The NEW Build Your Own Arcade Controls
Main => Monitor/Video Forum => Topic started by: MiteWiseacre on April 15, 2019, 11:42:30 pm
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Hi, I have decased my Sony KV 27fs120, discharged and built a frame out of angle iron stock which is bolted to the television ear mounts. I am nervous about powering it up after reading some vague comments saying those ears that the grounds are attached to are hot when the tv is powered on. This seems unlikely to me, should have have used wood? Is the entire frame really going to be energized?
Thanks for your help.
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They used metal frames in arcade machine
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I read that arcade monitors use some kind of transformer to make the frame safe, anything further on this?
Edit: I tried powering it up and nothing. Doesn’t even make a sound. I’m afraid I killed it somehow. Is there a main fuse or anything simple I can try to bring her back to life?
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I read that arcade monitors use some kind of transformer to make the frame safe, anything further on this?
Edit: I tried powering it up and nothing. Doesn’t even make a sound. I’m afraid I killed it somehow. Is there a main fuse or anything simple I can try to bring her back to life?
Some montior used transformer and other do not ,
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What are you trying to do?
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Building a MAME cab, wanted to get the width of the television down so the cab would fit through doorways. So I decased it and made a frame for it. Really tried not to mess with any internals as I worked on it. Flipped it back up and attempted to power it up but it is unresponsive
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Building a MAME cab, wanted to get the width of the television down so the cab would fit through doorways. So I decased it and made a frame for it. Really tried not to mess with any internals as I worked on it. Flipped it back up and attempted to power it up but it is unresponsive
First thing to do would be check your mains supply to it with a multi meter if you get no response at all from it.
If thats ok then I would be looking at on board fuses.
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I broke the control board it seems :hissy:
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I broke the control board it seems :hissy:
What you do to it!?
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I think when I had it screen down I picked it up out of the front plastic to set on a blanket, the main board likes to slide ahead out of its tray...
PSA - find a way to secure the board or get someone to help you, you might break something
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You actually snapped it you mean?
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Yah there’s a crack across it near the power button, I’m trying to find a replacement now. Found one for a 32 inch that’s similar but only one plug instead of two, hopefully the leads match up
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Damnn yeah thats pretty catastrophic!
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I read that arcade monitors use some kind of transformer to make the frame safe, anything further on this?
While isolation transformers do provide a certain degree of safety, older arcade monitors used a regulator chip to make the high voltage power supply used to make the 20 some odd kilovolts of power used to drive the tube... an isolation transformer was used to isolate the AC mains coming in becasue one half of the incoming power (the neutral) is tied to ground. this does not work with this type of supply. the regulator backfeeds into the "ground" and kills the operator since it's not supposed to be connected to ground... effectively making the chassis HOT with high voltage. hopefully the chassis blows up somewhere and kills itself before the operator has a chance to touch anything metal. isolating the chassis still makes it HOT, just not in respect to ground...making it (more) okay to touch.
newer monitors/tv's use what's called a "switchmode" power supply. these have dedicated electronic power supplies that are used to power the various power rails needed in a monitor. these are already electrically isolated from the mains supply and tied to chassis ground already, and do not require isolation.
if a TV/monitor was made in the last 30 years, it will have this type of supply. and the isolation transformer should probably be removed to eliminate them a source of issues later. arcade monitors only used the old regulator style for simplicity and cost to produce and eventually swapped to switched mode supply in the mid 90's (most likely becasue the regulators went end of life and weren't available as new parts anymore.)
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Look up you local classified ad paper or sites. I found 4 KV 27FS120 for free here.
As a side note I also did remove one and made a frame for the cabinet but I used wood it works fine and with 2X4 it fit flush with the tube.
https://imgur.com/M53bwbt (https://imgur.com/M53bwbt)
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Thanks for the info guys!
Yah I saw a couple more identical Sony ‘s in the classifieds, can probably scoop another for $20
Such a shame though
These are less than 20yrs old so my frame sounds fairly safe.
