The NEW Build Your Own Arcade Controls
Main => Monitor/Video Forum => Topic started by: Lutus on August 29, 2006, 06:09:12 pm
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Ok, started tinkering with my new dig dug machine. Upon purchase the guy told me that the monitor "didn't work" so I disconnected the power connector into the Electrohome G07 monitor and booted up the machine.
Sweet motherly goodness... All the lights came on, coin door, led on the PCB, marquee lamp. I heard the boot up blips and beeps. I walk around the front and drop a quarter in and the volcano button lights up. I put in another quarter and the second volcano button lights up. I start up a game and play for about two seconds before dying (since I can't see anything)
Back on topic...
I checked the voltage coming out of the power supply to the monitor and it was 0 volts. So it's not that the monitor doesn't work but it is definently not getting any power.
1. What else should I measure?
2. Is this a "big blue" capacitor problem?
Thanks guys.
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Check for a blown fuse/broken fuseholder problem. Possibly a broken wire or connector somewhere in the wiring harness too.
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Thanks Ken,
I did check the fuses, they are not blown.
How would I check the fuseholder and which wiring harness?
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Think of your monitor in the same terms as any other AC appliance. If it's not plugged in and getting power, it won't run.
Follow the wires coming from the monitor's power plug straight back to where it comes into the cabinet. If there are any faults in this line, correct them.
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Ok, now I am getting around 116 volts into the monitor but the monitor does not come on. I checked the fuse on the monitor and it is not blown. The neck does not glow either.
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Make/model of the monitor, please.
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Sorry, Electrohome G07
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Monitor needs a capkit for sure and that should get it to power up.
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Ken you are truly the monitor ninja.
But seriously, since a cap kit is around $10 and this thing is old, should I go ahead and buy the repair kit for $28 from Bob Roberts that includes
-Cap kit
-Flyback
-HOT
-2 fuses
and just sit on the flyback and hot in case they are needed in the future?
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If it has the original flyback in it then I'd go ahead and get the deluxe kit. Never know when that original flyback might die/explode!
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Excellent, ordering now!!! Will update after the caps are put in.
Preferably die, not explode. ;)
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Alrighty, got the cap kit in (except for the upgrade capacitor), replaced the flyback, and the HOT. I still get no neck glow. I take the thing back out and start checking around.
I believe the problem lies in the HOT. The casing is NOT shorted ground although when I checked the two pins of the HOT they were connected to ground. I desoldered these wires and then checked just the wires to ground and they are shorted there as well. Both of them are connected to the chassis near the HOT without even being connected to the HOT. I believe on the back of the PCB they are labeled as S3 and S4. Is this correct or is another component causing this?
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i am not familiar with electrohome monitors,but all work the same,do you have a clicking or chirp coming from the monitor or is it dead quiet-if you have a ticking type noise the psu circuit is in trip caused by things like unstable h.t,shorts etc,now i have had many faults on monitors whereby the h.o.t is short and also one or more polypropylene capacitors are shot(its usually the one on the collector leg of the h.o.t),you need a cap tester to test these as the values are very small and most multimeters can't read them,sometimes you can see if one has failed because they split and have small burn marks(btw polypropylene caps look like rectangle boxes usually blue,yellow or brown).
if your getting no noise at all then you should be looking towards a component failure in the primary a/c side of the psu-its helpful to have a schematic of the chassis as they usually give voltage test points to help you pinpoint the problem area
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Like grantspain was saying... sounds like it's still an issue in the psu.
The tube heaters (neck glow) power is derived from the flyback, but since you've replaced that already, then you need to verify that it is getting proper voltage from the psu section.
B+ voltage is the key to narrowing it down.
Think of it as the "bridge" between the psu area and the rest of the chassis.
Measure the B+..... if it is not correct, then you defineately have a psu issue.
TP-91 should be at 120V DC adjust with R909 (VR909).
If this is higher than like 138V , then the monitor goes into shut-down.
Check power regulator X04 if readings are off also. (2SC1106)
Check the HOT itself out of cicuit to be sure it hasn't blown. (2SD870)
The casing is NOT shorted ground although when I checked the two pins of the HOT they were connected to ground. I desoldered these wires and then checked just the wires to ground and they are shorted there as well. Both of them are connected to the chassis near the HOT without even being connected to the HOT. I believe on the back of the PCB they are labeled as S3 and S4. Is this correct or is another component causing this?
Did these show as being shorted together? (wire to wire)
Ther are a couple diodes to double check, D502 - D503 and there also appears to be several critical caps in that area to look at, C512 through C516.
Also on a side note... anything on the scematic having an ( ! ) should be checked. For instance there's a fuseable resister FR901 in there that may be open.
(assuming I am looking through the right manual http://arcarc.xmission.com/PDF%20Monitors/Electrohome%20G07-CA0.pdf (http://arcarc.xmission.com/PDF%20Monitors/Electrohome%20G07-CA0.pdf))
Hard to say without actually probing around the board itself, could be way off base here.
(been a long week, I'm just rambling now)
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Thanks as always for the replys.
Grantspain: I am getting no chirping or buzzing that I can tell. Definently no neck glow.
Kevin: The wires that go to the HOT, when not attached to the HOT, ARE shorted together. The HOT measures good when out of the circuit. I see what you mean about the B+, the pdf you gave me of the monitor says to allow it to warm up for like five minutes before testing and adjusting. Is five minutes truly necessary?
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Alright, the part that is shorting is the transformer labeled T501. It is shorting on the "two-prong" side which I assume is the primary side. When I remove the T501 then the short dissapears and everything then checks out as normal.
Should this be replaced and would this cause the monitor not to power up in general. I have not power it up to check the B+ voltage knowing that this is possibly the problem.
