Sanyo DS25530 - Modding Help

[2Beeried]

Good Afternoon,

Wondering if anyone can point me in the correct direction here. Recently picked up a DS25530 that had a broken back plate, which I fixed, but was unable to tell when I purchased it that it was RF-only, as the the input was lost to the inner cavity.

Opening the back up, I have found that it is a hot chassis, so I was going to write off being able to add component or more, until I saw that the board is silkscreened for component. Is this something I can populate and tie back into the boards logic and add component to this TV? I found another Sanyo that I think shares the same board but with the component populated, but I am unsure if it is 1 to 1, it is the DS31650. Any guidance here would be amazing, thank you in advance.

Have a number of pictures on imgur for it: DS25530 Images

and here are the documentations I have found for them:
Google Drive

[vol.2]

Originally Posted by 2Beeried

Is this something I can populate and tie back into the boards logic and add component to this TV? I found another Sanyo that I think shares the same board but with the component populated, but I am unsure if it is 1 to 1, it is the DS31650.

I believe that the unpopulated area looks like it's isolated with optical ICs, so I think it's definitely designed from the factory to have that option.

HOWEVER. You would need to check with the service manual and probably also have the datasheet to the jungle IC (the audio video input/output IC) to

1) confirm that the inputs can be setup without altering the system memory

2) have a complete part list to populate the missing ICs from the PCB

My hunch is that you will not be able to "turn on" the composite inputs because those inputs are enabled by setting up registers in the memory, and that is done in the factory by flashing to an EEPROM on the board that talks to the main video IC and sets up the environment.

In essence, you would have an input with no way of switching to it.

But you can read the service manual to figure that out by finding the main video IC and then locating the datasheet for that IC. In the datasheet, there should be a section on programming the IC from memory, and how to set it up. If that section exists, then it's not going to work.

The other option is that the inputs are set with a switch that changes an enable pin or something like that. So you might be able to fool the set into displaying from the composite inputs if that's the case, but it's very unlikely. The reason they started using EEPROMs and large integrated video ICs has to do with cost reduction of all the old analog parts they used to use.

[2Beeried]

I believe the Jungle is an LA7673, labeled on the schematic as IC101. Now would the Jungle be the main IC or would it be the other one? The other one is an LC8641208, labeled as IC501. The Front IO panel is connected to IC501 from how I read, but the composite video is connected to both, with R-Y, G-Y and B-Y running directly to and directly from IC101. (I have said schematic added to the imgur as a jpg, but also in the google drive as a PDF for ease of use)

On the EEPROM side, if it is controlled by EEPROM, are they able to be translated and modified now-a-days? I have EEPROM flashed in the past from scripts and such, but never had to read, decode and create one myself, so I don't have the faintest idea of how possible this task is, unless I could flash onto it using an image from one that has component with the same board, like the DS31650 if they are using the same everything, with one just having component populated.

[vol.2]

Originally Posted by 2Beeried

I believe the Jungle is an LA7673

Yes that is a jungle IC. You would need the datasheet for that to do anything with this.

On the EEPROM side, if it is controlled by EEPROM, are they able to be translated and modified now-a-days?

Yes, it is possible to flash a new EEPROM and replace the old one with a new set of instructions to adjust the functions, but you would have to both know how to program it (all this information is always included in the jungle IC datasheet) and you would also have to know exactly what you are doing. If you are capable of reverse engineering the TV's EEPROM, there wouldn't be anything I could help with.

As far as I can tell, the datasheet for the LA7673 isn't out there anywhere.

It may be possible that it could be done without messing with a ROM, but I would probably need that datasheet to be sure myself. You might be able to figure it out by writing down on the ICs in the schematic and looking for an ROM attached to the 7673. If there are no ROMs or memory in the set at all, then that would be a more positive indication that it's not necessary.

[jhalphen]

Hi to all,
Hi 2Beeried,

Found these two Jungle chip data sheets LA7672 & LA7674 (not LA7673) but probably quite close.

Personally, i would forget populating a board, optocouplers & E-PROM reprogramming, sounds very Rube-Goldberg to me.
Run the TV through an isolation transformer. The Composite Video Out on the jungle chip (seems to be pin 44 on your Zip schematic).
Looking at LA7674 data sheet, RF Video Composite Out is 44, pin 41 is Ext Video Input and pin 43 is the switch to choose between RF & Composite input. Everything is already built-in!

Best Regards
jhalphen
Paris/France

[Alex KL-1]

jhalphen,
Sounds like a interesting idea.
Generally jungle IC that are separated from the µcontrollers have chances to be "fooled" with new input signals if we cut the internal video coupling and inserts signal here, but it this LA7673 have a pin for select input, like it's cousins, better yet!

