Electrohome G07 vertical collapse of death

[Lucky1]

Hello,

G07907 CBO

Vertical Collapse



Checked or changed parts:

All electrolytic caps
FR401
X401 (new)
X402 (new)
C402 Tantalum cap next to IC501
IC501, swapped with a working one of another G07
Trim pots -All new pots
400's Resistors
400's diodes
A couple of ceramic caps
Yoke and tube are working fine with my other G07 chassis and neckboard.
Checked twice all solders for cracks and reflowed'em all.


B+ = 120.4 Vdc


Thanks

 

[brokentoken]

I had one that was giving me trouble and it turned out one of the new transistors I got was bad. I would double check X401 & X402 to make sure they are good and have good continuity.

C402, which is a blue tantalum cap, seems to come up in a lot of vertical deflection troubleshooting posts.

 

[tron guy]

I forget which one so check D101-D103. It will beep or read short (diode mode), if its bad.

 

[Lucky1]

I forget which one so check D101-D103. It will beep or read short (diode mode), if its bad.

D101-D102-D103 are part of the Blue, red, green respective circuit. D401 and D402 tested good (just retested now).
Thanks

 

[Lucky1]

Got it working by touching pin 3 and 3 of IC 501.
I was probing the IC501 legs for dc voltage. All the pins 1 to 8 of the vertical section show little less than half of the voltage shown on the attached image. As soon as I unplug and plus it back, the vertical collapse comes back

Boosting the screen knob makes the picture brighter for a split second than it loose a bit of brightness. That can be a week flyback I would presume.

Closer, but not quite successful.

 

[tron guy]

D101-D102-D103 are part of the Blue, red, green respective circuit. D401 and D402 tested good (just retested now).
Thanks

Yeah apparently and the v circuit because I documented in here previously that a bad d102(iirc) was the solve of a 6 month v collapse issue.

Sounds like a small crack / bad connection if you had it going for a few. I am not looking at chassis right now but I had a broken diode ((in that row of diodes and resistors just right of fr401, looking at the top), that when I pushed in the chassis the leg made contact and fired up, I let go and back to collapse. Get something plastic and start pushing around on the chassis in different spots(carefully, this is obviously dangerous), see when/where it fires back up.

 

[Lucky1]

Yup, as soon as I make contact between pin 2 and 3 on th IC501. But to get the full screen, i need to turn the v height and V hold pots all the way up or down.

Pin 2 (out) and 3 (in) are related to V amp in the IC501. Voltage is still too low on these.

 

[Lucky1]

X401 Collector Base Emitter are at 112 Vdc. On my working chassis, the collector is at 112 Vdc, base and emitter are at 42 Vdc. I changed , again, the X401 and I still get 112 at the C-B-E. I've checked for continuity on the traces and nothing there.

The IC501 does not get the proper voltage and it's coming from that part of the circuit. I'll change Cap C412 and C408 even if they tested good.

 

[Ohmerone]

Check the g07 -901 schematic
Has the voltages posted.
You need to check the voltages
On x402 base should be less then a volt
With a drive pulse and collector around 45 v
Check R420 10 ohm
Or it has no drive from the ic
Could relate to the pots you replaced
Check the values are correct

And you need 11 vs on pin
6 of the ic.
Luk

 

[Lucky1]

Yeah apparently and the v circuit because I documented in here previously that a bad d102(iirc) was the solve of a 6 month v collapse issue.

Sounds like a small crack / bad connection if you had it going for a few. I am not looking at chassis right now but I had a broken diode ((in that row of diodes and resistors just right of fr401, looking at the top), that when I pushed in the chassis the leg made contact and fired up, I let go and back to collapse. Get something plastic and start pushing around on the chassis in different spots(carefully, this is obviously dangerous), see when/where it fires back up.

Well, D102 was bad, you were right!! Didn'nt have the part so took one out of my working chassis. I can't really get a full vertical height though. It powers straight like if I touched the pin 2 and 3 on IC501. So it is a gooood thing. But i still get about 6 volts at pin 6, and others (1,2...8) are still half the voltage. X402 is now at 22.5 volts. Half the voltage, there's half of the parallel circuit that might not be working (behond my electric knowledge).
I believe D103 is also bad...

 

[Lucky1]

D103, there's an error on the markings. Not the same +/- on the part side...

 

[Lucky1]

D103. Dead

All voltages are good now.

@tron guy , thank you so much, it would have taken me forever to find this.

So, Diodes 102 and 103 were bad.

Thanks to all who helped me. This monitor is going back into the Sega Hang-On Deluxe bike : https://forums.arcade-museum.com/th...ng-on-deluxe-ride-on-bike-restoration.506122/

 

[tron guy]

I finally got sick of knowing all of my parts were good and there were no bad traces, so I eventually tested EVERY SINGLE Part on the board as I tested compared to a working board until I found those.

Way to hang in there.

 

[Lucky1]

I finally got sick of knowing all of my parts were good and there were no bad traces, so I eventually tested EVERY SINGLE Part on the board as I tested compared to a working board until I found those.

Way to hang in there.

Thanks again. Man VS Machine. I was going to check all parts. This saved a lot of time.

Now is the time to fix the hang-on pcb.