Siglent SDS1202x-E fried FAN driver transistor - SOLVED -

[tppc]

Hi everyone,
the fan on my SDS1202X-E oscilloscope started making erratic and really annoying noise.
So I decided to replace it with a quieter one from Noctua.

Before ordering the new one, I wanted to check the voltage on the fan connector (test probes under the PCB).
This is when I accidently shorted one pin to the chassis and fried the SMD transistor that drives (or used to drive  ) the fan.

The positive end of the fan is connected to GND.
The negative is driven by the Collector or Drain of the fried transistor.
The Emitter or Source of the transistor goes to -10V supply.

Can anyone help identifying this mystery transistor?
What was it before it became an ugly piece of coal?

BTW, for those interested in reducing the fan noise of their SDS1202X-E oscilloscope, NOCTUA NF-A6X25 fits well.

Best Regards.
 

[tppc]

Hi everyone,

long story short :
- Does anyone have even a partial schematic showing the fan drive section?
or
- Is anyone willing to open his SDS1202x-E and read the marking on Q34?

Best Regards

[CharlotteSwiss]

Noctua is a guarantee. I have the SM, but it only reports Q34, no information (only 12vdc to power the fan). The diagram I have is completely useless. If no one helps you, I will open my 1202. But in a few days, I'm away from home. HI

[tautech]

Q34 is marked A2RX however that is some distance from the fan connector. 

I have a dead warranty replacement SDS1202X-E PCB here if you need further help.

[tppc]

Noctua is a guarantee. I have the SM, but it only reports Q34, no information (only 12vdc to power the fan). The diagram I have is completely useless. If no one helps you, I will open my 1202. But in a few days, I'm away from home. HI

Hi,
I am a big fan (pun intended  ) of Noctua. I replaced nearly all the fans in my instruments with quieter Noctua models.
You won't need to open your scope, since Tautech found the marking on Q34.
Thanks for your offer anyway. 

Kind Regards

[tppc]

Q34 is marked A2RX however that is some distance from the fan connector. 

Yes, the distance to the fan connector is normal.
Q34 switches -10V VEE coming from the power supply.
It is located right behind the PSU connector.

A2RX : I could just guess the A on the fried one. 
I didn't find yet the reference corresponding to this marking, but I will search.

I have a dead warranty replacement SDS1202X-E PCB here if you need further help.

Hopefully, I will not cause any further damage while replacing Q34. 

Thanks so much for your help. 

[tautech]

Quick look brings up this but unsure if it's the correct package:
https://www.onepcba.com/XC6114A323MR

[tautech]

Think it's just A2R.....
https://www.aliexpress.com/item/32330365420.html

[CharlotteSwiss]

Hi,
I am a big fan (pun intended  ) of Noctua. I replaced nearly all the fans in my instruments with quieter Noctua models.
You won't need to open your scope, since Tautech found the marking on Q34.
Thanks for your offer anyway. 

Kind Regards

Better if I don't have to open my 1202; it won't be difficult to change that Q34.
Looking at your image of the board, I see that down at Siglent they spare no expense with hot glue on the components 
I also replaced all the fan with Noctua ones, my PCs are ultra silent. I also use Noctua coolers. HI
 

[tautech]

Looking at your image of the board, I see that down at Siglent they spare no expense with hot glue on the components 

Only on the PSU and it's not hot snot, it's silicone. 

While the PSU is a Siglent design they outsource production.

[SeanB]

Would move those screws and nuts in the bag though, using 2 cable ties to attach them to the metal chassis, probably using the round punched holes to the side of the fan, keeping them from touching the components, even if the bag disintegrates. Would also run the nuts up to the top by the screw head as well.

[tppc]

Think it's just A2R.....
https://www.aliexpress.com/item/32330365420.html

Hi everyone,
I could not find any result for the codes A2RX or A2R.
A2 could be almost anything from diodes, mosfets to voltage regulators...
Can anyone have access to the SDS1202X-E parts list and check the reference for Q34?

Best Regards.

[fzabkar]

https://www.micro-bridge.com/data/syncpower/SPN3402.pdf (A2yw)

https://www.aosmd.com/sites/default/files/res/datasheets/AO3402.pdf

http://markingcodes.com/search/c/a2xx

[tppc]

thank you very much!
SPN3402 seems to be the right one.

I desoldered the broken transistor but now the scope does not power up anymore 
All PSU voltages OK except -VEE which reads -8.8V instead of -10V.

I need to investigate more. :'(

[tautech]

Think it's just A2R.....
https://www.aliexpress.com/item/32330365420.html

Hi everyone,
I could not find any result for the codes A2RX or A2R.
A2 could be almost anything from diodes, mosfets to voltage regulators...
Can anyone have access to the SDS1202X-E parts list and check the reference for Q34?

Schematics are not available.
I've done the work for you and given you a link to the transistor.

I have a SDS1202X-E warranty claim PCB should you need other parts identified.

[CharlotteSwiss]

Q34 is used to have -10Vdc for the analogue circuits

[fzabkar]

Is Q34 the pass transistor in a linear -10V AVEE supply?

[CharlotteSwiss]

I think so, the image is from the Siglent service manual, but it doesn't say anything more.

[fzabkar]

I think so, the image is from the Siglent service manual, but it doesn't say anything more.

Then it could be a PNP transistor. You need to trace the circuit in this area.

[tppc]

I think so, the image is from the Siglent service manual, but it doesn't say anything more.

Then it could be a PNP transistor. You need to trace the circuit in this area.

I did trace the area :

The positive end of the fan is connected to GND.
The negative is driven by the Collector or Drain of the fried transistor.
The Emitter or Source of the transistor goes to -10V supply.

[tppc]

Think it's just A2R.....
https://www.aliexpress.com/item/32330365420.html

Hi everyone,
I could not find any result for the codes A2RX or A2R.
A2 could be almost anything from diodes, mosfets to voltage regulators...
Can anyone have access to the SDS1202X-E parts list and check the reference for Q34?

Schematics are not available.
I've done the work for you and given you a link to the transistor.

I have a SDS1202X-E warranty claim PCB should you need other parts identified.

Thanks for your help. however, The aliexpress link does not give the transistor reference and the product is not available. 

[tppc]

Is Q34 the pass transistor in a linear -10V AVEE supply?

no, the -10V AVEE commes from the PSU board (SMPS, not linear)

Q34 is used as a swich to power the fan from GND to -10V AVEE

[tppc]

Q34 is used to have -10Vdc for the analogue circuits

(Attachment Link)

Yes, it is a test point on the main board.
-10V AVEE can also be probed on pin 9 of the power cable plug

[fzabkar]

Is Q34 the pass transistor in a linear -10V AVEE supply?

no, the -10V AVEE commes from the PSU board (SMPS, not linear)

Q34 is used as a swich to power the fan from GND to -10V AVEE

Then how can removing the transistor that switches the fan prevent the -10V supply from working properly???

I desoldered the broken transistor but now the scope does not power up anymore 
All PSU voltages OK except -VEE which reads -8.8V instead of -10V.

Or are you just saying that you have now encountered a different fault unrelated to the first? I'm confused ...

[tppc]

Or are you just saying that you have now encountered a different fault unrelated to the first? I'm confused ...

Yes, I think it is unrelated. Maybe I broke somthing while disconnecting the PSU 12 pins connector.

I need to take out the main board and inspect it carefully. (which I did not do yet)