[zeno]

Ditto vol.2 comments.
The other thing is its a lot of time & effort. 25" & 27" sets with
a good jack pack are a dime a dozen. RF only by that era are rare &
limited to the cheapest sets. Personally I would replace it.

Zeno
LFOD !

[vol.2]

Okay. Everyone made me do more work lol.

I found a pinout for the 7673



This seems to match the 7672 fairly closely, so it does appear that this is switch situation and not an EEPROM situation. It's an earlier set than I realized.

The main obstacle here is going to be whether or not a delay line is necessary. I couldn't really tell you that.

From the 7672:



So, if you need to add a delay line, the turn on voltage for the external video is ~3V. If you don't need a delay line, it's 5V.

This is on Pin 43 of the main IC. It was designed to just have a "video" switch on the front of the TV that toggled this. You might be able to find that circuit in the other TV you mentioned was similar.

However, I would still do the whole optocoupler thing if it was me. I don't want to drag out a heavy isolation transformer each time I want to use my TV, and I don't want to pay for one to dedicate to this purpose. Last time I checked, the cheapest Triad transformer I could buy for this purpose was about $65 before taxes and shipping from Mouser or Digikey. If you, jhalphen, have some inexpensive source for well made and reliable mains isolation transformers, I'd love to hear about it.

That said, it's still going to be a lot of work, and there's every chance that it's not going to play out as easily as you might hope it will. I would only do it if you are simply committed to the journey. If you just want a working TV, then you're time and money is better spent on a different set.

[2Beeried]

I'm definitely keeping my eyes out for another local CRT at this size for the cheap, but I like to work with what I have also and learn as I can. What originally was going to be a "Well damn, oh well" turned into what seemed like a potentially decently fun project, if only for the project itself.

Run the TV through an isolation transformer.

I am rather new to CRT Modification, are you meaning that I should inline an isolation transformer? Or just plugin the CRT as a whole into an isolation transformer? I am assuming this is so I don't create a lovely live circuit through a component jack and fry whatever unfortunate device gets plugged in.

Looking at LA7674 data sheet, RF Video Composite Out is 44, pin 41 is Ext Video Input and pin 43 is the switch to choose between RF & Composite input. Everything is already built-in!

As I read this, it sounds like I can bring in the component video into pin 41, and then run a signal to pin 43 to get it to switch to composite. Am I understanding this correct? Would I need to run the composite in through an optocoupler or is that resolved with the isolation transformer?

Also, I am fully willing to risk and/or scrap this entire tv, that's not a concern to me, so if anyone wants to me to guinea pig any ideas let me know. It's not my only CRT, I have a smaller one that does have component, so I am unworried if this one goes bust.

[Alex KL-1]

The isolation transformer permits to ground the AV inputs safely to the TV signal ground, but like vol.2 mentioned, this have a cost. Perhaps all the parts for complete the optoisolator section can be cheaper, then.

If the LA7673 have the delay line issues with direct AV, you can insert a 10k pot in the AV select pin (43) for matching the luma with chroma (using the Vcc suply of the IC, and other side of the pot to ground; the center wiper goes to the select pin). If it follow i'ts cousin logic, one correct voltage level will enable the correct needed function. Just in case of image mismatching when trying that.

[jhalphen]

Hi to all,

Thanks! to Vol.2 for the LA7673 pinout.

Isolation transformer: anyone who works with modern electronics needs one.
All modern gear use SMPS (Switch Mode Power Supplies) which equates with HOT chassis.
Iso-Tx's are often found for cheap at vintage radio/Ham swap meets or contact a local radio club, often old-timers give away items as they thin out/dispose of collections.
Radio clubs & shows calendar:
https://antiqueradios.com/forums/viewforum.php?f=24

Video in mod: i would stick with Composite Video. Component or RGB is a whole other ball game.

Opto-isolator: i suggest you build this design, it works and has very good video bandwidth, 17MHz at -3dB.
Full details including PCB layout here :

https://antiqueradios.com/forums/vie...lator#p3685058

Best Regards
jhalphen
Paris/France

[2Beeried]

Awesome, thank you everyone, gives me an idea of where to start and what to look for, and I completely missed vol. 2's post while writing my previous post, hugely helpful and answered questions.

So seems to be I have a parts list I can start building out at the minimum.

And yes, I apologize for the confusion, composite in is what I am looking for, not component. I am putting together a GBS-C while researching this, both terms are in the same "project" folder in my head right now.