U3000 (33K3301) squealing all of a sudden

roothorick

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So some time ago I mostly disassembled a U3000 then reassembled it inside my Pump. I left off the degaussing coil, and lo and behold, gaussing issues cropped up over time. So, hell with it, I took it partway back apart, put the coil on, and now my colors are perfect, but it's giving me a loud, obnoxious squeal. It looks like it's working perfectly, no visible picture problems (well, a pincushion that was always there and some minor convergence problems), but the noise is too much. It sounds kinda like the quiet whine of a standard res monitor, only very very LOUD. It seems to respond to the computer, so it must be coming from horizontal deflection... but hell if I know what to do about it.

This ring wasn't there when I had the coil off, but it doesn't seem to make a difference whether the coil is connected or not. I have to leave it alone for now because of another person in the house needing to sleep for an early shift this coming morning, but it's gonna eat at me all night. I was thinking about cleaning the legs on the chassis-mount transistor and its connector, or maybe wedging something into the flyback to see if it's ringing.

Thoughts? Suggestions?

-E- When the pizza guy came I took the opportunity to give it one last shot. I shuffled the main board over a little bit then turned it on, and lo and behold, the squeal was gone... for a while. I heard it again while I was in the kitchen. So, it's heat sensitive! Lovely.
 
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got the same trouble with one of our Daytona USA monitors.... which is some goofy Sanwa model I haven't been able to track a model # down for.

I'm leaning towards it being a flyback thing. I've noticed the picture getting progressively fuzzier on our Road Burners (U3000) so who knows, maybe these flybacks are beginning to take a shit next. curious to know what you come up with.
 
I turned it on again today... it seems a lot quieter now. Also, it's not squealing on dark images anymore. In fact, the volume of the squeal seems to be directly proportional to the total brightness on screen. Seems odd that it sounds like 15kHz when this is a 31kHz monitor...

I think at the volume level it's at I can just live with it. I just need to figure out the pincushion and tilt adjustment...

-E- Left it on for ~30 minutes, walked downstairs... no more squeal. Ah, hell with it. It is jumping a little with sudden changes in brightness but it's so subtle it doesn't really bother me. If I can figure out a way to solve the distortion from the neons' EMI I'll be satisfied.

Actually on that note... is "jumpiness" while moving the V-size pot a sign of future problems?
 
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I turned it on again today... it seems a lot quieter now. Also, it's not squealing on dark images anymore. In fact, the volume of the squeal seems to be directly proportional to the total brightness on screen. Seems odd that it sounds like 15kHz when this is a 31kHz monitor...

I think at the volume level it's at I can just live with it. I just need to figure out the pincushion and tilt adjustment...

-E- Left it on for ~30 minutes, walked downstairs... no more squeal. Ah, hell with it. It is jumping a little with sudden changes in brightness but it's so subtle it doesn't really bother me. If I can figure out a way to solve the distortion from the neons' EMI I'll be satisfied.

Actually on that note... is "jumpiness" while moving the V-size pot a sign of future problems?

I'm no scholar on that subject either, I would say the U3000 was probably of a slightly better build quality compared the K7x00s and U5000s (U3000 is more like a K8000 on crack) so I can't really say much about the adjustment pots going bad on them, but I would think if the monitor ever goes crazy when you're adjusting anything vertically that it's probably directly related to some issue with the vertical IC on the chassis. it could be cold solder somewhere or anywhere.

I have zero idea for how to test B+ on those, but I would lean towards that maybe causing your original problem. the "jumping" on bright screens, you're not talking about blooming are you? that could be a filter cap issue. filter caps generally have long lifespans, I'm guessing cause they're so much larger, but like I said in my first reply about the flybacks, the U3000s are probably entering that age where they're going to start turning to shit in general now. lol
 
I'm no scholar on that subject either, I would say the U3000 was probably of a slightly better build quality compared the K7x00s and U5000s (U3000 is more like a K8000 on crack) so I can't really say much about the adjustment pots going bad on them, but I would think if the monitor ever goes crazy when you're adjusting anything vertically that it's probably directly related to some issue with the vertical IC on the chassis. it could be cold solder somewhere or anywhere.

