View Full Version : What happened to my Master System?
Johnny Pow!
05-01-2009, 03:52 PM
So that Master System I got a couple weeks ago? I just got to it, and lo and behold...there's a problem. It doesn't seem to be quite like any that our search engine came up with. Upon fire-up...
There is NO:
Audio
Video
Green power light
There IS:
Heat from the Model 3025 AC adapter
Heat from the unit itself
Heat but no power must mean something's going on somewhere in there, yeah? I did see a thread about a bad voltage resisitor in the guys. Does that sound like the deal here?
gokugohandave
05-01-2009, 04:06 PM
It may the voltage regulator. I had the same problem with a famiclone and member ooxxoo or whatver helped me fix it. Later that day same thing happened to my MS. Heat but no power. Check the regulator with a multimeter.
Johnny Pow!
05-01-2009, 04:13 PM
Ooh boy! First time with a meter. Anyone got whats and wherefores on how to use it this way?
gokugohandave
05-01-2009, 04:25 PM
know how to use a meter? open the MS up and locate the regulator. It will look like this attacthed with a screw to a heat sink : http://www.radioshack.com/product/in...ductId=2062599
gokugohandave
05-01-2009, 04:27 PM
turn your meter to the 20vdc setting and place the negative on the center pin, and with letters facing you the positive on the left, it should read 9v. Place the positive on the other side and it should read above zero.
gokugohandave
05-01-2009, 05:03 PM
Yeah I just checked mine and its 5v out, seeing as how it is a 5v regulator. Myself or im sure someone else on here would be happy to do it for you if you dont like soldering.
ooXxXoo
05-01-2009, 06:48 PM
Yeap!...Sounds like your SMS voltage regulator (7805) is dead....
...
...
fahlim003
03-06-2011, 07:16 PM
Sorry to bump this but I have a Master System that will not boot up with working AC adaptors and as I've read, mainly on this forum, it could be the 7805 voltage regulator.
Using my voltmeter as suggested by gokugohandave I do not get a reading with Negative on centre (C) and Positive on left leg (I) with the logo side of the 7805 facing me.
I'm going to pick a couple up tomorrow for the replacement however, I wonder if anyone could tell me what the white paste/goo was between the heat/rf shield and the VR? Was it thermal paste or something else, specific to voltage regulators.
Just normal thermal paste. You can get a tube of it for around $3 at Radio Shack (and I think you can even still get 7805s there as well). You may be able to just scrape the old goo onto the new regulator as well.
DogP
FABombjoy
03-06-2011, 09:45 PM
No voltage on the input? Have you checked for a bad power jack / power switch? It may not be the regulator.
I'd use your VOM to follow the input voltage, starting at the power jack, and see where it's disappearing.
fahlim003
03-06-2011, 10:32 PM
No voltage on the input? Have you checked for a bad power jack / power switch? It may not be the regulator.
I'd use your VOM to follow the input voltage, starting at the power jack, and see where it's disappearing.Yeah, no voltage - when no power is applied...
All the same, I don't have a Master System or compatible adaptor to test this with. I need to go back to a local game store to test it again and I don't have the means to fiddle around with a voltmeter in there. For the record, if it's toast what should the reading be on the VR with an adaptor plugged in and the power switch respectively on and off?
FABombjoy
03-07-2011, 09:39 AM
Input on the regulator should be 9-ish volts. If it isn't at least 7.5 then the regulator won't function correctly. Assuming correct voltage on the input, output should be 5v, maybe even as low as 4.85.
Oobgarm
03-07-2011, 10:42 AM
I'm running into a similar issue. Checking the meter at the rear input shows 12.5. The regulator gives nothing. Using an official SMS adaptor.
FABombjoy
03-07-2011, 01:07 PM
In both cases you have to follow the input voltage around the board to see where it's disappearing. Unfortunately I'm not familiar enough with the power section of the SMS offhand, and the schematic that I found online has a power section that doesn't appear to be the same as the production US SMS (it shows both +12 and +5 at what appears to be a power connector)
Oobgarm
03-07-2011, 09:15 PM
So I replaced the regulator, and now I get an input, but no output. The mind boggles.
FABombjoy
03-07-2011, 09:39 PM
Hmm... perhaps check for a shorted diode or other component near the regulator attached to its output.
fahlim003
03-08-2011, 05:53 PM
Good news - swap was a success. I didn't probe around with the VM but in replacing the 7805 with a new one with fresh thermal paste it works without a hitch. A nice bonus is seeing Snail Maze is on this version too. I tested it out with the 1602 Genesis Mk1 adaptor which has slightly higher current but otherwise the correct voltage amount and setup.
http://img16.imageshack.us/img16/7585/0803111.jpg
I found this SMS last week for $4 and the other day I scored the sweet (and enormous) Super Beta VCR which I was running the SMS through to test.
Thanks to those in this thread for help and advice, it's appreciated.