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CRT TV EEPROM & Micom hacking for RGB (+tube swap for 48cm to 51cm TV)


buttersoft

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This thread started out being about swapping a 48cm tube onto a chassis that originally had a 51cm tube, but has turned into a discussion of EEPROM and microcontroller hacking to enable RGB on old Australian (possibly NZ) SD CRT TV's on which it appears to have been disabled by the microcontroller (Micom). Discussion of the latter begins a few pages in, and it's all very much a work in progress.

 

Note that not all old sets need the above, in progress hack in order for you to RGB mod them. As a very rough guide, if the neckboard has colour pots for RGB bias/gain, you probably don't need to worry, injecting signals into the jungle IC should just work. For newer sets without neckboard pots, try inserting RGB, and see if it works.

 

Remember that the shumps thread is a better place for information on the subject of RGB hacking!

 

I've been hunting for more RGB-moddable chassis to drive 20"/48cm TV tubes - the standard 2ohm/14.8ohm ones in old cabs. They're getting harder to find though.

 

After @namastepat's just-make-it-fit suggestion I was wondering about swapping out the chassis from a 51cm TV and using it on a standard 48cm tube. Do the 51cm tubes typically have the same yoke resistances and pinout? Is the required HV going to be much different? I know I've seen chassis that will suit multiple tubes.

 

At the moment I'm looking at this job here - https://my.mixtape.moe/rnatkf.pdf.

 

That service manual says the chassis can handle 14", 20" and 21" tubes. (In this particular case I suspect the 20" and 21" tubes might be the same thing but US vs Aus names? i.e both the same 51cm tube, not a 48cm one?)

Edited by buttersoft
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Need to recalibrate a few things some times, but if the yoke is the same and tube pinout is the same, then it can be made to work.

 

48cm and 51cm tubes are both different sizes, if that is what youre asking at that end there? Theyre not just the same tube measured differently.

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Need to recalibrate a few things some times, but if the yoke is the same and tube pinout is the same, then it can be made to work.

 

48cm and 51cm tubes are both different sizes, if that is what youre asking at that end there? Theyre not just the same tube measured differently.

 

Good to hear. Do you know if the yoke and pinout are typically the same though? What are the typical readings and pin no.s for a 51cm TV tube? I'm sure Joey would know... I might grab one and test it. EDIT: I suppose i could try reading tubular, but if there's a shortcut here i'll take it :)

 

It's the chassis swap i want to do, the tubes sizes were more about Aus vs American terminology - we'd call a 48cm a 20" tube, they'd callit 19". We'd call a 51cm tube 21", but i'm not sure what they'd call it. The service manual lists 14", 20" and 21", but i thought the last two might be describing one tube, not two different sizes :)

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Good to hear. Do you know if the yoke and pinout are typically the same though? What are the typical readings and pin no.s for a 51cm TV tube? I'm sure Joey would know... I might grab one and test it. EDIT: I suppose i could try reading tubular, but if there's a shortcut here i'll take it :)

 

It's the chassis swap i want to do, the tubes sizes were more about Aus vs American terminology - we'd call a 48cm a 20" tube, they'd callit 19". We'd call a 51cm tube 21", but i'm not sure what they'd call it. The service manual lists 14", 20" and 21", but i thought the last two might be describing one tube, not two different sizes :)

 

If the tube is from the same series the pinout will be the same. Its in the service manual.

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@soyl any chance you'd know the answer to this one? I'm looking to swap a chassis from a 51cm/21" tube to a 48cm (US19"/A20") tube. Assuming both have the same B10-277 socket, and roughly the same yoke resistances, what else should I look out for? Would you happen to know typical yoke measurements on a 51cm TV tube, or are there too many different types? Are they all B10-277 pinout?
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@soyl any chance you'd know the answer to this one? I'm looking to swap a chassis from a 51cm/21" tube to a 48cm (US19"/A20") tube. Assuming both have the same B10-277 socket, and roughly the same yoke resistances, what else should I look out for? Would you happen to know typical yoke measurements on a 51cm TV tube, or are there too many different types? Are they all B10-277 pinout?

