(Topic ID: 260369)

SWEP1 Ducksan CRT gradually getting brighter after a few minutes

By xteslax

4 years ago


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  • 22 posts
  • 10 Pinsiders participating
  • Latest reply 3 years ago by FlipFun
  • Topic is favorited by 2 Pinsiders

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20200301_221447 (resized).jpg
screen_2 (resized).JPG
screen_cold (resized).JPG
screen warm (resized).JPG
screen_1 (resized).JPG
flyback_under_after (resized).JPG
flyback_under_before (resized).JPG
flyback_top (resized).JPG
flyback (resized).JPG
neck pcb connector (hole?) (resized).JPG
neck pcb (no glue splotch) (resized).JPG
neck pcb (with glue splotch?) (resized).JPG
#1 4 years ago

Does anyone have any idea why my monitor gradually gets brighter?

My SWEP1 has its original Ducksan CGM-1901 C/W monitor within it. Picture looks great initially, except over time it gets brighter and shows retrace lines (I think that's what they're called). The retrace lines are not moving, just static diagonal lines with 1 faint vertical line near the middle. The gradually increasing brightness washes out the whole picture in a green hue over time, making the retrace lines visible. I am able to turn the brightness down (with the front control panel) to return the picture to normal (black looks black again, colors look good, and retrace lines disappear), which needs to be done every 5-10 minutes. Eventually, I am unable to turn down the brightness (dial already at its lowest setting), so I turn the machine off. I do not feel comfortable leaving it on for too long.

Over the weekend I re-capped the neck and chassis PCB boards with this cap kit ...
https://www.arcadepartsandrepair.com/store/components/capacitors/ducksan-cgm-1901-series-monitor-cap-kit-105c-nichicon/

When I bought the machine 5 years ago, the monitor was not working. At the time I had replaced the large filter cap (it was leaking) and neighboring rectifier (may have been blown, don't remember) on the chassis PCB to get the monitor working, so I did not replace these again during my weekend re-cap. It has had this issue of gradually getting brighter ever since. I just dealt with it by not leaving the machine on for very long and turning down the brightness.

I would like to repair it, so I can leave it on for long periods when friends (and kid's friends) are around. It's most-likely to be enjoyed, if it's on when guests arrive. I've been considering a conversion to LCD, but I feel like I am close to fixing it.

I am not experienced at CRT repair. I was happy to see the CRT working after I re-capped it (a little stressful replacing 40 caps), but disappointed that it hadn't fixed the original issue. I have read many newsgroups, but do not have a clear idea of what's wrong.

I've attached a few images ...
- neck pcb (with glue splotch?)neck pcb (with glue splotch?) (resized).JPGneck pcb (with glue splotch?) (resized).JPG
The neck PCB top (before re-cap), showing the brown stuff that was under the red cable's connector and all over the neighboring 10K resistor. It looked like the resistor was leaking, but I've never heard of that. I think it may be a splotch of glue.

- neck pcb (no glue splotch)neck pcb (no glue splotch) (resized).JPGneck pcb (no glue splotch) (resized).JPG
Close up after cleaning possible glue splotch. The resistor looks ok.

- neck pcb connector (hole?)neck pcb connector (hole?) (resized).JPGneck pcb connector (hole?) (resized).JPG
The under-side of the neck PCB (midway through re-cap), showing a strange hole (in red) in the PCB where 1 of the connector's pins exists. I'm not sure if this requires a connection to the large PCB trace (ground?) or if it is just to help support the connector to the PCB. I was thinking of creating a jumper (with thick wire) to a nearby pad (in orange), but I was too scared of destroying the CRT.

I would appreciate any help. Thanks!

#2 4 years ago

Sounds like the flyback is starting to drift.

#3 4 years ago
Quoted from Dr-Willy:

Sounds like the flyback is starting to drift.

I've heard these are hard to get a hold of. Any idea where I could find one? Are they interchangeable with another manufacturer's flyback? Thanks.

#4 4 years ago

I have had flybacks do this and go out of focus after a few minutes on.

#5 4 years ago
Quoted from xteslax:

I've heard these are hard to get a hold of. Any idea where I could find one? Are they interchangeable with another manufacturer's flyback? Thanks.

