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 Post subject: Another spongebob 13inch crt rgb mod atempt.
PostPosted: Sat Apr 03, 2021 6:12 am 



Joined: 29 Mar 2020
Posts: 34
Thanks for reading , so i got me one of those spongebob 13 inch crt tv, that i would like to do the rgb mod mostly as i want to put 2 crt monitors together to create a mini punchout cabinet. Ive allready tried to mod one of those winnie the poo tv and failed, so ill be more carefull on this one.
The bad news is that this is not the same model as the original rgb mod done here https://tinkerplunk.wordpress.com/spongebob-tv-rgb-mod/
as it has some diferences, but it comes pretty close to the other model.
Main diferences are as shown in this picture are:
Spoiler: show
Image

Also i dont have the osd source chip , rather i have one small one at the bottom
M37150M8
Spoiler: show
Image

and the other chip,jungle chip , its the same one
140398-DI2
Spoiler: show
Image

So acording to his instructions,
Quote:
From these I was able to trace the RGB and blanking lines, where I removed the inline resistors.

So i think i need to remove the resistors at 262,263 and 264 and 265 right? he didnt have them so he just removed the jumpers i guess?
then he said
Code:
I then used a schematic provided by Syntax on the shmups forum to replace the resistors with values that would allow me to mix in the RGB from the RCA jacks with the OSD signal without losing the OSD or requiring the use of a switch.

He still talks about the same resistors right? and acording to his schematich he added 2.7k for the rgb and 180 for the blank right?
If so, for me would be just replacing the existing resistors.

then he said:
Quote:
I replaced the existing blanking resistors with the values from the schematic, and then just put a wire from a 5V signal on the board to the non-ground leg of the grounding resistor.

Thats were the 180 resistor will go.
Plus adding the 5v line

Then:
Quote:
I replaced the in-line OSD resistors. I then put one leg of 75 ohm resistors 2 ground and pointed them up out of the board, then put the inline resitors of the external signal into the other side of where the original grounding resistors were, mixing with the OSD, and then going through the existing 0.1μF caps into the jungle chip.

So this one as he states, i just should add 75ohm resistors terminated to ground
but since i dont have resistors there on my chassis, what kind or resistors should i add? non? or should i add the ones i removed from ther other place? or perhaps the same value ones as he did 360ohm according to his schematic
Spoiler: show
Image


Thanks for reading and hope someone will point me in the right direction, thanks.


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 Post subject: Re: Another spongebob 13inch crt rgb mod atempt.
PostPosted: Tue Apr 06, 2021 12:25 am 



Joined: 29 Mar 2020
Posts: 34
So easter got in the way, i did not had any advance on this mod, so today i went to buy the resistors, and dumb me, asked for 2.6 resistors intead of 2k.6 so the guys a the store gave me 3ohm resistors so i gues is my fault for not being clear. anyway i proceeded to add the 75ohm resistors terminated to ground, added the 180ohm resitor to blank , added the 360ohm resistors together with the 75ohm resistors, and i will have to wait for tomorrow to buy 2k.6 resistors as the original moder did.

In the mean time, i did found a diode on the blanking way that reads 589 on my multimeter, that might be the reason the original moder used 360ohm resistors toghether with the 75ohms terminated to ground.....

Gosh i wish i could see the talks he had with syntax, as im doing this blind as there are no schematichs online for this. Anyway

Im still tryibng to understand why the the original mod was done with 2.5k resistors? Anyone that can help me understand that? ive seen more than 100 reads on this topic but not a single coment, so feel free to comment and if you can help me , i would really apreciate it, thanks for your time.


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 Post subject: Re: Another spongebob 13inch crt rgb mod atempt.
PostPosted: Tue Apr 06, 2021 7:49 am 


User avatar

Joined: 09 Aug 2017
Posts: 1516
Location: Australia
Follow the pictures in MarkOZlads signature.


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 Post subject: Re: Another spongebob 13inch crt rgb mod atempt.
PostPosted: Tue Apr 06, 2021 4:42 pm 



Joined: 29 Mar 2020
Posts: 34
Syntax wrote:
Follow the pictures in MarkOZlads signature.

Hey syntax thanks for watching me. I do have have a dumb question, as i want to learn.

