PCS500 internal trigger FAiL (Calibration.log)

Instruments PC Oscilloscopes and Recorders
1

Please, help!
PCS500
charge-pump capacitors OK
voltages good (+4,99v & -4,99v)

Calibration results:
CH1 offset at 15V/div : 118 OK
CH2 offset at 15V/div : 114 OK
CH1 offset at 5V/div : 3 OK
CH2 offset at 5V/div : 4 OK
CH1 offset at 15mV/div : 5 OK
CH2 offset at 15mV/div : 12 OK
CH1 offset at 5mV/div : 15 OK
CH2 offset at 5mV/div : 38 OK
CH1 offset at 20us/div : 0 OK
CH2 offset at 20us/div : 0 OK
CH1 offset at 10us/div : -1 OK
CH2 offset at 10us/div : -1 OK
CH1 offset at 5us/div : -4 OK
CH2 offset at 5us/div : -4 OK
CH1 Trigger low : 2 FAIL
CH1 Trigger middle : 2 FAIL
CH1 Trigger high : 2 FAIL
CH2 Trigger low : 2 FAIL
CH2 Trigger middle : 2 FAIL
CH2 Trigger high : 2 FAIL
EXT Trigger middle : 94 OK

Thank you!

2

Can you use the oscilloscope but not the triggering?
If yes, there may be some hardware defect in the triggering section.

3

I can use it, but functionality is limited , because square signal during calibrating 10x probe is not “square”, and triggering CH1 CH2 need for me.
I not yet understand principles of internal triggers -analog or digital IC fails ? All voltages is good (+5D, +5A, -5A. LED1 on).
74HC4316 analog switch is OK ? How can I test signals on inputs of 4316 (see waveform)?
Now I have another PCS500, what test points can I compare ?
Thank you!

4

First connect some signal to the scope input.
When the CH1 triggering is selected the signal coming to pin 1 of IC35 should be seen on the output pin 2.
Corresponding when CH2 triggering is selected, the signal on pin 4 should be seen on pin 3.

To check that there is not a software or calibration problem, please do following test:
Connect the working PCS500 to the PC.
Run the software and select the Calibrate & Exit option of the File menu.
After succeeded calibration connect the defective PCS500 to the PC.
Now do not calibrate it but test if the triggering works OK.
If not working, there may be some hardware problem.

5

Yes, I know-hardware problem… Where?
Signal TRG_LEVEL for triggers from DAC TLC5620 all time =0,02V
May be TLC5620 burned out?
I will made serial bus sender for testing DAC and next circuit.
Sorry for my English
bears vodka balalaika :wink:

6

[quote]Sorry for my English
bears vodka balalaika ;)[/quote]It’s OK!

[quote]May be TLC5620 burned out?[/quote]This may be the cause of the problem.

7

Hi
TLC5620 DAC is works OK.
But two iC in chain are “semi-broken”:
iC 32 (NE521D comparator input 1B)
iC 37 (CLC5622iM pin7, output of fast hi current amplifier)
But why? May be this wire was shorted by nearest steel spring contact (it was not tight screewed).
I find replacement of CLC5622iM=LMH6724, not solder/test, order and wait

8

OK - It seems that you have now located the defective components.
It is strange why they have damaged.