 

Heater voltage, G2 calibration, drive settings, its all in the service manual ;)

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@soyl any chance you'd know the answer to this one? I'm looking to swap a chassis from a 51cm/21" tube to a 48cm (US19"/A20") tube. Assuming both have the same B10-277 socket, and roughly the same yoke resistances, what else should I look out for? Would you happen to know typical yoke measurements on a 51cm TV tube, or are there too many different types? Are they all B10-277 pinout?

 

They're a mix of small/narrow neck 29mm (B10-277) and minineck 22.5mm (B8-294). Thomson, Samsung and Philips only used the former and those cover the vast majority of 21" TV tubes. Mininecks are mostly found on Japanese tubes (like the Toshiba JAR family). The yokes are pretty much in the same range as the typical 20" ones (H inductance: 2.00-2.70mH; V inductance: 24-30mH; H resistance: 2.3-3.5ohm; V resistance: 13-15ohm). And as always with tubes from different manufacturers the filament is rated differently (higher/lower current more than voltage) so the resistor in series with the heater voltage may need to be changed accordingly.

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The yokes are pretty much in the same range as the typical 20" ones (H inductance: 2.00-2.70mH; V inductance: 24-30mH; H resistance: 2.3-3.5ohm; V resistance: 13-15ohm).

 

Ok, so the 51cm tube that's with the chassis has the right pinout but slightly lower resistances - 2.1ohms & 10ohms @ 20mH. (A51JSY63X, 6.3v heater, 50V G1, CR-23)

 

There is a 48cm tube listed in the service manual for this set, though I do not know its yoke resistances or inductance - (A48QAD220X, 6.3v heater, 70V G1, CR-23)

 

And i have a few 48cm tubes with the classic 2.3ohms & 14.2ohms. (A48KMX12XX or equivalent, 6.3v heater, 50V G1, CR-23)

 

So the pinout is right, and the horizontal coils might be ok, but the vertical coils and G1 seem a bit... interesting. Why is the compatible 48cm tube listed at a higher G1? That's the bias voltage, isn't it? The service manual probably isn't complete, but there's a handwritten note scrawled on the only schematic (last page) saying it's for both the 51 and 48cm tubes. No alternate or swapped parts are indicated, so how would the increased G1 be handled? And I was hoping there'd be a single series resistor to swap out for the vertical deflection, like for the heater even if i don't need to swap it, but no such luck. I'll keep staring at the schematic.

 

I guess I'm asking for advice from here. This is more a test case, as there are no pots inside beyond the B+ setting, no real description of the EEPROM table, and I don't have the remote to get into the service menu. But working, suitable 48cm sets are getting harder to find :(

 

EDIT: Service Manual linked in original post.

Edited by buttersoft
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You're using a chassis, not a rejuvenator. The cathode-G1 voltage is handled by the chassis which varies the negative bias of the G1 grid through the brightness control. You shouldn't worry about that.

 

As for the lower values of the vertical coil, the chassis will likely handle that with no problem (horizontal yoke, now that would be a totally different matter). There is surely a resistor in parallel with the vertical yoke and one in series with one side of the vertical yoke. It's possible to lower the value of these resistors to accomodate vertical yokes with lower impedances.

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There is surely a resistor in parallel with the vertical yoke and one in series with one side of the vertical yoke. It's possible to lower the value of these resistors to accomodate vertical yokes with lower impedances.

 

Ok, so this following is the schematic for the v-def section. The resistors are higher values than i other (arcade) chassis i've tinkered with, and the circuit is more complicated. There is a resistor in parallel (r408) but not exactly one in series. I was planning to start by replacing r408 (470ohms 1/2W) with a network + pot that would go between 400 and 500ohms at its limits. Does that sound reasonable?

 

Also schematic of the V-def IC, if it helps.

 

Cheers for the help thus far, btw. Much appreciated.

