Has anyone replaced the Graticule lights with LEDs?


 

Has anyone tried replacing the incandescent lights that illuminate the
internal graticule of scopes like the 7000 series mainframes with LEDs? The
most common arrangement on the 7000 scopes is three little bulbs and it
seems like the illumination from them could be improved considerably with a
strip of LEDs. That might also make it possible to change the color of the
graticule (just a guess).

It probably wouldn't be too hard to 3D-print a holder / diffuser for the
LEDs to act as a substitute for what Tek uses now for the incandescents.

Dennis Tillman W7pF


Eric
 

Dennis

I have it works well and is not to bad to implement I have done the mod to a
2x7603's a 7704A and a 7854 for the indicators I have not done the graticule
lights in that one yet. I can post pictures or provide any details you might
need.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dennis Tillman
W7pF
Sent: Saturday, May 22, 2021 10:13 PM
To: TekScopes@groups.io
Subject: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

Has anyone tried replacing the incandescent lights that illuminate the
internal graticule of scopes like the 7000 series mainframes with LEDs? The
most common arrangement on the 7000 scopes is three little bulbs and it
seems like the illumination from them could be improved considerably with a
strip of LEDs. That might also make it possible to change the color of the
graticule (just a guess).

It probably wouldn't be too hard to 3D-print a holder / diffuser for the
LEDs to act as a substitute for what Tek uses now for the incandescents.

Dennis Tillman W7pF


Brenda
 

I have tried to use LED's for my 500 series scopes and they didn't work out very well for me at all. I really wanted to try it for my RM565 as that scope has a bright blue CRT and with a white graticle, it does strain my eyes. I am glad that Eric has been able to get it to work for him! I have also tried it with my 535A and that didn't work out too well either.

Although this is kind of in line with the topic, could one use a small bridge rectifier with a small cap to run the LED's from DC instead of AC? My eyes are sensitive to flicker.

Brenda


Eric
 

Brenda, in the 7000 series scope this is easier because the lamps are on a DC rail already. I cant remember off the top of my head if it is 5vDC or 12vDC rail. But I can also add that this works with the 485 as well. All the lamps are in parallel so a current limiting resister is all that is needed for keep from roasting the leds. In the 7854 it is more complex I added the current limiting resister to the collector side of the driver transistors of the indicator lamps. I think if I remember right there is 12-15 transistor that need modification. But a 1206 chip resister mounted vertically to the pad works just perfectly. The AC issues Is one of the reasons that I have not done anything to the 576's with leds due to the graticule lights being run off of a 50 vAC rail no reason this cant be adapted to a 500 series scope but the circuit would be a bit more complex maybe using a driver transistor to give the Leds constant current instead of constant voltage. The only real foreseeable issue with the 500 series would be placement and thermals all those tube run a little toasty.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Brenda via groups.io
Sent: Saturday, May 22, 2021 10:53 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

I have tried to use LED's for my 500 series scopes and they didn't work out very well for me at all. I really wanted to try it for my RM565 as that scope has a bright blue CRT and with a white graticle, it does strain my eyes. I am glad that Eric has been able to get it to work for him! I have also tried it with my 535A and that didn't work out too well either.

Although this is kind of in line with the topic, could one use a small bridge rectifier with a small cap to run the LED's from DC instead of AC? My eyes are sensitive to flicker.

Brenda


 

Hi Eric,
Can you take some pictures of what you did, and put together a little
write-up of how you did it? What type of LEDs you used? Where you got them
if they were unusual? etc.
I would love to do this for several of my scopes since I take a lot of
pictures and the yellow-orange incandescent light looks awful in photos.
Plus it is so uneven and invariably fades away as you go from the right side
across the graticule to the left side of the CRT.
Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Saturday, May 22, 2021 7:38 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

Dennis

I have it works well and is not to bad to implement I have done the mod to a
2x7603's a 7704A and a 7854 for the indicators I have not done the graticule
lights in that one yet. I can post pictures or provide any details you might
need.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dennis Tillman
W7pF
Sent: Saturday, May 22, 2021 10:13 PM
To: TekScopes@groups.io
Subject: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

Has anyone tried replacing the incandescent lights that illuminate the
internal graticule of scopes like the 7000 series mainframes with LEDs? The
most common arrangement on the 7000 scopes is three little bulbs and it
seems like the illumination from them could be improved considerably with a
strip of LEDs. That might also make it possible to change the color of the
graticule (just a guess).

