Need help with Orion 13in Arcade Monitor Repair - Page 1
Forum section: electronics / repair

author: trad1984
author_rank: Contributor
timestamp: February 04, 2020, 03:32:06 am
content: Hello,I am trying to fix a 13in Orion CRT arcade monitor that stopped working. I removed the monitor from the cabinet and located a few burned up resistors and a transistor that I think is bad. I tried to look online, but couldn't find a schematic anywhere. I am having trouble identifying the burned resistors. Any help with identification or troubleshooting the board is appreciated. I attached a picture of the three burnt resistors I am trying to identify along with a picture of the area on the board where I removed them from. The two smaller resistors were side by side in the R503 and R504 spots on the board. The other larger resistor (10 k ohm?) was at the R502 spot. I checked all of the diodes and capacitors in the area and didn't find any problems, but the transistor I circled seemed to be bad.

author: james_s
author_rank: Super Contributor
timestamp: February 04, 2020, 05:50:04 am
content: The one resistor that is darkened is probably still reasonably close to the correct value so you can measure it. The really toasty ones are gonna be hard to identify without a schematic. Your options are pretty much either find someone with the same model monitor or one that's similar enough to have the same parts there, or reverse engineer enough of the circuit to figure out what those parts do and take a guess at reasonable values.

author: trad1984
author_rank: Contributor
timestamp: February 04, 2020, 05:57:07 am
content: That is what i was afraid of, unfortunately it is pretty rare. I think I figured out the larger one (1M Ohm). Any thoughts on what might have caused them to burn up in the first place?

author: james_s
author_rank: Super Contributor
timestamp: February 04, 2020, 06:11:39 am
content: Usually burned up resistors are caused by shorted semiconductors, look carefully for shorted transistors and diodes.

author: fzabkar
author_rank: Super Contributor
timestamp: February 04, 2020, 06:17:55 am
content: Could we see a photo of the whole chassis?Where does the 7-pin connector go?Can you identify any part numbers on the flyback transformer? The FBT can often identify the chassis. ISTR that Daewoo TVs sometimes used an Orion chassis, or vice versa.

author: trad1984
author_rank: Contributor
timestamp: February 04, 2020, 06:19:45 am
content: I did check all the diodes in the vicinity and they all checked to only allow flow in one direction. I'm not an expert, but i think the transistor that i circled in the photo is bad based off of the testing methods I found on YouTube. I will probably give replacing that a shot. I don't have a full chassis photo on me right now, but I will take one when I get back home tonight and post it.I will check on the fly-back transformer part numbers and the destination of the 7-pin tonight also.

author: trad1984
author_rank: Contributor
timestamp: February 04, 2020, 10:45:43 pm
content: I posted some additional photos below. To answer the questions from yesterday,1. I couldn't identify any info on the flyback transformer but I did take a picture of the monitor and neck board.2. I added a picture of the entire board as requested.3. The 7-pin connector goes to the monitor adjustment board (see picture).Thanks for all the info, you guys are awesome.

author: floobydust
author_rank: Super Contributor
timestamp: February 05, 2020, 12:08:15 am
content: CRT monitors have a model number, chassis number, CRT number, serial number, manufacturer's name.You'd have to find the chassis number for any luck in finding the schematic. That would be somewhere on the main board as a sticker or pcb silkscreen, check both sides. I can't see much from the fuzzy pics.Or search for the game's name i.e. Zaxxon to find the monitor's schematic in that service manual.Orion CRT sticker is M34JZT20X is I think 34cm CRT, not the monitor's model number.The 500 reference designators are likely the horizontal output section.You'll have to stare at the board and look for the root chassis number.

author: trad1984
author_rank: Contributor
timestamp: February 05, 2020, 12:40:19 am
content: Ok thanks, I'll take another look when I get back home. Any clue what the format would be? The only markings I could find on the chassis is a serial number that is on the side of the silver shield around the flyback transformer. It is shown in one of the pictures I posted and I believe it is 98074607.

author: trad1984
author_rank: Contributor
timestamp: February 05, 2020, 02:08:56 am
content: Upon further investigation here are the numbers i found:On the CRT:37452091M34JZT20X98074607On the chassis (near the flyback transformer):VGA 37211460On the chassis (near the power input):KTV-253297013712I will see if I can find anything else. I also did a search for the crt model number and found a citrx schematic that appears to be pretty close, but not exactly my chassis.

author: james_s
author_rank: Super Contributor
timestamp: February 05, 2020, 02:21:54 am
content: The number on the CRT itself is not gonna be much use, it's extremely likely that the same tube was used in other displays, is that a VGA arcade monitor?

