Full screen white is dim

[castlesteve]

There are so many adjustments when finally getting the monitor up and running again.

So if all the colors look great (color bars, grid align etc)... and a small or medium white square is nice and white.

But when I go to a full screen white, the whole monitor dims quite a bit. 

So what would I do to adjust this?

Thanks,
Steve

[SirPeale]

Well...

1) caps.

2) how many times in game does the game go full white? 

[castlesteve]

New board.... Wei Ya 826HR

What I described is really noticeable with white (like in windows when you open a new windows explorer).  But it happens on any scene change in a game where there is a lot of color... ie all green, all blue... anything that paints the entire screen.  It goes bright for a brief time then dims quite a bit

It seems like the board cannot supply enough current... it has enough for quick updates but cannot sustain large color images at full intensity.

Adjust B+?  Raise the gain on all RGB?

-s

[Ken Layton]

Maybe your picture tube is getting weak. If this monitor is being used in a mame application, maybe the video signal needs an amplifier.

[castlesteve]

The picture tube is fine.  It was working perfectly (before I blew apart my original chassis board-- it was unrepairable as it apparently had been modded many times before). 

This for some reason does not seem like a video amp problem because I get great colors ... it just cant maintain a full screen image well.  It pops up excellent and then dims about 25% and stays at that level... until you go to a dark image.

When I adjust up the gain, it just bleeds at the top portion 5-10% of the screen.  That give any indication?

I dont want to adjust B+ without knowing what the effects will be.

Also, I have a large coil on the board... what does it do?  All of the pots are labeled, but this is a coil about 2" tall.  It looks like it can be adjusted in the barrel.  Dont know.

Thanks,
Steve

[Ken Layton]

That coil sounds like either the width coil or a pincushion adjust coil.

[castlesteve]

Got those. 

Here's a pic of the board.  See the big white coil...

[Ken Layton]

By chance what was the original monitor? Is this being operated in a 100 volt power application (like a Nintendo cabinet or Sega cabinet)? If so that may explain the problem.

[castlesteve]

Hmm.

Well its was a wells 25k7197 ... and the board before I got it was totally rewired and hosed.  I removed all the rework and put a cap kit.. and it was fine... until a year later when i blew it up... im still fuming about that one.

Its original cabinet is a midway nba jam...  All original wiring except the iso transformer has been replaced.  Last i checked, im getting 120V from on the monitor side of the iso.

As a side note, i went and ordered a video amp just in case.  Even though it didnt need it before, this Wei Ya may need a little extra.

Any idea what that coil is?


Thanks for your help!

-Steve

[FrizzleFried]

That coil looks to be a horizontal width coil...

[SirPeale]

Well its was a wells 25k7197 ... and the board before I got it was totally rewired and hosed.  I removed all the rework and put a cap kit...

Explain the rework.  Wouldn't be wires and parts on the bottom of the PCB would it?

[castlesteve]

ok... just to back track a little.  I am an Electrical Engineer.. so, I understand fully PCBs, components, OEM rework, and hack jobs.  This, in all obviousness, was a complete hack job... and not standard rewiring or engineering changes to the board.  All kind of extra caps and resistors soldered to the top and bottom side of the  board to vias, and heavy gauge wire running amuck.  I removed all of this, back to stock, replaced all the caps... and it worked pretty well.   A year later, after i made my crucial mistake of no iso transformer, the board blew many traces and more than likely blew more than enough parts on this already pretty abused (and likely tired) board for me to even bother tracking down.  It was certainly easier to replace the board with a new one that has the same specs and a couple more dials than to waste months of parts ordering and tracking down.

All that said, i understand that it is desired to keep the original board as it is well designed.  I can attest to that... my replacement seems to work (ok)... although i am not done configuring it yet.  However, the wei ya has some tradeoffs that i prefer even to a possibly better working all around original "Wells" board.

I'd love to get this board running as well as the previous... but this one already is showing signs of improvements in some areas. 

I recall the other board having a 50/60hz pot... that maybe i tweaked a bit to correct the top of the screen problem.  Additionally, i am hoping a video amp will solve the color problems.

Thanks all for your suggestions!    I guess ill just find out next week when the parts come in.

-Steve

[castlesteve]

Ok so I installed the video amp... and fiddled quite a bit.  I had to crank back the RGB gains, and adjusted the "screen" and "brightness" just so that most of the problem is gone....

but the problem is still there.  Even on the nokia screen test...

whenever there are large screen color changes (full screen images), it displays the whole image bright, then dims quite a bit.

So, my last adjustment would be B+.   Would someone please give me a couple of pointers on if (or how) I should test/adjust this?  What voltage should I be measuring or looking to achieve?

If I measure say 120.5 VAC... what would the ramifications if I experimented by raising it to say 125VAC? 

Thanks again everyone,
Steve

[Harry Potter]

Funny. I've been having a very similar problem with a new arcade monitor I got about 6 months ago.

Image is very crisp but if there are major colour changes, it'll go bright and then dim.

[castlesteve]

Glad im not insane.  It really sounds like the board cannot sustain enough current for these image changes... which is why i would like to try to investigate B+, as it is the only adjustable high voltage pot on the supply part of the circuit.. but I cannot get any real replies here. 

Maybe I am missing an obvious monitor FAQ on how to adjust B+ for optimum performance (hint hint everyone!)

Happy New Year to you all.  Im stuck at home this year as my wife is now +5 days overdue for labor of our first.

-s

[con]

Hi,

I also have an older wei ya 828-hr chassis hooked up to a 26" Videocolor
tube. I am experiencing similar symptoms to what has been described in this thread... picture goes dim when monitor displays bright  full screen colours ie white, bright yellow blue etc.

Well, i have tried adjusting the B+ voltage pot and i can say that there was
a slight improvement. But tube still goes dim when bright colours are displayed.

Must be my crappy Videocolor tube??

[castlesteve]

I adjusted my B+ from 115 up to 125V... with no real improvements.  At 128V, I started getting a little snapping... so I backed back off to 120V.  I read somewhere that 115V is correct for this board... but unconfirmed.

-Steve

[Ken Layton]

There was another thread were someone was having problems and they emailed Wei-ya directly.

[Grauwulf]

I have seen various complaints about the replacement chassis (both jenn-shin and Wei-ya) being under powered and causing the problem you guys are describing.

Castlesteve> If you haven't tossed your K7000 chassis yet, it will likely be a simple fix to get it up and running again if you want to put it back in. I have yet to see one of those monitors with any damage other than a couple of blown rectifier diodes and maybe a burnt trace or two from being plugged in without an ISO. Worth fixing in my opinion if it was working fine prior to that.

[castlesteve]

I still have it.  I may resurrect the effort...