It probably wouldn't be too hard to 3D-print a holder / diffuser for the
LEDs to act as a substitute for what Tek uses now for the incandescents.

Dennis Tillman W7pF













--
Dennis Tillman W7pF
TekScopes Moderator


Eric
 

Dennis,
I have uploaded 3 photos of a 7603 in action to the album section. I
have another link that I will be sending you off list. As well. The LEDS I
used were 5mm SUPER bright white LEDS they fit nicely. They are actually and
adafruit part number the 754 I am not sure what the underling part number is
but you get 25 Leds for $5.90 shipped. So not to bad. If I remember
correctly they are the same ones I used in the 400 series as well they are
NOT however the ones I used for the indicators in the 7854.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dennis Tillman
W7pF
Sent: Saturday, May 22, 2021 11:30 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

Hi Eric,
Can you take some pictures of what you did, and put together a little
write-up of how you did it? What type of LEDs you used? Where you got them
if they were unusual? etc.
I would love to do this for several of my scopes since I take a lot of
pictures and the yellow-orange incandescent light looks awful in photos.
Plus it is so uneven and invariably fades away as you go from the right side
across the graticule to the left side of the CRT.
Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Saturday, May 22, 2021 7:38 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

Dennis

I have it works well and is not to bad to implement I have done the mod to a
2x7603's a 7704A and a 7854 for the indicators I have not done the graticule
lights in that one yet. I can post pictures or provide any details you might
need.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dennis Tillman
W7pF
Sent: Saturday, May 22, 2021 10:13 PM
To: TekScopes@groups.io
Subject: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

Has anyone tried replacing the incandescent lights that illuminate the
internal graticule of scopes like the 7000 series mainframes with LEDs? The
most common arrangement on the 7000 scopes is three little bulbs and it
seems like the illumination from them could be improved considerably with a
strip of LEDs. That might also make it possible to change the color of the
graticule (just a guess).

It probably wouldn't be too hard to 3D-print a holder / diffuser for the
LEDs to act as a substitute for what Tek uses now for the incandescents.

Dennis Tillman W7pF













--
Dennis Tillman W7pF
TekScopes Moderator


Harvey White
 

I recommend a separate dropping resistor for each LED, the LEDs are not necessarily matched and one can hog all the current (and die...).  There's a 5 volt supply just for the lamps, IIRC.

Harvey


On 5/22/2021 11:09 PM, Eric wrote:
Brenda, in the 7000 series scope this is easier because the lamps are on a DC rail already. I cant remember off the top of my head if it is 5vDC
or 12vDC rail. But I can also add that this works with the 485 as well. All the lamps are in parallel so a current limiting resister is all that is needed for keep from roasting the leds. In the 7854 it is more complex I added the current limiting resister to the collector side of the driver transistors of the indicator lamps. I think if I remember right there is 12-15 transistor that need modification. But a 1206 chip resister mounted vertically to the pad works just perfectly. The AC issues Is one of the reasons that I have not done anything to the 576's with leds due to the graticule lights being run off of a 50 vAC rail no reason this cant be adapted to a 500 series scope but the circuit would be a bit more complex maybe using a driver transistor to give the Leds constant current instead of constant voltage. The only real foreseeable issue with the 500 series would be placement and thermals all those tube run a little toasty.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Brenda via
groups.io
Sent: Saturday, May 22, 2021 10:53 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

I have tried to use LED's for my 500 series scopes and they didn't work
out very well for me at all. I really wanted to try it for my RM565 as that scope has a bright blue CRT and with a white graticle, it does strain my eyes. I am glad that Eric has been able to get it to work for him! I have also tried it with my 535A and that didn't work out too well either.

