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i've made the test that you seggest and semm that the attenuator works.
I can allign manually the level of the 495 with the front trimmer using the RF generator as reference.
But the autocalibration routine always fail.
If i give 0dBm the routine start and appear a square wave.The dispaly says to use the AMPL trimmer for made the square wawe as a straight line but i can't reach the straigth line.
--- In TekScopes@yahoogroups.com, Bob Koller <testtech@...> wrote:
The first thing I would check is the input attenuator. If you input, say, 0dbm from your generator, what is the on screen amplitude display? Is it close to the top of the screen with the input atten knob at 0db? Next, reduce the sig gen output in 10db steps and verify the steps with the 495 input atten knob. One of the first things to suspect is a damaged input attenuator, and /or damaged mixer. Of course, many other things can cause this, but these are suseptable to external input overload.
--- On Sun, 7/3/11, hh <ciulandro@...> wrote:
From: hh <ciulandro@...>
Subject: [TekScopes] Problem calibration TEK 495P
Date: Sunday, July 3, 2011, 2:19 AM
i've this problem on my Tek 495P.
When i start the calibration routine,with the internal generator 100Hhz -20 dB,the routine fails because the processor says taht there is any signal calibrator is present.
I've checked the output signal at 100Mhz -20 Db and is ok.
So i've connected to rf input an external RF generator at 100MHZ and the test start only when i give a signal @ 100Mhz 0(zero) dB.
Seem to be a loss of gain.
What can i verify in the instruments for repair this loss of gain?
Thanks for Any help.