Sounds like there could be a problem with the bandwidth limit switch or
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On 12/19/2019 1:15 PM, kdlamet@... wrote:
First I come here a lot for the great info, but seldom if ever post. I recently picked up a non-working 7904 from eBay and was able to repair the 670-1613-00 HV board. After getting it working I began collecting and repairing Plugins.
I had pretty good success until running into a 7A26 and now this 7A16A.
The issue: everything passed cal until the bandwidth section. Using an SG503, 012-0408-00 cable and 50 ohm terminator into the 7A16A set to 10mV input range and 6 division input, it drops to less than 1div around 50 Mhz. 4.2 division occurs at ~ 28 Mhz. The SG503 and cable are working as I get good response from my 2465A.
Initially the 7A16A had bad contact on all ranges of input - cleaned ONLY with 99% IPA. Also input BNC connector had an intermittent ground - internal to the connector. This was replaced with a 7A26 donor part.
It appears to be in the Attenuator section as I see the loss of bandwidth at the output prior to going to the main amplifier board.
Any assistance/info/guidance on this issue would be Greatly appreciated.
Thanks in advance.
P.S. A little background.... 40+ years Electronic Technician - Private industry / DOD. No Engineering. I've fixed it all Radios/TV/Auto Stereo/RADAR/Test Equipment(PMEL).
Bruce Atwood PhD
Department of Astronomy
The Ohio State University
100 West 18th Ave., Room 4055
Columbus, OH 43210