Replacing Anritsu VNA crt with composite LCD panel - Page 1
Forum section: electronics / projects

author: precaud
author_rank: Frequent Contributor
timestamp: May 20, 2018, 04:40:01 pm
content: The crt of my Anritsu MS420K VNA will need to be replaced at some point. That is a given.So I'm looking into LCD replacements.Internally, the video signal is the ol' composite video, nowadays referred to as AVI. Handily, Anritsu provided a video output jack on the rear panel in case you wanted to use a larger, external crt. The same signal is sent to the internal crt.So I bought a nice little LCD screen which used to be made by SuperCircuits. It's the right size, has AVI inputs, perfect.Except - the image is offset vertically up and to the right, enough to clip off the top line of the display.The SuperCircuits unit has some basic adjustments (bright, contrast, etc) but none for image positioning. I talked to them on the phone, this is a long-discontinued model, they didn't know what to suggest.I'm a dummy when it comes to video protocols. Is this something that can be adjusted on the source end? The internal crt has adjustments but that doesn't change the video out signal.Any help/suggestions would be appreciated.

author: Whales
author_rank: Super Contributor
timestamp: May 20, 2018, 05:14:12 pm
content: Any option by the name of 'overscan'?

author: precaud
author_rank: Frequent Contributor
timestamp: May 20, 2018, 05:21:39 pm
content: Nada. Just brightness, contrast, sharpness, etc. ... nothing that affects the positioning, geometry, size ...

author: precaud
author_rank: Frequent Contributor
timestamp: May 20, 2018, 05:58:07 pm
content: This is the pcb inside the SuperCircuits. The main IC that handles the video is a TSC7996. I find absolutely no info about this thing.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: May 21, 2018, 01:07:43 am
content: I know this is a stretch but bear with meHave you looked at the signal on a scope to see if the apparent blank space on the left is actually real? Maybe the VNA compensates for this and what you see on the LCD is "true". Maybe it does this deliberately to provide more leeway for adjustment.Do you have another CRT with composite in (like the 1997 Sony Trinitron that is my primary - and only - TV) or a flat screen TV with composite input to see what they display?Another thought is that the composite signal is purely for external use and the internal CRT is driven by something else.See, a stretch...

author: helius
author_rank: Super Contributor
timestamp: May 21, 2018, 01:58:20 am
content: Quote from: precaud on May 20, 2018, 04:40:01 pmSearching Google for "composite AVI" returns nothing relevant to analog video on the first page.Searching for "CVBS composite" returns 20 hits that are all relevant.I think you need to adjust your search terms.

author: precaud
author_rank: Frequent Contributor
timestamp: May 21, 2018, 02:04:38 am
content: Quote from: JohnnyMalaria on May 21, 2018, 01:07:43 amI'll take a stretch!QuoteYes, I have used two external crt monitors with it and it works fine with both. No adjustments needed to be made with either one.The blank space on the left is not a big deal, I can work around that. The upward image shift (and resulting missing top line) is the one I need to solve.QuoteTechnically true. But they're assembled from the same signals. They're not combined for the internal crt driver.

author: precaud
author_rank: Frequent Contributor
timestamp: May 21, 2018, 02:06:56 am
content: Quote from: helius on May 21, 2018, 01:58:20 amI wasn't searching for that. I was searching for a data sheet for the TSC7996 video chip.