Although this is kind of in line with the topic, could one use a small bridge rectifier with a small cap to run the LED's from DC instead of AC?
My eyes are sensitive to flicker.

Brenda











Jean-Paul
 

Dennis: The lamps used in 7000, 2465, etc are all long life GE/Chicago miniature specified at 50,000 hrs.

The color, beamwidth and other characteristics of an LED are very different than an incandescent lamp.

An incandescent lamp that is unbased has almost spherical light distribution.

LEDs have a beamwidth much narrower solid angle eg 25-90 degrees.

A graticule with lamp in a hole, uses light at 90 deg to the lamp axis,

I have replaced many of these with the correct incandescent lamps (still available) and have yet to have a burn out after a new lamp is placed.

Best Regards,

Jon


 

Hi Jean-Paul,

I understand the physics of the incandescent bulb Tek uses. I have many spares of all of the incandescent Tek put into their scopes, plugins, TM500 instruments etc. So I have no problem replacing burned out ones wherever I find them.

I am not surprised the graticule bulbs last a very long time. There is no magic to doing this. All you have to do is keep the current below their rated current to extend their life. But this is precisely the drawback of using incandescent bulbs. If you want a crisp sharp trace on the CRT you must keep the beam as dim as possible on 7000 series scopes. This is due in part to the expansion mesh and other compromises that had to be made to keep the length of the CRT within reason.

With the beam current set low for a sharp beam it is necessary to keep the graticule lamps as dim as possible so their light doesn't wash out the beam. When an incandescent bulb is so dim its light is in the red and infrared part of the spectrum so the graticule appears orange in the photograph. One reason I was interested in using LEDs was because their color does not change as they go from dim to bright. Another reason I was interested in them was they come in an enormous range of colors.

Finally, the third reason I was interested in LEDs is my hope that they can fix the biggest problem of all that incandescents have - their light does not spread evenly across the CRT. In a dimly lit scope photo the right side of the graticule may be visible in a photograph but the left side of the graticule will be much dimmer if visible at all.

Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jean-Paul
Sent: Saturday, May 22, 2021 10:55 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

Dennis: The lamps used in 7000, 2465, etc are all long life GE/Chicago miniature specified at 50,000 hrs.

The color, beamwidth and other characteristics of an LED are very different than an incandescent lamp.

An incandescent lamp that is unbased has almost spherical light distribution.

LEDs have a beamwidth much narrower solid angle eg 25-90 degrees.

A graticule with lamp in a hole, uses light at 90 deg to the lamp axis,

I have replaced many of these with the correct incandescent lamps (still available) and have yet to have a burn out after a new lamp is placed.

Best Regards,

Jon







--
Dennis Tillman W7pF
TekScopes Moderator


Clark Foley
 

Hi Dennis,
You have an interesting upgrade idea. I have not made such a conversion to LEDs for the graticule, but I have struggled with non-uniform illumination many times for promotional photographs. We always used a flash for the close-up photos.
I think that you could overcome the directional nature of the LEDs by abandoning the graticule diffuser assembly and substituting an array of closely spaced-surface mounted LEDs (a.k.a. light bar). Perhaps one LED aligned with each grat line. The nice thing about the four-holer 7k mainframes is that there is a little bit of space above the face plate to add a second illuminator. Grat lights above and below with help with the gradient from bottom to top and the closely spaced LEDs will reduce the old bulb hot spots.
I realize that this is no help at all, but it fun thinking about it.

Clark


DaveH52
 

In a few days, I'll be disassembling my 2465 again to install a replacement module for U800. Since it will be totally disassembled, I'm seriously considering replacing the graticule lamps with red LEDs. I plan on 'frosting' the tops so the light will be more diffused. It worked well for the meter on my Kenwood TS-440, except I used white LEDs for that.