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Just an update/conclusion on this thread.
I attempted to soldier the broken control board, after doing so the TV powered on but kinda went crazy (be careful decasing these because the main board likes to slip out)
Found another kv27 f120 took it apart and swapped it into my metal frame, being more aware of how the process goes and what to watch out for. I suppose it was a happy accident ruining my last set because the picture and geometry on this one is way better!
At the end of the day, my all metal frame has not fried me yet. The TV was made in 2004 so I’m sure it’s much safer than older models. I wouldn’t state definitively that it is safe but it does seem to be relatively so.
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I read that arcade monitors use some kind of transformer to make the frame safe, anything further on this?
While isolation transformers do provide a certain degree of safety, older arcade monitors used a regulator chip to make the high voltage power supply used to make the 20 some odd kilovolts of power used to drive the tube... an isolation transformer was used to isolate the AC mains coming in becasue one half of the incoming power (the neutral) is tied to ground. this does not work with this type of supply. the regulator backfeeds into the "ground" and kills the operator since it's not supposed to be connected to ground... effectively making the chassis HOT with high voltage. hopefully the chassis blows up somewhere and kills itself before the operator has a chance to touch anything metal. isolating the chassis still makes it HOT, just not in respect to ground...making it (more) okay to touch.
newer monitors/tv's use what's called a "switchmode" power supply. these have dedicated electronic power supplies that are used to power the various power rails needed in a monitor. these are already electrically isolated from the mains supply and tied to chassis ground already, and do not require isolation.
if a TV/monitor was made in the last 30 years, it will have this type of supply. and the isolation transformer should probably be removed to eliminate them a source of issues later. arcade monitors only used the old regulator style for simplicity and cost to produce and eventually swapped to switched mode supply in the mid 90's (most likely becasue the regulators went end of life and weren't available as new parts anymore.)
I'm a bit confused reading this thread, Shawn are you saying that isolation transformers are not a good idea in general or just in this case, my cabinet is a generic jamma cab and it has what I believe to be a Hantarex MTC 9000 monitor 19" or 20" I think, it runs from a 128vac Isolation transformer and 240vac for the degaussing coil, the gameboard psu is a powermaster x II (which I think is a switched mode psu) with the usual 5v 12v and -5v, I was actually going to remove my monitor as I had interference on screen and a member on here advised me to connect thr FG to GND on the psu and it has cured the interference everytyhing seems fine now.
Just checking I am safe to continue using the monitor this way with the isolation transformer etc?
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I'm a bit confused reading this thread, Shawn are you saying that isolation transformers are not a good idea in general or just in this case
whether it's required or not is determined by the type of power supply in the monitor. while it does provide some safety to the service tech in some specific circumstances... it's not particularly required for safety or anything.
TL;DR :
if the monitor has a regulated power supply, then YES you require the isolation transformer.
if the monitor has an SMPS power supply, then NO it does not require an isolation transformer.
I think, it runs from a 128vac Isolation transformer and 240vac for the degaussing coil
occasionally overseas cabinets made in japan (where the voltage is 110 volts) will use a standard 110 volt monitor with a stepdown transformer (240v input to 110v output) where a cabinet is sold into a country where the voltage is 240v. this standardizes parts. in cases such as these, you would have to retain the step down transformer if the monitor is regulated, (since the stepdown transformer also acts as isolation from the mains...) but could be omitted it if the monitor has been replaced and contains an SMPS powered monitor...since the SMPS can deal with voltages typically from 90 all the way up to to 250 volts.
TL;DR:
if the monitor has a regulated power supply, then YES you require the stepdown transformer.
if the monitor has an SMPS power supply, then NO it does not require the stepdown transformer.
you can retain the isolation transformer even with an SMPS powered monitor. just be aware that the isolation transformer has a limited output and may cause issue if the monitor connected to it has been changed in the past to a different unit and is close to or exceeds the safe output current carrying capability of the transformer. (transformer would run hot and possibly fail)
and yes, the hantarex 9000 requires isolation.