HELP! 300mA fuse on DK monitor keeps blowing
Ken Bloch
There's a small .3 amp fuse on Donkey Kong's monitor chassis I have
which blows whenever you power the machine on.
When it goes...POOF!...No sound/no video
Any ideas?
Thanks!
-Ken
kbl...@teknoir.com
dick millikan
transistor, Most of the time you blow this fuse it's because
the Hor. output transistor is shorted.If the fuse now stays good, change
the transistor.
Dick
Mark Shostak
Ken Bloch (kbl...@teknoir.com) wrote:
: There's a small .3 amp fuse on Donkey Kong's monitor chassis I have
: which blows whenever you power the machine on.
Two words: Fly Back
Hi Ken,
I recently repaired one of these monitors and hadn't
gotten around to posting my experience. I learned a
lot about what *not* to do on this chassis. I guess
this is as good a time as any to post it.
In addition to the one I fixed, I have seen several
of these monitors with shorted fly backs, as that is
the part I was looking to scavenge off other boards.
Maybe John R. or someone with similar experience can
confirm or deny the frequency of this failure.
Check the fly back:
* With the monitor unplugged,
Put your ohm meter between the 300ma fuse holder
(with a good fuse installed) and ground.
* If the fly back is shorted, this will be 10 ohms
or less; continue below.
* If not, look elsewhere for your problem.
* To confirm the fly back is the cause of the short:
* *DISCHARGE THE CRT ANODE*
* IF YOU DON'T KNOW WHAT THAT MEANS, *STOP HERE*.
* Remove the fly back.
* Repeat the measurement, and ensure the reading goes
up by hundreds if not thousands of ohms.
If you confirm the fly back is bad, here is some Sanyo data:
The fly back in my monitor was: Sanyo part number: F5024 AJA
Sanyo's phone numbers:
415-960-8582
800-421-5013
714-763-3777
800-726-9662
I finally found one that wasn't smoked in another chassis.
I never had any luck with Sanyo.
Other *Important* Information:
No Vertical Deflection:
If the monitor is set for service mode, the vertical
deflection will be disabled. As this monitor usually
mounted vertically, this results in a bright vertical
line on the screen. This is not a fault or deflection
problem. It's merely the flip of a switch.
Bench Testing:
This monitor is designed for 100V AC operation (Japan's
line voltage). I'm not sure how it would like American
120. I used my variac to drop it to 100. Also, this is
a hot chassis. Use an isolation transformer.
Connector Keying:
Nintendo did a great job of keying *almost* every con-
nector in Donkey Kong. Watch out for this:
When reinstalling the pc board in the monitor, pay close
attention to the connectors on the audio amp board. There
are two, three pin connectors. One cable goes to the
main monitor board and supplies B+, which is the amps
operating voltage. The other cable goes to the control
board for volume adjustment.
If these two connectors are reversed, monitor B+ (130VDC)
will be sent into the game board. This produces a flame
fest that any RGVACer would be proud of.
If this happens, the fix is to replace the 1K 1/4 watt at
location R13 and the trani next to it. If you can fix the
monitor, you can figure out which connector goes where;
you just have to know to look for it.
Hope this helps someone avoid stepping in the same piles of
s#!t I did.
Cheers,
Mark
LRosent345
In article <33AF15...@wport.com>, dick millikan <dmil...@wport.com>
writes:
>Ken Bloch wrote:
>>
>> There's a small .3 amp fuse on Donkey Kong's monitor chassis I have
>> which blows whenever you power the machine on.
>>
>> When it goes...POOF!...No sound/no video
>>
>> Any ideas?
>>
>> Thanks!
>> -Ken
>> kbl...@teknoir.com
>Try taking off the collector lead on the horizontal output
>transistor, Most of the time you blow this fuse it's because
>the Hor. output transistor is shorted.If the fuse now stays good, change
>the transistor.
Unless the culprit is really the flyback. Then you may just blow the new
fuse and the new HOT. Check the flyback closely for cracks, oozing, soot.
Mark Shostak
LRosent345 (lrose...@aol.com) wrote:
: In article <33AF15...@wport.com>, dick millikan <dmil...@wport.com>
: writes:
: >Ken Bloch wrote:
: >Try taking off the collector lead on the horizontal output
: >transistor, Most of the time you blow this fuse it's because
: >the Hor. output transistor is shorted.If the fuse now stays good, change
: >the transistor.
: Unless the culprit is really the flyback. Then you may just blow the new
: fuse and the new HOT. Check the flyback closely for cracks, oozing, soot.
Actually, when the flyback shorts, B+ is shorted directly to ground.
The HOT is *not* taken out because it never sees the excess load.
Apparently one winding (or internal diode) with a direct connection
to ground shorts to another winding that is connected directly to B+.
The four shorted flybacks I've seen have not shown any external signs
of malfunction (cracks, oozing, soot, etc.).
Also, the HOT in this chassis has a built in damper. Keep it in mind
when testing this part.
Cheers,
Mark