 

teac_ctm5122h Vertical def circuit.PNG

 

TA8403K-circuits.jpg

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Lowering R408 and R403/R405. The resistors in series to ground may need some change too.

 

tda8403k.jpg

 

But I've seen different chassis with the same vertical IC and the same tubes that had different resistor values.

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So the tube swap itself went fine. The 48cm tube looks roughly the same as the 51cm did. I'm unable to find the service codes for this set, nothing on google has worked with the remote app on my phone, though the channel/menu/other buttons all work fine.

 

Horizontal trimming I can handle with GM and ArcadeOSD. Next comes figuring out the resistor values for fine tuning the vertical size. Would love to be able to do vertical position as well.

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Testing goes well. I took a look at the circuit, and decided that given the coil was only 10R, and R408 was in parallel, it was safe to change it by a little and fire the set up.

 

Seems to work. I tried 330R, then 220R, then 120R, and the result was a slightly smaller screen each time. I figure this will be due to less current going down the V-coil, more across the resistor. The overall resistance due to R408 and the coil changes from 9.78R with R408 at it's original 470R, to 9.2R with R408 at 120R. I plan to buy a 500R 2W pot and a few 20R or 60R resistors and leave it at that. That is, unless i can see something wrong with that.

 

I do have to make sure i can RGB hack this chassis too, but it should be straightforward.

 

EDIT: resistance, impedance - potato, pohtah-toe. Or not, but i forgot to write that :)

Edited by buttersoft
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So the RGB hack is not going as expected. The process itself works fine, but the resulting picture is full of noise. And the noise grows to massive levels when I take the OSD out of the circuit completely - the set even starts making audible noise. I've seen something similar from a video amp with filter caps across the power supply rails, and removing them cleared it up. In this case I'm still thinking. Might be related to filter caps, might be paths around the missing teletext IC's, might even need C-vid fed directly to the jungle IC rather than through the AV switching chip.

 

Can you make a video of this process?

Aussie Arcade

 

Videos are not my thing. And the amount of effort required to produce something useful is way beyond me - you couldn't just film yourself modding a set and expect people to learn much.

 

If you have a TV you're looking at, post up the model no. or even better a link to the service manual/schematics. I'll try to figure out what comes next. The principle is pretty simple, but keep in mind that not every set you pick can be hacked at the drop of a hat. Or you can drop by the TV RGB mod thread on hardware subform on Shmups and do the same.

 

Also, here - http://www.aussiearcade.com/showthread.php/86693-RGB-hacking-consumer-CRT-TV-s

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Videos are not my thing. And the amount of effort required to produce something useful is way beyond me - you couldn't just film yourself modding a set and expect people to learn much.

 

No worries.

 

Out of curiosity, how many sets have you managed to successfully hack?

 

 

 

Sent from my iPhone using Aussie Arcade

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Out of curiosity, how many sets have you managed to successfully hack?

 

Only two. A third failed due to my corrupting the set's EEPROM by mistake in an only peripherally related incident. The fourth is one i'm talking about in this thread, so technically the RGB hack works - the noise making it unusable is unrelated to the core subject and something i hope to trace once i build my oscilloscope ;)

 

This'd be another reason i shouldn't make a vid, and why you'd be better off with the shmups thread. It used to be kinda disorganised, but MikeMoffit came back and cleaned up his OP and now it's a really good resource. You'll notice i quote from it in the thread i made on here. There's a list of sets known to work, and if you read through it, in a few pages you'll start to notice that everyone is doing the same thing to each set, with a few different details around the edges.

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No way you were going to be able to do this without failing once in a while.

 

I find the whole thing fascinating. How long have you been involved in learning about this?

 

A lot of sets are designed the same way, and getting RGB into them is really no harder than just using a PVM, if you can solder. A lot of sets aren't designed that way as well, or not quite, and then it gets tricky. I've only been pulling CRT's apart for... 18months? Before that i was using PVMs, and learning about the video signals and the fact an arcade PCB outputs RGB was a big help, i'd say. I don't really know very much, overall. There are a lot of members here who know way more than I do, which is handy when i need to ask for help yet again :)

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If you have a TV you're looking at, post up the model no. or even better a link to the service manual/schematics. I'll try to figure out what comes next.

