I would be very carefully checking every physically large component and reseat any cables/connectors. Since it all began with a mechanical event, the problem started because of a mechanical issue too such as momentary loss of contact or a bad solder that developed from that impact.

The monitor looks to be pretty complicated, with lot of places where any failures can be. I don't think I will try to familiarize myself with it yet. What are the parts with reduced and/or missing voltages ? And do any change when input resolution is changed ?

Whoa Tiido! I did not expect to see you over on Vogons. I know about your CCAM for Genesis. Thanks for joining in on the topic! 😁

I will trying to post some photos later on today of what I am dealing with, but I agree that something mechanical took place. The bed slats I am talking about are those Ikea Lönset, you might be able to google the image. One of these is just 20lb/9kg. It was standing up when it tipped over backwards, so I honestly think the centrifugal force of its weight plus the acceleration of gravity may have been just enough to push in the high voltage cable and lose temporary contact to the CRT with its hooks, and then cause problems down the line. All the boards inside of the monitor look very solidly protected, except for that strap on top. I'll show what I mean as soon as I can.

It does help that I was in the room when this happened, as it happened. The impact did not sound loud either. I did make the effort to grab the slats on time, but I was a couple of feet too far away to reach. I believe that the impact was not strong enough not loosen any of the cables or connectors. I unplugged most of them to rotate the main board for better probing access. I saw no improvement when I reconnected them. I've had this monitor for more than 15 years and it has not shown any sign of circuitry problems, except for 2 pre-existing things which do not appear relevant to this specific problem.

One of 2 things I am referring to are a buzzing sound from the PSU. I'm not too concerned of that right now, as the connector from there to the mainboard have given me correct voltages except for 1 pin, which is the other thing. It is a 215V lead to the heater. The heater was already glowing when I first took off the case, so this 215V lead might have to do with a certain intermittent brightness problem I was seeing last year. The pin on the header was not having any continuity to the PSU board. I resoldered it since I saw it. The schematic shows that this specific pin is only heater-related, so this fix definitely did not bring back any picture.

I'm still thinking that the fact that the monitor was on when the impact happened that a certain voltage/current spike or sag on the main board caused some form of component damage. If the monitor was still off when this happened, maybe I would still have picture today.

I've spent the last weekend going back and forth between these PDFs to understand what is happening on the circuit level. I am still at work, but when I am done, I can start trying to explain what I learned about the boards inside my own monitor, along with the measurements I took, from the flyback transformer, back to the deflection processing board.

When I had the laptop unplugged from the monitor, Linux went down to 640x480. I plugged it back in while probing the monitor. I remoted to the laptop to switch the resolution back to 1600x1200. Linux switched back fine. Still no picture on the monitor. Also, the status LED has been functioning as normal (solid green when on and connected to the laptop, solid amber when disconnected from the laptop).

Fly is frequently fails due to windings breaking down and shorting out. This usually takes out the horizontal transistor with it. But not always.

Also, there is very few options as long as you match horizontal transistors exactly or exceed it, usually works.

Provided that you address all the other issues especially capacitors.

I was in that era back then and writsressed the transition era from CRT to LCD, 2003 to 2010 at that tv shop.

Cheers,

CORRECTION: I said 215V line earler, but it was a 190V line I fixed on the PSU board.

I already took most of the shell off before I actually began taking pictures. I did not get the chance to take a picture of the flyback transformer area but I took shots of the side of the mainboard with the deflection sub-board, a shot of the bottom of the mainboard, and also 'fantastic' shot of what would be the back of the monitor. The strap I'm talking about is in one of these shots, it would attach to this aluminum piece of the monitor's shell. I don't have a shot of the high voltage cable below the strap. I'll attempt to post it during the day tomorrow.

As you might notice with the deflection board, the IC itself is not in view because it is soldered underneath.

Thanks for the insight, pentiumspeed. I'm curious myself if any transistors or transformers did end up blowing but it seems I would know more if there is once I get that horizontal drive waveform going again. I reviewed what I measured so far and I am not seeing notes about the grounds of the affected components, so I should check them before going further. The deflection board itself might need to be desoldered for me to really check the state of the deflection IC's connections to the headers, etc.

This is a better view of the strap, and the high voltage cable below it.

I verified the ground points for all ICs and passive components involved with what I am looking at, and they all appear grounded.

