19K4914 blowing its fuse

mshaw

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Howdy! I've got a WG 19K4914 (in Gauntlet) that is blowing the 4A fuse (F501).

A brief history: Had this game for a few years and red never worked very well on it. So, I figure probably a cracked solder joint, might as well do a cap kit while I'm inside. I did the cap kit, resoldered everything I could, and the game worked great for 2-3 months, nice picture, full color, etc. Then the fuse blew. Then I had to move, so now a year later, I am finally working on the game.

I removed the deflection transistor (Q352) and tested it; all terminals read closed relative to each other, so obviously the transistor was fried. I replaced it with an NTE 98 and replaced the fuse. Fired the monitor up and the fuse blew after first becoming spectacularly orange. I thought I heard deflection chatter initially, but the tube definitely didn't glow. Taking the new transistor out and testing yields results that I am uncertain about thanks to my crappy meter, but it does appear to be blown. Regardless of its status, though, I am assuming that something else is wrong.

One of the two bolts that attaches the bracket on top of the flyback is broken (see the hole on the left in the attachment), but it was already broken when I initially removed the monitor to do the cap kit. Could this have an effect on things? The other bolt is firmly attached and the flyback doesn't seem loose. From what I have seen on the web, it looks like testing a flyback is a PITA to say the least, and often they are rather proprietary, so there isn't a highly specific procedure.

I'm wondering where to proceed at this point:

Remove and attempt testing the flyback?
Just replace it?
Are there other places I could/should be looking?

Also, my once-trusty analog multimeter is very old, and seems to be on its last legs. Any specific (or general) recommendations for a replacement?

Thanks,
Matt
 

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na i don't think that would affect anything being broken. you still have one good bolt in there.

get a new digital MM it will save you allot of headache trying to measure allot of the parts you need to check.

get a fairly good one auto ranging is the best.
fluke 77 III is what i use and i love it.

yes check diodes 501-506 your VR and your H.O.T.

i would start there. report back after you get them checked.:)

Peace
Buffett
 
Finally did some testing...

Hi, I know it's been forever, but we wound up moving twice in the interim and I haven't had a chance to get back to this until now.

So I tested resistance on D501-D506 (in place on the board) and all came back somewhere in the range of 240K - 300K, same both directions. So nothing melted into a short, but shouldn't I be getting low resistance one way and very high the other? Or maybe I'm not testing the right way?

I also checked between all pins (3 + the case) on the VR (Sanken STR381). No shorts. I don't know what else I can really measure/check on that either.

On the original H.O.T. (D898B), all pins are shorted to each other. None are on the one I replaced it with (NTE 98), even after the fuse blew again. Just testing these for continuity; again, I have no idea if there are more specific things I can check for.

Any advice on how next to proceed?
 
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the diodes should be blocking the signal 1 way and passing it the other.

pull one leg and test again.

sounds like you may need to send it in for repair.

Peace
Buffett
 
Hmm. Actually I think I'm seeing the effects of some of the capacitors here (e.g. C503), so I may have to remove the diodes if further testing is required. I can say for sure that none of them are straight up shorted out.
 
I think my Fluke 77-IV is working well, I'm just not receiving the kinds of results expected in diode testing mode. I will have to desolder and try again, as suggested. Meanwhile, this variable coil seems to have a resistance of 0.2 ohms, which is low enough to trigger the beep for continuity testing. I haven't touched its adjustment wheel at all, just wondering if that is within the expected range? I realize that the resistance presumably becomes impedance when the coil is in use, but not sure what to expect from it when just measuring it by itself.
 

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