RE: Tracking down a voltage dependent chip

I know it's in the video board (2 board set).

And it's in the sprite ram path which is unfortunately write only. So the
fluke is being of marginal help here. I need to write some programs to
clear the screen and play with the sprite ram to see if I can get some solid
results.

David

From: owner-rasterlist@vectorlist.org
[mailto:owner-rasterlist@vectorlist.org] On Behalf Of John Robertson
Sent: Sunday, September 22, 2013 9:53 AM
To: rasterlist@vectorlist.org
Subject: Re: RASTER: Tracking down a voltage dependent chip

Hi David,

No self test that I've ever heard of. Good job for the Fluke 9000 series
tool.

How about trying this - use a few independent power supplies, connect the
commons together to the logic boards and supplies, then separate the +5 and
+12 and -5 for one of the boards and run that board up/down on the three
voltages to see if it is sensitive. If not then move on to another board...

I'm working under the assumption that you have a multi-layer boardset
here...

You can also isolate the 5V bus and power it separately if you have only a
single board (cut and add remote power).

If you can identify the board then you are that much closer to finding the
culprit! Heat gun (tiny nozzle) and cold spray can help too..

John :-#)#

On 09/21/2013 11:39 PM, David Shoemaker wrote:

Well that didn't get me anywhere, still digging.

Any idea if these boards have a self test mode? Would help to have a stable
screen to debug.

Thanks,

David

From: owner-rasterlist@vectorlist.org
[mailto:owner-rasterlist@vectorlist.org] On Behalf Of Rodger Boots
Sent: Saturday, September 21, 2013 3:42 PM
To: rasterlist@vectorlist.org
Subject: Re: RASTER: Tracking down a voltage dependent chip

Bipolar (TTL (7400 series) and ECL and the old frame buffer RAM) speeds up
as it gets warmer. MOS (large RAM/ROM/EPROM) slows as it warms.

Everything gets faster with increased voltage.

So you can lower voltage until it starts acting up then either warm bipolar
or cool MOS a bit and note the effect.

Also, ECL was used in early Nintendo and it ran from a separate -5.1 (?)
supply, make sure to check that. It doesn't sound like an ECL problem,
though.

On Sep 21, 2013 5:24 PM, "David Shoemaker" <davids@oz.net> wrote:

I have a DK which if the voltage is low at all (like 4.95v) will start to
display graphic corruption (Kong gets stripes and princes hair starts to go
to the wrong place). Any suggestions on finding the chip involved? I have
done this before by piggybacking the ram / buffers around the sprite but in
this case I get no change.

Thanks,

David

-- 
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Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
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"Old pinballers never die, they just flip out"
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