WG K5515 / 720 Monitor issue

Jedidentist

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Howdy folks!
So I bought this 720 in non-working condition...but working prior to going into storage. After looking through everything and replacing all of the fuses I could, I still have nothing. I can coin it up and seem to be able to hear it play blind. I bought a second video PCB, as I just happened to come across one on E-bay and jumped on it. My original video PCB didn't seem to light up on powering up, but this one does...in neither case did it change the functioning of the monitor. Power's coming out of the switcher and transformer okay, and checked the end of the wire going into the monitor's PCB. I've replaced and reseated all of the wiring. I also removed and replaced the flyback, just in case there was something loose there. I'm not even getting a glow on the neck, and no humming whatsoever from the monitor...no arcing or anything. What do you guys think I should try next? Replace the caps? Flyback? All of the above? Keep in mind that even though I'm using all of these terms, my knowledge is EXTREMELY limited...only what I've picked up over the past few months. Thanks!

Derek
 
I'd try to connect up another monitor to the 720 cab as well as connect the 720 monitor to another machine. It will not display correctly in either case (assuming that the other monitor/cab are standard res) but it will help you identify which component is not functioning.
 
Good idea for trouble shooting...if I really had that option. I've got a System 1 machine (Indiana Jones), but not sure of the compatibility, and wouldn't want to risk screwing it up. And unfortunately, I don't have a work area with a bunch of spare things around. Would it make any sense that a monitor would go from working to completely non-functional after 2 years of storage because of just bad caps?
 
It could, but I would think a cracked solder joint in the power section of the monitor is more likely. As for the IJ, the monitor would work fine for what I am suggesting. You only have to swap one connector between monitors, and it will not damage anything.
 
Unfortunately, I've got a multimeter, but have extremely limited knowledge on how/where to use it. Yes, I've read tutorials, etc. but unless I know exactly where to hook it up, I can't measure things such as "B+". Yes, I'm hopeless, I know. I watched this little vid:

http://www.youtube.com/watch?v=2LqmDMEI1fI

...but I can't really find that part on my board...I may just be blind. This is what I'm working with:

IMG_1039.jpg


IMG_1022.jpg


This big black cap looks a little corroded on the bottom left there (blurry...tough to focus)

IMG_1029.jpg


IMG_1037.jpg


IMG_1038.jpg


Anything look really out of the ordinary? Where can I test B+? And before anyone points me to BYOAC FAQs, I just tried to register there, but I'm waiting and can't seem to find the FAQs...are they hidden when you're not logged in? I know this is asking a lot, but I can't do much else on this this weekend and my guy won't be here until at least monday, so I thought I'd try something. Thanks so much!

Derek
 
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I'm reading through those FAQs and going through the monitor manual...I still can't figure out where to measure B+, so I guess I'm just stupid. In any case, while reading through another thread I saw that someone posted this picture of the same monitor:

IMG_1225.jpg


Well, guess what mine looks like:

IMG_1033.jpg


According to you, Peale, this is a "TO-3 style transistor".

Would this result in absolutely zero life to the monitor? Where's the easiest place to pick up one of these babies?
 
Heh... uh, I don't think that worked when it went into storage if that's missing... that's kinda important ;) . I believe that's Q352, which is the HOT (part # 2SD870). Bob Roberts should have them. You might ask if he's got screws for it too, since yours are missing.

DogP
 
I'm already on it... Found it here:

http://www.mikesarcade.com/cgi-bin/store.pl?sku=TRNS89

but we've also got a good electronics store that I'm going to check out on monday. Sorry I posted before using my brain...I should know better than that. In any case, I checked the cab to see if it was laying there, but to no avail. Since I hadn't pulled out the board, I didn't see it was missing on the side. However, I would think that this would complete my circuit, and without it, no go...right? Well, we'll see on monday...
 
I think the 25" used 2SD871...

I just checked the manual I have for the 25" k5515 and it says 2SD870.

And yeah... it definitely wouldn't work without that, though people don't typically pull those for no reason (unless maybe they needed it for another machine), so it seems likely something else is wrong with it.

DogP
 
Unless they had no need for a 25" chassis and needed it to fix a 19" chassis...
 
Well on the side where it was previously mounted, there's some sort of substance that I can scrape off. Looks like Bondo or some sort of dried out adhesive. I supposed it could have just fallen off. That being the case, I would expect to have found it, but maybe not. As someone else had posted (the pic I borrowed showing the transistor in place), I guess these things can corrode...maybe the guy started recapping the monitor, saw the corrosion, removed it and didn't have a spare, and never got around to it? Guess I'll find out on monday...
 
that stuff you see is heat sink compound. helps transfer the heat from the HOT to the wall so it can disperse easier.

When you replace the transistor, don't forget to put a mica insulator between it and the side wall - otherwise you will blow the transistor, fuse, and maybe something else right away. Sometimes the parts suppliers don't include them...
 
Well, as a follow-up to this, I finally got my transistor and the other transistor-looking thingy on the other side. Matched up the exact part numbers and had to order them from two different suppliers. Got new mica insulators and heat sink compound. Hooked them both up tonight....and nothing :( The TO3 transistor looking thingy on the left heats up, and I got a shock from it, but the 2sd870 transistor on the right doesn't get warm. I was really hoping that by just replacing these two parts, that would do the trick, but I still don't get a single hum or glow from the tube. I guess I now just need to go along the whole board and see what tests bad. Unfortunately, I don't really have the know-how for that one. Maybe I can call an old-school TV repairman? The guy I'm working with right now isn't great at monitors...but he can replace my caps, so I suppose I should move on to that as my next step.
 
I've never heard of a TV repairman doing any more than taking people's money when asked about arcade monitors. Are there any KLOVers local to you that could help? Or you could mail the chassis off to someone to get it repaired.

DogP
 
Well, as a follow-up to this, I finally got my transistor and the other transistor-looking thingy on the other side. Matched up the exact part numbers and had to order them from two different suppliers. Got new mica insulators and heat sink compound. Hooked them both up tonight....and nothing :( The TO3 transistor looking thingy on the left heats up, and I got a shock from it, but the 2sd870 transistor on the right doesn't get warm. I was really hoping that by just replacing these two parts, that would do the trick, but I still don't get a single hum or glow from the tube. I guess I now just need to go along the whole board and see what tests bad. Unfortunately, I don't really have the know-how for that one. Maybe I can call an old-school TV repairman? The guy I'm working with right now isn't great at monitors...but he can replace my caps, so I suppose I should move on to that as my next step.

Did you go through the entire chassis and check for cold solder? Also, it's possible that some of those new caps might have no been soldered in correctly or you have a broken trace.

I really doubt a TV repairman is the answer. There are some people here who repair these and you could also try Arcadecup.com or P&L in California. I used P&L a few times and had mixed results, but they will take your stuff back and work on it again during the warranty period.
 
I finally decided last night that I'm not going to screw around with it anymore. I don't want to waste any locals' time and I'm not going to bother the guy who's been helping me...because even he stated that he's not a "monitor guy". I've got it all packaged up and I'm going to ship it out to Arcadecup.com right now because he'll even repair the flyback. The $135 is a steal in my mind for me to have piece of mind and just be done with the frickin' thing. I'll post when I get it back!

Derek
 
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