I need help with a sony/tektronix awg2041 arbitrary waveform generator

[toolnuts]

Hello,

Newby here - first time on this forum.

I bought an tek arb off ebay, and it has a problem with square waves. on the non-inverted
output a 10Mhz square wave has a chunk out of the corner of the rising edge/corner, and the decending
edge/corner. I suspected a high frequency problem so I downloaded the service manual and looked up
the procedure for calibrating the HIFREQ, but the the one R253, and C251, and C253 made no difference
at all.

One problem it said to use the waveforms off the calibration and verification floppy, and I don't
have that floppy. Would any of you be able to send me a copy of that floppy.

Since I didn't have the floppy, I used the pulse function from the Function Generator.

I can't find a component level schematic for this device. I called Tek but they said we don't have one any more.

Would any of you have a floppy or any advice on how to tackle this problem?

I looked at the inverted and non-inverted signal at their respective caps and they look the same,

but the non-inverted ouput lookes like PacMan took a nibble out of the rising edge corner and
the falling edge corner. The inverted output look OK, but with some mild overshoot. Might
be to high a gain somewhere.

Any help would be greatly appreciated.

Best Regards,

Paul Hoffman 

[tautech]

Welcome to the forum.

Some pics from your scope would help.
You can upload them by placing the file in Attachments, the + below the Reply text box.

[toolnuts]

Here is a scope shot of the square wave (see attachment)

[tggzzz]

What is the source impedance, the cable length, the cable impedance and the terminating impedance? If you assume the velocity of light in the cable is 200e6m/s, what is the length corresponding to the duration of the "rising edge corner"? Compare that to the cable length.

I'll bet there is an impedance mismatch.

[tautech]

Is that a 50 input indicator on the display ?

Without schematics I'd just trace the signal path back through the output stages until you find where the corruption appears, then check all componentry in that area.
Another thought, have you checked how clean the PSU supply is in this AWG ?

[toolnuts]

Hello all,

To answer one question - it's 50 ohm on both ends.

It's not very easy to trace out on a 6 or 7 layer board, with all surface mount components, and
components mounted on both sides of the board.

The inverting output is fine. If I had a schematic I might be able to tell, what in the
path of the non-inverting output might be causing the bandwidth choke.

Regards,

Paul