Re: TDS3044B repair

Harvey White

If you have some familiarity with LCD displays, or CRT displays with separate drive, then *if* the signals are good, you should be able to recognize them.  If they're bad, however, well.... Let alone which test point is what......


On 11/6/2019 10:08 PM, Tom B wrote:
Hello All,

I am just catching up on this thread.

There is a youtube video on replacing the CCFLs with LEDs here

The part number for the TDS3000 (no letter) display is listed in the service manual as an NEC NL6448AC20–06.  These displays are available on ebay and other places for about $60US.   I think the part number for the B model is NL6448BC20-08, but I am not 100% sure of that.  These displays are running about $80-$100US. The only difference I can find in the in the datasheets between NL6448AC20–06 and the NL6448BC20-08 is that the -08 model has higher luminance.

Can anyone verify the part number on the TDS3000B display?

I will check for the for the signals that Harvey mentioned when I have time.  The pins that go to the display are really hard to get to because of the way this thing is built.   There are the test points on the main board, but the service manual makes no mention of what they are for.

Tom Bryan

On 11/6/2019 10:58 AM, Harvey White wrote:
This is the first item that came up when searching for CCFL LED replacements;!b9GWhakWANQ!1VZO1N_UzGPrK5tvZk-sSIE3W2ulp1zapXqXmDScqYhd9jWmbO6SGjvZhNdA$
no idea if they have anything that will fit.

I have made CCFL replacement strips for some odd displays, the older Optrex DSTN color displays and the FG0800 8 inch VGA display.

Due to the lack of 12 volts in a battery operated project, all of them are designed to run the LEDS in parallel, at about 15 ma per led, about 9 per 4 inch strip.  The strips are designed to be stacked, resulting in parallel operation.

Whether or not the lamps can be reasonably replaced depends on the manufacturer.  In the Optrex displays, remove a screw, swing a shield aside, and pull out the tube.  In the FG0800, it's more involved (and takes 4 strips), even more if you wanted the side. The silly tube is a top, left, and bottom assembly.

The replacement should be made to run off the (suspect 12 volts) supply, and a simple PWM would easily replace the inverter.  I'm sure it varies wildly.

I know there's a market out there, and the more common the display, perhaps the easier it is to find the LED replacement, or even the tube itself (which I'd recommend unless you want to go LED).

I went LED because the power consumption in battery operated equipment goes down by 50 to 75%, and I'm not happy with 1600 volts running around an experimental setup.

So give these people a try, they seem to be going laptop, so no idea what else they do.

You might also want to look here:;!b9GWhakWANQ!1VZO1N_UzGPrK5tvZk-sSIE3W2ulp1zapXqXmDScqYhd9jWmbO6SGtNxwsuf$
10 dollars.


On 11/6/2019 10:03 AM, David Kuhn wrote:
" there are commercially
available LED backlight kits to replace the CCFL lamps.  "

I would be in your dept if you could point me to an LED replacement for the
fluorescent tubes in the NEC displays like that are used in the TDS3000
series (no bloody A, No bloody B or C).  I'll get the actual NEC LCD part
number and reply again later.  I wonder if the LED replacement is made to
run off the fluorescent tube inverter supply?  I ask that because that
supply has software control line to control the brightness. LET is
probably off or on, unless it is designed to run off the inverter or a
software equivalent inverter is available (retrofitting old equipment not
designing new stuff).


On Tue, Nov 5, 2019 at 2:31 PM Harvey White <madyn@...> wrote:

On 11/5/2019 1:59 PM, David Kuhn wrote:
Sorry for the response delay.

I am in Lewistown, PA.  How cheap are the displays and where are you
finding them?  I have found the ones, used in the Ultrasonic instruments
mentioned, on Alliexpress, and EBAY (haven't ordered any from either
but I can not find the backlight tubes, which I find is usually the
with the displays.  The displays may be just slightly different than in
TDS3032, but if so, only mechanically.  The connectors are the same, and
really think the part numbers are the same.  It's not a real easy
replacement in those TDS scopes.  It looks easy, but it's a pain in the
Depending on the manufacturer of the display, there are commercially
available LED backlight kits to replace the CCFL lamps.
You may want to buy the TDS3GV on EBAY.  I can't use a TDS3032 without
but I have written a lot of service software in VBA and VB6 that
automatically sets up the scopes and gets data from them. I can also
project my TDS3032 to the 32" TV mounted on the wall above it (an older
Sceptre with VGA input) and that's pretty cool.

Again, if the cables are seated well, I doubt the LCD is bad with an
all-white display.  My thoughts are a main PCB issue. A TSD3GV could
me wrong.
If you find an all white display, then depending on the type of display
(positive or negative) you'd suspect no signals to it, or improper signals.

The display is likely to take either 5 or 3.3 volts, recent ones that I
have take 3.3.  Older STN displays can take 5.  The white is the result
of the backlight working, but no active pixels at all (hence no
polarization, etc....).

Like a CRT display, you'll be looking for a horizontal sync (at perhaps
30 Khz), vertical sync (say 60 or so Hz), a DE (likely at horizontal
rate and active high), and a pixel clock at about 25 or so Mhz.  You'd
also expect supply voltages to be somewhere on the display. If the
timing is right and the voltages are there, then the display ought to be
showing something.  If not, then look at the other pins, they should be
R,G,B digital signals, either in 565 (for a 16 bit panel) or 666 (for an
18 bit panel).  If there's any activity on them, then with the right
sync signals, they ought to be giving something on the display.



On Tue, Oct 29, 2019 at 10:55 PM Tom B <tbryan@...> wrote:

Hi Dave,

I  tried the "B Trig" and nothing happened.  Displays are fairly cheap
but I don't want to buy one unless I have to.

Thank you for the offer.  I would be a long while before I make it up
that way.

What town are you in?


On 10/29/2019 4:52 PM, David Kuhn wrote:
I'm in central, PA, about 3 hours from you if you ever want to come up
try it here with one of my VGA/GPIB modules.

Before that.  Power it up while holding in the "B TRIG" button (might
different on the TDS3014), which on my TDS3032's causes a RESET.  I've
that fix display issues after replacing the battery NVRAM in in the
The display in the TDS3032, is the exact same LCD used in the GEIT
XS and USN60 instruments.  I have worked on many.  I have never seen
LCD fail on those instrument where it's all white.  Typical, if not
is smeary displays that lines seems to go out of sync.  Dim, of course
broken backlight tubes.


On Mon, Oct 28, 2019 at 10:50 PM Tom B <tbryan@...> wrote:

Hi Rich (?),

Thanks. I am located in Maryland near Washington DC.

If anyone in the Washington DC area has a TDS3GV that I could come
and quickly test my scope with, I would appreciate it.

Tom Bryan

On 10/28/2019 10:29 AM, Oz-in-DFW wrote:
I'd still remove and reseat both ends.

Where are you in the world?  I have a VGA/serial/GPIB card in my 3014
that we might be able to mate with your scope briefly.

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