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JunitoNo1

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Hello, everyone.

I have an issue with my NNC currently. The image controls for the Toshiba may or may not be functioning correctly.

Quick facts:
Toshiba D29C051
Model PB9930-2
20210713_130357.jpg

20210713_135017.jpg


My issue started when I decided to try and center the picture. The 4 buttons behaved in the following:

FUNCTION: brings up the menu and cycles through the menu with another press. Cycling was random as it would select up or down with no real pattern.

UP: Behaved as the select button to enter a sub menu and increase a value by +1

DOWN: No function whatsoever

DEGAUSS: Does just that

Long story short, got my picture stuck all the way to the rightside.
20210713_053918.jpg


I attempted cleaning the tact switches, which helped the random selection on the function button, it's now only cycling down one per press. Still no response from the down button, though.

I took a meter to pins 40 and 42, which get continuity when the down button is pressed, so I'm assuming no issue with the button at this point.
20210715_053532.jpg

With this out of the way, I'm suspecting an issue with the board on the tube, but I'm unsure of how to diagnose that.
20210714_041129.jpg

I've reached out to a member of the forums about an extended remote board for my cab, but until I hear back, I'm stuck trying to figure this out.

Also, seems like I can't even select the RESET option in the menu, UP works on every option but that. Is there a secret way of selecting this? Maybe another method of reseting the picture?

I would really prefer to avoid touching anything on the tube, as I'm still not very experienced with these things. Any advice on the matter would be greatly appreciated.
 

archimage

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It could be a bad wire messing with the controls, had this problem before, changed the cable and everything went fine
 
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JunitoNo1

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It could be a bad wire messing with the controls, had this problem before, changed the cable and everything went fine
I'll try and run some new lines to see if that'll solve my issue. Fingers crossed.
 

JunitoNo1

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So the remote and cabling are for sure good, continuity everywhere.

Anyone have a schematic for the chassis board? I wanna know where pins 38-42 lead to.
20210716_050744.jpg


@nem had suggested in another thread the possibility of corrupted firmware. Is there a way to diagnose something like that?

I'm pretty frightened of doing any genuine repairs on that board. If it comes down to it, how hard is it to get a hold of a replacement board? And will it be plug and play?
 

nem

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It's just the down button that's not working, right?

It's not a firmware issue. Did you have a replacement remote on the way just to rule that one out for certain?

I don't believe there's a schematic available. You'll just have to follow the traces and see where they go.
 

JunitoNo1

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It's just the down button that's not working, right?

It's not a firmware issue. Did you have a replacement remote on the way just to rule that one out for certain?

I don't believe there's a schematic available. You'll just have to follow the traces and see where they go.
Correct, it was just the down button.

Still waiting on a reply back for that replacement board you linked me to. In the mean time, I've ordered some replacement tact switches that I'll swap in and try my luck with. After that, I'll wait one the extended board, however long it'll take.

If I'm feeling brave enough after all else is said and done, I'll pull the main board out and dig deeper into this.

I'm still very new to all of this, so I'm out of my comfort level with a lot of these repairs.
 

JunitoNo1

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So I replaced all the tact switches. Same scenario as before. No function from the down button, though I'm getting continuity from it, and the reset option is still unusable.
20210717_140346.jpg
20210717_140326.jpg

Now, ill wait for the extended remote before attempting anything else.
 

dewmansnk

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OpOpenFunctionUpDownDegaussColorGeometry
Pin
385v
395v0v
404.6v0v4.0v?
414.6v1.0v0v4.0v
42Gnd


Here are some old notes I made on the remote board. If you want to test down, you could use a little wire and jump pin 40 to 42 to ground out pin 40 and simulate a down button press.
The geometry hidden menu I couldn't remember the voltage hence the (?). The degauss might not be complete either, but down should be correct.