And for anyone who has been looking at the schematic for my monitor, I have been focusing on all page 2 (except a1-a3 [..] f1-f3, h1-h5, i1-15, a11-a16[..]f11-f16), the left side of page 3 up to cell 5, and most of page 4. I think the rest of the pages/sections are not relevant to the current problem I am having.

Go over soldering joints with magnifying glass carefully, what you want is sign of cracks. Paint heavily with flux paste and resolder, clean up old flux. What you want is important electrolytic capacitors large and small checked with a ESR meter it is not featured on your muiltimeter, you want to buy one made for measuring ESR, these capacitors are important in power supply and the horizontal circuit including the horizontal driver circuit that drives the main horizontal transistor.

After that, you go around fixing remaining issues after getting horizontal stuff running. Remember not to ignore the vertical deflection circuit, especially the retrace capacitor attached to the vertical IC driver.

Strap is all plastic shielding sheet over the HV suction cup, just in case any arc that escapes.

That is typical Nec design, nice look.

Cheers,

Oh yeah before I go on about this, I should probably mention that I have taken circuit theory and electronics classes when I was in university, then I did small laptop and flat-screen repairs (part replacements), then I've been getting into lightly modding electronics recently, along with more advanced repairs of broken things that I have. Before this monitor, I have been able to safely discharge and replace the flyback transformer for a 19" TV, a couple of years back. This is all I have for CRT experience. Hopefully I can get this monitor showing picture again, to add to this experience 😀

For a while, I had a PDF for the schematics of the FE950/FE1250, for the moment that it would be needed, like this one. I used this PDF at first as a reference then quickly found out that the components were not matching up. The only thing I really found useful was the troubleshooting flowchart for the FE950. The pins did not match up, but it had me check for the voltage of SCREEN. I found it on my monitor and measured 0V, so that was a small confirmation that the flyback transformer is not energized and there is nothing running in the kVs.

I did not use this PDF beyond that, then searched and found the correct documents for my specific model and mainboard (FE1250+). To get more clues, I searched the flyback transformer's manufacturer part number, and I found no matches. Then I found some indirect information on where I might be able to order one, using the monitor's model number. I then searched the part number for the horizontal output transformer (HOT), and this search is what lead me to the PDF for the DPro2070SB/FP-2141SB. When I looked at the schematics in here, I found plenty enough similarities with what I am concerned about, to decide to use the troubleshooting flowchart in here.

IC5C0, IC601, and the HOT use the same part number between both models. Both monitors have a DBF (dynamic beam focus) and HD (horizontal drive) transformers. Both have an IC701 to regulate the voltage of the flyback transformer and both are using op-amps to drive the HV side of the FBT. They both have a 7414 and a TL083 working between the relevant transformers and the deflection IC (IC601). The pinout between the mainboard and the deflection board are the same, as well. These show generally similar circuits for generating these high-voltage signals. They may have been drawn by the same team, even, where only certain areas of the schematics got updated and others stayed relatively the same. I expect the voltage readings to be wildly different between the PDFs here and there, so this is why I have only been using the DPro2070SB/FP-2141SB one as a guide for what areas to test, and I have been using the PDF for my own monitor, along with some deduction, to figure out what measurements I should be expecting.

The manual for the DPro2070SB/FP-2141SB feels like a nice one that is targeted for authorized service centers and repair-persons. Only about 3 pages of details about the chips. The one for my monitor, however, feels more like a step away from a datasheet of each IC, filled with flowcharts and waveform examples. Pgs 18-34 explain the bulk of what is happening in the HV area and with IC601 and pgs52-55 explain some more of what IC601 is doing.

@pentiumspeed, I just saw your latest reply before posting the above. Yeah, I get it that there is the possibility of bad capacitors, but given the lack of AC just about anywhere, I think I should focus on getting that restored before hunting down a bad capacitor. What I was going to do now is explain the function of each large component, what I'm expecting based on the manual, and what I am measuring instead. The general flow of the HV area seems to me that some initial waveforms are generated from IC601, some AC is simulated by transistors in groups, controlled by ICs, and these simulated forms of AC are what energize the transformers.

The HD signal comes from Q501-Q504 to energize the HD tranformer. This makes Q550 generate a horizontal flyback pulse (called AFC) that goes back (double-inverted ) to IC601.

