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Old 07-07-2014, 01:00 PM   #1
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Join Date: Nov 2004
City & State: Woodland, CA
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Default Cardexpert Tseng ET4000AX VL-Bus Recap

Paid way too much for this card when I got it. It's indeed very fast in Mode 13 (gotta love Tseng's awesome host FIFO!) but the output was too bright and slightly fuzzy on top of it. (Soft VGA outputs drive my eyes insane!)

First, I replaced all the ancient 10uf grounding/decoupling tantalums with 10uf 50v Chemi-Con KY. That alone yielded a noticeable improvement in picture quality - finally I could make out the edges of the pixels, and also just tangibly reduced the amount of noise going over my sound card. (Tantalums may not lose much capacitance over time during use, but the ESR is a different story...) Looking over the card a bit more in detail, I discovered that Cardexpert left off several decoupling caps near the DRAMs and left half of the VGA output filtering caps unpopulated. In addition to that, the three 10pf filter caps that were on there were over-softening the picture.

So I ordered a bunch of 8.2pf ceramic discs and got to work: I first replaced the three 10pf filter caps with the 8.2pfs, and I added 8.2pf caps to the missing pads. I also added the missing decoupling caps to the DRAM.

The end result is a now more correctly-bright (read: darker) and considerably sharper picture. Bright white on gray and cyan still suffers slightly from over-brightness, but everything else is good enough for now. At this point, the remaining softness and slight over-brightness is more likely the fault of the cheap Music Semiconductor RAMDAC used on the board. (Too bad Cardexpert soldered it to the board!) Mode 13 looks gorgeous (well as gorgeous as it can look :P), with razor sharp square pixels and perfect colors. 640x480 and 800x600 look decent too, not turning into a blurry mess at least. (The card interlaces its 1024x768 output... yuck!)

So yeah, old VGA cards for Byzantine era computers can be improved by recapping as well...
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The ever-amazing (and ever-affordable) KY, Chemi-con's best kept secret.

I'll probably be the only person going to SteamOS once it gets out of beta (ha ha.)
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