Shorted tube arcade monitor ? - Page 1
Forum section: electronics / repair

author: decoder_82
author_rank: Regular Contributor
timestamp: April 18, 2022, 09:56:14 am
content: I am trying to repair a Taito CM-R14 arcade monitor.Initially the monitor had a blown fuse. I replaced the fuse. When power is on, a very loud noise comes from the tube and arcs appear inside the tube.Here is a video showing the issuehttps://imgur.com/a/ZC3t4OFAnyone has seen a similar issue ? does it mean there is a short in the tube?

author: inse
author_rank: Super Contributor
timestamp: April 18, 2022, 10:45:21 am
content: Wow, never seen such fireworks inside a tube.Are you sure the tube is still under vacuum?Pull off the PCB and check the connector and neck for cracks or damage.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 18, 2022, 11:01:22 am
content: Are you sure the voltages applied to the grids are not excessive? If there's HV leak to some of the grids, the sparks could happen.If there were mechanical impacts or vibration, there is a possibility a grid or element got displaced and is shorting others. In this case, the tube is toast, unfortunately.Good luck!

author: decoder_82
author_rank: Regular Contributor
timestamp: April 18, 2022, 11:04:30 am
content: I did not notice it directly but you are right, there is no more vacuum inside the tube.After careful inspection there is a hole in the neck of the tube. See pictures.It means there is no way to repair it. The only option would be to find another tube (which will not be easy)

author: CaptDon
author_rank: Super Contributor
timestamp: April 18, 2022, 01:18:03 pm
content: Very sad, It takes unreasonable force to snap that nipple off. Looks like someone got heavy handed with the neck board and rocked it or cocked it as to great an angle!!! New C.R.T. time!! If the yolk is glued to the tube you may have to find an exact model replacement. Fortunately most yolks were removable.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 18, 2022, 02:57:41 pm
content: To remove the yoke, you can usually put a current-limited power supply (1 or 2A should be enough) and, as it warms up, it melts the glue just enough to remove it.

author: decoder_82
author_rank: Regular Contributor
timestamp: April 18, 2022, 03:43:33 pm
content: Actually the yoke was quite easy to remove. Now I have to find a compatible tube. Not sure how to determine replacement that would be compatible.

author: inse
author_rank: Super Contributor
timestamp: April 19, 2022, 02:22:33 am
content: Back in the TV workshop days, a CRT swap was a very rare occasion.You would need a pattern generator an an idea how to set the convergence rings.All the best for your restoration project.

author: decoder_82
author_rank: Regular Contributor
timestamp: April 19, 2022, 05:00:17 am
content: The best would be to find a tube with the yoke. But not sure how easy it will be. If I can find another Hitachi compatible tube, then yes purity adjustment will be fun :-)

author: james_s
author_rank: Super Contributor
timestamp: April 19, 2022, 06:51:04 am
content: It's quite common for those exhaust pips to get broken off, they are actually fairly fragile and the neck PCB provides some leverage. These are open frame monitors so with some cabinet designs it's easy for something to hit the board and break it off.I have done lots of tube swaps with arcade monitors using old TV tubes. Be sure to keep the yoke with the chassis, they are matched and in most cases the TV yoke will NOT work properly with the arcade chassis but you can measure the inductance of the windings to see if it's close if you want, the horizontal is the critical one. Aligning the yoke on the new tube is the hardest part of the project but it usually can be done. I have found that usually if the tube physically fits and has the same diameter neck it will almost always work. You will need a test signal source that can display solid red, blue and green screens to set the purity and a white grid pattern to set the convergence.

author: decoder_82
author_rank: Regular Contributor
timestamp: April 19, 2022, 09:51:06 am
content: Yes no problem I have a pattern generator so making the purity and convergence adjustments will be OK.For the tube, besides shape and size, is there anything I should consider ? Are the pins on the tube neck always in the same arrangement ?Can I use a JVC tube instead of the original Hitachi ?

author: GLouie
author_rank: Regular Contributor
timestamp: April 19, 2022, 05:05:41 pm
content: This may be heresy, but when my arcade CRT dies, I think I'm going to look at a video signal converter and use a modern LCD display.

