Need help with Sanyo 20 ez (DKJR)

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Hello everybody, my first post here.
Of course, asking for help 

I've got a DKJR with a Sanyo 20 EZ from a coworker.
The monitor showed the typical narrow/folded picture, so I went ahead and recapped it.

I haven't checked all the capacitors I have removed, but as expected, C407 was dead. I have many capacitors already so I didn't have to wait for a kit, however, I couldn't find in my parts any high temp 10uF/160V, so I installed the old C471 (that measured fine) in place of C407 and used a 10uF/450V/85C as C471. I decided to do this because C407 seems installed in a hotter spot. The intention was to get the monitor going while waiting for the correct caps.
The monitor worked flawlessly, B+ was already 109V and  I was able to adjust the width of the screen.
I turned off the monitor to get ready to adjust B+ (I had to scrape the B+ trimmer a bit because there was some paint) and once I tried to turn it on again, nothing happened. No picture whatsoever.

I have followed the typical flowchart, but my case doesn't seem to be there. Apparently everything works.
More specifically:
- B+ can be adjusted to 108V (some fluctuations in the 0.05V range).
- I can see that the mainboard works (there is audio and it reacts to the controls).
- With a scope I can see the video signals going from the mainboard to the little inverting board.
- The inverting board outputs the video signals and they are present on the connector that is on the 20 EZ board.
- Both fuses are OK.
- The image is not there from boot. Apparently there is no HV shutdown, still I did what the flowchart suggests in the case of a HV shutdown, adjusted all brightness trimmers halfway and set B+ to 108V. Still no image.
- The CRT heater glows (faintly, not sure if it should glow brighter).
- If I put my arm close to the screen the hairs on my arm get attracted by the glass (HV present?).

As I don't know what else to do, tomorrow I will take everything apart and check C407 and C471.
However if anybody has any idea on what the issue could be, I can really use some help.
Thanks!!




 

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Today I have bought two 10uF/160V/105C capacitors and installed as C407 and C471.
No difference, still no image present.

Is there any schematic around that has typical voltages/waveforms that are are expected at the various test points?
I have no experience with CRTs, so the plain schematic doesn't help much.
Thanks

[Etienne MacGyver]

Strange, all the sympthoms you describe point to a working monitor

but lets start with the basics, it started after you removed the seal on the B+ pot, why not replace that pot and see whats up ?

hairs on the arm attracted to the tube does indicate you have HV

Do you have a pitch black screen ?  what happens when you crank up the brightness to the max on the fly back, do you have anything on the screen then ?  (and i mean not an image, but at least some thing else than the pitch black screen ?)

if you have the time, watch these, lots of info on monitors here :

CRT monitors-Part 1 of 4

CRT monitors-Part 2 of 4

CRT monitors-Part 3 of 4

CRT monitors-Part 4 of 4

Classic Monitor Repair 01 of 03

Classic Monitor Repair 02 of 03

Classic Monitor Repair 03 of 03

here some links that might be usefull:

http://home.comcast.net/~mtpacifico/_kenskorner/files/Sanyo%2020EZ%20Troubleshooting%20Guide.pdf

http://www.arcade-museum.com/manuals-monitors/sanyo-ezv19raster.pdf

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Thanks Etienne,
I have double checked the B+ pot and it looks fine.
With the docs that you have linked I can run a pretty comprehensive check. I also should try to replace the NP capacitors that I didn't replaced the first time.
I will update the thread as soon as I know more
Thanks again!
G.

[gimgim]

Me again...
It took me a little, but I am finally back working on the Sanyo. More frustration.
I've replaced the NP caps and bought a digital scope in the meanwhile.

The monitor still has no picture. I can adjust B+ to exactly 108V (very stable) and I have the 16V on JP7.
If I increase the "screen" pot on the flyback, I can see a yelowish image and a raster scan. Flipping the service switch shows a bright vertical line.

With the scope I've checked the point BC/BB/BD. From a schematic I have, I should read 2.9Vpp. I can see the signal, but in my case it is 1Vpp or so. The signals arrive to the CRT neck board but at the collectors of the transistors I can read abut 150V more or less constant. Except for the B+, all trimmers are in their middle position.

Any idea what should I check? Is it possible that one of the caps I have used to recap the monitor was bad? Any educated guess?
Thanks.

[level42]

Doesn't the 20EZ has a switch that turns of the screen ? Maybe you maven it accidentally or it has a bad contact ?

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No, no switch that I know of.
I have watched the full series of Randy Fromm's videos, and it looks like a blanking problem, but I can't figure out what to check...

[Wurstkopp]

Do you have a ground connection on the neck board?

[gimgim]

> Do you have a ground connection on the neck board?

Yes, I've double checked after your suggestion.
I am going to try borrowing an ESR meter to check all the caps I've replaced, may be one was bad.

[gimgim]

I've got a ESR meter and checked all caps, nothing strange.
The problem is definitely with missing video signals.
With respect the attached schematics:
- Signal circuit board 1 (Green) is about 3.5V
- Left of R213 I have 7V or so (the Zener diode, I assume)
- Voltage drops to 1V at the base of TR205. Voltage at BB is also around 1V.
- The same happens to the other two colors.
- R241 was running too hot (checked with a thermal camera) and looked cooked. I've replaced it with a 1W resistor.
I have reflowed the neck board and the control board, checked grounds, wires, etc...
Turning brightness and sub-brightness do not change anything.

Any suggestion?
Also, assuming that ALL trimmers have to be adjusted, how do I set up the monitor from scratch?
I have both the 108V and the 16V, but I wonder if the color drive and color trimmers on the neck board could cause this (I don't think it's the case, but I don't know what else to try....)
Thanks