T501 is in this schematic:
http://www.lizardlickamusements.com/documents/g07/g07_manual.pdf (http://www.lizardlickamusements.com/documents/g07/g07_manual.pdf)
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So with it out of circuit you should have continuity between the two red dots or the two green dots, but not across between green and red at all. (that make sense?)
And you may want to double check all the transistor directly related in that circuit.
X01 - H.O.T. , X501 - Horizontal drive (X1501 in the parts list / X501 on the schematic)
I know you said you replaced the HOT, but any kind of short may take it out again and run ya around in circles unless you double check everything especially when something else may be causing it. (possibly that transformer T501)
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That's weird, I replied an hour ago and my post completely disappeared!
T501 is the horizontal drive transformer. With as many electrohomes as I've fixed, I've NEVER seen that go bad. It normally shows very very low resistance.
You did check the "B+" voltage didn't you?
The main voltage regulator transistor might be bad or possibly any other components in the power supply section. R908 resistor is included in the Zanen Electronics capkits.
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I will check the B+ voltage after work today.
Ken, you say that it is a low resistance, how low? I am measuring 55 some odd ohms on one side and 0.2 ohms on the other side.
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When I check this B+ voltage... what is the minimum things to plug in?
-Power (duh)
-Degauss wires?
-Anode cap?
-Don't plug in gameboard signals
What about the other plugs? (Escpecially the ones to the yoke?)
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IMHO, after doing a cap kit and verifying that the HOT and fuses are good, the first thing you should be doing is testing the B+ voltage. The easiest place to pick up the B+ signal is at the front tab (closest to the tube) of the big ceramic resistor on the side frame. Just ground your other lead to the side frame by the flyback. If it's not reading 120v, try and adjust it, if it won't adjust, you very likely have a voltage regulator problem. If you want to test the HOT, put your meter on diode test and touch the red lead to the case of the HOT and the black lead to the side frame. If it's shorted, it's bad, anything else and it should be good. I know you said you have tested it, but I'm not sure what procedure you've been doing. If your HOT is shorted, one of the fuses will be blown.
To test your B+ you will need to have the yoke wires hooked up, tha anode cap and your power. You do not have to have the degauss coil or video signals going to the monitor. Hopefully this helps you out.
James
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Alright, I checked a couple of things.
Rechecked fuses and what not.
Final verdict of the B+ voltage: 0.00 V
What does this indicate. I double checked the test point I used.
I placed the ground probe on the monitor frame. Is this correct? And what does the 0 Volts mean?
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0 volts means it's not turned on. ;D
(power supply section problem)
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Check resistor R902 which is a 2 ohm, 7 watt white ceramic resistor. It may have gone open circuit.
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Check the other end of the big ceramic resistor, you should have about 160v there. If you don't the power supply section isn't getting any power at all, and you need to work your way back from there. You should be attaching your groud lead of your meter to the metal frame of the chassis though, not the metal frame of the monitor.
Also, how are you checking your fuses? Just a visual inspection won't cut it here.
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I will test the resistor, and retest the B+ voltage (to assure I am using the correct grounding point) this afternoon.
I have been checking the fuses with a multi-meter.
"0 volts means it's not turned on." :laugh2: :laugh2: :laugh2:
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Alright, still have 0 volts at B+.
The 2 ohm resistor is still good.
STATUS: Holding for more ideas.
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Did you test for voltage on the other end of that resistor? If you're not getting any power there either, you probably have a supply problem. Verify that you havd 110-120v AC at the power connector for the monitor. If you do, then you have to have a closer look at the chassis to make sure there are no broken traces between the power wires and the rectifier diodes.
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I was just looking into this and discharged that big ol capacitor and needless to say that puppy was JUICED!
C904 is the capacitor I discharged. Nearly had to change my pants. :laugh2:
Ok, seriously though, I am getting the hang of this. After crapping my pants I measured the output voltage of the diode bridge with the monitor on. I measured 158 V at the output of this bridge which also happens to be across the capacitor I had discharged. (Lucky me, that way there was no surge to the multi-meter). Will keep on but let me know what you think.
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Okay, well if you have voltage at the bridge, and the big filter cap is charged you need to double check the small fuse. The only time that big cap should hold a charge is if that fuse is blown. I find it intersting though that you are getting voltage out of the bridge, but not out of the voltage regulator, I don't think I have ever had one fail in a way that produced 0volts to the monitor. They always seem to fail and drive the voltage high.
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Sir Grauwulf you are more right than you know. I checked every voltage from the B test points all the way back to the diode rectifier and you are right, it was the small fuse believe it or not. I checked it initially with a multi-meter but must have tested the wrong point which would have saved me some time.
Final Verdict: During the capkit I found two caps with broken legs and the flyback appeared to be cracked so I replaced those and it still didn't come on. Upon a full day of checking, come to find out it was the small fuse.
Well, the broke flyback and old caps originally blew the small fuse. So after fixing those and then replacing the fuse it is all good.
Thanks to all you guys who have helped me. Dig-dug is back to digging!!!
100% sweetness!!!!!!!!!
Thanks again.
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Awesome job !!
Ain't it just a kick in the butt how well bactracking like that works. And at the same time you might find that it's the simpleist of things that cause alot of headache.
Great job.... you repaired what I like to call "a basket case". :applaud:
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Glad to hear you got it up and running.
It's satisfying getting a machine back up and running. :cheers:
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I have been following this thread and I just love to see the kind of help that is available on this board. Kudos to everyone.
Back to lurking.
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jan25th I agree. BYOAC is the best forum I have ever been apart of. Thanks again to all you guys. You all are great.
I was a lurker for around a year then started getting more involved. A great past time.