G07 monitor fuse blowing
Duncan Brown
I've fixed lots of monitors in my time, but now I have one that has me
temporarily stumped, and I was hoping someone might be able to help me out,
before I waste any more time or fuses...
I have an Electrohome G07 monitor in a Williams Robotron cabinet. It blows the
1.25A fuse (F901) about a second after powering it up. The obvious parts (X901
and X04) check identical to the same parts in a working G07 (taken
out-of-circuit to get accurate readings, using the diode check function on a
meter.)
So it is probably something connected to the B1 rail that is drawing too much
current. Is there a "typical suspect" here? Or should I just keep plodding
along, checking everything connected to that rail? At 50 cents a pop for
fuses, the "swap, powerup, power down, swap, powerup, power down" method of
hack troubleshooting could get expensive fast...
Thanks,
Duncan
Duncan Brown
>
> I was going to say the same thing only I can almost assure you that
> the flyback is bad; I have seen this MANY times. In most cases, the
> flyback will have a hole burned in it and if you keep replacing the
> fuse, it will eventually begin to spew HUGE amounts of thick black
> smoke. You can get flybacks at a reasonable price ($40) from Zanen
> (the Get-Well Kit people).
Gee, guys this is depressing! This Robotron cabinet was pulled from my arcade
in late 1983 after less than two years of use. I used it for the development
of "Alien Arena" (long story, if you have to ask, don't...) which took about a
year. From that time until now, it's probably seen less than 50 hours of "on"
time, and has been stored in human living space the entire time. (I have
Defender running in it right now...) This is positively the cleanest monitor
you'll ever see outside of the Electrohome factory floor. For a circa 1982
game, it has seen an insanely low number of hours of use.
Could it really still be a bad flyback? In terms of use, this thing ought to
still be under warranty!
In my own (apparently limited!) experience, I have never seen a raster monitor
flyback go bad. Color X-Y flybacks are another matter entirely. They
routinely got that "plumps when you cook 'em" look to the case. So I will be
appalled if I'm the victim of a bad flyback now, on this of all monitors!
Fwiw,
X01 measures identically to another one on a good monitor. I guess I could try
trading that and the flyback from the good monitor, and if that fixes it just
order a new flyback and transistor and not risk further symbiotic part failures
by replacing them one at a time.
Sigh...
Duncan
-Schieve,R.L.
Andy Fromm (arcade repair Guru) had a great article in the
September 1993 RePlay that talked about typical monitor failures
for the older 19" monitors like the GO7. Here is what he says
when fuse F901 is blown:
"If the fuse is blown, check the horizontal ouput transistor
(X01). The HV unit (flyback transformer) may also be bad. Inspect
for cracks or burned marks. The HV unit and horizontal output
transistor often fail in pairs. The flyback fails first and takes
the transistor with it. Don't be surprized if the flyback
transformer blows up after you replace the horizontal output
transistor and fire up the monitor to test it. It happens all the
time."
Rick Schieve
Gregg Woodcock
> >I have an Electrohome G07 in a Williams Robotron cabinet. It blows the
> >1.25A fuse (F901) a second after powering it up. The obvious parts (X901
> >and X04) check identical to the same parts in a working G07 (taken
> >out-of-circuit to get accurate readings, using the diode check function on a
> >meter.)
> "If the fuse is blown, check the horizontal ouput transistor
> (X01). The HV unit (flyback transformer) may also be bad. Inspect
> for cracks or burned marks. The HV unit and horizontal output
> transistor often fail in pairs. The flyback fails first and takes
> the transistor with it. Don't be surprized if the flyback
> transformer blows up after you replace the horizontal output
> transistor and fire up the monitor to test it. It happens all the
> time."
I was going to say the same thing only I can almost assure you that
the flyback is bad; I have seen this MANY times. In most cases, the
flyback will have a hole burned in it and if you keep replacing the
fuse, it will eventually begin to spew HUGE amounts of thick black
smoke. You can get flybacks at a reasonable price ($40) from Zanen
(the Get-Well Kit people).
--
THANX...Gregg day 214.684.7380 night UNLIST/PUBL TEXAS NOT CANADA!
wood...@bnr.ca or wood...@nt.com or bn...@cleveland.freenet.edu
*CLASSIC VIDEOGAME COLLECTOR BUY/SELL/TRADE PRE-NINTENDO (ARCADE/HOME)*
"If you quote me on this I'll have to deny it; I won't remember because
I have such a bad memory. Not only that, but my memory is *terrible*."
