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


Dave Peterson
 

This thread is validating my suspicions. I was surprised to accidentally come across a cal service website offering calibration for a 465 while looking for what the waveform on TP1478 (or something like that) was supposed to look like. Part of the Z-axis compensation adjustment. As Jeff noted, they're available, for more $$ than I payed for the scope.

I'm sure I could adjust my scopes as well as, if not better, than a dedicated shop. But I know the difference is that I don't have certified standards to validate against. But then my balancing thought is what you're saying about 0.1% - how many significant digits can one achieve with these things. Trying to adjust a 465 pot to less that 1% is just not possible. Doesn't stop me from trying. Wink. But if I have two or three instruments agreeing to 1% I have good confidence that my adjustments are valid. But that's not really what "calibrated" means.

Again, the issue circles back to what one is trying to sell. If I sold as "calibrated" I wouldn't do that without: A) charging for it, and B) providing the paperwork proving it. I like the term "performance verified". Or otherwise functionally and performance verified or validated. I'll have to investigate what eBay calls "Refurbished". Then again I'm probably holding myself to a standard that other sellers may not. I gotta be me.

I've got a ways to go before I'll feel comfortable reselling a scope as refurbished and verified. I also don't see myself selling one until I am comfortable saying that. If I wasn't comfortable selling it as validated I'd have to sell it as parts. Which I'm also not thrilled with. I don't see a market for selling a "calibrated" 465 vintage scope. I'd leave that to the buyer. If they need that, then it's part of their operating expense anyway.

Thanks for your inputs. Enlightening, educational, and entertaining, as always.Dave

On Monday, December 7, 2020, 03:30:32 PM PST, demianm_1 via groups.io <demianm_1=yahoo.com@groups.io> wrote:

My experience with cal labs has not been encouraging. Mostly they want to run instruments through the automated cal procedure. Anything else will be expensive (labor). And its really whether the instrument is within tolerance (go/nogo). Its not adjusted to perfect.  If adjustment/repairs are needed the rate can be astonishing and keep in mind on these older instruments the repairs are not 10 minute fuse replacements. They are usually really difficult things to figure out.

However for a scope a time mark generator and a leveled signal generator would cover most tasks. CRTs are not .1% instruments so no need to get that involved. I picked up a Ballantine 6130 time mark generator and a Tek 191 leveled generator (to 100 MHz) pretty reasonably. With those you could say "performance verified" instead of "calibrated".

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