Re: 465/475 Volts/Div range LED swap problem.


Dave Peterson
 

Sorry Dave.

The link was to the thumbnail. The full picture can be expanded by finding it in the thread:

https://www.eevblog.com/forum/repair/tektronix-465/msg697587/#msg697587


Not so much theatrics as impatience on my part. I'm cleaning up my LTSpice simulations to upload to the files area, and need to build up a photo album. In the interests of saving on the TekScopes group space usage I need to resize all my pictures by quite a lot.

No need to apologize. Pardon my impishness and impatience.

Yes, the 10x diode stays on weakly. I tried all manner of remedies, but the basic issue is that Q386 needs enough base current to drive the 1X LED, and that current is always enough to cause the 10X LED to start illuminating. I'd just ordered a batch of 100 2N3904's to replace one missing in the scope. So decided to wire one parallel to the 10X LED. I was really trying to minimize the complexity of this solution. This was the best I could come up with.

Posting the LTSpice files now. Want to/will add a writeup PDF too.

Dave

On Saturday, February 20, 2021, 10:11:48 AM PST, Dave Voorhis <voorhis@gmail.com> wrote:

On 20 Feb 2021, at 17:54, Dave Peterson via groups.io <davidpinsf=yahoo.com@groups.io> wrote:

Here's a hint:

https://www.eevblog.com/forum/index.php?action=dlattach;topic=45906.0;attach=157509;image

What's wrong with this picture?
It’s too small to see?

Sorry to be grumpy, but I’m not finding your guessing-game approach much fun. Could you share the problems you’ve found and the solution you’ve developed and, with respect — and unfortunately there’s no write to say this as politely as I would say it in person — please spare us the theatrics?

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