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Why is my cab blowing the plug fuse?

Printed From: ukVac.com
Category: Technical
Forum Name: Tech, Maintenance & Repairs
Forum Description: Need Help? Ask Here
URL: http://www.ukvac.com/forum/forum_posts.asp?TID=359337
Printed Date: 18 Aug 2017 at 2:23am


Topic: Why is my cab blowing the plug fuse?
Posted By: Flinnster
Subject: Why is my cab blowing the plug fuse?
Date Posted: 13 Aug 2017 at 12:19am
Oh dear. I have a jamma converted Dino King cab that's now blown the 5Amp fuse in the plug at the wall three times this weekend.

It had done it once before, when it had all the Dino King original internals in there, so I'd just put that down to it being the one that the op had used for years and put it down to age.

Soo... I did some tests to try and isolate the issue.

- First of all I removed the ISO transformer and monitor power from the incoming mains filter.
   Because I can hook up a couple of Dino King cabs next to eachother, I was able to run the video via VGA out to another fully working cab next to it. I spent a good while running jamma boards, MVS, PGM with just the switching power supply providing power to the coin door area + jamma edge and no issues at all with the fuse all day.

- Then I reversed the above, this time removing the switcher from the incoming mains, and just powering up the ISO transformer. Everything worked fine for a good few hours, switching on and off and no issue. Then the cab wouldn't switch back on, tested the fuse and yep it had gone.

So, the issue is related to the ISO transformer, the service panel with the degauss + power switch, or the monitor itself. Literally nothing else was in the cab when the fuse went.
Also it wasn't losing power while playing. It must be blowing the fuse when the power is switched off. Normally I power down the cabs by switching off the wall sockets.

I've checked resistance levels / continuity on all the cables + conections in the above stuff and it all seems similar to the other identical cabs I have. Any ideas? Cry

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Wanted: - PCBs: Rainbow Islands, Bomb Jack, Rolling Thunder
- Parts needed: Naomi non-swivel castor / wheel, coin mech metal clip for Dino King Door



Replies:
Posted By: bomjac
Date Posted: 13 Aug 2017 at 7:45am
Cold be inrush to the transformer. Basically a transformer can sometimes draw 10-20 times rated Amps on power up. So potentially a 150VA transformer can be up to 3000VA.

Try replacing the fuse with a slow-blow fuse.


Posted By: SUPERSPRINT
Date Posted: 13 Aug 2017 at 10:12am
Can you disconnect the monitor and try that?


Posted By: jengineer
Date Posted: 13 Aug 2017 at 10:13am
Unless I'm going crazy..., change the 5A fuse to a 13A fuse,

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ooooooh if I had the space (and the money) I'd have that...


Posted By: SUPERSPRINT
Date Posted: 13 Aug 2017 at 10:17am
Blowing fuses mean a short circuit somewhere and a considerable one. The issue will not go away until you find the short. Fitting a higher amp fuse could prolong the fault and cause more damage. The machine is desgined with 5amp protection, likely it only pulls 1 amp during use.


Posted By: bbz149
Date Posted: 13 Aug 2017 at 2:07pm
Originally posted by jengineer jengineer wrote:

Unless I'm going crazy..., change the 5A fuse to a 13A fuse,
if all fails there's always Tin Foil

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Posted By: Flinnster
Date Posted: 13 Aug 2017 at 6:31pm
Originally posted by SUPERSPRINT SUPERSPRINT wrote:

Can you disconnect the monitor and try that?


Yeah that's one test that I've not yet performed - just running the ISO on it's own connected to nothing (ie. disconnect monitor power). That would mean I'd have:

(MAINS WALL SOCKET)-->(MAINS FILTER)-->(ISO TRANSFORMER 230v side) / (ISO TRANSFORMER 150v side)--> ..nothing..


Would that put undue stress on the transformer though?
Of course the fuse only blows on either power down or power up (I can't tell which). During operation there don't seem to be any issues - I don't lose power suddenly while the cab is 'in use'. It's always just a case of switching back on and going 'oh, not working now' Ouch


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Wanted: - PCBs: Rainbow Islands, Bomb Jack, Rolling Thunder
- Parts needed: Naomi non-swivel castor / wheel, coin mech metal clip for Dino King Door


Posted By: smarty
Date Posted: 13 Aug 2017 at 6:46pm
Hi Dave, 

I'd think about bypassing the mains filter, they will have components inside that could fail, caps, resistors and inductors. When these fail they always seem to go short and blow fuses, I suspect this is the start of your going bad. I can't see an unloaded transformer making a fuse blow assuming it still happens in the scenario directly above my post.

Cheers, Mart.


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http://www.jumpnfire.com" rel="nofollow - jumpnfire.com

MOST WANTED CABS:


Posted By: bomjac
Date Posted: 13 Aug 2017 at 6:52pm
Quote When a transformer is first energized, a transient current up to 10 to 15 times larger than the rated transformer current can flow for several cycles. Toroidal transformers, using less copper for the same power handling, can have up to 60 times inrush to running current.
.

Google this sh*t if you don't believe me.



Posted By: SUPERSPRINT
Date Posted: 13 Aug 2017 at 6:54pm
So you change the fuse, turn it on and it works? Then when you go to turn it on again the fuse has blown?


