Hitachi CM721F issue.

[stevo1210]

I recently got a 19" Hitachi CM721F CRT monitor for free. It's very good as the picture quality is crisp and clear.
Except occasionally for some strange reason during operation, it clicks and the screen expands like a baloon and then shrinks back to normal and all is well again.
Why is this happening? and how can I fix it?

Thanks.

[stevo1210]

Re: Hitachi CM721F issue.

oops. should have put this thread into the computer displays section as I'm talking about a pc monitor.

[kc8adu]

Re: Hitachi CM721F issue.

sounds like a bad flyback.
does it make clicking or snapping sounds when you turn it on and off?
had a ton of panasonic and the veiwsonic rebadges with the exact same issue.
its common in modern flybacks where there is a breakdown in the multiplier.

[Wizard]

Re: Hitachi CM721F issue.

Click often sounded like especially when there is high voltage arcing. Dump it.

Fly is big problem finding one that is GOOD quality.

Cheers, Wizard

[stevo1210]

Re: Hitachi CM721F issue.

It doesn't make any clicking noises when I turn it on and off.... in fact, it's the quietest monitor I have in terms of start up noises.
The click noise, accompanied by the image expansion only occurs when in operation at occasional times.
If the flyback has issues, is it going to be lethal if something does go wrong some time down the line?

thanks

[Wizard]

Re: Hitachi CM721F issue.

Usually terminal once clicks with the pic expansions happens, eventually. More components die and leave monitor useless.

[weirdlookinguy]

Re: Hitachi CM721F issue.

What year was it made? This model had a 5 year warranty from Hitachi. If it's still valid, it would be interesting to see what they would do to fix it since the days of CRT are long gone.

[i4004]

Re: Hitachi CM721F issue.

>If the flyback has issues, is it going to be lethal if something does go wrong some time down the line?

lethal for it, not for you...hehe...

you could try opening it and looking if hr diemen makes substitute trafo....
there should be some number on it that identify it.
how acceptable the price will be to you, i cannot say.

oh yeah, whatever you do, do it while it's unplugged.
if you wanna swap the trafo, there's a special prodecure to bleed the possible remaining voltage...

[Wizard]

Re: Hitachi CM721F issue.

Yes to everything, HR diemen is excellent third-party transformers. Worth looking into, need the transformer #. Also you should able to find NOS transformer on ebay and everything else.

Cheers, Wizard

[stevo1210]

Re: Hitachi CM721F issue.

Hmm.... sounds too expensive to fix by the sounds of it. What are some good crt displays out there these days? I saw some Dell crts with trinitron tubes for $15 at the e wadte place.... dunno if they are any good, but they are made in Japan so I think their quality should be ok?

[Wizard]

Re: Hitachi CM721F issue.

Unfortunely the CRT is worthless these days because trinitron CRT is already over 3-4 years old by now and now have some wear on them. The last production of brand name CRT was 2 to 3 years ago.

Point yourself to used LCD monitors instead. Pay bit more.

Cheers, Wizard

[momaka]

Re: Hitachi CM721F issue.

Unfortunely the CRT is worthless these days because trinitron CRT is already over 3-4 years old by now and now have some wear on them.

I don't think that would matter much, of course unless you're a graphic designer who needs a monitor with accurate colors. Most CRTs have excellent colors even if they are slightly older.

@ Stevo: I've got an old 1997 Dell (Sony) Trinitron D1025HTX 17" from craigslist 2 years ago for free. Still has much better colors than the family Dell PC (with LCD) in my house.
Usually, those Dell CRTs don't go above 1280x960, but their refresh rates are decent enough. IIRC, mine can go 75Hz @ 1280x960 - enough to eliminate that blinking at 60Hz.
Inside when I opened mine to clean the dust bunnies, it looked very solid (well I guess like any other CRT) + it has Nichicon/Rubycon/UCC caps.

Also, try playing around with the refresh rates and different resolutions for your 19" Hitachi. See if you have the same problem at the lowest resolution with the lowest refresh rate.

[stevo1210]

Re: Hitachi CM721F issue.

Just a question, but can Sony/Dell Trinitron based displays have bad flyback systems? I'm not sure if that's the case for Sony CRT TVs, because I have a Sony 51cm TV from 1989 still in operation and it ain't got a bad flyback at all... it just works so well. All of the TVs I have here are Sony CRTs [1x 68cm WEGA (1999), 1x Sony 68cm CRT (1994), 1x 51cm Sony CRT TV from 1989], albeit for one LG 106cm (42") Plasma TV we got in 2004.

Oh and I had a look at the sticker behind the Hitachi monitor.... apparently it's made by Compal systems in China and it was made in 2002, so it's well out of it's 5 year warranty now.

Thanks.

[Wizard]

Re: Hitachi CM721F issue.

To give you a data point, I had a NEC 4fgx or something. It do that *loud* SNAP! once in a while even 3-5 times a day and pic goes out and come back like balloon puffed and let air out a bit to correct size. Eventually disposed of it. Bad fly or CRT.

It WAS awesome monitor and again was freebie.

Cheers, Wizard

[Krankshaft]

Re: Hitachi CM721F issue.

I had an old Sylvania 27" TV from the early 80s.

It had an arcing problem (I suspect now it was internally from the flyback but I didn't know that then) I replaced it in 03 and someone scooped it off the curb. There were minor firing lines in the picture but nothing too noticable.

It was a very nasty crackling noise.

[stevo1210]

Re: Hitachi CM721F issue.

Point yourself to used LCD monitors instead. Pay bit more.

Ok, I listened to what you wrote above and did exactly that today. I got myself a used LCD monitor. My new monitor is a CMV 15" LCD for $55 or so and it's probably the clearest LCD I've bought. The colours are fantastic and the brightness is perfect.
Guess the CRT is now going to the donations bin very soon so I can clear up some space.

Thanks.

[Wizard]

Re: Hitachi CM721F issue.

Finally. LCD 15" Eh. Better than what you had. LCD 17" should be starting to be cheap on the used market. Funny, I never had 15" or 17" LCD monitor on my dime for new one because LCDs were horrible even 4 years ago even used except notebooks. But I did pick up few used 17" and repaired them, and a new 19" LCD. That was just 2 years ago, march 2007 on my money that replaced dimming samsung 2003 17" flat CRT. CRT monitor was again my coin, brand new since I demand BEST from a monitor possible within reason budget.

Also make a once over inspection the monitor for caps and solder joints.

Cheers, Wizard