Re: 7A26 attenuator compensation problem


On Sat, Jan 26, 2019 at 10:20 PM, Cliff Carrie wrote:

you will probably need to do a full attenuator recalibration
If it turns out that way which I think is quite possible given what was said.

The key is still the most sensitive setting which bypasses all that attenuator stuff. Literally. What is it 5mV on that ? And also no X10 probe, 1;1. Eliminate ALL sources of frequency abberations, then you are down to the amp itself. If that ain't right nothing else will be right.

Clean all of the resistor leads and the attenuator module pins with a good contact cleaner
My 465B has a very similar setup and I now suspect one of those modules has an intermittent connection inside. I cleaned everything and resoldered any connections that didn't look perfect and it acted up again. By the way, that PC board, at least in the 465B - is plastic. The soldering iron will melt it. Mine, well it will never have the ground reference again on that channel because of how that board is. I will replace it one of these days but it works well enough right now. The damn thing has to cone from a 465B, I can't find anything else that fits, so far. The regular 465 no, 465M no, 475 no. Didn't check much further, but my co-conspirator found that some parts of the 7A26 fit the 475 attenuator. I got the part in but by the time that was done it was late and we wanted beer so next time I got to put it all together. That is next on the agenda. I hope I remember where everything goes {:-)

I think that attenuator might be compatible with the 475. (not A) I know some mechanical parts are, not sure about the cam itself, we didn't need that.

I hope these attenuators are not the downfall of these scopes. Everything else seems almost easy until you get to them. If they send these things to a landfill I don't know what. I don't want a new LCD thing that looks like a game boy and needs a software update every nine days. We have to be able to deal with these attenuators, it seems they are at that age now... There is no fail. There is no try. There is only do.

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