This project finally got popped of the stack and finished, and I wanted to "close the loop" on it. The culprit turned out to be C112, a 47uF 50V in the monitor section. Ian nailed it. Thank you! Cheers, Garrett On Fri, 26 May 2017 15:22:48 -0400 Garrett Nievin via vcf-midatlantic <vcf-midatlantic@lists.vintagecomputerfederation.org> wrote:

Hi, Ian!

http://imgur.com/a/Z4s7V

Here is the image on imgur. I turned the brightness way up, put a loopback on the serial port, and typed all these characters. Everything seems to work correctly except for this negative video drive.

I'll definitely check those caps. I replaced the 2.2 uf tantalums just because I had some on hand, but haven't replaced any other caps yet.

Thank you!

Cheers, Garrett

On Fri, 26 May 2017 08:36:31 -0400 Ian Primus via vcf-midatlantic <vcf-midatlantic@lists.vintagecomputerfederation.org> wrote:

...

I've been really busy lately - sorry I didn't see this earlier. The picture did not come through - the list doesn't support attachments, could you upload it to imgur or something?

IIRC, there isn't a way to invert the video on the ADM3A with a switch, it sounds like you have a failure in the monitor section. It is very possible for a component failure to drive the video negative like that. Check C119 and C112.

-Ian

On Sun, May 21, 2017 at 4:07 PM, Garrett Nievin via vcf-midatlantic <vcf-midatlantic@lists.vintagecomputerfederation.org> wrote:

...

I'm restoring a Lear Siegler ADM-3A, and I'm not the most CRT-savvy guy around (but I did really enjoy Ian's excellent class at the most recent VCF-E).

Attached is a photo of the issue. If I crank the brightness to clearly see the raster, I can see that the text is actually displaying as dark instead of bright.

Pointers?

Cheers, Garrett