author: trad1984
author_rank: Contributor
timestamp: February 05, 2020, 02:24:38 am
content: Yes, I think it is a VGA monitor. I am a newbie, but the game does have a VGA cable output.

author: james_s
author_rank: Super Contributor
timestamp: February 05, 2020, 02:27:36 am
content: I wondered about that due to the "VGA" on the label, I'd guess that same tube got used in numerous VGA PC monitors, which does not really help you here. Most arcade monitors were CGA resolution.

author: trad1984
author_rank: Contributor
timestamp: February 05, 2020, 03:00:13 am
content: Yeah, unfortunately I think I might be out of luck. I haven't been able to find anything on this monitor anywhere. I may have to break down and convert it to an LCD somehow, but that would be a first for me.

author: PKTKS
author_rank: Super Contributor
timestamp: February 05, 2020, 09:52:42 am
content: Quote from: trad1984 on February 05, 2020, 03:00:13 amPlease this is a WILD GUESS based solely upon experiencein doing things like this wo schemaGuessing by position near the transformer I wouldsay that this parts are a secondary regulator takenfrom the mains flyback going elsewhere.It may have a short which caused this burnt...A zener or regulator likely near by...w a diode rectifieralso near by... all that seems burnt...Wild guessPaul

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 05, 2020, 01:28:14 pm
content: The grey printed tracks on the top silkscreen aren't that easy to follow...Can you also post a photo of the copper side, from the corner where your burnt components are and including FBT and vertical output IC (the one on the smaller heatsink).If the FBT isn't the cause of this I'm sure it can be repaired easily enough.The most obvious cause here would be someone having plugged the connector to the adjustment board incorrectly. (Shifted or flipped.)

author: Kilo Tango
author_rank: Regular Contributor
timestamp: February 05, 2020, 01:53:15 pm
content: Maybe check from resistor pads to ground to see if there are any shorts or heavy loads along those lines, that would explain why the resistors blew. Sometimes they used resistors as ( cheap ) fuses, in case of overload the resistor would blow and save cooking the board.Googling KT-2532 brings up a hit for the "Vintage Arcade Preservation Society" and it is possible that the chassis manufacturer is Kortek ( ? ). Maybe worth looking on here for info as well ?.https://forums.arcade-museum.com/showthread.php?t=337418Cheers Ken

author: Kilo Tango
author_rank: Regular Contributor
timestamp: February 05, 2020, 02:03:06 pm
content: In fact googling Kortek VGA monitor brings up plenty hits, including " Kortek Monitors Tips, Tricks and Cap kits " which might be a useful source of information. Guess they were commonly used in arcade machineshttps://forums.arcade-museum.com/showthread.php?t=157123Cheers Ken

author: james_s
author_rank: Super Contributor
timestamp: February 05, 2020, 06:33:37 pm
content: I would try posting on the VAPS forum or some other arcade forums with a picture of the monitor and see if anyone can identify it for you. This is obviously not a one-off design, there are others out there.

author: floobydust
author_rank: Super Contributor
timestamp: February 05, 2020, 06:50:44 pm
content: Can you look for more numbers, it should have a 14 (for the size 14"), like KT-1402 or KT-1403 kind of thing. It's not easy to find data on Korean CRT monitors.The CRT tube is made by Orion. The small transformer (line filter) is Kortek part KTV-2532.You might have to sketch out where some of the burnt parts connect to.Some Kortek service manuals:https://elektrotanya.com/showresult?what=kortek&kategoria=&kat2=all&page=0

author: fzabkar
author_rank: Super Contributor
timestamp: February 05, 2020, 07:39:53 pm
content: This circuit diagram looks promising:https://elektrotanya.com/kortek_telcovision_kt1403v_sch.jpg/download.html

author: trad1984
author_rank: Contributor
timestamp: February 06, 2020, 02:59:07 am
content: Thank you everyone for all of the information. I will take your advice and post this on one of the arcade forums as well. I added a few photos of the back side of the board (copper side) as requested. Unfortunately, I couldn't find any other numbers anywhere on the board.

author: trad1984
author_rank: Contributor
timestamp: February 06, 2020, 03:57:30 am
content: Ok, so I think I found it online finally. There is a picture here:https://www.worthpoint.com/worthopedia/merit-telco-monitor-chassis-board-139252646It looks just like my board and is titled: TelcoVision Type 51 VGA Chassis also labeled KT-1403V which would be a Kortec as suggested above. Now I will just have to see if I can find the manual.

author: fzabkar
author_rank: Super Contributor
timestamp: February 06, 2020, 04:57:58 am
content: Is the schematic I posted not good enough???