Well, that symptom is it wobbles back and forth for half a second or so anytime you move the vertical size pot. Doesn't do it for the vertical position pot though.

I have zero idea for how to test B+ on those, but I would lean towards that maybe causing your original problem.

It's so trivial it's kinda silly. Just jam your leads into the connector on the PSU board. I don't know what a DMM is gonna tell me though. I suppose I could put it on a black screen, check it, then check it again on a white screen.

the "jumping" on bright screens, you're not talking about blooming are you? that could be a filter cap issue. filter caps generally have long lifespans, I'm guessing cause they're so much larger,

It's not so much bright screens as sudden, quick changes in brightness. On a static white screen it's the right size; if the image flashes white it'll expand slightly but quickly snap back, even if the screen stays white. I suppose that could be B+ drifting and vertical deflection compensating. As I said, it's rather subtle, and it doesn't bother me. If it's not a sign of bigger problems, I'm gonna leave it the hell alone.

but like I said in my first reply about the flybacks, the U3000s are probably entering that age where they're going to start turning to shit in general now. lol

I always thought the K7000 flybacks were just kinda shit in the first place? Aren't flybacks good for 30+ years so long as they're made right?
 
Well, that symptom is it wobbles back and forth for half a second or so anytime you move the vertical size pot. Doesn't do it for the vertical position pot though.



It's so trivial it's kinda silly. Just jam your leads into the connector on the PSU board. I don't know what a DMM is gonna tell me though. I suppose I could put it on a black screen, check it, then check it again on a white screen.



It's not so much bright screens as sudden, quick changes in brightness. On a static white screen it's the right size; if the image flashes white it'll expand slightly but quickly snap back, even if the screen stays white. I suppose that could be B+ drifting and vertical deflection compensating. As I said, it's rather subtle, and it doesn't bother me. If it's not a sign of bigger problems, I'm gonna leave it the hell alone.



I always thought the K7000 flybacks were just kinda shit in the first place? Aren't flybacks good for 30+ years so long as they're made right?

those monitors Wells put out in the 90s were kinda crap in general. I speak of course of the U2000/U5000, K7400/K7500, and DEFINITELY the K8000 and some other odd models. I've had to change a few of them out for drifting brightness/focus and I even had a K7000 with a black knob flyback that put a blue tint in the picture for some reason, and I parted out a dead chassis that had a new-ish flyback for it, and the picture looks perfectly white balanced now.

I have a U5000 that I seem to have decent color on all the guns, but I can't for the life of me get it to white balance right. puts out a purple tint on certain white screens no matter how much adjusting I do. so, hey, maybe the flyback needs to get changed out on that one too. those tubes are also especially garbage, all those Zenith ones. some of the K7x00 shipped with Samsung tubes, and I can't vouch for the 33"/39", those might've been different too, like RCA or Philips. the Zenith ones almost always have gun short/weakness issues, and even still after being rejuvenated.
 
I doubt it's 31khz you are hearing, the human ear shouldn't be able to hear that. It might be a small transformer or coil on the chassis, possibly in the SMPS circuit. My suggestion would be to remove it from the cab and power it up, then try to identify where it is coming from.

Failing that I would suggest turning up the volume of the machine.
 
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I doubt it's 31khz you are hearing, the human ear shouldn't be able to hear that. It might be a small transformer or coil on the chassis, possibly in the SMPS circuit. My suggestion would be to remove it from the cab and power it up, then try to identify where it is coming from.

My theory is it's a subharmonic of horizontal deflection, at around 15.5kHz. It could be the switcher, but why would they run the switcher so close to a subharmonic of the sync frequency? That's asking for resonance problems.

Failing that I would suggest turning up the volume of the machine.

Ahahahahahahahah... you do realize exactly what machine we're talking about, right? Putting the volume up above the halfway point isn't safe for buildings built against old code...
 
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