Also, there is that 3 position switch on you chassis - towards the back, near the flyback (S404 on the silkscreen) - That switch is for adding in a horizontal shift, either left, right or center. It looks like yours is switched out of center so might be adding a little horizontal shift that you are not expecting.
 
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JunitoNo1

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OpOpenFunctionUpDownDegaussColorGeometry
Pin
385v
395v0v
404.6v0v4.0v?
414.6v1.0v0v4.0v
42Gnd


Here are some old notes I made on the remote board. If you want to test down, you could use a little wire and jump pin 40 to 42 to ground out pin 40 and simulate a down button press.
The geometry hidden menu I couldn't remember the voltage hence the (?). The degauss might not be complete either, but down should be correct.

Also, there is that 3 position switch on you chassis - towards the back, near the flyback (S404 on the silkscreen) - That switch is for adding in a horizontal shift, either left, right or center. It looks like yours is switched out of center so might be adding a little horizontal shift that you are not expecting.
I'll try jumping the pins to see if anything happens.

And you're referring to this switch, right? I'll position it center and see if anything happens.
20210716_050748.jpg
 

JunitoNo1

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OpOpenFunctionUpDownDegaussColorGeometry
Pin
385v
395v0v
404.6v0v4.0v?
414.6v1.0v0v4.0v
42Gnd


Here are some old notes I made on the remote board. If you want to test down, you could use a little wire and jump pin 40 to 42 to ground out pin 40 and simulate a down button press.
The geometry hidden menu I couldn't remember the voltage hence the (?). The degauss might not be complete either, but down should be correct.

Also, there is that 3 position switch on you chassis - towards the back, near the flyback (S404 on the silkscreen) - That switch is for adding in a horizontal shift, either left, right or center. It looks like yours is switched out of center so might be adding a little horizontal shift that you are not expecting.
So I centered that switch, didn't change much.

I ended up putting two wires directly to pins 40 and 42 on the main board, then seating the remote connector on top. I was able to open the menu and cycle through still, but down did nothing again. I checked with my meter, and I am getting continuity on those wires.
20210718_053349.jpg
20210718_053922.jpg

So after bypassing everything leading to the board and still having no success, is it safe to bet the trace is broken somewhere along the line on the board?
 

dewmansnk

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IMG_3903.jpg


IMG_1875.JPG


You can see roughly center image is the remote board connector (notice the silk screen '42', '41', '40', '39', '38')
and the MCU is upper left.

Remote board pin 41 looks like it goes through a wire jumper (JP077), then a resistor (RA15) on its way to MCU pin 16. Also looks like it might get an external pull-up(RA14?) along the way.
 

JunitoNo1

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IMG_3903.jpg


IMG_1875.JPG


You can see roughly center image is the remote board connector (notice the silk screen '42', '41', '40', '39', '38')
and the MCU is upper left.

Remote board pin 41 looks like it goes through a wire jumper (JP077), then a resistor (RA15) on its way to MCU pin 16. Also looks like it might get an external pull-up(RA14?) along the way.
Thanks so much for the photos. Ill use these as reference to skip over the trace and just put a small wire from the down pin to wherever it leads.
 

JunitoNo1

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IMG_3903.jpg


IMG_1875.JPG


You can see roughly center image is the remote board connector (notice the silk screen '42', '41', '40', '39', '38')
and the MCU is upper left.

Remote board pin 41 looks like it goes through a wire jumper (JP077), then a resistor (RA15) on its way to MCU pin 16. Also looks like it might get an external pull-up(RA14?) along the way.
So pin 40 leads to these two points. I have continuity there. And RA13 leads into one of rhe legs of the chip next door. Not sure where to go next.
20210720_045206.jpg
 

JunitoNo1

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So I pulled the board to investigate, nothing stands out to me.

Still no response from the down button and the reset option.
20210722_013639.jpg
 

JunitoNo1

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Update:

With some help from @DragonMinded, I checked the ohm values on the remote boards resistors. All in spec. I followed that up with checking the values of the resistors on the chassis that pin 40 (DOWN) lead to. Failing values.

