Pc engine coregrafx- no response (bad fuse, value/type needed)

[bartre]

So my tried and true PC engine won't give me anything.
No video, no audio.
I stuff my backup pce into my beefcase and all is well.
The system has rgb and region mods, with the region mod done by a much more amateur me.
What should I be looking for when I get in there?
Also, have there been any new region mod solutions?

[MNKyDeth]

First thing is find out if it is actually turning on or not.

Open it up and check the fuse. Make sure it's not popped.

Get out your voltage meter and test the legs on the 7805 to see if the proper voltage is going into it and coming out of it.

Left leg = 12v
Center leg = ground
Right leg = 5v

If that looks good I would start looking for other issues, bubbly caps, corrosion around any of the chips. Bad wiring from the mods and then make sure the ribbon cable is still solidly into the mainboard of the unit.

If all that looks good, replace caps and pray.

PS. I should clarify, the Left leg I said 12v in reality it could be between 9v - 16v from the typical power supply used. 7805's I think are rated up to 35v and they still only put out 5v so no matter what the Right side should be 5v or very close. All of the extra energy no matter how much the 7805 is fed it will dissipate it into the machine as heat.

[bartre]

Hmm.
No response on the 7805.
Where's the fuse?

[MNKyDeth]

Under the metal heatsink I think.

If that is blown then replace it. If it is not blown, replace the 7805 with a new one.

You can see it in this image behind the two caps to the right side of the 7805.
https://i.ytimg.com/vi/u80Ed-_XAfg/maxresdefault.jpg

[SignOfZeta]

I got a free Core Grafx once from a guy and the only issue was that fuse.

I think he was testing a home made controller with it and over loaded the system via the controller socket.

[bartre]

okay, what kind of fuse do I need?

[MNKyDeth]

I am at work at the moment so I cannot look up the value of the fuse.

But console5 has some for the Duo's.

https://console5.com/store/components/fuses.html

Not sure if they have the same ratings or not as the one in the PC Engine.

[bartre]

Thanks, much appreciated.
It does look like my fuse is blown:

[MNKyDeth]

If your multimeter can do continuity tests. You can test the fuse with that. Just put the probes on either end of the fuse. If you hear the beep it's not blown. If no sound, it's blown.

But yeah, usually when they are not clear and see through they are popped.

But that also means something caused it. So buy two new fuses. That way if it happens right away to the new fuse you can start tracking down any shorts causing the issue.


Once you take that fuse out you should be able to see the writing on it and determine the amp size of the fuse and buy appropriately.

[bartre]

Yep- very much popped.
I'll pull it later.
But do I need to worry about the 7805 generating heat?
I.e.- do I need to use thermal paste when I put the heatsink back?

*edit*
Looks like a 1A fuse
Is this one a suitable replacement?: https://console5.com/store/fuse-125v-1a-pico-turbo-express.html

[MNKyDeth]

I always wipe off the old stuff and apply new thermal paste to the machines I work on.

You should put some on there when putting it back together as it allows the heat to transfer more efficiently to the heat sink.

[bartre]

Thanks, I'll do that. Though oddly enough there was none between the heatsink and the regulator when I got to it.

Can I just use any 1 amp fuse? does it have to be fast/slow blow?
this one looks good to me:
https://console5.com/store/fuse-125v-1a-pico-turbo-express.html

[mickcris]

defiantly use a fast blow.  as long as its a 1A 125v fast blow then its fine.  ive used a pico fuse in a coregrafx before as it was all i had on hand.

they should have fuses at the home depot or an auto parts store (not 100% sure about that). Better if you have a Radio Shack or Frys around.   most of the glass fuses have a rating of 125/250v and are fine.  most likely they wont have one with leads but you can just cut the old one out and leave the leads and solder one inbetween.  if you dont want to wait for one in the mail.

http://www.homedepot.com/p/Cooper-Bussmann-GMA-Series-1-Amp-Silver-Electronic-Fuses-2-Pack-BP-GMA-1A/100210685

[SignOfZeta]

Maybe you should weld a socket in there. There's a good chance the issue is due to the mods installed and it might pop a few more times before you figure out what the cause is.

[blueraven]

Thanks, I'll do that. Though oddly enough there was none between the heatsink and the regulator when I got to it.

Can I just use any 1 amp fuse? does it have to be fast/slow blow?
this one looks good to me:
https://console5.com/store/fuse-125v-1a-pico-turbo-express.html

Mickcris is right.

Bartre, I have a 12-pack of the glass 1A fast-blow fuses. I could send you one in an envelope.

I had to replace about 3 last month.