Here is what the 7A13 should look like at the 1mV/Div at 100Mhz and 5Mhz with a FG input. The un-used input must be set to ground or terminated or set to internal Vc or to the same impedance as the used input or the displayed amplitude could be what you're observing will be wrong. This is a basic rule of using diff input amplifiers.
Text book measurements like these are of extremely limited information and telling of what the 7A13 can do in real world test set up requirements. These basic measurements are what the modern DSO's do so very well at complete with a on display box full of data. No user interoperation needed. This is the great appeal for the vast majority of time domain instrument users. These are the types of measurements that have the lowest meaningful data and usefulness for the stuff I do.
7A13, 1Khz sine, 1mV/Div, 100 Mhz, single ended input:
![](https://lh3.googleusercontent.com/-qSKbd59OGIY/VSAMY32L31I/AAAAAAAABzM/BpIArm5DPKM/w1398-h1048-no/7A13%2C%2B1Khz%2Bsine%2C%2B1mV%2C%2B100Mhz%2BBW.JPG)
7A13, 1Khz tri, 1mV/Div, 100 Mhz, single ended input:
*Notice the over shoot spike at the peak of the triangle wave.
![](https://lh3.googleusercontent.com/-zUtRb6H8Jew/VSAMVWE3D5I/AAAAAAAABy8/t8atwC95UpU/w1398-h1048-no/7A13%2C%2B1Khz%2BTri%2C%2B1mV%2C%2B100Mhz%2BBW.JPG)
7A13, 1Khz tri, 1mV/Div, 100 Mhz, single ended input:
![](https://lh3.googleusercontent.com/-9sNmvShhADU/VSAM6C8HWTI/AAAAAAAABzc/p03QtsvQi_0/w1398-h1048-no/7A13%2C%2B1Khz%2Bstep%2C%2B1mV%2C%2B1Mhz%2BBW.JPG)
7A13, 1Khz sine, 1mV/Div, 5 Mhz, single ended input:
![](https://lh3.googleusercontent.com/-L6gcVAErorM/VSAM6a9n2TI/AAAAAAAABzg/JovH-Y4UlLA/w1398-h1048-no/7A13%2C%2B1Khz%2Bsine%2C%2B1mV%2C%2B5Mhz%2BBW.JPG)
7A13, 1Khz tri, 1mV/Div, 5 Mhz, single ended input:
![](https://lh3.googleusercontent.com/-1BixYXeOHMQ/VSAMWBeZfJI/AAAAAAAABzE/GXtFUB8ukQA/w1398-h1048-no/7A13%2C%2B1Khz%2BTri%2C%2B1mV%2C%2B5Mhz%2BBW.JPG)
7A13, 1Khz step, 1mV/Div, 5 Mhz, single ended input:
![](https://lh5.googleusercontent.com/-SICp7n4htsc/VSAM67NZv8I/AAAAAAAABzk/EGKbws1kIp0/w1398-h1048-no/7A13%2C%2B1Khz%2Bstep%2C%2B1mV%2C%2B5Mhz%2BBW.JPG)
For comparison, Tek 7A22.
The noise spectra can be determined by usual observation in real time, in these time exposure images that data is mostly lost as the exposure time integrates the noise camera exposure time. The peak noise and much more visual information is not visible in these images. A video would illustrate this better than still images.
7A22, 1Khz sine, 10uV/Div, 1 Mhz, single ended input:
![](https://lh4.googleusercontent.com/-2WmxVVJoiSQ/VSATcBt2gVI/AAAAAAAAB2A/9WO_EBtQEUo/w1398-h1048-no/7A22%2C%2B1Khz%2Bsine%2C%2B1Mhz%2BBW.JPG)
7A22, 1Khz Tri, 10uV/Div, 1 Mhz, single ended input:
![](https://lh3.googleusercontent.com/-4T5FQ51XfjY/VSAOQ1asc9I/AAAAAAAAB0M/NTIcaDRjL5s/w1398-h1048-no/7A22%2C%2B1Khz%2BTri%2C%2B10uV%2C%2B1Mhz%2BBW.JPG)
7A22, 1Khz step, 10uV/Div, 1 Mhz, single ended input:
![](https://lh5.googleusercontent.com/-eNul4XmU7YM/VSAPSMGKe5I/AAAAAAAAB0g/vfrqC0Xb-Zw/w1398-h1048-no/7A22%2C%2B1Khz%2Bstep%2C%2B10uV%2C%2B1Mhz%2BBW.JPG)
7A22, 1Khz sine, 10uV/Div, 100 Khz, single ended input:
![](https://lh3.googleusercontent.com/-HE_KRBE224M/VSANZEYD-mI/AAAAAAAABzs/kHR4VgDZHuk/w1394-h1046-no/7A22%2C%2B1Khz%2Bsine%2C%2B10uV%2C%2B100Khz%2BBW.JPG)
7A22, 1Khz tri, 10uV/Div, 100 Khz, single ended input:
![](https://lh3.googleusercontent.com/-1fbiUzlvTu0/VSAN_BQXzOI/AAAAAAAAB0E/5hmjWgvH960/w1394-h1046-no/7A22%2C%2B1Khz%2BTri%2C%2B10uV%2C%2B100Khz%2BBW.JPG)
7A22, 1Khz step, 10uV/Div, 100 Khz, single ended input:
![](https://lh3.googleusercontent.com/-r0GgBRYOq2A/VSAOxqwx8eI/AAAAAAAAB0U/bxe3TRdarKo/w1394-h1046-no/7A22%2C%2B1Khz%2Bstep%2C%2B10uV%2C%2B100Khz%2BBW-A.JPG)
*Some one with a modern new "fancy dancy" DSO need show-prove this exact measurement at 10uV/Div, 1Mhz BW and 100Khz BW at the DSO's input. NO ADD ON, Pre-amps or external aids.
These inverted contact Tektronix relays were used in a LOT of tek instruments. They have very good BW and very low coupling from the coil to contacts. Over time like most all mechanical devices, they can wear out. Do wiggle them in their sockets as the sockets are know to become intermittent if the instrument is not used. Replacements can be the original Tek part or Teledyne T0-5 relays. Send me a PM if you need help with these.
Bernice
Much better now (with ground spring), although it keeps on jumping to two division, but changing the Volts/div to 2 mV and back to 1 mV get's it back.
I just hope is not the miniature relays that is causing the volts/div to half every now and then or I'll have to deal with this:
(with google translate from German to English)
But it seems the 7A11 I got, also has the same relays.