author: precaud
author_rank: Frequent Contributor
timestamp: September 06, 2020, 02:40:48 pm
content: Reviving this thread I started a couple years ago. I still want to replace the crt in my Anritsu VNA. I decided to try one of the 5.6" VGA LCD panels with AV input from China:https://www.ebay.com/itm/402350006760The controller board uses an MST703-LF processor, which has been around for a while and from what I've read seems to be well-regarded. A complete data sheet for it is also available:http://www.datasheetcafe.com/mst703-datasheet-pdf/It arrived yesterday. Unfortunately the seller sent a different board, one which uses an SSD102 processor. I can find no info on this video processor. I wrote and asked him, he said it's an "updated version". Yeah, right.I tried it out, and it does work better than the LCD display in the first post a couple years ago. The display quality is better. It positions the Horizontal display correctly. The vertical is positioning is wrong, still shifted up but a little bit less. Most of the top line is still missing, with blank space at the bottom.So it appears that these video processors all do some sort of 'automatic' horizontal and vertical positioning, but not all do it the same.Does anyone know of, or have an example of, one that does it correctly? Or has position adjustments in their menu?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 06, 2020, 03:14:10 pm
content: I had the same problem as you when using a Commodore 64 with various LCD TVs.I use an external video conversion device to connect to a computer monitor.For examplehttps://www.ebay.ca/itm/Inline-IN1402-Video-Scaler/312791573324?hash=item48d3d4a34c:g:qtEAAOSwxlxdllEKManualhttp://www.audiorama-berlin.de/pdf/1402man.pdfMaybe you can connect your VNA to a box like that? Then you won't be relying on the LCD panel's interpretation of the video signal.

author: precaud
author_rank: Frequent Contributor
timestamp: September 06, 2020, 03:40:59 pm
content: Quote from: Alex Eisenhut on September 06, 2020, 03:14:10 pmThanks, that's interresting. I was wondering if this was the norm, but I don't have another device with composite output to test.QuoteInteresting. Not an ideal solution (large-ish, will it fit in the analyzer?), but I'll look into it. Is "video scaler" the common name for these things (assuming there are others)?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 06, 2020, 04:01:58 pm
content: Well if you think that's large, you won't like the other ones...https://www.ebay.ca/itm/323833507844And yes a scaler is what you want. However they are all very variable about what they let you do.The search term for the inexpensive units is something like av to vga.https://www.ebay.ca/itm/AV-to-VGA-Adapter-1080P-HD-Mini-VGA-Converter-ABS-Shell-Video-Converter-for-N9D6/254675126555?hash=item3b4bd2091b:g:cyYAAOSwsKFfGvr1Don't be fooled by the USB port, it is not for controlling the unit (AFAICT) but for power. These don't come with a power supply. They also have absolutely no controls except for the output resolution.I bought a bunch and the cheap ones work "good enough" for a C64 but the 64's video has large borders so there's lots of leeway.

author: precaud
author_rank: Frequent Contributor
timestamp: September 06, 2020, 04:19:45 pm
content: Yikes. I see what you mean.So, it seems none of these scalers or format converters have position controls. That makes it a cr@p shoot to try AV-to-VGA, and then VGA into the LCD controller board.That AV to VGA adapter has a switch on the side for 720P or 1080P. Makes me wonder how it would handle a 4:3 AV image.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 06, 2020, 04:34:21 pm
content: The Inline unit has position controls. It also has a serial port for controlling parameters at your leisure. It uses a removable 3 pin terminal block instead of a 9 pin connector for that. Not a big deal IMO.Page 8 of the manual shows the menus and size and position controls.

author: precaud
author_rank: Frequent Contributor
timestamp: September 06, 2020, 04:55:35 pm
content: Ah, ok. It looks like the scaler is the way to go, thanks for the suggestion.EDIT: I just picked one up on eBay:https://www.ebay.com/itm/Extron-IN1402-Inline-Video-Scaler-60-729-01-Tested-works-fine/142914358314The manual for it is still available:https://media.extron.com/public/download/files/userman/IN1402_Man1204RevA.pdf

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 07, 2020, 01:35:20 am
content: Well I hope it works for you, the price is hard to beat. Powered off the mains so if the unit doesn't work, hey, free project case with power supply!

author: precaud
author_rank: Frequent Contributor
timestamp: September 07, 2020, 02:04:49 am
content: Just what I need - yet another project case!

