REPAIR: 33250A incomplete square wave waveform

[ThaiGuy]

I recently got a 33250A, everything is working fine except for the square wave waveform. Anyone encountered this problem before or any one have idea on how to fix it. Thank you in advance

[MegaVolt]

What is the signal source? Have you tried signaling from another source?

[HighVoltage]

did you set the scope and 33250A generator to 50 Ohm?

[coromonadalix]

and please do not double post in different sections

[wasedadoc]

What is the signal source? Have you tried signaling from another source?

The 33250A is the source. It is a waveform generator.

[wasedadoc]

did you set the scope and 33250A generator to 50 Ohm?

1. It is a 1kHz signal. Source and term impedance will have negligible effect.

2.  Even at higher frequencies, source and term impedance issues alone do not cause asymmetric distortion.

[TheSteve]

You will want to work your way through the troubleshooting focusing on the ECL logic.

[wasedadoc]

Looks like an analogue fault to me.

Change the generator frequency to 5 kHz and change the scope timebase to 100us.  If the waveform shape still looks exactly the same then start by assuming a digital fault.  If the waveform shape/amplitude is different, suspect a problem from the output of the DAC onwards.

Service manual with schematics: http://ridl.cfd.rit.edu/products/manuals/Agilent/function%20generator/33250-90011_service_guide.pdf

Page 203. U1904 pin 22.  Waveform Ok or not?  If yes, there isn't much between that point and the final output.

If no, see Page 201. The DAC (MAX555CCB) is the large square at top left.  Output goes to pin 3 of the relay and thence into one or other of the two filter networks.  Appropriate filter output is at pin 8 of the relay.  OK or not there?

If not then a digital fault or faulty DAC/surrounding components.  If yes follow the analogue path through towards U1904.  Check supply voltages to all the ICs in the path and to all the clamp/protection diodes.