Nanao MS8-26SU/Daytona Monitor secondary fuse blown

[Leif]

I've posted this over at KLOV as well as sega-naomi... just posting here to see if I can get another set of eyes or opinions.

I have a daytona twin that I purchased two weeks ago... The right side since purchase has not "fired on."  I have narrowed it down to the monitor after switching componenets back and forth and narrowed it down to the monitor.  I located that fuse F902 is blown.  This is the 2amp secondary fuse.

I have the monitor board pulled from the cabinet and I don't see anything "visually" wrong other than the fuse being blown... no leaky caps, no trashed diodes or burned out resistors.

When I replaced the fuse it just continues to blow.

Any ideas?  Thanks for those of you that have answered me on the other forums, I appreciate the replies so far... just looking to put a nail in this coffin.

[phi ho]

Check Q533 (D1880) and Q901(C3306) .This monitor also needs a iso transformer.

[Leif]

Check Q533 (D1880) and Q901(C3306) .This monitor also needs a iso transformer.

I am assuming Q533 is mounted on the heatsink in the picture below.  I will check both of these when I get a chance today or tomorrow (I'm getting another set of eyes over tomorrow to help).





This is where I get frustrated though is with these schematics.  The schematics match everything on my board EXCEPT the fuse that goes on F901 (primary).  The schematics clearly show (see below in the southeast quadrant) that the F901 is a 3A fuse and my board CLEARLY reads (see above) 6.3A.  This leads me to believe that A) the schematics are wrong or B) these are not the right schematics for my board.

http://technical-department.servegame.com/monitor_schematic_diagrams/nanao/ms8schematic.jpg

In any event the fuse that keeps blowing is F902 located eastnortheast of F901.

[Leif]

Check Q533 (D1880) and Q901(C3306) .This monitor also needs a iso transformer.

Testing Q533 and Q901 and getting OL in the expected directions and 0.0 in the other directions.

[phi ho]

Just for your information:
Take those transistors out of the circuit ,  with the DMM set for diode measuring and the following values are what I read from my known good transistors
Q901:
Red test lead to B,black to C: .499
============B,===== E: .536
Black test lead to B,red to C: OL
============ B, ==== E: OL
Red test lead to C,black to E: OL
Black test lead to C,red to E: OL
Q533:
Red test lead to B,black to C:.452
=========== B,====== E:.027
Black test lead to B,red to C: OL
============ B,===== E:.027
Red test lead to C,red to E:OL
Black test lead to C,red to E:.464
Hope this will help

[Leif]

Just for your information:
Take those transistors out of the circuit ,  with the DMM set for diode measuring and the following values are what I read from my known good transistors
Q901:
Red test lead to B,black to C: .499
============B,===== E: .536
Black test lead to B,red to C: OL
============ B, ==== E: OL
Red test lead to C,black to E: OL
Black test lead to C,red to E: OL
Q533:
Red test lead to B,black to C:.452
=========== B,====== E:.027
Black test lead to B,red to C: OL
============ B,===== E:.027
Red test lead to C,red to E:OL
Black test lead to C,red to E:.464
Hope this will help

VERY good info to have... I will do this tonight.  The nice thing about having a twin daytona is you can test the working side.  I'm getting HUGE differences in resistance on both of these transistors against their working counterpart.

What's the likelihood that the damage is just these two components?

[Leif]

All testing yeilded 0.0 or OL.  Replaced Q901 and Q533 with new transistors.  Monitor came on but with a white line across the middle so there was a collapse.  You could see the graphics change across the horizontal line.  I tried to see if I could adjust out of it, grabbed the vhold and heard a high pitched noise, a pop, and blew the secondary fuse again.

Checked the HOT and it was blown again.   

[grantspain]

check/change
C433 25volt 10uf electrolitic
R433 2k2 resistor (1/4 watt)
q401,q402-2sd1136
d431,d432
then change the hot

[Leif]

check/change
C433 25volt 10uf electrolitic
R433 2k2 resistor (1/4 watt)
q401,q402-2sd1136
d431,d432
then change the hot

From the looks of the schematics this is the Vertical Deflection circuit?

[grantspain]

yes,you said you have a horzontal line,i.e vertical frame collapse-probably the most common fault on ms8 behind the cap on the neck card-i am guessing your tube is mounted in the standard elevation as its it a daytona,i have 3 twin daytonas

[Leif]

yes,you said you have a horzontal line,i.e vertical frame collapse-probably the most common fault on ms8 behind the cap on the neck card-i am guessing your tube is mounted in the standard elevation as its it a daytona,i have 3 twin daytonas

Yes standard Daytona location.  Nice collection of cabs if you're running 6 seats!  So you're saying to test the caps on the neckcard that fits onto the tube.

What was odd (or at least to me) is this line was changing colors like there was info being sent to it... it was just squished into a 1/3"-1/2" line.  When we first powered on we had the usual deflection line (thin BRIGHT white line)... then it started moving as the game booted up.

[grantspain]

basically you have lost vertical deflection,these nanao are renowned for this problem.the reason you saw some graphics in the line is because the monitor was running but without the vertical scan
some monitors carry on running with the vertical collapse but the nanao do not
if you look on your chassis you will see the area around those components very discoloured due to heat
the cap on the neck card is c332 i think,for cartain its a 10uf 250v-if this goes leaky you get a crappy definition picture and brightness issues

if you change the parts i said in the last post then i am certain it will work

my daytonas

[Leif]

basically you have lost vertical deflection,these nanao are renowned for this problem.the reason you saw some graphics in the line is because the monitor was running but without the vertical scan
some monitors carry on running with the vertical collapse but the nanao do not
if you look on your chassis you will see the area around those components very discoloured due to heat
the cap on the neck card is c332 i think,for cartain its a 10uf 250v-if this goes leaky you get a crappy definition picture and brightness issues

if you change the parts i said in the last post then i am certain it will work

my daytonas

That is the perfect backdrop to that set of machines... heavenly indeed!

I will change out these components after testing tonight or tomorrow time permitting... I would assume failure of these parts is what is causing the HOT to burn out?

You've been a great bit of help Grantspain!

[grantspain]

these ms8 chassis do do wierd stuff when the deflection circuit is faulty,will it take the hot out-i dunno but its possible

[phi ho]

I'd like to add one more thing.About one year ago,I had to repair a MS8 in my Virtua racing which have the symptom like yours.So I replace Q901,Q533 and fuse then turn on the monitor.Every thing seem OK but after about 15 minutes,I've got black screen and Q901,Q533,fuse all spoiled.I try to replace these parts again and the same thing happen but while it's still running,I touch and fell C537(4.7uF/100V)really hot.So I replace Q901,Q533,C537 ,fuse and the monitor works until now.

[grantspain]

worth changing the cap phi ho mentions as well

[Leif]

check/change
C433 25volt 10uf electrolitic
R433 2k2 resistor (1/4 watt)
q401,q402-2sd1136
d431,d432
then change the hot

From the looks of the schematics this is the Vertical Deflection circuit?

All of these tested ok.

[grantspain]

tested the caps with a capacitance meter?
also check the yoke readings for the vert and hor