TDS3000 series CCFL upgrade to LED

[Tracker]

Just sharing this.
Used a standard CCFM conversion kit from Banggood.
Worked out very well.

https://www.banggood.com/490mm-LED-Backlight-Strip-Light-Kit-DC-10-30V-22-Inch-CCFL-LCD-Screen-to-LED-Monitor-Module-p-1832364.html?cur_warehouse=CN&rmmds=search

Note: when cutting the strips down to size, be sure to reduce the current proportionately by using a 1k pot on the dimmer line.
The LED's are arranged in groups of 3 series , each group is in parallel.
You will need to pull the 'enable line' high to activate the converter.

The Tek 3000 series CCFL is powered from +5V which can't be used, so you you will need to locate +14v on the main control board, pins 5 & 6 if recall correctly (pin 1 is ground).

End result is a massive improvement over the old CCFL.
But you loose the brightness control from the instrument, not a big deal to be honest.


 
 

[Teichhermelin]

Very nice!

[james_s]

Loosing the brightness control would bother me just on principal. I've never looked at the signal that controls that, is it just PWM? It may just be a matter of hooking up a wire to make that work. Certainly there are lots of LED drivers with PWM brightness controls, I've used the PT4115 IC and it has both PWM and analog support.

[sean0118]

I haven't checked but from memory it should be possible to add brightness control:

www.reflektor.kz/articles.php?article_id=45

[Tracker]

yep it should be.

The Banggood controller board can be adjusted with a DC level between 0 and 3 volts.
So even if the Scope generated PWM, a PWM converter board or even filter could be used.

Buy honestly I never had the need to adjust the brightness, but I guess that it would be handy if you used the scope in portable mode.

[james_s]

I don't adjust it very often but I do occasionally dim it when I'm using it in subdued lighting. The dimming is not as useful as it could be though, there are only 2 or 3 settings.

[sicco]

I ordered the same Banggood LED strips with chopper board.

What I got was red wire = GND, black wire = V+…. I was lucky, there was no Bang. But this is not Good I’d say. Anyway, it survived, tied one of the two yellow wires (enable) to V+.

I did end up using double sided tape on the back of the LED strips. Without tape I could not keep the strips pointing the right way.

I left out intensity control. I always run off mains power, so no need to sacrifice backlight intensity for battery life.

The dial on the front panel BTW does not influence screen backlight intensity for the old CCFL lamps anyway. So you’re not losing anything by not having backlight intensity ‘replicated’: the dial just mimics analog scope intensity  in software by turning on/off more pixels.

[james_s]

That's true about the dial, but there is a menu setting that offers 2 or 3 different backlight intensity settings. I agree that there is rarely a need to turn it down though.

[sicco]

Yes, I found the Backlight Intensity dial eventually under the Display button, H,M,L.

As the LED strips are 3 times longer as needed, and I had another TDS3012, I decided to give that a go also. My learnings today: best to get rid of the chopper board and just power the LED strips from DC with a small current limiter/controlling resistor. I picked the +5 and -15V rails to get 20 VDC, then the two strips in series and 150 ohms as current control, 25-30 mA is good enough for me already, but maybe go much higher if you want more light.  The strips have every 3 white LEDs in series, so 3xV_LED, and that's 7 to 9 V ish)).

I think it's better anyway to not have a LED chopper circuit inside the scope, I have the impression that in the first one I did, with the PWM chopper, I now see more noise/ripple on my channels as before...

Plus: do re-use the metal frame that had the old CCFL glass tubes, then no need for double sided tape for holding the strips in position anymore
Plus: leave out the entire high voltage chopper board. The scope works fine (for me) without it.
 

[JJ2PNX]

Hi,

I built dedicated LED driver board for this scope.
https://www-momose-com.translate.goog/hirofumi/elec/BacklightLED/index.html?_x_tr_sch=http&_x_tr_sl=ja&_x_tr_tl=en&_x_tr_hl=ja
(google translated, originally in Japanese)
Dim and backlight-off works as same as CFL board.
This CFL inverter dimmer control interface is a bit strange voltage level.

[jgorsk]

Here is another LED driver for the TDS300 backlight.
It's based on the LT3922. Maximum LED current is controlled
with R1 value. Imax = 100mV / R1

[wraper]

End result is a massive improvement over the old CCFL. 

And completely messed up color reproduction. Most likely LEDs are not suited for display backlight and use simple yellow phosphor over blue LED die.

[jgorsk]

With natural colour LEDs, the colour reproduction isn't great. That's true.

I will be trying custom LED boards with LEDs that have similar colour temperature
to CCFL light. I will try Lumileds L130-3090001400001

My CCFL lamps were worn, changing them with LED backlight seemed like
a quick and easy solution but I ended up designing my own driver board
and LED backlight boards too.

[james_s]

Hi,

I built dedicated LED driver board for this scope.
https://www-momose-com.translate.goog/hirofumi/elec/BacklightLED/index.html?_x_tr_sch=http&_x_tr_sl=ja&_x_tr_tl=en&_x_tr_hl=ja
(google translated, originally in Japanese)
Dim and backlight-off works as same as CFL board.
This CFL inverter dimmer control interface is a bit strange voltage level.

Very nicely done!

[Abel]

From time to time some subjects get revived. If there is any interest:
a linear solution (see attach) with dim control for TDS30xx(X).
Maybe a little more information will help upfront: the dim functionality uses the original control signal from scope (roughly 1.55 to 2 V) and the +5 V supply via the 6 pins connector that the CCFL controller/driver used. However, additional voltages are needed (-5V and +15V), both available from the scope PS (detailed information w/pictures in file).
AB

[jgorsk]

RGB LED backlight produces a lot better colours. I tried the ASMB-UTF2-0E20B LEDs. 27 of them per side.
18 or 21 LEDs per side would probably work as well. I can get colours very similar to the original or even better.

[Wahyueko]

Nice sharing , i want to try with my tds3054b