Galaga upright - Monitor repair (continued from price check thread)

jbrisenojr

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Galaga upright - Monitor repair (continued from price check thread)

Good idea.. Just sent you a email that might help with the G07...

I got the cabinet in the garage right now with my other arcades and shot a quick video to show the condition.



let me know what you guys think and where i should to start on trying to fix the monitor.

As the title says this is a repair thread that initially started as a price check thread and now is focused on repairing the G07 monitor in my Galaga upright cab.

I quoted the last post from the original thread for continuity and the video i shot of the cabinet.
 
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Okay well i got bored and went downstairs to probe around in my galaga cabinet. I followed the flow chart for the G07 and probed the fuses first. They looked okay and continuity test was good. Then i probed the R1 resistor and the voltages were off or low according to flow chart.

Before probing C904 i decided to back up to the power supply and I found that the DC voltages (i.e. 5 volts) were measuring correctly but the A/C voltages out of the power supply were only around 81 volts (and yes i made sure to switch from d/c to a/c to measure them). This same 81 volts was present at the fuses on either side so I am sure my readings are correct.

So my question, is it possible for the switching power supply to have good d/c voltages and bad a/c voltages? I want to make sure that im not doing something wrong before i assume its the PS and order a new one (preferably an original PS).
 
Probed R1 tonight to verify its a voltage issue and R1 probed at close to 220 ohms which it is rated at so that tells me its good. So i am still thinking its the switching power supply that's bad.
 
Unplug the monitor and measure the ac on the plug going into the monitor... You can also measure ac coming out of the isolation transformer..
 
Unplug the monitor and measure the ac on the plug going into the monitor... You can also measure ac coming out of the isolation transformer..

im unsure on how to accomplish this... do you mean remove the neck board? and which plug going into the monitor?
 
im unsure on how to accomplish this... do you mean remove the neck board? and which plug going into the monitor?

No the ac plug that comes up from the isolation transformer and plugs into the monitor chassis.. Its a white 2 pin plug on a G07.. your looking for around 115ac
 
Unplug the monitor and measure the ac on the plug going into the monitor... You can also measure ac coming out of the isolation transformer..

No the ac plug that comes up from the isolation transformer and plugs into the monitor chassis.. Its a white 2 pin plug on a G07.. your looking for around 115ac

okay thanks, i just probed inside the 2 prong connector and it reads 118v a/c
 
just reprobed the ceramic resistor and now its reading about 150v d/c, i must have been measuring incorrectly the other night, so according to the flow chart if voltage too high i need to remove X701? i will have to do this tomorrow as its getting late.
 
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okay thanks, i just probed inside the 2 prong connector and it reads 118v a/c

Thats a good reading...:)

just reprobed the ceramic resistor and not its reading about 150v d/c, i must have been measuring incorrectly the other night, so according to the flow chart if voltage too high i need to remove X701? i will have to do this tomorrow as its getting late.

Making progress.....
 
Okay so this entire time i have been probing with the chassis still inside the cabinet... well i finally had time to remove it from the cab and probe around... i started back at square one to make sure my values were correct..

Starting at the fuses i started with continuity and get to F901 and see the soldering job that i did not notice while it was in the cab (pictured below)... the fuse is soldered directly to the board and the red wires to either side of the fuse... well upon closer examination the fuse is blow and the reason i still get a good reading on continuity is because the wires are electrically the same point as the fuse they are coming from.

So F901 is blow and i inspected and probed the HOT X01 as recommended in the flowchart and its good based on voltage reading from continuity check, so now i need to figure out why the fuse had wires directly soldered to it from F902 and replace the fuse... and figure out if the overvoltage reading i got on R1 caused it to blow and why there is overvoltage.
 

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I have never seen wires like that soldered on a G07 fuse??

Very common when people don't have the correct pigtail fuse. Start by replacing the fuse with the correct pigtail fuse and removing the wires.

Next, test the HOT to verify that it is good. If it is good and the F901 fuse is blown, most likely your fly is bad.

Meter set to diode function
black lead to case of HOT
red lead to each of the legs, one at a time
Expected reading is .400 - .600, anything else is bad
 
Very common when people don't have the correct pigtail fuse. Start by replacing the fuse with the correct pigtail fuse and removing the wires.

Next, test the HOT to verify that it is good. If it is good and the F901 fuse is blown, most likely your fly is bad.

Meter set to diode function
black lead to case of HOT
red lead to each of the legs, one at a time
Expected reading is .400 - .600, anything else is bad

I checked both HOTs .. X01 and X701 I believe they were and in diode check they were about .450ish but ill check them again once I desolder fuse
 
There is only one HOT, the other is the Regulator (2SC1106)

O okay, i thought it was another HOT since flow chart refers to X701 as just a transistor to unsolder if voltage too high.

I havent removed it yet but when doing the diode check the voltages read normally around .500.

I also need to figure out the correct fuse to replace F901
 
So now im more confused ... the wires lead to a large fuse attached to the chassis which im assuming was a crap way of replacing the F901... i though it was connected to the F902 but was rushing and realized F902 is on the board and this is a totally different fuse added in circuit
 

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if you are still kinda confused on how to measure the H.O.T. or the VR and some of the other transistors you can use this video as a guide.

the B,C,E can and will be different on some of them but the concept is the same.




Peace
Buffett
 
Okay so removed the X701 voltage regulator and now i have neck glow and a white screen....
 

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