Eric
 

I have updated the album on the group with some more shots of the LED mod to a 7603. I have the 7704A at work so I will have to get some pictures Monday. The second 7603 has the ND filter on it. I only have 1 clear. My 7704A I believe has TEK blue filter on the face. The LEDS used a 3 X 5mm ULTRA bright white from adafruit. I need to open the here in a little to find out what the dropping resister value is. But the LEDs I believe have a 2.5V forward voltage and I think the lamp supply is a 5V rail so you only need to drop about 2.5 Vdc with the resister. Max current for the LEDs is 20mA. If there is interest I can shoot some video on it. Of note the scope intensity is only just over 1/4 ON so the tube is not being driven hard at all.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Clark Foley
Sent: Sunday, May 23, 2021 3:49 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

Hi Dennis,
You have an interesting upgrade idea. I have not made such a conversion to LEDs for the graticule, but I have struggled with non-uniform illumination many times for promotional photographs. We always used a flash for the close-up photos.
I think that you could overcome the directional nature of the LEDs by abandoning the graticule diffuser assembly and substituting an array of closely spaced-surface mounted LEDs (a.k.a. light bar). Perhaps one LED aligned with each grat line. The nice thing about the four-holer 7k mainframes is that there is a little bit of space above the face plate to add a second illuminator. Grat lights above and below with help with the gradient from bottom to top and the closely spaced LEDs will reduce the old bulb hot spots.
I realize that this is no help at all, but it fun thinking about it.

Clark


Harvey White
 

LEDs can be gotten in different dispersions, some, for instance, I think at 130 degrees.  If you have a 3D printer, you might be able to make a light shroud depending on your needs.  If you can do PC boards, then I could recommend a 3 color LED.  How to profitably control it is another matter.  Otherwise, pick a color depending on what you want.

It might get close to an incandescent lamp.

Harvey

On 5/23/2021 5:15 PM, DaveH52 wrote:
In a few days, I'll be disassembling my 2465 again to install a replacement module for U800. Since it will be totally disassembled, I'm seriously considering replacing the graticule lamps with red LEDs. I plan on 'frosting' the tops so the light will be more diffused. It worked well for the meter on my Kenwood TS-440, except I used white LEDs for that.





Eric
 

Led moding a 7000 Series Scope after crawling in to my head from a year ago.

The LEDs used were Adafruit / 754 Super bright White Leds. Important notes on these Vforward for the diode being white is 2.5Vdc this is important later. Led Size is 5mm Clear

Dropping resister – None

Power supply open circuit voltage – 8.1 Vdc at full illumination

LED wiring parallel like the old light bulbs

The lamp illumination is current limited by the scope its self. When the LEDs are connected and the illumination on FULL the voltage across the connector in the scope is only 3.2 Vdc this means that the Leds are only drawing about 40mA each this was verified on a 577. This is why the leds don’t burn up with no current limiting resister. This is running the leds at about 2X design spec but after running one like this off a lab power supply for a few hours it is barely warm to the touch and has not moved from a round 0.031 mA current draw Amp meter in the power supply so not the best thing in the word for measurement.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Harvey White
Sent: Sunday, May 23, 2021 6:31 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

LEDs can be gotten in different dispersions, some, for instance, I think at 130 degrees. If you have a 3D printer, you might be able to make a light shroud depending on your needs. If you can do PC boards, then I could recommend a 3 color LED. How to profitably control it is another matter. Otherwise, pick a color depending on what you want.

It might get close to an incandescent lamp.

Harvey


On 5/23/2021 5:15 PM, DaveH52 wrote:
In a few days, I'll be disassembling my 2465 again to install a replacement module for U800. Since it will be totally disassembled, I'm seriously considering replacing the graticule lamps with red LEDs. I plan on 'frosting' the tops so the light will be more diffused. It worked well for the meter on my Kenwood TS-440, except I used white LEDs for that.






