Monitor went pop! Hitachi 29" GMK-29FSN

[jwmii2]

Well i was restoring a neo candy 29 (my second one) and i was playing with the video settings. The monitor is a 29" hitachi dual mode (15 & 24hz). I had a multi game board inside the machine to test out some stuff and it supports 15hz, 24hz and vga 31hz. I was wanting to see if 24hz (ega) mode looked any sharper than 15hz (cga). So i changed the setting on the multigame board and the screen got all garbled up as expected. So then i changed the monitor to 24hz mode and everything was ok, the only thing is the image was kinda small in the center of the screen. I didn't think i could stretch the image out enough so i decided to go back to 15hz (cga) mode. I changed the setting on the multigame board and then all in the sudden the screen went blank and i heard a small pop. Ever since then i haven't been able to get it to show an image at all on either 15hz or 24hz modes. I also tried switching settings on the game board to see if maybe i could get it to display anything on 24hz mode but it doesn't show anything. I can hear a small pulsing behind the monitor like its trying to turn on, however i'm not sure that sound hasn't always been there, so i'm not too sure what to do. Does anyone have any suggestions on what the problem may be? I'm pretty good with electronics (cept in this case, heh) so i can possibly fix it if someone can point me in the right direction. I also checked the 2 fuses i could see on the monitor pcb just under the monitor and they both look fine, however there may be more fuses i havent been able to spot. Anyhow if i'm not able to fix it i may just take it to a tv repairman and see if they can do anything. but in the meantime any help is much appreciated. Thanks

[northerngames]

possible it ruined the main IC chip.

feeding a 15K monitor 25K or vice versa can damage some monitors if they dont have the preventive goodies on to save it from harm when being feed the wrong display type.

[grantspain]

sounds like you blew the horizontal output transistor

[jwmii2]

How hard is that to fix or replace?I may be able to do it myself if i knew what to look for. Any additional info is appreciated.

[grantspain]

well i am trying to work out if you have a toei or nanao chassis,the job itself is easy to do but you would have to remove the monitor chassis to do the job and of course that involves discharging the tube
unless i know the exact chassis then i cannot say where you can find the HOT,normally its either clipped or bolted to the heat plate the surrounds the flyback transformer and would have a number like 2sc2354 or bu508

have you worked on monitors before?

[jwmii2]

I have not worked on a monitor before, but i do know how to discharge it, and am confident i can discharge it without getting hurt. My only worry is that i don't know where exactly this component is. Also i have another question the switch to change resolutions is 15/24hz but it is a pushbutton switch, which position is 15hz, in or out?

[grantspain]

i can inform you of all if you can supply some good photos of the chassis,i don't want to guess the chassis being used and its important to note different countries used different monitors,for instance you can find either a wells gardner u5000,hantarex polo 1 dual sync or a nanao ms8-fan in a sega daytona

normally the frequency switching is done via a jumper plug on the chassis itself or it may be auto switching

[jwmii2]

Well theres a button to push to change the resolution. Either in or out, which i'm not sure of at this point, i just don't want to fix it and have the same problem again, is my main concern. I just find it odd that it accepted the 24hz signal in 15hz mode but then when the monitor was in 24hz mode changing the signal to 15hz evidentially blew something.

[jwmii2]

So you want me to remove the pcb from the monitor and take pictures of it, or leave it in the cab and take a pic? Just checking.

[grantspain]

you can leave it in the cab,just get some good all round pics

[jwmii2]

Ok great i will take some pics here shortly, i just need to charge the battery in the digicam. I'll have some pics within an hour, really sorry for he delay, i had no idea the battery was dead :/

[jwmii2]

Also wheres a good place to get a HOT? I was checking billabs last night and it says the site is closed until the end of the year, so are there any other places to obtain them? Thanks

[grantspain]

HOT=horizontal output transistor
all you need to do is google the number on the transistor,ebay is always good
you do need to prove it is the transistor using a multimeter,i suggested it as it is the most likely thing to have gone faulty

[jwmii2]

Ok no problem. Do you have any tips on testing the HOT with a digital multimeter? Its been awhile since i've tested a transistor.

