Author Topic: Upgrading the HP/Agilent 8714C from green CRT to color LCD  (Read 18489 times)

0 Members and 1 Guest are viewing this topic.

Offline TheSteveTopic starter

  • Supporter
  • ****
  • Posts: 3742
  • Country: ca
  • Living the Dream
Upgrading the HP/Agilent 8714C from green CRT to color LCD
« on: November 18, 2015, 05:29:52 am »
Today I finished installing an 8.4 inch TFT LCD panel in place of the original green CRT in my HP 8714C Network Analyzer.
This mod should work for the 8714C, 8714ET and 8714ES as they all have a VGA out connector on the back.

I bought the LCD panel and VGA driver board from ebay for $80 USD shipped - the seller shipped the entire kit inside a foam crate, it was extremely well packed.
This is the specific auction http://www.ebay.com/itm/191341791384 - I made a best offer to get the 80 dollar price.

The original green CRT runs off 12 volts and uses 1.2 amps of current. The LCD runs off 12 volts and uses 1 amp of current so power wise it was quite compatible.
The VGA out on the network analyzer is 640x480 @ 60 Hz which is the native resolution of the LCD which makes for a very sharp display.

The original green CRT is in a self contained metal cage that pulls out with the main power supply from the network analyzer easily. It is connected via a shielded 20 pin ribbon cable which provides ground, 12 volts, mono video, horizontal and vertical sync. The VGA output is only on the back of the analyzer. Luckily HP left 3 unconnected wires in the 20 pin ribbon cable which is exactly what I needed for the VGA red/green/blue signals. This meant the only mod to the main board itself was running 3 small coax cables with each of the colors from the test points near the VGA connector to the unused contacts on the ribbon cable.

Once the CRT was removed I was left with a nice metal cage to install the VGA controller and a small adapter board I threw together to translate from HP's 20 pin ribbon cable to the video and power inputs of the VGA controller.
I decided to install the board inside of a secondary metal box, it made mounting easy and adding an extra level of shielding is always a positive. The LCD panel is mounted to the same 4 frame bolts that held the original CRT using a pair of adapter brackets I made out of 1/16th inch aluminum. The brackets also allowed me to fine tune the position of the panel as well as adjust the spacing from the front cover.
Speaking of the front cover - the inside of it was molded to match the curvature of the original CRT. The only permanent change I made during this mod to the analyzer was to mill away the curves so it would sit flat against the LCD panel giving it a factory look.

The project so far has exceeded all of my expectations. One last step I plan to do in the future is switch the LCD panel from CCFL back light to LED. That will be one less switching power supply running. I can also make up a circuit using the original CRT brightness pot on the left of the analyzer to adjust the LCD brightness. I did test the radiated noise from the panel and in front of the analyzer with my spectrum analyzer before and after and am happy to report I am detecting no additional noise which will interference with test results.

I figure for the dollars invested this is a pretty nice upgrade. The original green CRT is very sharp and easy on the eyes but the LCD really gives the machine a much more modern look and some color which is nice - btw the colors are all adjustable.
VE7FM
 
The following users thanked this post: tv84, KE5FX, VSS

Offline TheSteveTopic starter

  • Supporter
  • ****
  • Posts: 3742
  • Country: ca
  • Living the Dream
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #1 on: November 18, 2015, 05:30:11 am »
Pics of the main board coax cables, LCD brackets, the front cover before milling and the front cover after milling.
« Last Edit: November 18, 2015, 05:32:34 am by TheSteve »
VE7FM
 

Offline TheSteveTopic starter

  • Supporter
  • ****
  • Posts: 3742
  • Country: ca
  • Living the Dream
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #2 on: November 18, 2015, 05:30:25 am »
LCD panel during initial testing and a shot of the what the stock analyzer looks like with the green CRT, some how I didn't end up with a picture showing the panel mounted to the analyzer before I put the front cover back on.

« Last Edit: November 18, 2015, 05:38:24 am by TheSteve »
VE7FM
 

Offline nidlaX

  • Frequent Contributor
  • **
  • Posts: 663
  • Country: us
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #3 on: November 18, 2015, 05:59:49 am »
Simply brilliant! :-+
 

Offline tec5c

  • Frequent Contributor
  • **
  • Posts: 423
  • Country: au
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #4 on: November 18, 2015, 08:22:05 am »
Nice upgrade  :-+

I have been considering looking for a LCD kit upgrade for my 8753A analyser, bit too busy at the moment though.

