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LWK
10-15-2014, 05:58 AM
Curious about this issue. I revived the light on the marquee, redid the cp wiring, restored the cp entirely, including a major reduction of the rust under it. Looks like a drink spill issue gunked it up. I reflowed the power supply, that is working. It's slowly coming together.

Well, I need to figure out this monitor, as it keeps blowing fuses every time I put one in the chassis. I see a sign of some type of burn marks on the psu section of the chassis, it's not so bad, but there is this polyester film capacitor there that looks like its slightly cooked.. Tested the diode's in that section, and they are good and one direction only. I am also wondering if the HOT is a issue here. Should I just replace this? Getting zero glow on the guns. Advice appreciated!

LWK
10-15-2014, 07:18 PM
Chassis is a GMK-29FS3

LWK
10-16-2014, 04:27 AM
HALP

ReplicaX
10-16-2014, 09:57 AM
Start with the basics.

Thoroughly look over the chassis and neckboard for cold solder joints and poor connections, look for burn components, ohm check your flyback to verify one of the coils isn't shorted or open. If no findings, I'd pull the HOT out of circuit and verify it is good.

LWK
10-16-2014, 10:43 AM
If the hot is in that power section.. Or is that the B+? I pulled out the transistor near the flyback, and I didn't see a issue there that raised eye brows. I pulled one from the power section.. That thing looks to be shorted, as it gives me a reading no matter where I place those leads, and the reading is 02 all over.. -_-

It's that FN 651 I listed earlier, maker is SK, which I'm gonna ebay tomorrow. I reflowed the chassis and looked at that stuff already. I noticed a cold two way solder joint on a small diode in that power section, might be the cause of what blew this sucker. Has burn marks near the power supply of the chassis, and they didn't destroy traces or anything.. Neckboard looks fine.

ReplicaX
10-16-2014, 10:55 AM
It's that FN 651 I listed earlier, maker is SK, which I'm gonna ebay tomorrow. I reflowed the chassis and looked at that stuff already. I noticed a cold two way solder joint on a small diode in that power section, might be the cause of what blew this sucker. Has burn marks near the power supply of the chassis, and they didn't destroy traces or anything.. Neckboard looks fine.

Yes, if it was shorted it is what's definitely blowing fuses. When you replaced the fuse did it blow instantly with power on?

LWK
10-16-2014, 07:29 PM
Instantly, tried many things, always blew fuses. You think I should just shotgun all those caps and replace this transistor? Other thread says those caps in the power section are notorious for failure.

Xian Xi
10-17-2014, 04:32 PM
I guess easiest way would be process of elimination. Just unplug stuff then plug in stuff one by one until it blows a fuse.

LWK
10-18-2014, 12:48 AM
Ordered two transistors. One im gonna install raw. If it blows, it might be a cap. Then I'll recap and do another transistor. If that blows, I'll replace the flyback. I'll update with what happens over the next few weeks.

LWK
10-20-2014, 08:05 PM
Replaced transistor, now its attempting to power, but the flyback is just making this buzzing noise. It's not the anode cup.

LWK
10-21-2014, 10:37 AM
I'm wrong. Flyback isn't buzzing, the horizontal driver transformer near the HOT I replaced is. I wish I knew if my FN651 was the proper HOT. I got this cab and that thing was desoldered.

ReplicaX
10-21-2014, 11:43 AM
I'm wrong. Flyback isn't buzzing, the horizontal driver transformer near the HOT I replaced is. I wish I knew if my FN651 was the proper HOT. I got this cab and that thing was desoldered.

No idea unless there are schematics out there. I don't own the same cab or chassis, if I did I'd glady give ya the part #.

LWK
10-22-2014, 07:34 AM
So what could cause that transformer near the HOT to make that buzzing? Getting no HV on this damn thing. Flyback isn't buzzing or anything.

leopold
06-19-2016, 08:45 AM
Hello,

Did you solved the problem?
I have the exact similar problem on a GMK-25FS2.
It's a very similar chassis.
The transformer close to the Transistor FN651 is buzzing 2 secondes and nothing.
No picture at all.
But it's not killing my fuse. My fuse is ok.

leopold
06-21-2016, 02:12 PM
Please.
Someone can help to contact by pm LWK to ask him to come on this thread?
I can't pm him... limited account.
thanks a lot guys.

LWK
06-22-2016, 09:29 PM
Sorry man, I ended up getting another chassis on yahoo japan. I recommend looking there. It might be a bad flyback I reflowed the entire new chassis and recapped it for longer life span.

leopold
06-23-2016, 01:30 PM
Hi LWK,

Thx for your answer.
The thing is mine is a version for 25" tube.
GMK-25FS2
it's pratically the same but not exactly.
Probably no chance to find one on Yahoo. not common at all
Did you tried something else on this old chassis? repairs?(the one broken, not the one from yahoo)
Changing caps in the PSU section?
the 3 big caps?
I will definitely have to try something on this chassis.
I already changed few caps in this section but with no luck.
I will continue in this all section and test diodes in the same time.
It might be the Transistor maybe, the FN651.
I will try to buy one on ebay.

Thank you in advance,
Leopold

LWK
06-27-2016, 06:40 AM
I would at least try to replace the horizontal output transistor, it'll probably blow again though. GMK series is famous for stupidity, you will often times find these cabs monitor converted in the second hand market. Desolder your existing HOT and make sure it's not open all over with your multimeter. I fixed my friends neo 25 cab, it was a bad HOT. Thing is, I don't think the driver transformer was buzzing like a bitch on his, his would blow fuses over and over. Your problem I HOPE was not like mine, where I just wondered eventually if the LFBT was just done.