Are you referring to the popular LV2000 (or similar type) "protection" board? This is not the same thing and doesn't provide the same mode of protection. The popular "input protection" board eliminates the possibility of over-stressed discrete transistors in the low-voltage power supply section in the case of a monitor with no signal applied for an extended period. It does this by providing proper voltage regulators instead of those transistors.
The "protection" circuitry of the P327 deflection board (and previous versions with the very long add-on board) creates individual and time-sensitive current limiting circuits for the main output transistors. If you remove the diodes and don't replace them, the output current limiting mechanism will go away. Even if there is an LV2000 present, it won't help limit the output current for games that obviously overrun the limits of the screen frequently such as Tempest, Star Wars, Major Havoc.
Cutting the correct diode may make the problem dissappear revealing root cause, but for the pennies per diode cost, I would certainly replace them all.
William Boucher
----- Original Message -----
From: Mark Shostak
To: vectorlist@vectorlist.org
Sent: Monday, December 21, 2009 7:19 PM
Subject: Re: VECTOR: Tempest foldover on right side
I was going to ask the same question, but I'd say, if you have a protection board, just cut the diodes out.
-Mark
On Mon, Dec 21, 2009 at 6:06 PM, William Boucher <boucher@mnsi.net> wrote:
I may be reaching a bit here, but does your monitor have the built-in protection circuitry (P327 board). D807 & D808 are known to create some bizarre behavior (folding, walling, linearity issues). Just replace them and all of the other similar diodes in the circuit with new 1N4148 type. The fact that it is walling on one side actually points to a specific diode in the circuit but I don't know which one without going back through all of the schematics. It would be better for the long term to just replace them all anyway and be done with it.
I have a discussion page dedicated to this problem here:
http://www.biltronix.com/wg6100_germs.html
William Boucher
----- Original Message -----
From: Kevin Moore
To: vectorlist@vectorlist.org
Sent: Monday, December 21, 2009 3:53 PM
Subject: Re: VECTOR: Tempest foldover on right side
One more interesting thing I just noticed. I increased the bounding box size about 1/2 more both sides for a total of 1 inch extra width. The fold over stays in the same place.
On Mon, Dec 21, 2009 at 2:41 PM, Kevin Moore <talon.k@gmail.com> wrote:
Been busy, but I had a chance to make a quick video. I taped off the region around the bounding box, so I would know where it was. It seems the problem is about 1/2 inch outside that box on the right side.
http://www.youtube.com/watch?v=2kMXHFCB5Zk
On Wed, Dec 16, 2009 at 7:31 AM, Andrew Welburn <andy@andysarcade.net> wrote:
Don't always assume that a recently replaced part is 100% good, i would still replace the transistor with another one as a way to eliminate that possibility.. you just never know :-)
Andrew Welburn
www.andys-arcade.com
----- Original Message -----
From: Kevin Moore
To: vectorlist@vectorlist.org
Sent: Wednesday, December 16, 2009 1:18 PM
Subject: Re: VECTOR: Tempest foldover on right side
Well the rom set is V2, good point on the boundary limit. I don't recall off hand, but when I get home tonight, I'll tape off the bounding box on the screen, and see. Wouldn't think it would be the Deflection trans, as I replaced all the Transistors with new when I re-capped, and did the LV upgrades. Don't think I have any V3 roms handy, but I'll check and see if that makes a difference.
Thanks for the input, gives me a few things to check.
Kevin
On Wed, Dec 16, 2009 at 2:43 AM, Andrew Welburn <andy@andysarcade.net> wrote:
If its bothersome, you could try replacing the relevant chassis deflection transistor, i've seen that before. Tempest unfortunately will force the monitor to display vectors way, way outside the visibile screen area, later romsets IIRR have a fix for this. Even if your monitor can produce a full image, certain parts of the game will overdrive the deflection such that the transistors will partially break-down, causing other areas of the screen to show foldover like this.
Its not clear if your boundary is inside or outside the real screen limit anyway without a photo. you should set the test mode pattern up to fill your screen then watch it in game, is the foldover inside this box?
I'd replace the relevant chassis transistor first with a new one then observe... Changing the romset to a later revision might also help, but this is much more laborious, and is ignoring a weakness in your monitor anyway.
Andrew Welburn
www.andys-arcade.com
----- Original Message -----
From: Kevin Moore
To: vectorlist@vectorlist.org
Sent: Tuesday, December 15, 2009 6:53 PM
Subject: VECTOR: Tempest foldover on right side
I've noticed that Tempest has a slight foldover when the player finishes a level, and the tube starts coming up. The left side the tube lines go infinity for lack of a better word, but the right side seems to fold over like hitting a wall, and it creates a straight line. Typically I just adjust the picture so that the monitor shroud covers this. Is this normal?
Thanks,
Kevin
---------------------------------------------------------------------------
** Unsubscribe, subscribe, or view the archives at http://www.vectorlist.org
** Please direct other questions, comments, or problems to chris@westnet.com
Received on Mon Dec 21 19:34:39 2009
This archive was generated by hypermail 2.1.8 : Mon Dec 21 2009 - 21:50:01 EST