Vectorlist Archives: Re: Gravitar text color/WG6100 issue

From: William Boucher <boucher_at_mnsi.net>
Date: Tue Mar 23 2010 - 18:22:44 EDT

Sounds like you've done lots of good work there. Don't confuse flicker with
jitter. The hi-score screens on Gravitar/BlackWidow/SpaceDuel always show
their slow refresh rates most on the hi-score screen.

I doubt that recapping the ARII will eliminate any remaining monitor jitter
but it's certainly worth a try. It regulates the +5V, +12V and -5V
supplies. It does not regulate the plus/minus 22VDC outputs. Replacing
C18, C19 (3300uF,35V) may help a bit though because these supply the vector
generator section. However, since they are regulated down to plus/minus 15V
locally in the vector generator section, I would expect there to be little
or no ripple after those two Vregs.

The 1ohm resistance you are measuring... is it possible that it's just your
meter? Two-wire meters tend to be pretty inaccurate below a few ohms. What
does it read if you just hold the probes directly together? A true 1 ohm
resistance through a molex connector terminal on a power supply rail is a
whole lot. If the monitor were to draw 3A through it, it would drop 3V
through the connection and the connection would also get very hot (P = VxI,
9W=3Vx3A). The total resistance should be measured in milli-ohms, far too
low to measure without a 4-wire ohmmeter.

The B+ should be 180V. The HV output should be 19.5 kV.

Adjust B+ as follows:

<the following quoted from 6100 faq>
Here is a trick for adjusting R918 without an HV probe. Hook up power to the
monitor (but without any input signals from the game board) and let it warm
up for about 10 minutes. Now measure the Video B+ voltage either at pin 5 of
P900 on the HV board, or at J501 on the neck board (refer to your
schematics). Adjust the HV so the B+ is 181v DC. Since the Video B+ and the
19.5 kV outputs are linked together, you will get the HV pretty close to
perfect.

Another post from today reminded me of this, check the two big cement
wirewound resistors on the 6100 deflection board. Have they been replaced?
They must be non-inductive otherwise they'll cause the shakes.

William Boucher

----- Original Message -----
From: "Andre Huijts" <a.huijts@upcmail.nl>
To: <vectorlist@vectorlist.org>
Sent: Monday, March 22, 2010 6:44 PM
Subject: Re: VECTOR: Gravitar text color/WG6100 issue

Coming back on this:

I just installed and adjusted a LV2000 and it works fine. I checked the xx15
regulators on the PCB and they work fine. Didn't change the caps yet though,
need to order them (using _good_ brand caps on this only).

Checked all diodes and they are fine. I did replace C100 and C101 by brand
new Panasonic one's.

There is no additional ground wire. Would it be a good idea to try to
install one (temporarley) I did measure the resistance between the monitor
metal side panel and the ground lug on the power brick and it's about 1 Ohm.
Not too shabby I think, or is this already poor ?

I can still see some minor jitter. It seems only there (or only visible)
when there's lots of (small) vectors on the screen like with the hi-score
screen.

Replacing the terminals in the harness connectors is a great idea anyway, I
just had the red pin came loose (causing of course no red on the screen).
Pushed it back and it's OK now, but it's too easy to remove it....

Well this cab still has the original Big Blue and the AR-2 is not re-capped
either so could that be an issue too ? I think the Big Blue has been blaimed
for lot's of troubles too. Thing is I can't measure anything with my Fluke
DVM, but how much ripple voltage is really needed to let a one pixel
movement be show ? Very little I bet !

Colors are fine after I replaced (and adjusted) the pots on the neckboard.

Thanks for the help so far.

O, I checked HV with my HV probe and it showed pretty low. What should B+ be
and where to measure it ?

Thanks, André

Op 13 mrt 2010, om 21:10 heeft William Boucher het volgende geschreven:

> Regarding the jitter problem...
>
> Check the output of the 7815 and 7915 regulators (VR1 & VR2) in the video
> section of the game board. If one of them is shorted through, jitter will
> result. I had a board with this fault and replacing the two regulators
> fixed the problem. Also good to do is replace the caps around these two
> regs (C111, C121 & C110).
>
> On the monitor deflection board, make sure that all 4 diodes D100, D101,
> D102, D103 are all good. An open diode will result in halfwave
> rectification instead of fullwave and this will result in a lot more
> ripple on the DC power supply lines. If you haven't already, replace C100
> and C101 (4700uF, 50V). A lot of standard cap kits do not include them
> because they are the largest and most expensive ones. They are very
> important however. I have posted an extensive replacement parts here:
> http://www.biltronix.com/arcade_electcomp_01.html#wg6100_rebuild_parts
>
> If someone has added an additional ground lead somewhere, just temporarily
> remove it. These add-on leads often cause jitter issues because they can
> create a ground loop as well as other issues. If removing the extra wire
> solved the problem, there are better ways to beef up the ground connection
> such as replacing the existing terminals in the original harness
> connectors with new gold ones.
>
> Text color problem...
>
> Try adjusting the bias and gain pots on the 6100 neck board to get the
> correct color balance. There is a pair of pots for each color. The
> manual for the 6100 explains these adjustments.
>
> And yes, some text is light blue (cyan). Screen shots (probably mame) on
> KLOV:
> http://www.arcade-museum.com/game_detail.php?game_id=8000
>
>
> William Boucher
>
>
> ----- Original Message ----- From: "Andre Huijts" <a.huijts@upcmail.nl>
> To: <vectorlist@vectorlist.org>
> Sent: Saturday, March 13, 2010 2:25 PM
> Subject: Re: VECTOR: Gravitar text color/WG6100 issue
>
>
> Forgot to mention that I also replaced the pots on the Gravitar game PCB
> to see if these were the cause of the jitter, but they weren't.
>
>
>
> Op 13 mrt 2010, om 20:18 heeft Andre Huijts het volgende geschreven:
>
>> Gravitar owners, I've been working on a WG6100 in a Gravitar and I wanted
>> to know, do we agree that the main texts on the attract screen are meant
>> to be light blue and not pure white ?
>>
>> When I compare the texts with f.i. the diamond test screen, the diamond
>> screen looks like true white.
>>
>> Can someone confirm this ?
>>
>> Another question about WG6100: this one has a very minor "jitter" on the
>> screen. I'd say that there is very small (extra) AC on the deflection
>> signals. It looks like it's mainly on the horizontal deflection but also
>> somewhat on the vertical.
>>
>> It causes the beam to not steadily hit the same dots on the screen. Note
>> that the metal screen is INSTALLED on the HV cage !
>>
>> Any idea where to look. I just did a cap-kit on deflection and HV board
>> (using Panasonic high quality caps, 105 degr.).
>>
>> I did not yet install a LV2000 (it's on it's way). Could it be in the low
>> voltage section ? I did _not_ replace the caps there because the LV2000
>> will get rid off them anyway.
>>
>> I've moved out the monitor out of the cab and ran it, and the issue is
>> the same so it's no cause inside the cab, it's on the monitor itself.
>>
>> Any tips welcome, thanks
>> !---------------------------------------------------------------------------
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>
> André Huijts
> andre.huijts@upcmail.nl
>
>
>
>
>
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> chris@westnet.com
> ---------------------------------------------------------------------------
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André Huijts
andre.huijts@upcmail.nl

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