Andy Warner
 

Eric, I have to say that the photos you uploaded make me want to swap out
the lamps on my 7904.
Normally, I'm a reasonable adherent to "it ain't (that) broke, don't fix
it", but your results look stunning.

I am surprised that the dimmer circuitry is good enough without
modification, do you observe any reduced useful range of the graticule
illumination control ?

On Sun, May 23, 2021 at 9:53 PM Eric <ericsp@gmail.com> wrote:

Led moding a 7000 Series Scope after crawling in to my head from a year
ago.

The LEDs used were Adafruit / 754 Super bright White Leds. Important notes
on these Vforward for the diode being white is 2.5Vdc this is important
later. Led Size is 5mm Clear

Dropping resister – None

Power supply open circuit voltage – 8.1 Vdc at full illumination

LED wiring parallel like the old light bulbs

The lamp illumination is current limited by the scope its self. When the
LEDs are connected and the illumination on FULL the voltage across the
connector in the scope is only 3.2 Vdc this means that the Leds are only
drawing about 40mA each this was verified on a 577. This is why the leds
don’t burn up with no current limiting resister. This is running the leds
at about 2X design spec but after running one like this off a lab power
supply for a few hours it is barely warm to the touch and has not moved
from a round 0.031 mA current draw Amp meter in the power supply so not the
best thing in the word for measurement.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Harvey White
Sent: Sunday, May 23, 2021 6:31 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with
LEDs?

LEDs can be gotten in different dispersions, some, for instance, I think
at 130 degrees. If you have a 3D printer, you might be able to make a
light shroud depending on your needs. If you can do PC boards, then I
could recommend a 3 color LED. How to profitably control it is another
matter. Otherwise, pick a color depending on what you want.

It might get close to an incandescent lamp.

Harvey


On 5/23/2021 5:15 PM, DaveH52 wrote:
In a few days, I'll be disassembling my 2465 again to install a
replacement module for U800. Since it will be totally disassembled, I'm
seriously considering replacing the graticule lamps with red LEDs. I plan
on 'frosting' the tops so the light will be more diffused. It worked well
for the meter on my Kenwood TS-440, except I used white LEDs for that.















--
Andy


Eric
 

Hey Andy I offered to make a short video on it and upload it to you tube. I have 2 different filters on the 7603's one is the ND the other is the clear. I will be uploading some pictures on a 7704A with the Beaverton blue filter as well. These we taken with a cell phone as the 7704 is my office scope. I go in to 3 different lighting conditions Lab lights off, dim, and full on and various intensities to show an idea as to the performance of the LEDs

Shoot me and off list e-mail and I will send you the link.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Andy Warner
Sent: Monday, May 24, 2021 7:12 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

Eric, I have to say that the photos you uploaded make me want to swap out the lamps on my 7904.
Normally, I'm a reasonable adherent to "it ain't (that) broke, don't fix it", but your results look stunning.

I am surprised that the dimmer circuitry is good enough without modification, do you observe any reduced useful range of the graticule illumination control ?

On Sun, May 23, 2021 at 9:53 PM Eric <ericsp@gmail.com> wrote:

Led moding a 7000 Series Scope after crawling in to my head from a
year ago.

The LEDs used were Adafruit / 754 Super bright White Leds. Important
notes on these Vforward for the diode being white is 2.5Vdc this is
important later. Led Size is 5mm Clear

Dropping resister – None

Power supply open circuit voltage – 8.1 Vdc at full illumination

LED wiring parallel like the old light bulbs

The lamp illumination is current limited by the scope its self. When
the LEDs are connected and the illumination on FULL the voltage across
the connector in the scope is only 3.2 Vdc this means that the Leds
are only drawing about 40mA each this was verified on a 577. This is
why the leds don’t burn up with no current limiting resister. This is
running the leds at about 2X design spec but after running one like
this off a lab power supply for a few hours it is barely warm to the
touch and has not moved from a round 0.031 mA current draw Amp meter
in the power supply so not the best thing in the word for measurement.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Harvey
White
Sent: Sunday, May 23, 2021 6:31 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with
LEDs?