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 07, 2020, 02:55:24 am
content: Hmmm well if you like never-ending projects have you tried a CRT rejuvenator on your VNA?

author: precaud
author_rank: Frequent Contributor
timestamp: September 07, 2020, 03:41:56 am
content: The crt is fine, it's some of the power and support circuitry that are flakey.Oh, and I do NOT like never-ending projects!

author: precaud
author_rank: Frequent Contributor
timestamp: September 07, 2020, 04:44:52 pm
content: BTW, the board sent is a UT-MD050056 v.3 made by Jinchi-UT :http://www.jianchi-ut.com/productinfo/884912.html?templateId=1133605The video processor it uses is SSD102 made by SigmaStar:http://www.sigmastarsemi.com/en/products/list.aspx?lcid=56Hopefully better for RGB input than composite...

author: precaud
author_rank: Frequent Contributor
timestamp: September 11, 2020, 11:05:58 pm
content: I got the IN1402 scaler today, and spent an hour or so fiddling with it. The results are not good. Display quality is significantly worsened. The image is shifted WAY left, and horiz position doesn't center it. The top line on the display is still cut off, and adjusting vert position doesn't change that. And, it turns out, this scaler doesn't offer much position or size adjustment range when going from composite to 640x480. As the manual clearly states, the IN1402 is primarily designed for scaling an image UP into higher-res displays, and 640x480 is the *minimum* resolution it supports.I convinced the eBay seller of the LCD panel to send me the board that was advertized. We'll see if that one fares any better.

author: Miti
author_rank: Super Contributor
timestamp: September 12, 2020, 03:13:33 am
content: Quote from: precaud on September 06, 2020, 02:40:48 pmI had the same issue with my LCD for the HP8590 series spectrum analyzer. You posted the same picture in my thread here:https://www.eevblog.com/forum/projects/hp-8594e-replacing-the-green-crt-with-lcd/Your issue is with the back porch on both horizontal and vertical, it is not the standard length that's expected from a video signal from VCR or DVD for example. Your vertical back porch is too short and horizontal is too long. Luckily, HP8590 has horizontal and vertical adjustments. In the end, I gave up the idea of using the AV input and I converted the 2 level AV signal with an FPGA into 2 color VGA. The result is promising, the only issue is that it's a bit hard (for me) to control the vertical an horizontal size. As is, the output VGA fills the LCD edge to edge and the 5.6" LCD is a little big, the 5" is a little small, the ideal size is somewhere in between.I have the exact same LCD panel as you 5.6" sizes with SSD102 and 5" with MST703-LF and I don't see any difference, they both work well.

author: precaud
author_rank: Frequent Contributor
timestamp: September 12, 2020, 02:46:25 pm
content: Hi Miti,Thanks for weighing in. Yes, I'm following your thread with interest.Looking at the makeup of the composite signal, your description of the "short back porch" makes sense.Sorry to hear that you had identical results with the SSD102 and MST703-LF. It seems unlikely that will solve my problem.IIRC, the composite signal is generated/assembled in 74LS logic in the MS420. Maybe time to study it and see if the timing can be tweaked. A project for this winter, perhaps.

author: Miti
author_rank: Super Contributor
timestamp: September 12, 2020, 03:39:46 pm
content: These LCD chips (MST703 and SSD102) are programmable and all the parameters are stored in an external EEPROM. I think your best bet is to figure out where the back and front porches are located in the EEPROM and try to reprogram them. I've attached the datasheet for MST703 in case you don't have it. You should be able to recenter the image.

author: precaud
author_rank: Frequent Contributor
timestamp: September 12, 2020, 04:01:52 pm
content: Thanks, yes I have that and have studied it a couple times and nothing jumped out as the thing to tweak. Maybe they use dfferent terminology. I'll look again.

author: Miti
author_rank: Super Contributor
timestamp: September 12, 2020, 05:15:14 pm
content: Look at indexes 4Eh and 4Fh.

author: precaud
author_rank: Frequent Contributor
timestamp: September 22, 2020, 05:56:56 pm
content: The seller sent me what was supposed to be the board he advertized, with MST703-LF video controller. I received it yesterday. Unfortunately it has the same SSD102 chip in it as the first board he sent.The image it presents is a little different. Slightly larger, but cutting off even more of the top line. No more or less useable than the previous board.I'm going to punt on this for now.