Presenting a capacitor chart for the glorious Sharp CZ-602D

[kamiboy]

So, your monitor has gotten a bit long in the old tooth, and you wonder whether to take the old gal behind the old barn and introduce her to your old boomstick, or refresh her leaky capacitors and squeeze a few year out'a her. You know she has it in her!

Well, here is a capacitor chart for the 602D, just to give you an idea of the nigh insurmountable task ahead of ye hopeful.

Seriously though, this beast is filled to he brim with capacitors, those 80'/90's engineers sure were fans of caps. There are 132 by my count, and the kicker is all of them actually look perfectly fine, no bulging or leaking evident at all, so I am wondering whether all this work, and the small fortune it will cost to swap them all is going to be worth it. Bah, it has to be done.

Honestly speaking though you could prolly get away with just replacing the ones on the power supply, chassis and neckboard, but that is still quite a few.

[Pinwizkid]

This is huge! Thanks for your effort.

-BB

[kamiboy]

Service announcement:

Looks like I dun goofed while noting down the capacitors. Firstly, I missed a few that were hidden underneath a RF shield, secondly I had failed to notice that a few of caps were actually bi-polar (BP). This is very important to note since you cannot replace bi-polar caps with regular ones.

I've updated and reuploaded the cap chart, so toss the old one and keep this new one. Alas I cannot guarantee the accuracy even yet since not knowing about the bi-polar caps when putting in my order for the replacements I am faced with the bitter pill of having to pay a rather lavish sum for a handful of extra caps due to very high shipping from any place online that sells the required caps. Drat!

[famiac]

How the hell did you remove the neck board is what i'm wondering.

[kamiboy]

It just slides out if you tug at it.

[famiac]

I'll have to take a look at my cz-605D. It looks permanently attached

[kamiboy]

I thought the same, and actually started desoldering the big circle of solder pads to detach it, but during the process I found that it just slid off and I felt really stupid.

Thing is I had seen videos of neck boards being detached before and just forgotten. Neck boards are generally designed to be plugged into the tail end of the tube via a circle of pins, so they can easily be slid off. If you see any pictures of a CRT chassis for sale you will see the anode cap, and neck board being there. They are part of the chassis, not the tube.

The only thing is that a single wire running around the tube is soldered on top of the neck board, you'll have to solder that off to completely separate the chassis from the tube. That is the only point where the two are permanently affixed.

[kamiboy]

No dice! After putting it all back together again I saw that the problem persists, so capacitors were not the issue here.

Drat!

[famiac]

What was/is the issue?

[kamiboy]

Seems it was actually some sort of cold solder joint on the neckboard. I reflowed every solder joint on it and now the problem seems to have gone away. At least the problem with the colour red continually going away and coming back.

I still suspect that there is a problem with overall brightness being too low. For you guys who have a X68000 monitor, do you need to crank the brightness knob on front all the way up to get an acceptable picture?

Mine is too dark when the knob is placed in the middle.

[Pinwizkid]

Seems it was actually soome sort of cold solder join on the neckboard. I reflowed every solder joint on it and now the problem seems to have gone away. At least the problem with the colour red continually going away and coming back.

I still suspect that there is a problem with overall brightness being too low. For you guys who have a X68000 monitor, do you need to crank the brightness knob on front all the way up to get an acceptable picture?

Mine is too dark when the knob is placed in the middle.

Been very busy with real life lately, but next time I get a chance, I will go through my adjustment knobs and give you a report. I seem to remember that more than one knob had an effect on the overall brightness and I tried finding a balance between the two, but I will let you know.

[kamiboy]

For my monitor at least there is only the one knob on the front that adjusts brightness. There are a few holes too though, that you need a screw driver to turn, but I've never messed with them.

[famiac]

Maybe there's a sub-contrast pot on the neck board?

[kamiboy]

There certainly are brightness adjustments once you pop open the back and get you hands dirty with the innards. You can usually adjust the brightness of a CRT using one of the two knobs on the flyback, with the other adjusting focus.

But the thing is this should not be necessary in my case. I remember losing brightness suddenly, with its intermittent return once the colour problems started. So I sort of suspect something may still be in need of service.

I only need to confirm the expected behaviour of the brightness knob on the front controls to decide whether my monitor might still need work or not.

[famiac]

Hey Kamiboy,

Did you also have a board like this?



I'm having trouble removing it. I don't want to use too much force.

Also, the neck board seems attached to the flyback. Any way of detaching it?

[kamiboy]

I had two boards that looked like those plugged into the chassis, and they came off easily. Looks like yours are soldered into place though, better just change the caps with it inserted.

As for the flyback, you see the neckboard is part of it, so there is no point in trying to detach it. Rather detach the neckboard from the tube and remove the chassis and it together.

To remove the neckboard solder off the metallic shield, then push in the three plastic tabs sticking out of the board and pull the board off gently.

[famiac]

Yeah i was able to remove the neckboard. Just wasn't sure if it was permanently attached to the flyback or not.

One of my boards came off, but the one in the photo is stubborn.

Ok. Looks like i'll be removing those caps in place...

[famiac]

Is it a good idea to replace the capacitors with aluminum polymer caps?

More generally, should i go for low ESR/low impedance caps?

[kamiboy]

Polymer caps are the best. But they cost a lot more and you cannot get them at the higher voltage ratings. Personally I just go with high temprature (105C) and long life (>=5000 hours) electrolytic capacitors.

As for low ESR, I've attempted to investigate this, but in order to fully understand the question I needed a deeper understanding of electronics. My takeaway was that for equipment of this vintage low ESR cannot do any harm. Not sure about benefits either, but if I have a choice I usually go for low ESR versions.

[famiac]

Cool. That's what i was thinking.

What i gathered from what i've read is that high ESR capacitors dissipate more heat and don't perform well with high frequency signals. Since we're not doing any pro-audio stuff here, i think ESR shouldn't have to be too low. However, when considering the power supply, low ESR and low impedance are helpful attributes that increase efficiency and lifespan of the device.

Man, i can't wait to take that analog electronics course...

[kamiboy]

You are prolly right about the power supply, but I think going with high temp long life caps will already cover your bases beyond necessity.

The only place where paying attention to ESR might be beneficial is the caps in the audio circuit. But I have a feeling the so called difference that low ESR caps make according to audiophiles is all placebo effect.

[famiac]

Agreed. Humans can't hear anything above 22kHz (even that's a stretch. Normal people can't do above 20kHz).

Anyway, I digress. Good thread Kamiboy. I'll be posting my CZ-605D cap sheet soon.

[kamiboy]

By the way, as it turned out my monitor didn't really need to be recapped. Visually all the capacitors looked fine and testing a few of them upon removal revealed that they were all prefectly healthy. My monitor's problems were all due to cold solder joints on the neckboard, prolly acquired during the process of being shipped half way across the globe twice.

Why are you recapping your monitor? Preventative maintenance, or do you have actual capacitor issues?

[famiac]

Coil whine + preventative maintenance