Repair Information for Ducksan CGM2907 / DS-2907M

[MikeDB]

Hi all,

New to forum so please bear with me.
I'm attempting to repair a monitor from a Silent Scope game. The monitor is a Ducksan CGM2907 - the main PCB indicates DS-2907M.

Monitor has no picture - I have already determined that the horizontal output transistor is blown - fortunately, the part number on the transistor is still identifiable.
But R659 is burnt and the color codes are unreadable. I am hoping that someone can tell me its resistance value. Even better, a copy of the schematic would be really appreciated so I can look at the circuitry associated with that resistor to see likely causes of the burnt resistor.

Thanks in advance,
Mike DB

 

[MikeDB]

Bumping this hoping someone can help.
I really need a schematic for the Ducksan CGM2907 (PCB DS-2907).

Anyone know where I can get one?

Thanks, Mike D.

 

[Romchik]

Hi,
It is 7,5kOm.
I have this one in my TuxRacer.
I had to replace almost all the electrolytic capacitors on this chassis. There was a issue with high ESR and low capacity.

 

[MikeDB]

Thanks for the reply.
Turns out that since my original posting I purchased a used, working Ducksan CGM2907. Unfortunately, although it does indeed work, it is a higher scan rate and thus not usable with our game.- It hadn't occurred to me that they were manufactured with different scan rates. Of course that did allow me to determine the resistor value I had originally asked about. Looking closer at the original PCB I also found two other that were burnt.

I replaced the resistors and I believe there was a shorted diode as well but it still didn't yield a picture. I haven't gotten back to it for some time do to further trouble shooting. I probably will in a few days.

You wouldn't happen to have a schematic for it do you?

 

[Romchik]

I have no schematic.
In my case, this chassis gave no images at all. And there were no sounds either. You can usually hear how the horizontal and vertical scans work. I had to replace all the electrolytic capacitors in general. All were high ESR.
Then, when the image appeared, it turned into a horizontal stripe. It became clear that the microcircuit has radial cracks at the soldering points. I tried more than six times to find where it is, but I could not find it. Then I simply soldered each soldering point again on the entire microcircuit. And the problem was gone. The chassis worked. It was very exhausting.

 

[MikeDB]

I've finally gotten back to looking at the Ducksan Monitor. (Been busy working with another guy on 1970's era SkeeBall machines.)
I wasn't sure in your last message what you referring to with the term "microcircuits" . Did you mean PCB circuit traces, because I don't see anything that I would refer to as microcircuits?

Monitor I'm working on is the 2907M which I've learned is a medium resolution as opposed to 2907v which is a higher VGA resolution. The flyback has TLF 115A-01-215CL printed on it with a line below that reads 0327 D C..
I get no picture - unfortunately I'm trying to get this to work on a bench without benefit of the CRT & Yoke which are about 30 miles away still in the cabinet. Unlike most that I've worked on where the CRT is mounted on a frame that also holds the monitor circuit board allowing so you can remove them together, in this case the CRT is mounted separately inside the arcade cabinet. Oh well...

If you ever come across a schematic for these beasts that you can share please let me know.

 

[Romchik]

Sorry for my english, you are right of course PCB.
If I ever come across this schematic, I'll be sure to share it.

 

[Ohmerone]

I've finally gotten back to looking at the Ducksan Monitor. (Been busy working with another guy on 1970's era SkeeBall machines.)
I wasn't sure in your last message what you referring to with the term "microcircuits" . Did you mean PCB circuit traces, because I don't see anything that I would refer to as microcircuits?

Monitor I'm working on is the 2907M which I've learned is a medium resolution as opposed to 2907v which is a higher VGA resolution. The flyback has TLF 115A-01-215CL printed on it with a line below that reads 0327 D C..
I get no picture - unfortunately I'm trying to get this to work on a bench without benefit of the CRT & Yoke which are about 30 miles away still in the cabinet. Unlike most that I've worked on where the CRT is mounted on a frame that also holds the monitor circuit board allowing so you can remove them together, in this case the CRT is mounted separately inside the arcade cabinet. Oh well...

If you ever come across a schematic for these beasts that you can share please let me know.

Not a good idea to work without the crt and yoke
Mainly can be done to check power supply and Drive circuits
Not safe to have FB working unless you have have experience with this
chassis to isolate the problem quickly.
Need to confirm the resistor is not shorted to ground
on either side of it.
did you replace it yet?
Maybe a photo of the bottom of chassis to look over the component
location's and circuits for the resistor
is it on a supply line? and what does it feed following the trace to and from it.
LUK