PCS500 not triggering

Instruments PC Oscilloscopes and Recorders
1

MyPCS500 trigerring do not work. No one channal (CH1, CH2 or EXT), selected as trigger source, do not triggering. Calibration is all right, with result :
CH1 offset at 15V/div : 120 OK
CH2 offset at 15V/div : 119 OK
CH1 offset at 5V/div : 1 OK
CH2 offset at 5V/div : 2 OK
CH1 offset at 15mV/div : 0 OK
CH2 offset at 15mV/div : 3 OK
CH1 offset at 5mV/div : -2 OK
CH2 offset at 5mV/div : 10 OK
CH1 offset at 20us/div : 0 OK
CH2 offset at 20us/div : 0 OK
CH1 offset at 10us/div : -2 OK
CH2 offset at 10us/div : -2 OK
CH1 offset at 5us/div : -3 OK
CH2 offset at 5us/div : -5 OK
CH1 Trigger low : 102 OK
CH1 Trigger middle : 128 OK
CH1 Trigger high : 154 OK
CH2 Trigger low : 102 OK
CH2 Trigger middle : 128 OK
CH2 Trigger high : 152 OK
EXT Trigger middle : 104 OK

I’m tested my PCS500 at two computers, results are identical - triggering not work, but all other function work properly.
Device age 11 months

2

Does the triggering occur if you move the trace’s y-position slider up and down? (Across the triggering level mark.)
Does the triggering occur if you first put the free running trace about to the middle of the screen. Then put triggering on and then adjust the triggering level adjustment up and down across the middle of the screen?

3

There is not one regime of triggering is not work. No one channel and external channel for trigeering is not work!

4

It seems your PCS500 is defective. There may be a component failure.

5

what is the component?

6

You have to follow the trigger signal in the trigger circuit to locate the defective component.
I think IC35 is defective.

The circuit diagram is on the CD in the folder: d:\Technical info\PCS500 2ch PC scope

Turn on the PCS500.
Select Ext. trigger source.
Set trigger ON.
Set trigger level about to the middle of the range.
Set Time/Div: 1ms

Connect sine or square wave: (1kHz, 5Vpp) to the EXT TRIGGER input of the scope.

Check the signal on pin 10 of IC35. There should be similar signal as on the EXT TRIGGER input (sine or square).

Check the signal on the output pin 11 of IC35.
There should be similar signal as on the input pin 10.
If not, then IC35 is defective.

If IC35 is OK:
Check the signal on pin 7 of IC37.
There must be square signal. Amplitude about 8Vpp.
If signal is there, then IC37 is OK.

Check the signal on the output pin 9 of IC32.
There should be signal as in this screenshot:

If no signal then IC32 is defective.

7

I found anomaly :
When CH1 switch to 0.15V/Div (or GND and from 15V/Div to 50mV/Div) and select as trigger source then triggering is worked properly, and in this case EXT.TRIG is worked properly to.
When CH1 lived at 0.15V/Div (or GND and from 15V/Div to 50mV/Div) then triggering at CH2, work on whole diapason of V/Did. and Time/Div.
When Ch1 switch out from 0.15V/Div (or GND and from 15V/Div to 50mV/Div) position then triggering at CH2 stop working. If Ch1 switch back to 0.15V/Div and trigger switch OFF and ON, then triggering on Ch2 is worked again.

Thanks.

8

This is very strange behaviour.
The reason for this is still unknown.