Posted By: SUPERSPRINT
Date Posted: 13 Aug 2017 at 7:05pm
Could be something as simple as the on/off switch, off side shorted?


Posted By: smarty
Date Posted: 13 Aug 2017 at 7:33pm
Clearly not BS Bomjac but wouldn't we see this more often in our cabs if it was a likely culprit? I don't think I can ever remember this happening in the cabs I've owned over the last 20 years.

Originally posted by bomjac bomjac wrote:

Quote When a transformer is first energized, a transient current up to 10 to 15 times larger than the rated transformer current can flow for several cycles. Toroidal transformers, using less copper for the same power handling, can have up to 60 times inrush to running current.
.

Google this sh*t if you don't believe me.



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http://www.jumpnfire.com" rel="nofollow - jumpnfire.com

MOST WANTED CABS:


Posted By: Vamino
Date Posted: 13 Aug 2017 at 8:07pm
Is your mains filter OK?

At work I recently had an old mains filter short out which caused fuses to blow and also tripped the RCD.
Once the old filter was replaced with a Schaffner EMI filter it solved the issue.




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Insert Coin[s]


Posted By: jengineer
Date Posted: 13 Aug 2017 at 8:12pm
Originally posted by bbz149 bbz149 wrote:

Originally posted by jengineer jengineer wrote:

Unless I'm going crazy..., change the 5A fuse to a 13A fuse,
if all fails there's always Tin Foil


Absolutely, either that or a nail



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ooooooh if I had the space (and the money) I'd have that...


Posted By: big10p
Date Posted: 13 Aug 2017 at 8:50pm
Hehe, a nail - operator special. Tongue

Long shot, but are you sure it's not something dodgy with the mains socket? I have 5amp fuses in all my cab plugs, and have never blown one due to power-on surge.


Posted By: Flinnster
Date Posted: 13 Aug 2017 at 9:14pm
Yep so I have 4 pretty much identical Dino King cabs. Sadly 2x are in one room, 2x in the other, so it's not so simple to test the same wall socket with all of them. But no, the other cab in the same room hasn't blown any fuses. I will do a bit more testing making sure it's in the exact same wall socket.

What I would say is that all four identical cabs have 5 Amp fuses in the plugs, and none have ever blown a single fuse since I've owned them other than this bugger!

Now, they are all wired the same really.. they all have mains in going via the noise filter (Sega's factory fit one) into the ISO transformer. I do have Jodo's conversion where the switcher is branched off after the mains filter, and VirtVic's old cab where the switcher is branched off differently before the mains filter. My two conversions are all spliced in after the mains filter (it's one of these that's blowing). But.. with the switcher removed from the equation and fuses still failing, I'm sure it's little to do with that side of things.

So the noise filter.. erm.. how on earth would I even test that. Yes I could bypass it I suppose (hehe.. with something similar to a nail ironically!)

For the on off/switch, I rarely touch either of them actually - they are usually both on and left on (one on the service panel, another at the cab rear). I suppose one could be failing somehow, I'll take a look. (I stll need to do that test with the iso transformer in isolation too).

Quote So you change the fuse, turn it on and it works? Then when you go to turn it on again the fuse has blown?

Pretty much this above yes. Although it's not instant and doesn't happen on the next cycle of powering on. Probably 4-5 times powercycling the whole cab while playing various game boards for a good while (no I've not tried rapidly switching on/off to see if it blows! Wink)

Cheers for all the info above guys, I ruddy hate mains AC LOL


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Wanted: - PCBs: Rainbow Islands, Bomb Jack, Rolling Thunder
- Parts needed: Naomi non-swivel castor / wheel, coin mech metal clip for Dino King Door


Posted By: bbz149
Date Posted: 13 Aug 2017 at 9:55pm
Originally posted by jengineer jengineer wrote:

Originally posted by bbz149 bbz149 wrote:

Originally posted by jengineer jengineer wrote:

Unless I'm going crazy..., change the 5A fuse to a 13A fuse,
if all fails there's always Tin Foil


Absolutely, either that or a nail

been a while since I've opened a plug to find foil

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Posted By: bomjac
Date Posted: 13 Aug 2017 at 10:28pm
Transformers do funny things. WouldnT be the first time I've had to close the breaker 3 or 4 times on one because some nugget engineer has set the inrush trip too tight.

Also had to repostion a UPS and run 100m of cable to it because it potentially could trip the 100A breaker that was planned for it with an inrush of 10 times that.

Pull the degaus circuit for a week or so and see of it persists. If you have a posh multimeter - set it to peak hold. That will tell you the inrush, but you would need to splot the supply and wire the meter in series.....Unless you happen to have a clamp meter.


Posted By: Vamino
Date Posted: 14 Aug 2017 at 8:06pm
Originally posted by Flinnster Flinnster wrote:



So the noise filter.. erm.. how on earth would I even test that. Yes I could bypass it I suppose (hehe.. with something similar to a nail ironically!)



Try swapping the whole power plate over to another cab that has no issues. If the problem moves with the plate then I'd be looking at the noise filter, if the problem stays with the cab then I'd be trying what the other guys have suggested.

When you don't know what it is, then the next best thing is knowing what it isn't! LOL

Good luck.


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Insert Coin[s]



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