Defender Power Supply - Need help

[acevedor2]

Hey guys, I have been having all kinds of issues with my Defender that
seem to come and go. The latest in the series of problems is the
monitor stopped working (displaying a picture).  It actually seems to
come on and give a slight glow on the screen, if you turn it off you
see the flash of white light before it goes black (just like if you
were turning off a regular TV). Problem is, no picture at all.

You can hear the sound and play the game, just no  picture. 

I am thinking power supply might be bad because I have had other Gremlins over the last month with it that seem to come and go.   What do you guys think?  If
it is the power supply, what kind/brand do you recommend, and do you
have a link to where I can get one.  I am just learning the "fixing"
part of this hobby.  Thanks again.  Cheers.

[Lutus]

You may want to put this issue in the monitor forum.  If the game plays fully blind and everything works except the monitor....

Have you installed a capkit on that monitor?

[SirPeale]

If it's playing blind, I don't think it's a power supply issue.  Sounds like a monitor issue.

[qrz]

if ur monitor is pwrd , u may wish to check q4 (blanking drive) on the game board .
the xistor is a 2n4403.......
monitor sync generation is performed by ic3b,4c,3a (7411,7421 and 7486 respectively)

qrz

[acevedor2]

Thanks guys, I am not sure where to start.  What is Q4?  Remember, I am a noob.  Everything works fine blind, just no monitor.  Would a cap kit likely fix this problem?  I have never installed one, but I have soldered before, so I should be able to do it.  Any thoughts?  Thanks again!

[qrz]

Q4 is the pc board transistor reference #  ( on game board) 
components will be listed this way in the parts list and on the circuit board .
since ur game is playing "blind", the monitor is suspect . (monitor make / model # ?)
upon pwr up , are there any operative sounds from the board , crt filaments lit,  etc ?
if nothing , start w/fuses and a visual inspection of the components.
if fuses intact and no obvious damaged parts , check the horiz output xistor for a collector emitter short  ( low ohms)
if all ok , a "cap kit" may help ( pending how complete the kit - never used one - )
faulty 'lytics are common in most electronic devices .....
and EVERYONE is a "noob" at some point   

qrz

[Lutus]

Make and model # are a must.

A cap kit is usually recommended because it will fix a multitude of issues but it is also suggested as a starting point since it is so inexpensive and somewhat easy to do.

A $10 cap kit has fixed two of the machines that I bought that both "played blind".  A one of them did have a blown fuse.

After the cap kit is done, qrz has a number of other good points to look into.

Merry christmas.

[acevedor2]

Thanks guys.  I'll pull the monitor model number this evening.  Just haven't had a chance to pull it out from the wall.  Where should I check for the fuse?  Not trying to ask a dumb question, but there are several fuses.  Is there one specifically for the monitor?  Thanks again guys and Merry Christmas.

[acevedor2]

Ok,
  I looked at all of the fuses on the board.  I found 5 of them on the board on the bottom (I think it is the PS board).  All of the fuses look good.  I could not find a model number on the monitor.  I have attached some pictures because maybe someone can give me a hint on where to look.  I couldn't find anything other than an RCA sticker on it.  It definitely looks original to the machine.  Again, I appreciate all of the help and patience with me guys.
Cheers!

[qrz]

looks like a wg-4600  ()
if so, check main line fuse ( on monitor pcb-follow the ac cord ) F601 3Amp
if ok, then check R701 6.8ohm 15 W. also check C608 47uF @160v
if h osc/out working, emitter of TR502 should read around 127v. no hout, v will be at raw b+
if no hosc , check C356 4.7uF@25v, C359 4.7uF@160v and C362 10uF@50v, R607 2.7K 5w

this should give u a start at troubleshooting .......

 bear in mind , voltage tests are taken with a LIVE chassis.

qrz

[acevedor2]

Thanks. I assume those designations, R701, etc can be found in the user manual?  I'll check again fir the fuse, but I looked and did't see an inline fuse. I'l start with the power cable and check again. I appreciate all of the help.

[acevedor2]

Just checked again. No in line fuses at all.  I'll check the voltages tomorrow.  I am stumped!

[qrz]

ok, the basics ......
follow the ac cord onto the monitor circuit board.  near this location, you should find a fuse....i.e.  a glass cylinder with metal caps on the ends.   size  1 X 1 1/4 " .  may be in a pc mount fuse holder or soldered direct to pc board ( pigtail ).   likely rated  3A @ 125-250v. 
disconnect the pwr cord at the plug (so as not to read through the isolation xformer ). measure across the fuse with a multimeter set on low ohms scale.
if fuse is good , there will be a low ohm reading. usually < 1 ohm.
if fuse is open ( bad), res will be whatever the meter uses to indicate infinite resistance ......
f, r , tr are reference #'s for the various prts......
f = Fuse
r=Resistor
tr = Transistor    note : most "modern" equipment uses "Q" as a transistor designation.
t = Transformer
y= crystal
l= coil/inductor
ic= integrated circuit
v= vacuum tube   used as:  V1 is tube #1  etc....
d= diode
dz or zd = zener diode
c= capacitor
there are more , and vary somewhat by mfgr , but this should suffice as most commonly found.....

these designations should be silkscreened on the board where the part is located ......

on this chassis,
r701 is likely the ceramic resistor located on the left heatsink . near the regulator xistor.....

have a schematic ?

qrz
 

[acevedor2]

Thanks.  I checked that fuse - it is soldered on the board.  It was good.  I can't seem to find R701, but I am still looking.  I tried adjusting the black knob on the back of the monitor board that is stenciled "screen" but all that did was make the screen brighter (i.e., when I turned it it went from Black to white) but it did not have a picture on it.  The sound is still there, and the game is playable aside from the fact that you can't see anything. 

[acevedor2]

Also, not sure it is supposed to be on, but the little tube at the back of the neck of the monitor is not on when the game is turned on.  Is that supposed to be on?