LEDs can be gotten in different dispersions, some, for instance, I
think at 130 degrees. If you have a 3D printer, you might be able to
make a light shroud depending on your needs. If you can do PC boards,
then I could recommend a 3 color LED. How to profitably control it is
another matter. Otherwise, pick a color depending on what you want.

It might get close to an incandescent lamp.

Harvey


On 5/23/2021 5:15 PM, DaveH52 wrote:
In a few days, I'll be disassembling my 2465 again to install a
replacement module for U800. Since it will be totally disassembled,
I'm seriously considering replacing the graticule lamps with red LEDs.
I plan on 'frosting' the tops so the light will be more diffused. It
worked well for the meter on my Kenwood TS-440, except I used white LEDs for that.















--
Andy


Eric
 

I just tested that it does actually but only on the very extreme right of the scope and outside the graticule area there is some very weak excitement of the phosphor. But I was only able to tell in a dark room. I had not previously tested it until now. And you have to slam the control from full to off quickly. My ring magnifier that uses a fluorescent tube actually excites the phosphor more then the leds. Significantly more actually.

Eri

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Ingo Scherer
Sent: Monday, May 24, 2021 11:51 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

Eric, it looks wonderfull.
Does the bright lighting excite any screen luminescence?


Jean-Paul
 

Dennis many thanks for the fine notes on the motive to replace the stock incandescent lamps with LEDs.

On 2465/7B, 7904, 7104 have got many scope photos with dimmed graticule and dim traces.

Using Adobe Photoshop , I add contrast and adjust brightness to balance the dim traces and the graticule.

Perhaps uneven graticule illum is caused by lamp positions in the graticule, or the design of the graticule?

Bon Journee,

Jon


Eric
 

More information on LED modifications and illumination. DO NOT attempt on the 7904A. The graticule lighting circuit is to put it mildly overly complex. It is no less then 3 power rails and 3 different circuit boards. Not sure what the need was for this complexity but it seems the balance point is current driven so the LED's cause it to go haywire. I will be looking in to the 7854 next as I would like to if possible get it done there and use that as my photo scope. I will report back when I know more.

Confirmed models so far
7603
7704A
465 with current limiting resisters 4 leds and 2 resisters,2 for each side of the board. It fits but it is a VERY tight on space.

Known issues
7904A

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Ingo Scherer
Sent: Monday, May 24, 2021 11:51 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with LEDs?

Eric, it looks wonderfull.
Does the bright lighting excite any screen luminescence?


Andy Warner
 

I have zero problem figuring out a rework plan to adapt the circuit to
drive LEDs.
The 7904 has the whole intensity/gate/manual thing going on instead of just
brightness, but you are right, the wiring goes to hell and back.

DFM never seemed to be very high on TEKs list of priorities.

On Thu, May 27, 2021 at 20:18 Eric <ericsp@gmail.com> wrote:

More information on LED modifications and illumination. DO NOT attempt on
the 7904A. The graticule lighting circuit is to put it mildly overly
complex. It is no less then 3 power rails and 3 different circuit boards.
Not sure what the need was for this complexity but it seems the balance
point is current driven so the LED's cause it to go haywire. I will be
looking in to the 7854 next as I would like to if possible get it done
there and use that as my photo scope. I will report back when I know more.

Confirmed models so far
7603
7704A
465 with current limiting resisters 4 leds and 2 resisters,2 for each side
of the board. It fits but it is a VERY tight on space.

Known issues
7904A

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Ingo Scherer
Sent: Monday, May 24, 2021 11:51 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Has anyone replaced the Graticule lights with
LEDs?

Eric, it looks wonderfull.
Does the bright lighting excite any screen luminescence?











--
Andy