Unfortunately I don’t. I would reach out to peter who is the owner of arcade parts and repair and see if he has a source.

#6 4 years ago

I agree it's probably the flyback. Is there a part number on it? Might be easier to find one with that.

Long term solution... go LCD.

#7 4 years ago

Check your G2 voltage to see if it's rising. G2 is the red wire in your photo that plugs into a lug on the board. If volts are rising over time, that is causing the brightness increase. Flyback can cause it, bad solder connections on the flyback can cause it on some monitors, CRT can cause it as well. When volts are high and too bright, unplug the board from the CRT and recheck. If volts drop back low after unplugging the CRT, problem is the CRT.

#8 4 years ago
Quoted from RobertWinter:

I agree it's probably the flyback. Is there a part number on it? Might be easier to find one with that.
Long term solution... go LCD.

I think the part number is DNF-E136049 (sticker on side, shown in flyback image).
flyback (resized).JPGflyback (resized).JPG

#9 4 years ago

Another comment of no help, but just for info, the glue you found near the resistors is glue they use to glue the G2 screen red wire that plugs into the board securely. All monitors regardless of brand pretty much do this. Chinese love glue, and believe in using it all over all these monitors.

#10 4 years ago

Mine has started doing this as well... increasing in brightness as it says on.
I haven't begun debugging - instead kind of living with it.
Following to see if there is a final answer.

#11 4 years ago

I appreciate the info provided so far.

Quoted from Zitt:

Mine has started doing this as well... increasing in brightness as it says on.
I haven't begun debugging - instead kind of living with it.
Following to see if there is a final answer.

I've lived with it for too long. No guarantee that I'll get to the bottom of the issue, but I'll try to dig in a little more. Though, I might bail and try a LCD conversion.

Quoted from Ronkz650:

Check your G2 voltage to see if it's rising. G2 is the red wire in your photo that plugs into a lug on the board. If volts are rising over time, that is causing the brightness increase. Flyback can cause it, bad solder connections on the flyback can cause it on some monitors, CRT can cause it as well. When volts are high and too bright, unplug the board from the CRT and recheck. If volts drop back low after unplugging the CRT, problem is the CRT.

Ok, I'm a little worried about doing this safely. I'd like to confirm that a replacement flyback is available before attempting anything too dangerous. Re-flowing the solder connections on the flyback and trying again seems easy enough (may try over the weekend, if I have time).

If I do this, I'm thinking of soldering some wire to the test points I should probe, so I can keep a safe distance and prevent myself from accidentally shorting something. A few questions ...
1. Do I measure AC voltage?
2. To what do I connect the other lead of my volt meter? To "GK"?

When you say "unplug the board from the CRT and recheck" ...
3. Do I turn the machine off and then unplug the neck PCB (I think "yes")?
4. Is it safe to unplug the neck PCB without discharging the monitor first (not sure)?
5. Do I measure "G2" again with the neck board off and the machine turned on?

I'm just gathering detailed information before deciding on my next steps. Thanks.

#12 4 years ago
Quoted from Ronkz650:

Another comment of no help, but just for info, the glue you found near the resistors is glue they use to glue the G2 screen red wire that plugs into the board securely. All monitors regardless of brand pretty much do this. Chinese love glue, and believe in using it all over all these monitors.

I'm glad to know that it was only glue. I was looking everywhere for the source of the leak.

#13 4 years ago
Quoted from Ronkz650:

... bad solder connections on the flyback can cause it on some monitors ...

Do you think what I found, shown in the 3rd picture of my first post for this thread, may be the cause? Though, this is on the back of the connector (of neck PCB). Thanks.

#14 4 years ago

Something else will eventually go wrong with that monitor. Definitely in your best interest to switch to LCD.

You can buy the parts from Rob
Kahr

Http://kahr.us

#15 4 years ago

The unsoldered pin on the socket is not used, so that is not the problem. To measure voltages, have your meter on DC, and hook the black lead to ground such as the steel frame of the monitor then measure the voltage on the heavy red wire that plugs into the lug on the board. Voltage is adjustable by one of the adjustments on the flyback and more voltage means more brightness. Voltage could be anywhere within a pretty large range, but normally 300-400v, can be adjusted down below 200v or as high as 650v or so. Measure voltage on the wire and compare readings when cold vs hot. If voltage is in fact rising, turn off monitor and instead of unplugging the entire board, all you have to do is unplug the red wire, then fire up the monitor and check voltage on the red wire. If volts have dropped back low, the CRT is likely bad (rare to cause this, but possible). If voltage is still high, chances are flyback bad, but try soldering the pins first.

