PCS500 Ch 2 Failure

Instruments PC Oscilloscopes and Recorders
1

Our great little PCS500 scope has worked for us for a couple of years with no problems. Recently opportunity opened to show off this great handy scope in the Engineering Dept at the Cal Poly University Lab while assisting students, who are getting turned on to this device. However, lately when I turn the scope on. Channel 2 has no response, Channel 1 Works fine. I ran the PClab2000se Calibration and get this failure.

Calibration results:

CH1 offset at 15V/div : 106 OK
CH2 offset at 15V/div : 280 FAIL
CH1 offset at 5V/div : 3 OK
CH2 offset at 5V/div : 51 FAIL
CH1 offset at 15mV/div : 3 OK
CH2 offset at 15mV/div : 51 FAIL
CH1 offset at 5mV/div : 11 OK
CH2 offset at 5mV/div : 102 FAIL
CH1 offset at 20us/div : -1 OK
CH2 offset at 20us/div : 201 FAIL
CH1 offset at 10us/div : -3 OK
CH2 offset at 10us/div : 201 FAIL
CH1 offset at 5us/div : -2 OK
CH2 offset at 5us/div : 201 FAIL
CH1 Trigger low : 104 OK
CH1 Trigger middle : 130 OK
CH1 Trigger high : 156 OK
CH2 Trigger low : 128 OK
CH2 Trigger middle : 128 FAIL
CH2 Trigger high : 128 FAIL
EXT Trigger middle : 123 OK

PPCS500-9
The +5 V regulators are a good strong +5.
Help would be greatly appreciated.

Thank you.

2

I think these results indicate the input amplifier or the input FET of CH2 is defective.
You may do some further tests by checking the output of the FET and the amplifier.
You may compare the outputs of CH1 and CH2 input FETs and amplifiers with same input to CH1 and CH2.
If there is big difference then the FET or the amplifier of CH2 is defective.

3

OK we’ll look into the input Amplifier Section of Ch. 2.
Is there anyway we could download or get a more detailed schematic diagram, other than what is provided on the CD that came with the unit under the troubleshooting section?

Thank you for your response.

4

You can use this link to download more detailed schematic diagram of the input section of the PCS500:
box.net/shared/flnvoycp78

5

Good Deal,

Thank you so much.