I did notice that there was some overlapping text on the LCD (best view in the first picture. Marker text for the smith chart overlapping with the j100 coord.), did this occur with the CRT also?
« Last Edit: November 18, 2015, 08:23:59 am by tec5c »
 

Offline crispy_tofu

  • Super Contributor
  • ***
  • Posts: 1124
  • Country: au
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #5 on: November 18, 2015, 08:24:21 am »
Fantastic!  :clap:
 

Offline VK5RC

  • Supporter
  • ****
  • Posts: 2672
  • Country: au
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #6 on: November 18, 2015, 08:36:54 am »
Lovely work, well done. :-+
Whoah! Watch where that landed we might need it later.
 

Offline TheSteveTopic starter

  • Supporter
  • ****
  • Posts: 3742
  • Country: ca
  • Living the Dream
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #7 on: November 18, 2015, 08:53:47 am »
Nice upgrade  :-+

I have been considering looking for a LCD kit upgrade for my 8753A analyser, bit too busy at the moment though.

I did notice that there was some overlapping text on the LCD (best view in the first picture. Marker text for the smith chart overlapping with the j100 coord.), did this occur with the CRT also?

Yes, the marker text has always overlapped if you have the right combination of options selected, no change going from the CRT to the LCD.

There are commercial made LCD kits available for the 8753A - not sure how affordable they are though.

I have never seen any kind of LCD upgrade for the 8714 series however while looking through the schematics to come up with my mod I did notice there is a provision for a factory LCD option. The parts are all marked no-load and I don't think they ever sold one with an LCD screen. I did ponder installing all of the parts but it looks like it would also need some firmware support which I doubt is present and the LCD output is 4 bit. The 640x480 panel I bought uses a 6 bit interface.

The LCD kit I bought also has a push button board to configure it, along with an on/off switch etc. The LCD happily powers on with that board not connected and works fine without it. I can remove the front cover of the analyzer and plug it in if needed - to adjust brightness, contrast etc.

VE7FM
 

Offline tec5c

  • Frequent Contributor
  • **
  • Posts: 423
  • Country: au
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #8 on: November 18, 2015, 09:26:13 am »
Thanks for the info, most appreciated.
 

Offline TheSteveTopic starter

  • Supporter
  • ****
  • Posts: 3742
  • Country: ca
  • Living the Dream
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #9 on: December 27, 2015, 08:33:44 am »
The LED strips I ordered 1.5 months ago finally arrived. They are long thin strips of white LED's mounted on PCB. They were shipped in a strong plastic tube to prevent damage yet some how the postal system still managed to fold the tube right over. This of course snapped the LED strips into pieces, they also managed to damage the included switching power supply. The LED strips I ordered were the shortest I could find on ebay but were still too long. As luck would have it the broken pieces were the correct length to convert the LCD screen to LED backlighting and to ditch the CFL tubes and inverter. They were also broken at just the right place as the LED's are in parallel sets of three LED's in series.
The original CFL tubes just slid out with no panel disassembly at all. I added some heatshrink tubing to the LED strips which gave them a nice snug fit when slid in to the LCD panel. For brightness I used a power supply to find what I thought was the optimal drive current and then added a single 20 ohm resistor in series with the LED strips which connect to the 12 volt power supply. So for now the brightness is fixed.
A further project is to use the original 8714C knob to vary the brightness. The pot is 100K so I'll need to come up with a simple linear based circuit(no noise) that can vary the current to the LED strips between 100 and 200 mAh.
Once installed the LCD looked same of course but has instant on backlighting with no inverter noise at all. I have attached pics of the original tubes and new LED strips.
VE7FM
 

Offline TiN

  • Super Contributor
  • ***
  • Posts: 4543
  • Country: ua
    • xDevs.com
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #10 on: December 27, 2015, 08:53:35 am »
Badass mod, reviving gear like a boss.  :-+
YouTube | Metrology IRC Chat room | Let's share T&M documentation? Upload! No upload limits for firmwares, photos, files.
 

