Capacitor Question

[enusbaum]

I discharged the CRT and verified it's voltage with a multimeter before I removed the anode. So I've got everyone all out and ready for repairs.

A question on Capacitors. Do I only need to change the electrolytic caps? I know the Horizontal caps are Polypropylene and there are also quite a few ceramic caps. Do they not degrade as bad over time? Should I look to overhaul those as well??

The issue I was suffering from was a rolling picture when the unit was started cold (being off for a week or so). The picture would roll for about 30 minutes before it finally stabilized. Also, once stabilized, the bottom left corner of the picture would "wobble".

As suggested by this board, I'm gonna just swap out the caps but wanna make sure that while I'm doing it I cover all my bases 

THANKS!

[grantspain]

very rare for ceramic or poly caps to go leaky,they tend to blow crapless if anything or split

i would concentrate on the electrolitics only and check very carefully for bad solder joints

[enusbaum]

Thanks! 

That's what I thought but wanted to double check.

[Ken Layton]

In general, 99.9% of the time it will be electrolytic capacitors that will have gone bad. Age, heat, and humidty can all dry out or make an electrolytic change value.

[Rickn]

So again, we missed out or perhaps I missed out.... monitor type size and model#??

But let's do some monitor basics  "NVD Monitor basics 101"

You have already gave us some great hints... vertical rolling when cold.

Is this a new problem  that developed recently?

Ok back to the monitor ... what model?

What type of sync input composite or separate.  This can be determined by how many signal input wires.. 5 for composite, 6 or more for separate.

Ok next any signs of bulging capacitors, we are looking for relatively small electrolytics such as 47 to 220 ufarads less than 50 volts.

Do not just look, feel with your finger tip ( of course power off).

After we check all that we may move on too how to use cold spray.

Hope this helps a little.

BTW I am creating a seminar and training material for  NVD Monitor Basics.

Good Luck

Rick@Niemandisplays.com

[enusbaum]

I've identified my CRT board as a Wei-Ya C829HR (from pictures I could find in their catalog).

I posted a picture of the board here:

http://www.enusbaum.com/gallery/v/ArcadeCRT/SDC10211.JPG.html

There are additional pictures of the tube in there as well but I haven't been able to identify any model # on any of the parts yet. Even the controller board only identifies the company (Wei-Ya) and I had to look through their catalog to find the actual product #.

I ordered all new Electrolytic caps from Mouser for about $8.50, so not too bad of a price to pay for a bit of an overhaul! 

[enusbaum]

OK! So I was able to order all but three of the capacitors I need from Mouser but it seems I'm having an issue finding a couple odds and ins.

The list I'm trying to find is:

50v 330uf
160v 1uf
75v 4.7uf

My local stores don't carry these and it seems Mouser (and Jameco) either don't carry them or they're on back order.

So I have two questions:

1) What suppliers do you use for your caps?? Mouser had ALMOST every one I needed 

2) The 75v 4.7uf is an odd cap. Every cap I find in this range (75v 1uf, 75v 100uf) is MUCH smaller than the one on my CRT board (Wei-Ya C829HR, picture here, it's the blue/purple cap in the font/center). Does this seem normal?? Looks like a mighty large cap for such a small value.

Thanks! 

[grantspain]

go higher on the voltage rating i.e 50v 330uf use 63v 330uf and so on

never go lower on the voltage rating and always get the correct capacitance value

[enusbaum]

So I think I figured out why the 75v 4.7uf cap was so large, it's bipolar! 

I ordered the right voltage/capacitance as a polarized cap... but now I see I need a bipolar.

Perhaps a stupid question, but what would be the danger of installing a polarized cap here?? The board is marked +/- for this cap.. so I'm not sure why a bipolar was used.

Thanks!

[grantspain]

hmm,yeah strange to mark a board polarity but install a bipolar
heck just install it,whats the worst that can happen-your cap will explode,big deal

[grantspain]

just make sure your face ain't anywhere near it

[enusbaum]

hmm,yeah strange to mark a board polarity but install a bipolar
heck just install it,whats the worst that can happen-your cap will explode,big deal

so an exploding cap wont put the circuit at risk??

it seemed strange to me that there'd be only ONE bipolar cap on the entire board.

[grantspain]

well if you are worried then get an exact match