author: trad1984
author_rank: Contributor
timestamp: February 06, 2020, 05:11:42 am
content: Actually, yes it works perfectly sorry.Looks like:R502 is 1/2W 10K ohmR503 is 180K ohmR504 is 100K ohmAnd the transistor that i suspect to be bad is a C3198.You guys are amazing, even with the little amount of detail I was able to provide.

author: floobydust
author_rank: Super Contributor
timestamp: February 06, 2020, 05:33:44 am
content: From the KT-1403V schematic, I can't really see anything shorting that would cause those parts to burn up like that. It's weird R502 10k 1/2W is in series with 180k or 100k 1/4W so where did the overload come from? Q501, C503 see only 12V.I found a factoryparts listfor KT-1403V pg. 60

author: fzabkar
author_rank: Super Contributor
timestamp: February 06, 2020, 05:51:07 am
content: Quote from: floobydust on February 06, 2020, 05:33:44 amI was thinking the same thing. :-?

author: floobydust
author_rank: Super Contributor
timestamp: February 06, 2020, 06:03:58 am
content: It looks like an automatic brightness limiter/sub-contrast section, and the only time I have seen stuff like that burn up was the flyback transformer return winding pin 6 going open-circuit and the HV return then ended up being the next leg pin 8. I can't see the x-ray protection open-circuiting R404, D401 etc. allowing pin 6 up to high voltage, either of which would cook R502.I would check ohmeter readings on T402 pins 6-7, 7-8, 6-GND to see if there is continuity or what readings there are.

author: trad1984
author_rank: Contributor
timestamp: February 06, 2020, 06:39:32 am
content: Ok, thanks floobydust! I will check those pins when i get home and I will post the results of what I find. I am assuming for ground I can just use the metal portion of the chassis? For what it is worth I do think that G501 is bad (based off of the transistor testing procedure I found on YouTube).

author: Moshly
author_rank: Regular Contributor
timestamp: February 06, 2020, 07:13:12 am
content: If you end up needing a replacement flyback or a whole replacement chassis you could try contacting TNT Amusements.https://www.youtube.com/channel/UCyjs8rzlagt8XfWxdPQnVRw

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 06, 2020, 04:11:59 pm
content: I have to agree with floobydust, considering the high values of roast resistors and their positions this is starting to like a defective FBT.I would check D401, C425 before coming to that conclusion though.

author: trad1984
author_rank: Contributor
timestamp: February 06, 2020, 09:31:07 pm
content: So I checked the pins as suggested and I get good continuity between 6 and 7 and from 6 to ground, but not 7 to 8. Also, I checked d401 and it is good, but I am having trouble checking c425. C425 shows continuity, but I can see the charge and discharge on my multimeter for some reason.

author: james_s
author_rank: Super Contributor
timestamp: February 07, 2020, 01:00:00 am
content: Is that out of circuit? If so it sounds leaky. A capacitor should show a resistance that gradually decreases to open circuit if you test it with the Ohms range on a multimeter. If it plateaus and never goes infinite then that's leakage.

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 07, 2020, 02:43:07 am
content: Quote from: trad1984 on February 06, 2020, 09:31:07 pmOpen between 7 and 8, so floobydust was right.Don't bother with C425.In some casesyou can scratch away at the potting around the FBT pins and find the open winding just before the wire is soldered to the pin. More likely you'll waste your time though...

author: trad1984
author_rank: Contributor
timestamp: February 07, 2020, 03:09:54 am
content: Ok, so just to confirm, the Flyback Transformer is bad right? I've looked online for a replacement and it appears there are some out there, but most are shipping from somewhere overseas and are pretty expensive. I may just break down and do an LCD conversion or see if I can get a completely new chassis.

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 07, 2020, 08:52:06 pm
content: Yes, if there is no measurable resistance between pins 7 and 8 the transformer is defective.

author: james_s
author_rank: Super Contributor
timestamp: February 08, 2020, 03:15:38 am
content: Just make sure you are counting the pins correctly, sometimes there is a spot for a pin with no actual pin there that still gets counted. If you are positive that it's defective then I would cut in there and try to fix it, nothing to lose at that point. You should also try all the usual arcade parts sources and see if you can find a replacement. CRTs are no longer made and they're getting harder to find so it's increasingly worth spending the effort to repair monitors I would have written off a few years ago.

author: trad1984
author_rank: Contributor
timestamp: February 08, 2020, 05:16:27 am
content: I will verify again tonight that I have the right pins, as for the cutting into the flyback, I wouldn't know where to start.

author: shakalnokturn
author_rank: Super Contributor
timestamp: February 09, 2020, 12:05:37 am
content: Quote from: trad1984 on February 08, 2020, 05:16:27 amScratching delicately around pin 7 or 8 is a good place to start.