Online Zero999

  • Super Contributor
  • ***
  • Posts: 19342
  • Country: gb
  • 0999
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #11 on: December 27, 2015, 05:04:55 pm »
The LED strips I ordered 1.5 months ago finally arrived. They are long thin strips of white LED's mounted on PCB. They were shipped in a strong plastic tube to prevent damage yet some how the postal system still managed to fold the tube right over. This of course snapped the LED strips into pieces, they also managed to damage the included switching power supply. The LED strips I ordered were the shortest I could find on ebay but were still too long. As luck would have it the broken pieces were the correct length to convert the LCD screen to LED backlighting and to ditch the CFL tubes and inverter. They were also broken at just the right place as the LED's are in parallel sets of three LED's in series.
The original CFL tubes just slid out with no panel disassembly at all. I added some heatshrink tubing to the LED strips which gave them a nice snug fit when slid in to the LCD panel. For brightness I used a power supply to find what I thought was the optimal drive current and then added a single 20 ohm resistor in series with the LED strips which connect to the 12 volt power supply. So for now the brightness is fixed.
A further project is to use the original 8714C knob to vary the brightness. The pot is 100K so I'll need to come up with a simple linear based circuit(no noise) that can vary the current to the LED strips between 100 and 200 mAh.
Once installed the LCD looked same of course but has instant on backlighting with no inverter noise at all. I have attached pics of the original tubes and new LED strips.
Good work!

Here's a constant current LED circuit which should do the job.
 

Online nctnico

  • Super Contributor
  • ***
  • Posts: 26751
  • Country: nl
    • NCT Developments
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #12 on: December 27, 2015, 08:12:54 pm »
Thanks  :-+ I never knew those LED based CCFL replacements existed!
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline plesa

  • Frequent Contributor
  • **
  • Posts: 965
  • Country: se
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #13 on: December 27, 2015, 08:42:40 pm »
 :-+ Upgrade!!
 

Offline Howardlong

  • Super Contributor
  • ***
  • Posts: 5315
  • Country: gb
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #14 on: December 27, 2015, 08:52:31 pm »
Very impressive!

I did the Newscope LCD mod to my 8753A some months ago, it's taken two decades off it. Of course there's no VGA output on the 8753A, they have an FPGA to do the CRT untangling.
 

Offline TheSteveTopic starter

  • Supporter
  • ****
  • Posts: 3742
  • Country: ca
  • Living the Dream
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #15 on: December 28, 2015, 02:16:01 am »
Here's a constant current LED circuit which should do the job.

Thanks for the schematic. I was pondering using a single supply opamp driving a pass transistor last night which would have been easy to make vary the voltage from 8 to 12 volts going into the existing 20 ohm resistor. I thought I would bread board your schematic though and it worked fine so I went with it. The BC237 was swapped for a 2N3906 and the two BC337's were replaced with a single TIP31C and a small heatsink I ripped off an old eprom programmer. I used the 4.7K resistor during testing but after installing it I wanted a little more drive current so I paralleled a 5.1K with it. This gives me adjustable drive current from 40 to 220 mAh. The new board is mounted in the original metal box I added, everything is working great. There was a small delay during final assembly when some hardware went missing. It was in a small plastic film container. It seems "Hunky Bill" thought it made a great toy as it rattled quite nicely when batted around. Attached are pics of the driver board, one showing it installed in the metal box, a shot of the LCD with the front panel removed and a picture of Hunky Bill in his "rest state" after taking a round out of any and all equipment in the shop.

I think it is finally time to stop taking the 8714C apart and put it to work!
VE7FM
 

Offline AF6LJ

  • Supporter
  • ****
  • Posts: 2902
  • Country: us
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #16 on: December 28, 2015, 03:17:47 am »
That's really great, looks good.
Sue AF6LJ
 

Offline andy2000

  • Frequent Contributor
  • **
  • Posts: 254
  • Country: us
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #17 on: March 30, 2016, 03:36:17 pm »
I just picked up an 8711C which I've turned it into an 8712C with all the software options.  I found that writing 00 for the four option bytes turned it into an 8730A tuner analyzer.  I had to use 8B as found on this page:

https://translate.google.com/translate?hl=en&sl=cs&u=http://minolta1.cninet.cz/HP8712C/&prev=search

Next I'm going to try to use the digital LCD interface.  It looks like a standard 4 bit parallel output which should work with many LCDs.  The LCD gets its data from the same source as the DAC for the VGA output, so assuming there's no issue with timing, I think it should work. 

