Tektronix 7704A - calibration procedure - Page 1
Forum section: electronics / testgear

author: Rax
author_rank: Super Contributor
timestamp: January 23, 2022, 07:30:41 pm
content: I'm embarked on this project and it's my first tackle of scope calibration (have done calibration, alignment, and adjustments on other things), and some required instruments are foreign to me.For instance, I acquired a calibrated time mark generator - a Ballantine 6130A-101, and if anyone has any manuals, it'd make me very happy if they would share a scan (willing to discuss a reasonable fee) - and have no idea how to use it. Research online has returned very little and when this is the case, I usually can rely on operating or service manuals to figure the equipment up.This far from the calibration procedure, I've completed the power supply (the 54.2V was barely .25V off further away from the allowed top of the range), and so I went through adjustment, which actually brought all other voltages closer to their requirement (though none was out of spec +- allowed tolerance).Thank you in advance for all points shared!

author: bdunham7
author_rank: Super Contributor
timestamp: January 23, 2022, 08:03:50 pm
content: First off, that Ballantine 6130A seems to be a relatively unknown but simple instrument. I've never seen one, but Radiomuseum.org has the schematics. Like similar devices, it gives you a calibrated pulse train up until a certain frequency, then a HF sinewave after that. The idea is that you use the precisely timed signals to adjust the various horizontal sweep rates of your scope. If your timebase is 1us/div, then 1 MHz pulses should line up exactly on the grid lines. In order to use it to calibrate your 7704, you would have to verify the 6130A calibration first, a sort of chicken/egg thing. Any modern DSO with enough bandwidth will be more than good enough to do the job.I have been able to get by without a time-mark generator by simply using an AWG and then an RF generator for the higher frequencies. The only time I've struggled a bit is with scopes like the 2465B that have a sort of automatic calibration where you aren't just tweaking a physical adjustment. Even there I was able to manage. If you read the 7704 calibration instructions carefully, you can probably figure out exactly what they are doing and what signals would work to make the adjustments.

author: Rax
author_rank: Super Contributor
timestamp: January 24, 2022, 01:50:02 am
content: Quote from: bdunham7 on January 23, 2022, 08:03:50 pmThank you, bdunham7, makes sense, I think I got enough to get started.As I said though, the Ballantine came with fresh calibration to me (sticker says June 2021, and has been with the facility since, until the point of being sold to me).

author: Rax
author_rank: Super Contributor
timestamp: January 24, 2022, 02:15:22 am
content: I think this is the idea, right? (see image)I aligned the leftmost pulse with the graticule grid. There's a creep with each subsequent pulse, which signifies need of adjustment?The time marker standard is extremely clean (frankly, looks new) and I enclose a pic of the front of the unit for a check of controls and such.

author: bdunham7
author_rank: Super Contributor
timestamp: January 24, 2022, 03:47:37 am
content: Quote from: Rax on January 24, 2022, 02:15:22 amYes, that's exactly how it works. There will be adjustments specified in the manual for various sweep rates.That unit does look minty. It may actually be unused NOS military surplus or something close to it. I had a look at the schematic and since everything is divided down or multiplied from a 10MHz OCXO, the calibration is probably just a go/no-go deal in most cases.