 

The model is the LG CA-20F80. My research says it has an MC-84A chassis.

 

I found a schematic, it appears to be clearly labelled with RGB Out from the "Jungle".

 

https://drive.google.com/file/d/0BxXDEFhRZ50MVGxNc3NWdzV3bDg/view?usp=sharing

 

Here is the data sheet for the jungle IC (well as far as I can tell)

 

https://drive.google.com/file/d/0BxXDEFhRZ50MbUlSOXg0ajZQc1U/view?usp=sharing

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The model is the LG CA-20F80. My research says it has an MC-84A chassis.

 

I found a schematic, it appears to be clearly labelled with RGB Out from the "Jungle".

 

https://drive.google.com/file/d/0BxXDEFhRZ50MVGxNc3NWdzV3bDg/view?usp=sharing

 

Here is the data sheet for the jungle IC (well as far as I can tell)

 

https://drive.google.com/file/d/0BxXDEFhRZ50MbUlSOXg0ajZQc1U/view?usp=sharing

 

Firstly, you don't want the RGB outputs - those go to the neckboard. You want the RGB-input pins, numbers 23-25 with pin 26 being fast-blanking (blanks the other inputs and only shows what's coming in through the RGB input pins). In theory, you remove the far leg of C216-218 from circuit and insert your own RGB through the cap there, at the normal 0.7Vp-p that everything but an arcade board will give you. You then remove the fast blanking pin from circuit and give it your own ~2-5V signal. You should be prepared to try a range of voltages for the last. Composite video (or luma, or just sync) goes where you would normally feed it into the set.

 

Try the above method first. If it's a teletext TV it might work. However, that jungle IC might be problematic. Note that the OSD is muxed into the RGB outputs of the chip, it's not going into the inputs; the latter is what you want to see. The 884x series are EEPROM controlled jungle ICs, i had a set with an 8841, muxed OSD, and i think the RGB was turned off. See page 15 of the datasheet, bottom left. Viletim theorised that if i could flip the IE1 bit (P17, 11/D7) the RGB inputs might work. However i fkd it up and corrupted the EEPROM. I never got to try it, and would be interested to hear if it works.

 

If you do give the EEPROM hack a go, make sure to make a copy first! Tie the write protect pin high so nothing can go wrong with the original, and play around with a copied chip. If it works though, you'll be able to control everything - V-size, V-pos, H-pos - the same way, you just have to figure out the data, which might not be easy. Tim suggested changing the colour saturation (on the same byte) to figure out where the IE1 bit was.

 

If this is too much, mail me the chassis because i'd love another crack! :)

 

Either way the tube might be in good shape, and should be a 48cm - correct? Those are worth hanging onto, IMO. Standard size for a lot of cabs and being an EEPROM set makes it a bit newer, i believe.

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Ok I'm picking up everything you're putting down so far.

 

I'll check to see if it's a teletext model. That seems like the most likely path to me.

 

Would there be a way to trick the tv into teletext mode in startup?

 

 

Sent from my iPhone using Aussie Arcade

 

- - - Updated - - -

 

Firstly, you don't want the RGB outputs - those go to the neckboard. You want the RGB-input pins, numbers 23-25 with pin 26 being fast-blanking (blanks the other inputs and only shows what's coming in through the RGB input pins). In theory, you remove the far leg of C216-218 from circuit and insert your own RGB through the cap there, at the normal 0.7Vp-p

 

Do you mean the C516-518?

 

C516-518.jpg

 

Would yo consider injecting the C-Sync into C514?

 

C514.png

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The set doesn't have teletext.

 

So if I'm understanding you, the jungle chip has RGB inputs but they are likely disabled by a switch set in the EEPROM.

 

Not very promising.

 

Is the muxing of the OSD rgb an issue because of transparency?

 

 

Sent from my iPhone using Aussie Arcade

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