 subwoofers (checked the mainboard while its happening, one of the 4 big transistors gets very hot rapidly)
i tried to wire in the woofers one by one to the system and it happens again (with wires sparking when getting connected)

can anyone give any suggestions or have any ideas to help out on this case?

You have a problem with some components which is old like capacitorr( dried out) or resistor what got damage bye heat so ur resistance got low and ur whole system will fail. You really need a oscilloscope to fix this problem. I’m afraid otherwise you can’t solve ur problem. Good luck with it!