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HP 8663a RF level issue

Question asked by maynardb on Jul 3, 2009
Latest reply on Jun 9, 2010 by tabbott
I have an HP 8663a signal generator, which seems to have an issue with maintaining a level output. Originally, it had an attenuation issue, that turned out to be a weak contact in one of the two attenuators. I corrected that problem, but when changing freqs, under 1Meg, it is pretty flat, Between 1  meg and 15 meg, it climbs about 25%, then  drops off until at 38 meg and climbs again in amplitude  up to 58 meg then [ my scope only goes to 60 meg, even checked it with another scope] it really loses amplitude. I tried verifying cabling, and 50 ohm termination, but this had little effect. My assumption is that this should maintain a flat response over its frequency range, but there is an amplitude correction function at high output levels, from what I've read.  From reading the operating and calibration manual, it appears that card A12A1 handles this function. I tried prompting for error codes, but didn't see any. I checked the freq accuracy against my counter, which goes to 1gig. It was right on, so it seems to be related to flatness of signal both on sweep, and rf output What would you say it is?. Also, is this a repair that can be done with limited equipment?