[grantspain]

in circuit meter from the metal heat sink the transistor is bolted to the centre pin of the transistor using ohms or diode test-if it is short then is is certainly knackered

[jwmii2]

Ok heres the pics you requested.

[grantspain]

i can't see the hot on any of your photos,it is a large transistor that will be near the flyback transformer
i did notice one thing though,if you look at the last photo you will see a large capacitor that looks like it needs changing

[jwmii2]

Which one? I can see about a half dozen decent size caps in the last pic. Thanks

[jwmii2]

Ok lets try this again, i got a few different angles so hopefully you can see abit more.

[jwmii2]

One other question would the HOT keep the monitor from turning on at all? I mean i don't get any sort of picture what-so-ever, but there is a slight pulsing noise if i listen behind the monitor. I just want to double check.

[jwmii2]

Ok just one more question. I've been browsing the forums in search of answers so i keep coming up with different possibilities. Anyhow i do know this monitor didn't have any issues displaying vga (31hz) signal as my multi-game board boots up in vga mode and then changes resolutions to 15hz mode once windows 2000 is loaded. What happens is i can see one half of the screen on the right hands side and the other half on the left hand side followed by a big black verticle bar down the very middle. As soon as it loads the frontend it changes resolution to 15hz and then everything is displayed properly. I've also had this board in my other cab for quite sometime and it seemed to work ok the exact same way. I'm just wondering if its because the monitor was on 24hz mode and the game board was on 15hz mode as to what caused this issue, because 31hz mode didn't seem to have any adverse side effects other than the split screen issue. What do you think? Thanks once agian for the time you've put into this thread

[grantspain]

giving this 31khz is what killed the hot mate,this is a dual sync chassis 15/24 only

the hot short will normally give you a pulsing or chirping noise
the hot must be well hidden in your photos as i cannot see it

[jwmii2]

But when it boots up in the bios screen and loading windows 2000 screen it seems to look ok just shifted is all, i wonder if maybe its operating at 15hz in the bios screen and windows boot screen as well?

[grantspain]

so are you saying this monitor is working now?
if you give a 15khz monitor a 31khz signal then you will get 2 pics,if you mess with the frequency too much you will fry the hot

[jwmii2]

No its not working now, i'm saying on my other neo candy 29 with the same kind of monitor in it and this unit thats not working right now used to be fine when it was booting up the multi-game board. So pretty much it was the 15hz signal while it was in 24hz mode that did the damage? Or at least thats what i'm assuming anyhow, if so that makes sense. Just checking. Thanks

[grantspain]

well i guess your next step is to get the chassis out of the cab so you can id the hot and check it

[jwmii2]

Ok well hopefully i can get around to this today. As soon as i get the chassis out i'll post some more pics of it so we can identify the HOT. Thanks again for your help.

[grantspain]

well the hot will be easy to id as it will be a 2sc xxxx and when you google the number  it will come up as a horizontal deflection transistor

[jwmii2]

Yeah we found the hot yesterday and a local tv repair shop is getting a replacement. He sais they have ones on hand that would work but in this case its probably best to get an exact replacement instead of using another one, so hopefully it'll be here by the end of the week and i can get back to enjoying and restoring my cab

[grantspain]

Yeah we found the hot yesterday and a local tv repair shop is getting a replacement. He sais they have ones on hand that would work but in this case its probably best to get an exact replacement instead of using another one, so hopefully it'll be here by the end of the week and i can get back to enjoying and restoring my cab

Well i hope it is that which is at fault and not something else

[jwmii2]

Yeah we are pretty sure, he came over to the house, helped me take the monitor out, discharged the monitor for me(didn't need it tho) and took the chassis back to the shop. Hes going to replace it and a few caps, so hopefully by the end of the week i'll be back in business. I figured i'd just let him do it as he came over and helped me take it out and did some testing on it to be sure. So anyhow i'll let you know how it goes.

[Ummon]

You're supposed to change those things when the power is off. Of course, it helps to understand how scanrates work. Hehehehe, it's not just a, 'oh, well, let's see how this works', kind of thing, like can often be the case with mechanical stuff.

[jwmii2]

Well i figured it would just show up distorted, not blow a component. Guess i learned the hard way, heh.