#16 4 years ago

That circled pin on the back of the neckboard is not used. Leave it alone.

If you have a picture tube rejuvenator, use it to test the picture tube to see what condition it is in internally.

1 week later
#17 4 years ago

Here are some more pictures of the screen during machine boot up ...
screen_1 (resized).JPGscreen_1 (resized).JPGscreen_2 (resized).JPGscreen_2 (resized).JPG
Note the slight discoloration on the lower right side.

Here is a picture of the screen when it is cold (with the reflection of the playfield) ...
screen_cold (resized).JPGscreen_cold (resized).JPG

... and another picture showing the retrace lines (after 20 minutes, though these can show up immediately if I turn the brightness up) ...
screen warm (resized).JPGscreen warm (resized).JPG

Quoted from Ronkz650:

..., but try soldering the pins first.

I re-flowed the solder for the flyback, wicking the old away, cleaning, and placing new solder. Here is a picture before re-flow ...
flyback_under_before (resized).JPGflyback_under_before (resized).JPG

... and another picture after re-flow ...
flyback_under_after (resized).JPGflyback_under_after (resized).JPG

Here is a picture of the flyback (fron its top), which shows some residue on top of it ...
flyback_top (resized).JPGflyback_top (resized).JPG

Quoted from Ronkz650:

To measure voltages, have your meter on DC, and hook the black lead to ground such as the steel frame of the monitor then measure the voltage on the heavy red wire that plugs into the lug on the board. Voltage is adjustable by one of the adjustments on the flyback and more voltage means more brightness. Voltage could be anywhere within a pretty large range, but normally 300-400v, can be adjusted down below 200v or as high as 650v or so. Measure voltage on the wire and compare readings when cold vs hot. If voltage is in fact rising, turn off monitor and instead of unplugging the entire board, all you have to do is unplug the red wire, then fire up the monitor and check voltage on the red wire. If volts have dropped back low, the CRT is likely bad (rare to cause this, but possible). If voltage is still high, chances are flyback bad, but try soldering the pins first.

I finally got a chance to do this. When cold it measured 265v (and rising slowly) and when warm (after 20 minutes) it measured 365v (and rising slowly). Unplugging the red wire (G2) and measuring made no difference to the voltage reading. It was about 370v (and rising slowly). What was strange is that the CRT did not display when the volt meter was connected. I only modified connections when the machine was off. I guess my flyback is bad.

#18 4 years ago

Sorry to hear that. I hope mine isn't bad as well.

4 weeks later
#19 4 years ago

Until you fix it...

Let your game warm up (to where it's too bright) and then turn the flyback down with the left POT (circled).

Then just make sure to let it warm up before you play.

20200301_221447 (resized).jpg20200301_221447 (resized).jpg
4 months later
#20 4 years ago

Any progress to solve the issue?
I have the same issue:
Important:
the Brightnes pot does not respond on screen when turning it. I measured the res value Of the pot with dmm while turning and it changes res value so seems working.
Caps?

#21 4 years ago
Quoted from FlipFun:

Any progress to solve the issue?
I have the same issue:
Important:
the Brightnes pot does not respond on screen when turning it. I measured the res value Of the pot with dmm while turning and it changes res value so seems working.
Caps?

I still have the issue. Still dealing with it. I have not tried DavidWatters suggestion because I missed his message. A few questions about the suggestion ...

1. Is this something that should only have to be done once? (My guess is 'yes'.)
2. Would counter-clockwise turn the flyback down? (My guess is 'yes'.)

I want to be careful, since I will be doing this while it is powered on.

Thanks,
Gus

1 month later
#22 3 years ago

David means you should mark the position. It will not solve the issue, you should do it every time. Turning the screen pot is no harm when fired on. A pitty we can not find the high voltage trafo.
Mine only comes perfect again for brightness when turning the screen pot. You use the brightness pot on the control panel to get a good brightness again?

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