RA12 should be 4.7 kΩ, its actual value is 1.48kΩ
RA13 should be 2.2 kΩ, its actual value is 1.48kΩ

I'll attempt replacing the resistors, once I can find where to buy them, and report back. Hopefully this leads to success.

Since I'm such a beginner with this stuff, I have a question: Just because I have continuity between these points doesn't necessarily mean the correct signal is getting through, right? The resistor is, I guess changing the value of the signal, and the board is looking for that specific value. With a failing resistor, the board ignores the signal with the incorrect value. Is this train of thought right?
 

dewmansnk

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Update:

With some help from @DragonMinded, I checked the ohm values on the remote boards resistors. All in spec. I followed that up with checking the values of the resistors on the chassis that pin 40 (DOWN) lead to. Failing values.

RA12 should be 4.7 kΩ, its actual value is 1.48kΩ
RA13 should be 2.2 kΩ, its actual value is 1.48kΩ

I'll attempt replacing the resistors, once I can find where to buy them, and report back. Hopefully this leads to success.

Since I'm such a beginner with this stuff, I have a question: Just because I have continuity between these points doesn't necessarily mean the correct signal is getting through, right? The resistor is, I guess changing the value of the signal, and the board is looking for that specific value. With a failing resistor, the board ignores the signal with the incorrect value. Is this train of thought right?

Did you happen to measure the resistors RA12 and RA13 in-circuit ? (Did you measure them while they are still soldered to the board) I am guessing that would explain the difference in resistance.
You want to verify that MCU-16 is getting pulled up to 5 volts, take a DMM and measure across MCU-16 and Ground with no remote board attached - it should be right around 5.0v.

You should also see the MCU-16 get pulled down to ground when you push the 'down' button. My guess is either MCU-16 isn't getting pulled up to 5v or worst case, the MCU pin is dead.
 

JunitoNo1

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Did you happen to measure the resistors RA12 and RA13 in-circuit ? (Did you measure them while they are still soldered to the board) I am guessing that would explain the difference in resistance.
You want to verify that MCU-16 is getting pulled up to 5 volts, take a DMM and measure across MCU-16 and Ground with no remote board attached - it should be right around 5.0v.

You should also see the MCU-16 get pulled down to ground when you push the 'down' button. My guess is either MCU-16 isn't getting pulled up to 5v or worst case, the MCU pin is dead.
I did measure them still in circuit. I checked all the resistors in that area and 12 and 13 were the only ones not showing a correct value.

So MCU16, you're referring to the chip directly next to the resistors and the 16th leg of it, right?
 
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dewmansnk

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I did measure them still in circuit. I checked all the resistors in that area and 12 and 14 were the only ones not showing a correct value.

So MCU16, you're referring to the chip directly next to the resistors and the 16th leg of it, right?

Yes, MCU-16 is the 16th pin of the MCU chip, the one directly next to the resistor. You can see the silkscreen pin (1) and (21) on the PCB, so that should help identify pin 16
 

JunitoNo1

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Did you happen to measure the resistors RA12 and RA13 in-circuit ? (Did you measure them while they are still soldered to the board) I am guessing that would explain the difference in resistance.
You want to verify that MCU-16 is getting pulled up to 5 volts, take a DMM and measure across MCU-16 and Ground with no remote board attached - it should be right around 5.0v.

You should also see the MCU-16 get pulled down to ground when you push the 'down' button. My guess is either MCU-16 isn't getting pulled up to 5v or worst case, the MCU pin is dead.
Ok, so checking pin 16, the highest voltage reading I got was 3.3v, most of the time fluttering around 2.1v or so. Not so steady hands. When grounded, it did hit zero.

So, what could be the cause of that leg not getting enough juice? Would it be the resistors? Or something else?
 
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