Keysight was nice enough to post schematics for the 871XC:

http://na.support.keysight.com/871x/schematics/
 
The following users thanked this post: TiN

Offline andy2000

  • Frequent Contributor
  • **
  • Posts: 254
  • Country: us
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #18 on: October 11, 2016, 04:34:31 am »
I finally go around to adding the digital LCD interface.  It all went smoothly and worked the first time.  I just need to remove the CRT and mount the LCD.  I used a Mitsubishi AA084VC03 LCD panel.  I'll post some more detailed pictures soon. 
 

Offline R005T3r

  • Frequent Contributor
  • **
  • Posts: 387
  • Country: it
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #19 on: October 11, 2016, 11:47:33 am »
Nice upgrade!  :-+ :-+

I'm very interested in these mods, maybe I can try to upgrade my old HP5402A with an LCD panel. The thing is, if something goes wrong I don't have any other scope...
 

Offline AF6LJ

  • Supporter
  • ****
  • Posts: 2902
  • Country: us
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #20 on: October 12, 2016, 06:48:26 pm »
This is very Cool, looking forward to more pictures and info.
 :-+ :-+
Sue AF6LJ
 

Offline TheSteveTopic starter

  • Supporter
  • ****
  • Posts: 3742
  • Country: ca
  • Living the Dream
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #21 on: October 12, 2016, 07:57:46 pm »
Yes, more info would be great. A cheaper and easier mod is anyways welcomed. It would be nice to ditch the VGA interface.
VE7FM
 

Offline andy2000

  • Frequent Contributor
  • **
  • Posts: 254
  • Country: us
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #22 on: January 22, 2017, 02:08:06 am »
Here are some more pictures of the project.  I'll post a list of part numbers for the ICs soon.  They were standard parts from Mouser.  I already had miscellaneous parts like caps and resistors on hand. 

U1025 is used for brightness control, but I didn't install it since I assume the firmware lacks support for that feature. 

I simply grounded the unused LSBs of the LCD. 

I mounted the LCD to a piece of Plexiglas which I attached to the CRT brackets on standoffs.  I used a router table to shave off the CRT bezel.
 

Offline andy2000

  • Frequent Contributor
  • **
  • Posts: 254
  • Country: us
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #23 on: January 28, 2017, 05:12:02 pm »
Here's a list of the part number I ordered. 

U1008 -- LX8385B-33CDD -- 3.3v regulator
Q1001 -- FDS6679 -- P channel MOSFET
R1025 -- SOMC160333R0GEA  -- resistor array, 33 ohms
R1026 -- SOMC160333R0GEA  -- resistor array, 33 ohms
U1012 -- SN74LVT125D
U1009 -- SN74LS123DR
U1010 -- 74LVT574WMX
U1011 -- 74LVT574WMX
J1020 --  A3E-50PA-2DSA(71)
 
The following users thanked this post: AF6LJ, Teuobk, Marcel G

Offline KrudyZ

  • Frequent Contributor
  • **
  • Posts: 274
  • Country: us
Re: Upgrading the HP/Agilent 8714C from green CRT to color LCD
« Reply #24 on: June 05, 2018, 12:19:33 am »
I recently bought a nice copy of the HP 8714ET and have just received my LCD from Shenzhen.
https://www.ebay.com/itm/VGA-LCD-Controller-Board-RT2270C-With-8-4-AA084VC03-640x480-LCD-Screen/181965840286?hash=item2a5e025f9e:g:1oUAAOSwbtVZV2uh
I paid $90 shipped. It arrived within 10 days and was well packaged, so I had a good experience with this seller.
I chose to go the analog VGA route as it seems to require fewer modifications to the analyzer.
Here is a picture of the LCD kit plugged into the external VGA port and powered from a 12 V lab supply (it draws about 1 A).
This is using two fluorescent backlights. I'm still waiting on the LED strips to come in to update the backlight and complete the mod.
Rudy
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf