8liners chassis on 25" CRT getting dimmer

[Lance]

I've had an 8liners chassis on my mame cabinet attached to a 25" monitor for a couple years but recently it has started to display a lot more dim then it used to.  Does anyone have any suggestions on things to check on what could be wrong?

It is the 8liners chassis for the 25"+ size that has the remote with the image settings.   It started getting dim when the machine was getting left on overnight from some of the folks at work. 

thanks,

lance

[qrz]

rejuvination may get some more time out of it . but , eventually the crt will die ......

qrz

[Lance]

I should have mentioned that turning the chassis off for awhile (an hour or so) and then turning it back on it is brighter, seems like it is a chassis issue not CRT.

Any ideas?

[Ken Layton]

Probably needs capacitors already.

[Lutus]

Agreed Ken,  and the caps are a much easier/cheaper fix than trying to round up a rejuvenator.

And if the caps don't fix it you are really only out 6-8 bucks.

[Lance]

Perfect, thanks for the replies..  Is there a tutorial somewhere on replacing the caps, is the idea to just replace every cap that is on the chassis board with one of the same value and same or higher voltage?

[Lutus]

Do a search for cap kit and you will get a billion (exaggerated) topics.

You have the exact right idea.  I am not familiar with that chassis but some places sell pre-assembled kits with the right caps in them and you just go to town soldering.

Either way, the outcome is the same.

[Rickn]

Hope ken is right and it is a cap kit???

It may be more serious though.... I am not sure how careful 8-liners is when they sell you a board. It is very importatnt that when they sell you a board they ask about the yoke and in this case more important the tube.

The heater impedance varies between manufacurers and therefore the value of the heater resistor needs to be right. If the heater voltage is higher than 6.3 volts then the life of the tube deteriorates exponentialy.

Good example is the radeon force countertop games. The original monitor in it had the wrong heater voltage and all of them are dying. We have doing a nice little business replacing the tube and correcting the heater voltage.

Chances are you will not have the right type of meter to measure this as it requires a true RMS voltmeter and if this is the case the tube is cooked... so go ahead try the cap kit and keep your fingers crossed.

good luck

Rick Nieman
www.niemandisplays.com

[grantspain]

i have been doing some research into these generic chassis such as weiya,jen shinn and rodotron,one thing i have noticed on american internet sites selling these chassis is how these companies provide information to match the yoke to the chassis-they all only provide yoke resistance matches whereas the most important info that can be provided is the inductance of the yoke
when a chassis is not matched to the yoke you can get geometry issues and brightness problems,also important to note that a chassis running at its tolerence limit will break down in a way you describe as basically everything is working too hard
i am at present working on a definitive guide to matching replacement chassis,at this point i have matched 3 chassis perfectly to replacements with a further 5 due this week.
also just to note i think i now know why the wgu5000 is such a difficult yoke to match and i am sure it is the same problem as the polo 2 dual sync/polo 1 dual sync-maybe Rick knows what i am on about

[ahofle]

Is there a tutorial somewhere on replacing the caps, is the idea to just replace every cap that is on the chassis board with one of the same value and same or higher voltage?

Here's a nice video tutorial:
http://forum.arcadecontrols.com/index.php?topic=76567.0

[Rickn]

I don't have a U5000m but if anyone has please let me know part # on the tube A63... and any numbers on the yoke.

If you have a scrap tube and yoke and are willing to donate the yoke let me know I may be willing to pay the freight for the yoke so I can come up with a replacement board set.

By the wayyou can post it here but if possible also e-mail me direct at rick@niemandisplays.com

This way we can do it right.

Thanks in advance

Rick Nieman
www.niemandisplays.com

[ToplessZ]

Got the part number for ya, im starting a new topic for it though..

[Lance]

Sorry to raise up a thread from long time ago but I finally got a new tube for my 8 liners chassis, the good news is it looks good as new.  What I'm wondering now is how to keep it that way.

Rick mentioned that I need to check that the heater voltage isn't too high, any tips on how to do this?  Is there just somewhere I add a resistor inline normally?

[Rickn]

If the heater voltage comes from the flyback, you need what is called a "True RMS Voltmeter" Not alll are created equal.

Here is what happens when the heater voltage comes from the flyback. There is a secondary winding on the flyaback that comes out at somwehere between 6.15 and say 7.5 volts at 15 khz.

This is rectified by a diode and then filtered by an electoltic capacitor. Then there will be a voltage dropping resistor to rdeuce the voltage to ideally 6.15 to 6.3 vrms.

This is where it becomes tricky. Because this voltage is derived from the original 15.75 khz of the HOT, the filter capacitor does not take all of the AC component out. This means that if you neasure it using a common DC Voltmeter, it will not be accurate.

If you use a true RMS Voltmeter, the higher the sampling rate the better.

A good true RMS meter will set you back a few hundred bucks, not likely you have one.

Please don't shoot the messenger but if the 8 liners board burnt out the first tube, my guess 6~7 months out of this one.

Good Luck
Rick
Rick@Niemandisplays.com
www.niemandisplays.com