Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!


Dave Peterson
 

I'm using OneNote on my workbench PC to document my progress as I go. It's a way to track what's done to this scope without penciling it directly in the SM. And a way for me to organize the procedures for myself.

The SM calibration is meant for folks who know what they're doing. I'm familiar with this as this is how it was in the Army. Know the process, but follow the manual as a guide and reminder. Like the tear-down guide I want to produce, I feel I can use my first timer's experience to perhaps clarify the cal procedure for others like myself.

So I have some overly verbose notes that I'd like to parse down into something more organized and concise. I'm happy to share. I am realizing that my "calibration" will be incomplete for some time. There's clearly some tooling that needs to be done before a true calibration can be had. The question is can a useful tuning guide be parsed out of the full calibration? I don't know yet what the consequences of not doing some of the cal is. Can the vertical channels and time sweep be adjusted well enough with basic tools to be serviceable? Can quality be gained incrementally? For myself, I think probably so. But I can't be sure yet. I don't have the full understanding and experience yet. Learning it and sharing IS the hobby.

I'm taking note of everyone's inputs. It's all gold! Thanks!
Dave

On Tuesday, December 8, 2020, 06:01:29 PM PST, Jeff Dutky <jeff.dutky@gmail.com> wrote:

Dave Paterson wrote:

I'd say this deserves a new topic under calibration, but I wouldn't want to loose the connection to all this good info in this one.
I intend to post my write up of this discussion, along with a summary of the 475/475A calibration procedure using the suggested replacement equipment, under a new topic (Scope Calibration Using Home Brew Equipment? I'm open to suggestions). I was actually going to ask for your input on the service manual calibration procedures, so that we could extend the document to include more than just the 475/475A (and maybe some of the 2200 scopes, but I'd rather not let scope-creep overwhelm me on this).

Concerning the "flaw" in your personality: there may well be tasks for which it is sufficient to blindly follow instructions, but my experience on the operations staff for a large government data system is that those tasks are few and far between. In most cases the person performing the task really does need to understand why they are doing each step, and, to a practical extent, what the effects of each step are likely to be. People who just follow the recipe without understanding the whys and hows tend to make a terrible hash of things without noticing, and it falls to those of us who do understand to clean up the messes.

The normalizers appear to be an in-line device that you attach directly to the BNC (or whatever) connector on the subject instrument, and has a second BNC connector to which you can presumably attach a signal source. Here is an eBay search showing some of the available parts: https://www.ebay.com/sch/i.html?_nkw=tektronix+normalizer (ignore the Normalizer Head and the Signal Normalizer Plug-In, I think)

-- Jeff Dutky

Join TekScopes@groups.io to automatically receive all group messages.