IC5C0 uses HD and AFC for controlling the MOSFET that powers the HOT, whose pins all measured 0V.

So I guess it would be like this:

-->- Q50x -- HDT -- AFC(Q550) -
^xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx\
HD (IC601,start) ->-------------- > - IC5C0 ---- Q5F1 ----> HOT (end)

The beam focus signals come from IC601, too. Horizontal and vertical both pass through an op-amp, then through 1-6 transistors then the DBF transformer. This transformer and Q7A6 are supposed to be powering the FBT, according to my monitor's PDFs.

I'm not seeing enough information about this IC601, though. Do these DBF focus signals generate once IC601 sees AFC appear, or do they generate independently?

I guess I could come back and cross this out if I am completely wrong, but assuming AFC is needed to generate the focus signals, that flow is supposed to look like so from my understanding:

-- ->-HDF(IC601)--HFocus(IC6A1)--Q7A1-Q7A5 - T7A1 ->- ef2 of FBT (end)
^
AFC(Q550, start) ->-VDF(IC601)--VFocus(IC6A1)--Q7A6 ->-FBT pin1 (end)

After going through all of this again, I'm seeing that I did not jot down the readings for IC701, which is a regulator for the FBT. The manual says that this IC can shut down the FBT, and the MPU IC can shut down the regulator, to shut down the FBT. I do remember that the regulator was being powered fine so it wasn't shut down, but I might as well measure those pins for completeness.

Despite the lack of notes on the regulator, I'm leaning on wanting to de-solder the deflection board and see what I measure when it runs by itself heh-heh-heh....

I just wanted to give a small update about this monitor repair. So, about 3 weeks ago, we received a record of 18+ inches (450+ mm) of rain in 24 hours where I live, and due to so much water, about 12 inches of it went inside my apartment. For anybody who has never experienced floods, when enough water flows in and continues flowing in, the plastic bins start floating. When the water gets high enough, even bins with CRT monitors start floating, including mine....

It was pretty nerve-wracking to save everything I could that was not already up high. I quickly was running out of table/counter space everywhere, but I made exactly one spot for this bin with the monitor. I lifted the whole heavy thing and walked through the apartment and the water to this spot. Things slipped and almost fell into the water. I feel like by the time I made it to this spot, the mainboard was basicly dangling by all the cables going to the CRT boards and the PSU board. The mainboard may have also bent a little while carrying all of this, but nothing that appeared extreme at that moment.

So basicly because of this flood, I can't do much with the CRT right now. I lost a bunch of wooden furniture and I have several other electronics that did get wet. I just finished the cleaning of the apartment and I have several more other things to clean/disinfect before I can get to these other electronics, then finally I can go back to the CRT, so this may be another month or so.

Those wooden bed slats were hit by the water and were growing mold, so I tossed those out. It does suck that they had to fall on the monitor first though......

While I do disappear some more to continue taking care of this mess, I was wondering if anybody here has been able to order CRT parts from the original manufacturers nowadays. Assuming the mainboard has not suffered any further damage from the flood, the deflection board probably would be the first part I would try replacing. I imagine getting just one of these boards from them would not cost more than $100, if it's possible to order, of course.

Has anybody here had any luck with ordering anything from NEC-Sharp (displays), Renesas (chips), or Mitsubishi Electric (boards) to repair a CRT or has buying a used or 'for parts' CRT of the same model been the only way to repair these nowadays? I ask this because I saw a relatively recent post on another website, where they were able to buy a replacement flyback transformer directly from Panasonic for a certain TV, but of course Panasonic and NEC are not affiliated. I'm very curious about this and I think this could be useful information for any other NEC CRT users out there doing repairs.

For anyone wanting to search the deflection board from their end, the PWB-DEFLSUB has part number CP210C095B10 printed on it. Interestingly, the schematic PDF lists the DEFL-SUB as CP980A151.

The chip on this board is an NEC uPD61882(BGC), listed as part number CP267P151(-01). I found datasheets for other NEC chips in the same family, but not the one for this particular chip. If anybody has a PDF link for the uPD61882 to share, that would be fantastic. I am definitely curious as to what exactly NEC ends up programming in the chips, and the answer might be in this datasheet.

Thanks in advance for any information or stories you have about ordering from NEC, Mitsubishi, or Renesas!