LCD Screen for Tektronix TDS-544A

Here a story how I replaced a CRT screen with LCD one.

Thanks a lot to the document named "TDS 520B Mod CM Digitizing Oscilloscope Component Service Manual", it reveals some details on scope's guts.

After my lovely CRT screen became a piece of glass, I started to look for alternatives our Chinese brothers can offer.
Not too many.
According to the Service Manual, the scope resolution is 640x480. But the problem is that nowadays it is not very easy to find an affordable LCD with such native resolution. 6.5" 640x480 screens are mostly used in cars and industrial equipment so they are not as cheap as widescreen 800x480 ones. For example, 4:3 screens start from $150 when 16:9 start from $60 with controller.

So I bought AT070TN90 7" 800x480 LCD panel with a controller for less than $70 with shipping from a US seller on eBay.
Luckily controller has 4:3 mode so LCD can display 640x480 picture without any pixel transformation issues. But the bad thing about 4:3 mode is that controller fills unused areas with blue. It sucks. I need to cover it with something. But I have to make a front panel for this screen anyway.

Finally I got new screen working. It took some time to complete. So here what else I needed:

• anodized aluminium panel (eBay)
• Radioshack perfboard
• 12V DC/DC converter (eBay)
• 1-ft VGA cable (eBay)
• aluminium bar to make nuts
• #4-40 tap
• some wires, screws, and washers
• epoxy glue
• nylon PCB stands

AT070TN90

Realtek LCD controller board

Frame was cut from anodized aluminium:

Last test

Radioshack perfboard, 12V DC/DC converter and LCD controller with 1-ft VGA cable

Where to get some power for the LCD

OSD menu buttons. LCD power wires connected to J574 are on the top.

 Finally I put it all together:

The resutl

But for some strange reason some pixels at the bottom of the screen are missing. No way to correct it using OSD menu, but it doesn't affect the signal graph area.

I'm satisfied (but CRT screen was much better). It is a nice feeling when you bring a good device back to life.

TEK Scope screen is dead

Bad thing just has happened!
I was watching strange signal shape coming out from my just assembled amplifier board when picture on the scope began to jump and scary pops and clicks started to come from my nice scope.
Thunderbolts inside a scope is not a very good sign, right? So another challenge is going to begin.
To be honest I'm not a fan of scope repairing... But high voltage transformer has died tragically.

Couldn't find a transformer like that on the Internet, found just a couple of LCD kits for almost thousand bucks. Well, I believe I can do it for less because the scope has a VGA output and it should be possible to connect a regular LCD to it.
I'm afraid a new LCD would not have better picture than CRT had, but I don't have a lot of options.

I know some people who have such color Tektronix TDS scopes have dead CRTs, so maybe I can find such a folk and give my CRT to him...

Scope Cleaning

All capacitors were removed with "twisting" method. I don't have hot tweezers to desolder large SMD capacitors and I'm afraid I would damage more pads if I used a single soldering iron. Almost all the traces left in place, I lifted just two pads which is not bad having almost hundred caps and all these leakages which could damage everything around.

After all capacitors were removed I had to clean all the acid residue. I found a lot of PCB cleaning stories. Seems that most popular way is to use Simple Green general purpose cleaner.
Simple Green + toothbrush + baking oven at about 150F made it virgin clean.

All capacitors are replaced with new low ESR leaded ones.

Before caps replacement

After all the caps are replaced. Still have Acquisition board fail...

Error log shows a mysterious error

I still have failed acquisition test, but scope seems to be working. 

Unfortunately I couldn't find where the problem can be. The only suspicious area is around U1602, where were a lot of corrosion. I replaced this opamp with a new one but could not find where one of the legs connected. Seems to be a broken trace. I would be happy to fix it but could not find where to connect it. Need to try to find out...

It  looked not very nice...

But I think I can live with non-calibrated scope.

Oscilloscope

Having a multimeter is not enough to build an amplifier. I need an oscilloscope.
Thanks to craigslist, I found a new challenge.
Tektronix-TDS544A. Cool 500MHz digital scope with 4 inputs. But there are some caveats...
Before buying I tried to google it and found that all these scopes have leaking SMD capacitors. Leakage leads to a number of different anomalies.
Seller of mine scope told me the scope powers up but he can't see a thing. Since it is all crap shooting I gave it a try.
As expected, a lot of capacitors have leaks.
The plan is:
1. remove them all
2. clean all the PCBs
3. clean again
4. clean one more time
5. solder new capacitors

Some leaks look very suspicious

The worst leak

let's clean it up