GO7 high voltage Shutdown Problem from Hell HELP!!!

rmackie6661

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GO7 high voltage Shutdown Problem from Hell HELP!!!

I have myself a pair of GO7's that I just cannot figure out. hopeing anyone might have some clues or hints.

The first one
shutdown with 160dc at the VR and the white WR resistor. I'm getting volts all over the board too. Took X701 out and it powers up awesome at 120v. put back in and nothing, in HV shutdown. Here's what I've tried and tested good.
New Power Reg, all the wire wound resistors, all the diodes, IC501, T501, X901, X902, X501, X701, filter cap and all other caps, new R908, New Hot, T502, i've checked the larger resistors too in the 900 area. All traces are good too. I've spend prob 6hrs on this stupid thing.



number two
HV shutdown mode with 160 a the VR and white resistor pull X701 and i get rester but it's scrambled and at 160v still cannot adjust.
This one I changed and checked everything again just like the top and it's got a new flyback too.

Any ideas? my only thoughts were what are those little black bowling ball looking things by the flybacks. they say something like vr### on them.[/
 
Is the Power supply working good?

You probably don't know, why not!!

One chassis at a time!!

#1 is the regulator working correctly?

Have you tesed it with the bulb yet?
 
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What's the bulb test. never heard of it and am having the same prob

You should know if the problem is in the power supply

or Not...

Use the bulb to find out!!

if you apply the bulb to the ground and the emitter Or Test point 91 and you

can clearly adjust the dc regulated voltage then your problem is

not in the power supply..

set up a female socket and wires with alligator clips about medium size

and 65 to 100 watt bulb incandesent, whatever you like depending on the circuit load.

Its not if the bulb lights its if the circuit is regulating..

you are subbing a load that would normal be the fly and yoke..

of coarse the bulb will light you can put 12vs on the bulb

and it will light, maybe not so bright, but your not testing the bulb your test the circuit..

the bulb will act as a variable load.

single filament only!!

you can apply the bulb even to a working circuit as a test on how

good the power supply is holding up. and at the same time you can

remove the HOT and just the B+ control turning counter clockwise

to end or clockwise to full power..monitor the dc??

On almost any power supply..you can do this as a test

in troubleshooting.

Then you can say my power supply is working good!

the problem must be some where else.

disabling the shutdown doesn't tell you a whole lot!

it does force the dc thru the chassis but the chassis

is telling you theres a problem an wants to disable the horizontal drive pulse.

thus shifting the load and the B+ has no load and jumps up

but with the bulb add in it would sub the missing load and if it works

then the dc will drop if the B+ control is set correctly!



You can get prepared to use the bulb after your b+

is higher from 110 to 160v dc

any lower and odds are you dont have enough voltage.

Ok in your case you dont have enough voltage..

remove the HOT and keep track of the wires connection

write it down or take a picture and dont break the disc cap

between the emitter and collector.

next measure the emitter voltage or TP B1 post the voltage

with out the bulb,,and record the voltage you want it to go up.

next measure the Base of X902 for 7.6 vs with the B+ pot pre-adjust this now!

Now measure every other spot X04,E,B,C

measure the voltage on X901 E,B,C

next measure the voltage on X902 E,B,C

and post the voltage's..

your looking to see how the power supply reacts with or without a load.!!

http://www.arcade-museum.com/manuals-monitors/Electrohome G07-904_Manual.pdf
 

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Very good advise there Never even Heard of that style of testing. I did swap the X701 with a good one from another board and same thing. It's gotta be something off the wall here. What do those little black bowling ball deals do that are sometimes buy the flyback and sometimes under the flyback. usually have a VR--- on them. Also what the heck do the four blue ceramic caps do next to T503?
 
#1 - Does the B+ at the resistor measure the same on both sides? I had that happen once when I accidentally switched the two wires when reconnecting the VR.

#2 - I'd look for little cracks around the traces to/from the flyback pins...
 
bulb

What's the bulb test. never heard of it and am having the same prob



Wellsgardner has a SB on it..

talking about it with the U2000/5000

how to test the power supply.

I'v been using it for over 40 yrs

you can use it between the dc to pin 1 of any flyback

to shift the load and make the fly work even if

it doesnt want to. then if theres a shorted winding in the fly

it will just burn up the fly and you know its bad now...

or whatever part is bad telling the shutdown circuits to disable the

drive pulse.


A fuse keeps Blowing and you want to let the cat out of the bag

as the saying goes.. replace the fuse with the bulb the bulb will lite alright

so will the defective part..lol

or it gives you a chance to montior voltages in the chassis.

I know monitor voltages at this website... nobody does that at this website..lol

What do measuring Voltages mean??? Theres only 1 voltage at the website

and its called B+ why would other voltages matter..

Even when they are posted on the schematic..I know I'm school

what do I know...

Can you tell if a transistor is working or not by the voltages

of coarse you can..
 
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