K4901 so close - then kick to groin

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I was attempting to adjust the screen positioning on my freshly recapped new/used flybacked chassis that has been running fine for what little use it'd had. In an effort to adjust the screen for the new board attached to it I heard a grrrrrrzzt and then no HV. Great! WTF you can't adjust your monitor lol??
So I checked the fuse, still good. Checked HOT and the VR on continuity test. VR checks out ok but the HOT beeped once. Hmmmmm .... so I replaced the HOT with a brand new one. (Before I powered up I checked it - one beep.)
I will be physically pulling the chassis tonight to inspect it. Any pointers where to check for problems on this pig?
 
I don't know if you can really test the hot in-circuit on this as I think there's the high voltage caps across it - so you'll get one beep both ways.

On the last one I fixed - one of the solder pads on the hot actually lifted - , check to see that your 130v test point is ok and look at the hot soldering closely to see if maybe you're having the same problem. It was really hard to see in fact I'm amazed I found it. The fuse was ok, everything looked ok it just didn't turn on.

From what I understand the flys don't go bad often but as with anything I'm sure they can and do, just not common.
 
The single beep you heard, probably followed by a climbing value, is your meter charging a cap connected to the HOT in some way.

It's most likely a cold solder joint. Have you verified your power wire pins aren't hogged out. I have often had issues like this when I pumped the connector and lost power. Usually I don't realize what I did, and I spend some time checking out the chassis before finally figuring it out...
 
thanks for the help guys I'll report back tomorrow. My wife and I have a running joke - I'm the $500 man (rip off from the Million Dollar Man). Seems like everytime I get into something it's $500. It'd be a welcmoe site to see a colder solder joint or lifted trace.

So how does a person test a HOT out of circuit?
 
thanks for the help guys I'll report back tomorrow. My wife and I have a running joke - I'm the $500 man (rip off from the Million Dollar Man). Seems like everytime I get into something it's $500. It'd be a welcmoe site to see a colder solder joint or lifted trace.

Now that's funny... :)
So how does a person test a HOT out of circuit?
It tests just like a normal transistor when pulled from the circuit, I believe.
 
It tests just like a normal transistor when pulled from the circuit, I believe.

Yep its just that depending on the monitor you have a couple diodes or hv capacitors across the legs while it's in circuit, so its hard to test sometimes, although my redneck-monitor-repair rule of thumb is - its either shorted or it ain't. That won't find an OPEN hot, but honestly I'm not sure I've ever seen one go open (unless it goes pop). If you test it in circuit and its showing shorted across all 3 legs, good chance its bad and has to be removed anyway. If you test it and its not quite shorted but maybe giving you the same or wierd readings either way - chances are there's a cap involved and at least a 70% chance its good.
 
I pulled the chassis and looked it over. There is nothing burnt, no cold solder joints and the fuses check out good, the HOT and regulator also checks out good. I'm kind of at a loss now. There's is NO HV on that monitor. I'm wondering if the flyback went south at this point. I realize typically a HOT will blow with the flyback but it's strange that the HOT and fuse is good. The sound it made when it went out reminds me of the sound you hear when a regulator gets grounded. It kind of sizzles and pops. Oddly enough when I was adjusting the monitor I swear I could here alot of extra crackling going on under the anode cup.
 
realize typically a HOT will blow with the flyback but it's strange that the HOT and fuse is good.

That is an incorrect statement. I've had plenty of monitors with bad HOTs and good flybacks.

You need to start at Step One: Measure the B+. That will tell you what to check next...
 
That is an incorrect statement. I've had plenty of monitors with bad HOTs and good flybacks.

You need to start at Step One: Measure the B+. That will tell you what to check next...

I did say "typically" :)
Hey Mod I've been searching high and low for a K49xx flow chart. Can you link me?

Damnit how come I couldn;t find this last night - for anyoen else who wants this flowchart link for many monitors
http://pounceatron.dreamhosters.com/games/monitor/monitor-troubleshooting-flowcharts.pdf
 
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Update - I have no voltage at R503. I have swapped regulators with a known good regulator. Flowchart says to replace R601 - problem is where the hell is that thing? I've stared at this board for 15 minutes and I'm "snow blind" now.
 
It's a big white 3.3-ohm 10-watt resistor - should look like a white rectangle - located near the power section, possible up on the side wall....
 
Checked R601 (thanks for the identifier Mod) and it specs out fine. Also pulled R503 and R506 which also check out ok. Any other ideas?

BTW - I have a second K4901 which works great (In a game I just acquired) - but I noticed one leg of C501 is actually pulled out of the board. I wonder - what's this component for and is this an issue?
 
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If you still have zero volts at R503, then it's obvious that there is something keeping the voltage from getting there.

Check your voltage regulator.
Check your fuse.
Check to make sure you have 120vac in.
Physically wiggle every single part between the AC input and R503 that sticks up from the board a little and watch the legs underneath. Reflow anything that even LOOKS weird...
 
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