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Neotec NT-500DX Repair

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Rocketeer2001:
The 3 bi-polar caps are on the neck board, but I don't have a bright to dark streaking like you mentioned, so that's probably not the issue.

There's this pot on the chassis board called VR 601 H.V ADJ. I don't know if that's for 'horizontal / vertical' or if it's for 'high voltage'. I don't know what this pot adjusts, but perhaps it has something to do with my ghost wave. After I get everything hooked back up in the cabinet I'll take a video of the issue.

Speaking of which, I did the big swap taking the Neotec out of the 'new' cabinet and taking the D9200 out of the 'old' cabinet. These SOB's are heavy! After removing the Neotec out the one cabinet and almost breaking our fingers and wrists (needed a helper, I don't see how anyone could remove these things solo), we decided to lay the other cabinet on it's back. It was a lot easier to just lift a monitor straight up and out rather than trying to lift it with outstretched arms while trying to jiggle bolts loose.

lilshawn:
that is a high voltage adjust. it's normally set at the factory and then never changed.

running the HV (AKA "B+") at too high voltage can cause excess x-rays to be produced and can cause an x-ray protection circuit to kick in and shut the monitor down.

same as stuff like transistors and FET's, sometimes HV caps (over 100v) can measure okay with the low voltage a meter/tester uses to test, but fail when you apply the full beans voltage to them. it's recommended if you haven't changed all the caps, to do so. sometimes they will cram a small one in behind the flyback out of sight. i don't remember if this chassis does that, but it's worth a look.

Rocketeer2001:
Yup, changed all the caps except those 3 bi-polar ones and the big filter cap in the power section. There was a few caps hidden between the flyback and the heatsink and I replaced those.

But if VR601 H.V ADJ. is the high voltage adjust, then what's this other one (VR501 B+ ADJ)  that's in the power section?

lilshawn:
sorry, i'll try to explain a little better.

in an SMPS supply, you take AC and turn it to DC. this DC voltage is B+ then you take the B+ and pulse it 10,000 times a second through a transformer and create all the voltages (190v 20v 12v 6v etc.)

but quite often in older monitors, you'd take AC, turn it to DC... then run it through a linear regulator module to create "B+" that you then use to drive the flyback and the horizontal youke winding... then also resistors and crap to tune the voltage down for the various other circuits.

so the nomenclature of "B+" is used for a couple different kinds of voltages.

in the case of the nt500, with an SMPS... it's technically named "B+" is created with a feedback loop to a control IC (IC501) it's peak is about 392VDC this is the B+ used to be pulsed through the transformer. the R501 adjustment allows more or less voltage through to the sense pin of the control IC to raise or lower this voltage.

while technically not "B+" the main high voltage (HV+) of 140VDC used to drive the flyback (and adjusted by R601) which would normally be "B+" in other older monitors.

so in a nutshell typically, the high voltage DC side voltage is just normally called B+

generally if I say B+, i'm usually referring to the high voltage used to drive the flyback and/or possibly the horizontal deflection yoke winding if it doesn't have it's own supply (like the WG 9200/9400 does). (sorry, it does share a supply, but each has its own drive is what i meant by that.)

in any case ramble ramble ramble.

the HV and B+ in this case, very likely don't need to be messed with. quite often the spec on B+ is something super dumb like maybe... 147vdc +/- 12vdc...  so honestly it could be anywhere from 135 to 159 volts and still be fine. hell i've read specs saying B+ should be like 113 and i measure it and it's 145... and then turning it down makes it collapse and die. so take any stats you see with a grain of salt, since really...much like cooking... it should be done by feel. if it feels okay... it's okay. maybe it's just cause i'm an old grey beard.

i'm going to bed now, i feel old.

Rocketeer2001:
Shawn, thanks for the thorough explanation. Sounds like I don't need to make any adjustments to those since they have a wide operating voltage range.

I was able to take a video of my ghost wave. It doesn't play well with the camera and I get some moire going on, but you can still faintly see the issue. Look for a vertical wavy ghost line on the left side of the screen:


What's odd is yesterday it was a thin white wavy line and I had the screen's focus adjusted pretty well. Today when I turned on the arcade the wavy line was now fat and transparent, and my previously focused images are now out of focus. Not sure what that's all about. I adjusted focus on the flyback again to get it more crisp, but I can't seem to get it as good as I had it, and the fat wavy line doesn't revert back into a thin wavy line.

Edit:
I was just playing with adjustments again and this time I can get that wavy line to be almost invisible and get the image sharper by tuning down the brightness (now at 50%) and contrast (now at 65%) in the OSD. It's not as bright as I'd like, but it has less image issues this way, so maybe that's the only fix I can do.

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