I do get how you guys get the value for the resistors highlited in blue. Its based on the value of the original resistor that are fisical or what the schematic says and if it has diodes or not, then you use the picture guide on Markoslad signature to calculate the value, right? im still trying to understand how you guys come up with the 0.5vp-p and 0.7vp-p, so ill keep reading.
What i dont get is, how you come up with the value of the resistors highlited in red.
i want to become like Markozlad and you , the type of helping guys , thats why imtrying to fully understand this formula, so thanks in advance for your time and any help.
Image


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 Post subject: Re: Another spongebob 13inch crt rgb mod atempt.
PostPosted: Wed Apr 07, 2021 1:38 am 



Joined: 29 Mar 2020
Posts: 34
So today i had my first fail, i added the 2.7k resistors and turned on the tv with my rgb emudrivers pc that i have currently working as a cocktail cab on an aa arcade monitor, anyway so i conected the cables turned on the tv, and i get red flashes only, more black screen time, i pushed the menu button, and i could barely see an image of the menu but in flashes as well.
So i started to double check my work, and all seem to be in place

2.7k resistor where the original resistors were.
Image

I could not fing 360ohm resistors at any of the electronics store so we conbined 2 to come up with 363, plus the 75ohm resistors terminated to ground and twisted together.
Image

And i should be getting the 5v from here as per instructed on the original mod
Quote:
I replaced the existing blanking resistors with the values from the schematic, and then just put a wire from a 5V signal on the board to the non-ground leg of the grounding resistor.


This is my actual image
Image
I added a cable to the back composite port and ground as well, same result.
Hope someone can help me here to figure out what im doing wrong. Thanks for waching


UPDATE:

So i double checked my work and turned out i had the 360+75 ohm resistors that need to be terminated to ground not installed as they should be, since i had to mix 2 to get 360ohm i was bypasing one of them and the toal value it was giving was, around 100, anyway, i joined them they way they should be in serie, not paralell, and now i have the correct value. So now i have a black screen, no image, but if i push the menu button i get
https://streamable.com/a2n9r4

I know the cable and the pc work on rgb, heres a picture of the system working
Image

One thing i forgot, is i dont have the control for this tv, so the tv is in channel mode, maybe thats why i dont have an image? perhaps i need to get a universal remote to set this on video, and that way hopefully ill get an image....stay tuned for more....


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 Post subject: Re: Another spongebob 13inch crt rgb mod atempt.
PostPosted: Wed Apr 07, 2021 8:25 am 


User avatar

Joined: 09 Aug 2017
Posts: 1516
Location: Australia
abispac wrote:
What i dont get is, how you come up with the value of the resistors highlited in red.


You measure them.


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 Post subject: Re: Another spongebob 13inch crt rgb mod atempt.
PostPosted: Sat Apr 10, 2021 3:56 am 



Joined: 29 Mar 2020
Posts: 34
Shit, i cant seem to find a remote to change the input on this thing, so i was wondering if anyone can give advice on how to force the video input on this thing?
Perhaps using the main chip to short 2 inputs?

Image

Maybe shorting something out on the remote circuity of the tv?

Im still looking for a working remote conte control, that acording to this guy on reddit, ge remotes should work, i found one on the flea market but it didnt had a search function
https://www.reddit.com/r/crtgaming/comments/j6gm4f/spongebob_crt_tv_remote/

So if you are a real technician that can give me some kind of help i would really apreciate, im eager to know if this mod was succesfull or not, plus i want to start my next project, thanks and have a great day.

Ps: I dont live in the US so going to wallmart and buy a cheap remote is not an option, but we do have plenty of flea martes during all week, i just have to be patient to find that one remote.


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 Post subject: Re: Another spongebob 13inch crt rgb mod atempt.
PostPosted: Sat Apr 10, 2021 7:05 pm 



Joined: 29 Mar 2020
Posts: 34
So i found a remote today, and went and hook the tv to the electricity and i got a loud pop near the 220 caps , so i checked the caps and a resistence and they where gone, so i replace them with some spare ones i had from other scrap tvs, and once i connected it again, POP, same shit, some for me thats it, im gonna scrap this project, as i dont get any interest from the public anyway, its not that important and not worth the time
Dont get me wrong, im learning and theres plenty of tvs to learn with, LOL i just want to get me a pair of 13 inch tvs and thats all.
I saw a couple of disney princes tvs for 10 bucks on facebook, i hope ill get them, as i saw a video on youtube from the segaholic guy, and they seem easy to mod...so this one is case closed...


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