author: trad1984
author_rank: Contributor
timestamp: February 09, 2020, 06:01:54 pm
content: Are you talking about just the soldering on the green side or actually removing the flyback transformer and cleaning the pins.

author: floobydust
author_rank: Super Contributor
timestamp: February 09, 2020, 06:58:40 pm
content: I found confusion about the flyback's actual winding configuration. OP should double check what he's finding. Just tell us the ohmmeter readings between pins 5 thru 8.Kortek KV-1403V flyback KFS-61202 or KFS-61202a crosses toH.R. Diemen HR 46100but the winding schematic is different, showing taps instead of separate windings and possibly mixing up pin 8 with pin 6? HR 46100 used for KFS61202A/KT2003V DUGO, KORTEC VS20475T, TATUNG 19"/20"TELCO VGA.KT-1403NA also used the same flyback, that circuit includes that pin 5 is GND, and primary 1,2,3,4 daisy-chained and secondary 6,8,7 is also daisy-chained.So the KT-1403V schematic is a bit misleading for the flyback windings.I would double check you're using the right pinout, and the one winding 7-8 is truly open-circuit. There must be continuity between 6-8, 8-7 I think.To remove the transformer from the board. You'd need a good solder sucker or lots of solder wick. I don't think flyback transformer open-circuits are accessible, to do surgery.They are potted and the only place to fix a bad connection is at the underbelly at the pins, and that is too much for me.KT-1403V repair info symptomshas some faults he found.

author: james_s
author_rank: Super Contributor
timestamp: February 09, 2020, 07:25:36 pm
content: Also for what it's worth, in ~20 years of repairing CRT monitors of various types I have *never* seen an open circuit winding in a flyback. I'm sure it happens occasionally but it's not something I've ever seen. Normally the failures I see are shorted turns, occasionally faulty diodes in the HV secondary, faults in the focus/screen pot assembly and arcing due to cracks in the casing.

author: floobydust
author_rank: Super Contributor
timestamp: February 09, 2020, 07:38:22 pm
content: Somehow pin 8 went up to high voltage. This is my theory for OP's burned up parts.I would think the flyback was arcing inside and that can eventually cause an open-circuit after the fine wire copper melts. But ohmmeter readings would be high due to carbon tracking. OP did not mention the values he is measuring. I've never seen a flyback that could be repaired, as much as I dreamed I could fix them.

author: trad1984
author_rank: Contributor
timestamp: February 09, 2020, 09:15:30 pm
content: All, thank you very much for all the replies, you guys are awesome. I would love to provide the readings, but I'm not sure I know how to do more than check the continuity. Are you suggesting I apply power to theboard and take the voltage readings at the pins?

author: floobydust
author_rank: Super Contributor
timestamp: February 09, 2020, 09:39:03 pm
content: No, just take some ohmmeter readings at the flyback and write them down and post the measurements here. Just to double check. I don't have any of your numbers. It's normal to get over 200 ohms for some HV windings, in case you are only using the continuity-function on your multimeter.Open-circuit (megohms) between 8-7 does confirm the flyback is toast. Something like between pin 6-8, 8-7, pin 8-5, pin 7-5, 9-7, kind of thing. I would look at the flyback outside to see if any signs of melting on the case too. Sometimes an arc will melt a small spot as a giveaway that the transformer has failed.

author: trad1984
author_rank: Contributor
timestamp: February 10, 2020, 12:08:18 am
content: So I tried to measure the resistance between the pens, but I cant seem to get any other value except 0 regardless of the ohm setting I use. The only place I dont get 0 is where the display doesn't change at all (no continuity) and this happens with any combination that includes pin 8.

author: floobydust
author_rank: Super Contributor
timestamp: February 10, 2020, 01:27:22 am
content: Pin 8 winding must connect to either pin 7 and pin 6, so the flyback is bad. I haven't seen a replacement but it goes under a few different part numbers/makes. You could call/emailArcadeshopand see if they have one or any ideas.I would look at fitting an LCD monitor from an old laptop or get a monitor that fits. You take a laptop LCD panel (with known part number) and connect to matching "HDMI+DVI+VGA+Audio LCD Driver Monitor Converter Lvds Board" from eBay.

author: james_s
author_rank: Super Contributor
timestamp: February 10, 2020, 01:44:34 am
content: 0 means zero ohms, IE no resistance, or rather resistance below what the meter is capable of measuring. This is normal for high frequency transformers, many of the windings are only a few turns. Open circuit is whatever it displays with the probes not connected to anything, on most meters it's something like O.L.

author: trad1984
author_rank: Contributor
timestamp: February 10, 2020, 02:09:09 am
content: Ok, that makes sense. I tried a second meter and was getting around .7 ohms on all the ones that had continuity. I try the arcade shop and see if they have a replacement.