Newscope's LCD kit for 8753a VNA - Page 1
Forum section: electronics / testgear

author: Howardlong
author_rank: Super Contributor
timestamp: November 19, 2014, 07:01:39 pm
content: FolksA couple of weeks ago, I upgraded my old HP 8753A VNA's CRT to a Newscope 9 colour LCD, commonly available on eBay. It took about a week to arrive here in the UK from the US. The old CRT was useable, but it's always been difficult to coax the screen into a reasonable brightness and focus across the whole area, and more recently the horizontal has become a bit twitchy, although while doing this update I believe it was just a dirty trim pot on the CRT board. Other than that, the supercap backup has never worked since I've had it so I always have to recal, and occasionally it turns on and doesn't recognise the test set's connected to it, but a reboot fixes that, and it's not getting any worse.BeforeThe original CRT is monochrome, so I was interested to see how the colour was going to work. The Newscope 9 replaces the entire CRT assembly, including a well populated display board, so there's an added benefit is that the old boat anchor is a bit lighter as a result.I've taken the VNA apart a couple of times before to adjust the CRT, so it wasn't any big deal getting inside it. Similarly, the CRT slides out once you've removed a number of screws.Original display board mounted on the CRTFocus and intensity connectors on the display board of the original CRTConnectors on the CRT, to remember where they came fromCRT unit removed, connectors labelled and orientation marks placedI followed the instructions and everything went well, and I tested the unit before putting the cover and various other bits and screen bezel etc back on.Replacement Newscope display boardLooks nice and crispOooh, colour! Looks really nice... until I cock it up, see laterI screwed everything back in (except the CRT of course!), fixed the Newscope display board to the chassis, and removed the protective LCD film. The cover was back on, power up and...... oh. A blank white screen. So I disassembled the VNA again, and tried to figure out what was wrong.White screen of deathI checked and re-checked the connections. I realised that I had put the main LCD cable on the wrong way around on the display board when fixing the display board to the chassis, so fixed that. A bit of a schoolboy error you may think, but the connector on the display board is marked with a small triangle on one end, the correct pin 1 locator. However, there is an immediately adjacent connector at the other end, which is marked "1" too, and I'd used that as the orientation mark. Doh!20 pin (10x2) connector P2 with pin 1 confusionSo I plugged it in the right way, but still, white screen, oh dear. So I checked the pins of the connector to see if there was any life. Certainly there's a flickering green LED on the display board indicating some sense is happening somewhere.Drawing a blank I contacted Newscope who have been very helpful. In the end I figured out the problem myself. When the protective film was pulled off the LCD display, I'd pulled off the polarisation film too <aaarghh!>. Now I had noticed it was unusually stiff to remove, so before I proceeded I double checked under the illuminated magnifier. Should've checked three times. I couldn't see any evidence that there were in fact two films.Luckily I'd kept the films fairly flat in a bag and had not disposed of them, so I put the polarisation film back on the display, removed the real protective film, and automagically things looked a lot better, except of course you're never going to be able to reapply a polarisation film as well as it was originally placed. So I now have some interesting minor marks on the display. Newscope have offered me a replacement LCD at a reasonable price, but I'm happy enough with the results for now, other than feeling extremely stupid for taking the polarisation film off in the first place.Glorious colour, except for my polarisation film reapplication errorGuess I need to re-evaluate this broadcast FM filter designIn conclusion, except for the connector alignment mentioned and my own idiot error with the polarisation film, the result is such an improvement, and having colour, although there are pretty limited palette and font options, is a real benefit, it makes the unit look 20 years younger.

author: xyloeye
author_rank: Contributor
timestamp: March 10, 2015, 05:20:44 pm
content: Great review. Thanks for taking the time. I'm planning to use the Newscope kit on my 3563 DSA. Good to know about the film issue.

author: KJDS
author_rank: Super Contributor
timestamp: March 10, 2015, 06:36:10 pm
content: That's useful to know. The screen on my 8753C is still ok but at some stage it will need a replacement.I do need to fix it as it's losing lock below 90MHz but that's for another topic.

author: Fraser
author_rank: Super Contributor
timestamp: March 10, 2015, 06:48:29 pm
content: Thanks for the post and associated pictures. That looks like a well sorted upgrade for CRT based equipment. Very nice.Aurora

author: Howardlong
author_rank: Super Contributor
timestamp: March 10, 2015, 07:31:00 pm
content: Quote from: KJDS on March 10, 2015, 06:36:10 pmNot sure if the 8753C is supported, but the 8753A and 8753B are.

author: free_electron
author_rank: Super Contributor
timestamp: March 10, 2015, 07:37:36 pm
content: for people that have trouble with these displays :the cerpots ( those white rpund ceramic potentiometers ) are a pest.there are two in there that are like 100 or 220 ohm and they burn out over time.most of the problems with those monitors are cause by those two pots

author: Mr Simpleton
author_rank: Unknown
timestamp: March 10, 2015, 10:24:15 pm
content: AFAIK the 8753A suffered from a poor CRT... and HP/Agilent really wanted these instruments to be off the market as they could not source a replacement CRT. They offered a very generous buy-back offer for us, and we ended up with the 8753E with a nice colour LCD. HP/Agilent paid almost £10k for our old model A.

author: rastro
author_rank: Frequent Contributor
timestamp: March 11, 2015, 04:23:53 pm
content: Quote from: free_electron on March 10, 2015, 07:37:36 pmI can attest to problems with these potentiometers as well. On a 8753B I fixes a focus problem after replacing the astigmatism pot. After that the display worked great.

author: tec5c
author_rank: Frequent Contributor
timestamp: November 07, 2015, 10:29:08 am
content: Apologies for resurrecting an old thread. I just wanted to see if the OP had any updated comments on this display replacement.I also have an 8753a VNA and am currently considering buying the LCD display kit to replace the CRT with.Any feedback on the modification would be nice.

author: Howardlong
author_rank: Super Contributor
timestamp: November 07, 2015, 11:09:51 am
content: Quote from: tec5c on November 07, 2015, 10:29:08 amNo, other than the comments already made. It's a very worthwhile mod, taking a couple of decades off your 30 year old instrument. The only question is what to do with the old CRT assembly? I am only keeping it in case I ever sell it, maybe someone will want the original, but the LCD is so much better.

author: tec5c
author_rank: Frequent Contributor
timestamp: November 07, 2015, 12:14:32 pm
content: Awesome... Xmas present to myself? Sounds good to me!Thanks Howard.