Looking for RCA TV repair manual RLDED3258a-b

[Serge 125]

Hi all!! Ok did google before comming here but no luck so I'm looking for a RCA TV Model # rlded3258a-b repair manual or schematics.

THANKS!!!

Serge

 

[Nigel Goodwin]

It's quite possible it's not available, 'modern' TV's are going that way with no schematics available at all, even for main dealers and service agents. If you're lucky you get a parts list - consisting basically of the PCB's.

Looking on YouTube, there's a video about the set - and it looks really crappy, one tiny little PCB and a few round the edge of the LCD.

What's wrong with it?, the video is about replacing the backlight LED's, which is a common failure on cheap sets.

 

[Tony Stewart]

time to retire the old 1360*768 LCD?

 

[Serge 125]

time to retire the old 1360*768 LCD?

Actuality it's a led tv.

 

[Serge 125]

It's quite possible it's not available, 'modern' TV's are going that way with no schematics available at all, even for main dealers and service agents. If you're lucky you get a parts list - consisting basically of the PCB's.

Looking on YouTube, there's a video about the set - and it looks really crappy, one tiny little PCB and a few round the edge of the LCD.

What's wrong with it?, the video is about replacing the backlight LED's, which is a common failure on cheap sets.

It's the lcd panel I get a white screen with an inch of black boarder with rounded corners. I do have sound but no screen. It looks the tcon is built into that lcd strip. So I know that the power and main board are working but will keep those parts and maybe practice desoldering on the main board's connectors with my Quick 861DW!!

 

[Nigel Goodwin]

Actuality it's a led tv.

No, it's an LCD TV with LED backlights - it's just an LCD TV.

 

[Tony Stewart]

There are many unused parts of your TV that are probably still good , like the analog tuner, and all the HDMI and analog tuner and interface functions. may still work so you can diagnose but it's the LCD monitor function or dependencies that are not working. I wonder if you tried VGA , HDMI and Menu or Input remote button with a PC what happens?

e.g.
I have a 56" Hitachi TV, and watch live TV , movies in theatres free , and web browse at high speed, but never use any of the TV functions of the set.

I use an external digital tuner to my router with antenna on my chimney and PC to drive the LCD in its native resolution using VGA and watch any media I choose on this 2nd monitor. Although it's getting old and I am tempted to tune the LED backlights to balance them as I think about the impact with a new 4k monitor on streaming movie bandwidth possible issues.

 

[Nigel Goodwin]

There are many unused parts of your TV that are probably still good , like the analog tuner, and all the HDMI and analog tuner and interface functions. may still work so you can diagnose but it's the LCD monitor function or dependencies that are not working. I wonder if you tried VGA , HDMI and Menu or Input remote button with a PC what happens?

e.g.
I have a 56" Hitachi TV, and watch live TV , movies in theatres free , and web browse at high speed, but never use any of the TV functions of the set.

I use an external digital tuner to my router with antenna on my chimney and PC to drive the LCD in its native resolution using VGA and watch any media I choose on this 2nd monitor. Although it's getting old and I am tempted to tune the LED backlights to balance them as I think about the impact with a new 4k monitor on streaming movie bandwidth possible issues.

That's an EXTREMELY rare fault - almost all LCD faults are the LCD screen module (including the backlights) itself.

Next most common, in particuarly cheap sets, is failure of rectifiers - due to their silly habit of placing them in parallal with no balancing resistors. In the past, a major fault was sub-standard electrolytics (particularly from Samsung), but I'd like to think they have learnt better now - although it took Samsung a good many years to do so.

 

[Tony Stewart]

- due to their silly habit of placing them in parallal with no balancing resistors.

Very silly indeed,

- the reason all diodes and LEDs of one type have different Vf tolerances at max power is only due to the internal bulk resistance, Rs and the temperature shift of the negative temperature coefficient (NTC) of the semiconductor threshold voltage which controls the junction temperature with thermal resistance.

Anyone can use linear regression with Rs and Vth to get Vf=Vth+Rs*If from the power rating of any diode type using Rs= k/P_max then choosing k for some value 0.25<k <=1 (if you know the Vth or knee threshold Vk) ( the more complex formula includes Temp and NTC)

The % tolerance is a manufacturing process limitation and capability of the epitaxial making equipment and any subsequent binning in the process. This is not published and requires a component engineer's skill to understand how it affects the design when doing cost-reductions.

The other major factor in power rating is the thermal resistance or conductance as parallel diodes heat up by thermal resistance * power, the ability of tracking each other vs independent maximum air flow vs , no thought at all about air flow and ambient temperature inside the set may cause this positive feedback effect called "Thermal Runaway" where the hotter diode drops to a lower voltage from the NTC effect which tends to draw more power. There is a formula for the critical threshold of thermal runway, but I forget at this moment. The "balancing resistors" are about the same value of Rs of the diode in question, in parallel which reduces the rate of change of temperature with current by 50% by doubling the total resistance and thus reducing the deviation or effective tolerance of mismatched series resistance for each diode.

If semiconductor or foundry datasheets actually put tolerances back in the datasheets, it would help, but they tend to simplify specs now and only include maximum values for Vf @ I to reduce cost and not tell you the real reasons why. It may be they outsource the production to a cheaper foundry with wider tolerances or reduced testing or buy from a different epitaxial wafer source.

When I could rely on diode tolerances, I could support designs that put them all in parallel at max current. I did this for one client who used a million of my different LEDs over a 10 year span and put them into products to light up sidewalks, tunnels and roads. But then the LEDs were 100% tested and binned in 0.1V bins and often tested within millivolts of each other , better than any discrete Zener. I only bought binned brightness +/-10% and +/-0.05V voltage at some premium to guarantee performance and also got reverse ESD protection diodes added to each LED due to sloppy customer handling processes. The premium wasn't too much as I chose the bins with the largest population that met my criteria and had close communication with my supplier for orders in the 20k ~50k pc per type range.

This " tangent " report is brought to you by Nescafe.

 

[Serge 125]

No, it's an LCD TV with LED backlights - it's just an LCD TV.

Yeah I new that sorry I didn't say it that way.

 

[Serge 125]

That's an EXTREMELY rare fault - almost all LCD faults are the LCD screen module (including the backlights) itself.

Next most common, in particuarly cheap sets, is failure of rectifiers - due to their silly habit of placing them in parallal with no balancing resistors. In the past, a major fault was sub-standard electrolytics (particularly from Samsung), but I'd like to think they have learnt better now - although it took Samsung a good many years to do so.

Yeah that is what I think is the proble the lcd screen module. There's (kinda) no tcon but I know the tcon is built onto that lcd strip.

Anyway it's an RCA tv and it's far from being a good tv, it's very cheap in price and quality.