Electronics > Repair

SDG1025 Damaged CH1 Repair

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hesam.moshiri:
I'm trying to repair my Siglent SDG1025 function generator which has damaged CH1. CH2 works properly.

I replaced two components (U19 and Q3=BAV99) but channel one shows a weird waveform.

U19 = THS3095 is a special OpAmp that can be turned ON-OFF via its PIN-8. so it's likely that it's OFF.

I spent a lot of time, but I could not find a trace connecting to PIN-8 of U19. I can see a tiny track and a VIA on the PCB connected to PIN-8, but it goes from mid-layers to somewhere unknown.
 
if somebody has this device please check the voltage on PIN-8 of U19, when channel-1 is active and Vpp is above 2 volts.

fzabkar:
https://www.ti.com/lit/ds/symlink/ths3091.pdf (datasheet)

As I see it, you need to compare the PD* voltage on pin #8 against the REF voltage on pin #1.

hesam.moshiri:

--- Quote from: fzabkar on November 18, 2024, 08:07:28 pm ---https://www.ti.com/lit/ds/symlink/ths3091.pdf (datasheet)

As I see it, you need to compare the PD* voltage on pin #8 against the REF voltage on pin #1.

--- End quote ---

REF (Pin-1) is grounded, so I'm looking for the PIN-8 connection on the board. The voltage on Pin-8 is low (max 0.4V)

fzabkar:
Are you able to trace pin-8 of the working channel back to its source?

hesam.moshiri:

--- Quote from: fzabkar on November 18, 2024, 11:54:44 pm ---Are you able to trace pin-8 of the working channel back to its source?

--- End quote ---

for sure if it was designed like that, I was spotting it. This opamp is only used for CH-1

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