Author Topic: Trouble with Iwatsu ss5711d oscilloscope  (Read 1268 times)

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Offline andrejsstrumfs

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Trouble with Iwatsu ss5711d oscilloscope
« on: August 14, 2017, 06:36:02 pm »
Hi everyone!

Couple of weeks ago i got a cheapish Iwatsu-5711d oscilloscope, which all in all works ok with one slight problem i would like to fix. The problem is - it won't trigger from channel 2, while triggering from ch1 and ch3 is ok. So i got a manual http://exodus.poly.edu/~kurt/manuals/manuals/Other/IWATSU%20SS-5711%20Instruction.pdf , hooked up ch2 to calibration source and started poking around with my other oscilloscope.
Trouble looks to be in the ch2 pre-amp circuit (page 111 in manual) - at first it looked like dead Q35 transistor - when i unclipped the P90 connector i got the same signal but with ~2x smaller amplitude when compared to ch1 trigger output. But with the connector on there is no signal at all. So i removed the transistor, checked for shorts and replaced the transistor with a new one. And got the same problem. Power sources are all ok. Resistors arund Q35 are all ok. Maybe someone can come up with idea?

Regards

Andrejs
 

Offline edavid

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Re: Trouble with Iwatsu ss5711d oscilloscope
« Reply #1 on: August 14, 2017, 07:18:15 pm »
But with the connector on there is no signal at all.
That's the first thing to fix.  Shorted cable or switch?
 

Offline andrejsstrumfs

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Re: Trouble with Iwatsu ss5711d oscilloscope
« Reply #2 on: August 14, 2017, 07:28:49 pm »
Quote
That's the first thing to fix.  Shorted cable or switch?
Yup, that was the very first thing i thought. But nope, the resistance for both ch1 and ch2 is ~47 ohms - looks ok according to schematics.
 

Offline edavid

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Re: Trouble with Iwatsu ss5711d oscilloscope
« Reply #3 on: August 14, 2017, 08:37:24 pm »
Quote
That's the first thing to fix.  Shorted cable or switch?
Yup, that was the very first thing i thought. But nope, the resistance for both ch1 and ch2 is ~47 ohms - looks ok according to schematics.

What happens if you disconnect the cable from P90 and connect a 47 ohm resistor there?
 

Offline andrejsstrumfs

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Re: Trouble with Iwatsu ss5711d oscilloscope
« Reply #4 on: August 14, 2017, 08:57:06 pm »

What happens if you disconnect the cable from P90 and connect a 47 ohm resistor there?


Same thing - no signal. But i noticed that with the resistor or connector in place i get -0.3V DC there. But even with no resistor or connector in place the amplitude is too small - about 50mV. On ch1 same signal was ~0.3V
 

Offline edavid

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Re: Trouble with Iwatsu ss5711d oscilloscope
« Reply #5 on: August 14, 2017, 09:59:38 pm »

What happens if you disconnect the cable from P90 and connect a 47 ohm resistor there?


Same thing - no signal. But i noticed that with the resistor or connector in place i get -0.3V DC there. But even with no resistor or connector in place the amplitude is too small - about 50mV. On ch1 same signal was ~0.3V

I guess you should connect the same signal to ch1 and ch2 and compare stage by stage.
 

Offline andrejsstrumfs

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Re: Trouble with Iwatsu ss5711d oscilloscope
« Reply #6 on: August 15, 2017, 04:14:53 pm »
I guess you should connect the same signal to ch1 and ch2 and compare stage by stage.
Thanks for help, turned out the problem was a tiny hair crack on pcb. Soldered and fixed :)

Andrejs
 


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