Re: Question about Midway Trog boardset

Not really. They have the capability to be good buffers, but the resistors
that follow totally kill the effect. In the old days the resistors would
feed the base of an NPN transistor. The collector would go to +5 and the
emitter would be the buffered output to the monitor (sometimes the emitter
would go to a resistor to ground, but in this case the monitor is providing
the termination).

You said you had another monitor, check to see if it will allow turning the
termination off.

On Tue, Jan 29, 2013 at 1:37 PM, Matthew Rossiter <matt@rossiters.com>wrote:

> Hi Rodger,
>
> You are probably right. A 10k pull up resistor does pull up the
> brightness a little. A 1k pull up resistor brings it up a lot.
>
> When you say "no buffering", aren't the 74ALS541
> <http://www.fairchildsemi.com/ds/DM/DM74ALS541.pdf>chips at U2 and U20
> doing that or am I getting confused?
>
> Thanks!
>
> Matt
>
>
>
>
> On 1/28/2013 7:04 PM, Rodger Boots wrote:
>
> 1084S has a 75 ohm input impedance, board can't handle that (no
> buffering). Game monitors are usually high impedance. Pullup resistors
> might help,
>
>
> On Mon, Jan 28, 2013 at 7:04 PM, Matthew Rossiter <matt@rossiters.com>wrote:
>
>> Hello Everybody,
>>
>> I have a quick question about a Midway Trog Boardset<http://www.arcade-museum.com/game_detail.php?game_id=10201>
>> .
>>
>> It seems to be working fine but the screen is very dim. The logical
>> response would be that it's the monitor. I'm using an Amiga 1084S Video
>> Monitor and it's perfectly fine (bright and colorful) for any other game,
>> so it has to be the boardset. I also tried sending the video to my other
>> flat screen computer monitor using an RGB/VGA converter, but the signal
>> drops out alot. So maybe it's sending out weak signals. The board
>> voltages look pretty good. Pretty much +5v and +12v.
>>
>> The Schematic for the Video Output sections is here<http://www.arcade-museum.com/manuals-videogames/T/trog.pdf>on PDF page 55. I'm not much of an expert on Jamma boards. Any
>> suggestions?
>>
>> Matt
>>
>>
>>
>
>

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Received on Tue Jan 29 16:13:51 2013