-Schieve,R.L.
Duncan Brown <brow...@eisner.decus.org> wrote:
>In article <34kfd9$q...@crchh327.bnr.ca>, wood...@bnr.ca (Gregg Woodcock) writes:
>>
>> I was going to say the same thing only I can almost assure you that
>> the flyback is bad; I have seen this MANY times. In most cases, the
>> flyback will have a hole burned in it and if you keep replacing the
>> fuse, it will eventually begin to spew HUGE amounts of thick black
>> smoke. You can get flybacks at a reasonable price ($40) from Zanen
>> (the Get-Well Kit people).
>
>Gee, guys this is depressing! This Robotron cabinet was pulled from my arcade
>in late 1983 after less than two years of use. I used it for the development
>of "Alien Arena" (long story, if you have to ask, don't...) which took about a
>year. From that time until now, it's probably seen less than 50 hours of "on"
>time, and has been stored in human living space the entire time. (I have
>Defender running in it right now...) This is positively the cleanest monitor
>you'll ever see outside of the Electrohome factory floor. For a circa 1982
>game, it has seen an insanely low number of hours of use.
>
>Could it really still be a bad flyback? In terms of use, this thing ought to
>still be under warranty!
Electrohome G07s eat flybacks. What can I say???
>In my own (apparently limited!) experience, I have never seen a raster monitor
>flyback go bad. Color X-Y flybacks are another matter entirely. They
>routinely got that "plumps when you cook 'em" look to the case. So I will be
>appalled if I'm the victim of a bad flyback now, on this of all monitors!
I've only seen one bad high voltage transformer in all the
Wells-Gardner color vector monitors I've worked on (dozens). Now
Ampliphone HV transformers is another (sad) story.
>Fwiw,
>X01 measures identically to another one on a good monitor. I guess I could try
>trading that and the flyback from the good monitor, and if that fixes it just
>order a new flyback and transistor and not risk further symbiotic part failures
>by replacing them one at a time.
>
>Sigh...
>
>Duncan
Rick Schieve
r...@intgp1.att.com
Clifton Koch
>In article <34kfd9$q...@crchh327.bnr.ca>, wood...@bnr.ca (Gregg Woodcock) writes:
>>
>> I was going to say the same thing only I can almost assure you that
>> the flyback is bad; I have seen this MANY times. In most cases, the
>> flyback will have a hole burned in it and if you keep replacing the
>> fuse, it will eventually begin to spew HUGE amounts of thick black
>> smoke. You can get flybacks at a reasonable price ($40) from Zanen
>> (the Get-Well Kit people).
>Gee, guys this is depressing! This Robotron cabinet was pulled from my arcade
>in late 1983 after less than two years of use. I used it for the development
>of "Alien Arena" (long story, if you have to ask, don't...) which took about a
>year. From that time until now, it's probably seen less than 50 hours of "on"
>time, and has been stored in human living space the entire time. (I have
>Defender running in it right now...) This is positively the cleanest monitor
>you'll ever see outside of the Electrohome factory floor. For a circa 1982
>game, it has seen an insanely low number of hours of use.
>Could it really still be a bad flyback? In terms of use, this thing ought to
>still be under warranty!
>In my own (apparently limited!) experience, I have never seen a raster monitor
>flyback go bad. Color X-Y flybacks are another matter entirely. They
>routinely got that "plumps when you cook 'em" look to the case. So I will be
>appalled if I'm the victim of a bad flyback now, on this of all monitors!
I used to work for a coin-op distributor as an electronic technician, and
fixed many, many monitors. Flybacks do go bad, though I consider it rather
rare. There's usually visual indications of arcing, but sometimes it's hard
to see the spot unless you actually see the arcing. It's been quite a while
since I've done this as a job, so I don't really remember what liked to die
on the G07 monitors.
Checking the horizontal output transistor with an ohmeter is pretty tough.
You have to disconnect it from the circuit, and the internal clamping diode
makes it tough to really tell if the internal junctions are in one piece.
If it is dead, it's often caused by something else, which can be tough
to track down. It could be as easy as a bad flyback or insufficient heat
sinking, but I've also seen cases where electrolytic capacitors that have
gone bad screw up the pulse getting to the horizontal output transistor
and cause it to fail prematurely, usually without any noticable effects on
the picture. Electrolytic capacitors really dislike heat, but age can do
them in also.
Cliff
--
-----------------------------------------------------------------------------
Cliff Koch
Motorola Cellular Infrastructure Division
ko...@meerkat.cig.mot.com