author: decoder_82
author_rank: Regular Contributor
timestamp: April 19, 2022, 06:09:12 pm
content: Yes that's an option but in this case I would like to keep a CRT monitor on it if possible

author: BrokenYugo
author_rank: Super Contributor
timestamp: April 19, 2022, 06:15:43 pm
content: Quote from: GLouie on April 19, 2022, 05:05:41 pmYou'll probably regret that if you have much of an eye for input lag, at least based on the one set of conversions I've played.

author: james_s
author_rank: Super Contributor
timestamp: April 19, 2022, 07:57:25 pm
content: Quote from: decoder_82 on April 19, 2022, 09:51:06 amYes they are almost always the same pinout, I have never personally encountered one that physically plugged in but wouldn't work.

author: james_s
author_rank: Super Contributor
timestamp: April 19, 2022, 07:58:05 pm
content: Quote from: GLouie on April 19, 2022, 05:05:41 pmLCD monitors look like shit in vintage arcade games, you may as well just play on a MAME cabinet if you're going to take that route.

author: decoder_82
author_rank: Regular Contributor
timestamp: May 06, 2022, 12:37:54 pm
content: I finally managed to fix it. I used this website to find suitable tube:https://tubular.atomized.org/tube/370ECB22. I had a 370EGB22 from a damaged Commodore 1802. As suggested above I kept the yoke from the broken tube and it worked nicely.

author: strawberry
author_rank: Super Contributor
timestamp: May 06, 2022, 04:42:49 pm
content: there are services available

author: james_s
author_rank: Super Contributor
timestamp: May 06, 2022, 04:58:53 pm
content: That's the Early Television Museum in Ohio, they got the equipment from Hawkeye which was the last operating CRT rebuilding plant in the USA and later when RACS in France shut down they got some of the equipment from there. AFAIK they are now the last rebuilding operation in the world, it's nice to see they got up and running.

author: BrokenYugo
author_rank: Super Contributor
timestamp: May 06, 2022, 07:02:13 pm
content: AFAIK while there are a couple projects in the works to reboot the rebuild industry, with at least the Early Television Museum one proving they can get results, currently nobody is offering rebuild services for any cathode ray tubes.It would be my assumption the economics just aren't there to do it on a realistic scale, it would probably have to run as a low volume job shop, with prices to match. This is after all skilled labor on specialized machinery, using parts that are presumably NOS or short order new production at high prices. It'd probably cost north of a kilobuck to have a tube rebuilt under such conditions and break even, not many vintage TVs worth that much, and the handful of arcade people running CRT monitor daily still have a fairly large pile of cheap/free consumer TVs to salvage tubes from.

author: strawberry
author_rank: Super Contributor
timestamp: May 07, 2022, 06:35:21 am
content: there are many people making quality vacuum tubes from scratchhttps://www.youtube.com/c/daliborfarny/videos''reboot the rebuild industry'' small workshops are not great promoting and demand is not great either to justify

author: decoder_82
author_rank: Regular Contributor
timestamp: May 07, 2022, 12:23:16 pm
content: Quote from: strawberry on May 06, 2022, 04:42:49 pmWow I did not know there were still people performing those kind of services. Quite impressive work !

author: PKTKS
author_rank: Super Contributor
timestamp: May 07, 2022, 12:51:54 pm
content: as said is quite common to have these parts broken...You need a new tube only... you can transfer the YOKE in full..You will need a proper convergence adjustment signal generator...Got one very early 80s and still have it working just fine...Made a half dozen CRT replacements with it...INDISPENSABLE TOOLPaul

author: james_s
author_rank: Super Contributor
timestamp: May 07, 2022, 05:33:25 pm
content: Quote from: BrokenYugo on May 06, 2022, 07:02:13 pmEven if it cost $2k to get a 19" color CRT for one of my vector games rebuilt I would pay it, $1k I wouldn't even blink. The Wells-Gardner K6100 monitors used an oddball RCA 19VLUP22 tube with a 100 degree deflection angle and a weird socket and they are very hard to find, a working used tube with some burn will fetch $400+. There is no substitute for a CRT vector monitor. I have a few TVs in storage for my other games that use a more common 90 degree tube but even those are drying up and the earlier TVs from the 70s-80s are themselves becoming collectors items.