VT132 stopped booting

[ronaldlw]

One of my VT132 boards stopped booting today. When I power it on there is no beep and nothing displayed on the vga output. If i unplug the VGA monitor cable then it will seemingly boot as I do get a beep, but obviously, I can't see anything on the display since it's unplugged. Nothing shows up if I plug the vga cable in after the beep.

My other board seems to be working fine when I swapped it out for the failing one.

I've looked and do not see any bridged solder pad or anything. It has been working without issue for a several months since I put it together.

Any suggestions on what to look for / test?

Voltages from the 5V and 3.3 v regulators appears to be fine and doesn't change depending on the vga cable being plugged in or not.

(Just the cable is fine, when I say vga cable plugged in I mean that it's going to a monitor on the other end)

I've tried with three different display options:

1. an 8" vga panel and control board that takes vga input directly
2. the same board, but going through a vga to HDMI converter to an HDMI input on the controller board rather than the VGA input.
3. a separate lcd monitor that has vga input.

I've poked around on the vga output with an oscilloscope, but I have no idea what I'm looking for. There does seem to be some output on most of the pins either with or without the vga cable connected.

Any help would be greatly appreciated!

[Retro-Tech-Reboot]

The VGA cable may be flexing the PCB allowing a bad/cracked solder joint to make contact. Try flexing the PCB with the VGA cable plugged in.

[ronaldlw]

Thanks for the reply. Good thought, but this doesn't seem to be the case, i've tried with several different kinds of cables, and the issue only happens when the cable terminates into a monitor (or the vga to hdmi converter in that case) if it's just the cable then it always beeps as expected. If the cable terminates to something it never beeps.

[ronaldlw]

I'm trying to connect to the the FTDI header so I can see logs and I'm not having any luck at all. I'm going to this page:
https://thehighnibble.com/vt132/maint/

And clicking connect and choosing my FTDI usb device and it says "failed to download manifest

Do I need to put the board into some special mode or do anything other than power it on with the FTDI usb interface plugged in before trying to connect?

I tried this with both the failing VT132 and the working one with the same results.

[ronaldlw]

I tried again to get to the logs after I'd already fixed the boards by connecting the FTDI cable and using putty terminal to the com port. Still doesn't work from the web page though. Maybe that page is broken?

[ronaldlw]

Ok, finally had some time to spend on this. Today my 2nd VT-132 stopped working as well :/

I dug around and did my best to figure out the connections for the vga output.
Some of the sources I used:
http://www.fabglib.org/conf_v_g_a.html
http://javiervalcarce.eu/html/vga-signal-format-timming-specs-en.html
https://www.espressif.com/sites/default/files/documentation/esp32-wrover-e_esp32-wrover-ie_datasheet_en.pdf

These are oriented as if you'll looking at the board like this:

The Horizontal Sync and Vertical Sync signals should be 3.3 volts that look like this:

(Horizontal sync is on top)

The Red Green and Blue signals should be 3.3V on the right of the resistors and between 0-.7 V on at the pads / left side of the resistors.

On one of mine the Horizontal sync was about 1.3V instead of 3.3V. Symptoms were that it would appear to boot up and beep but no video signal on the monitor. When measuring resistance between pin 37 and 36 (H sync and Red_1) it was around 10k, so there was some kind of shorting going on between those two pins (once it was "fixed" I'm getting multi mega ohm).

There wasn't anything obvious, so my guess is that there was some flux or something under the board or something like that. I doused it all with 99% rubbing alcohol and used a brush and then blew it out well. After letting it dry it started working.. for awhile.

After it stopped working again I went ahead and reflowed all the pins on that left side of the WROVER module and then did the alcohol treatment again. Now it seems to be working well and the signals all appear to be as expected (oscilloscope images taken after the fix)

The other board is the one that when the vga cable was plugged in there would be no beep and there was no video. I did the same thing as I did on the other board as well as reflowing all of the vga connector pins and that one is working now as well. (knock on wood)

Hopefully this will be helpful for someone else.

[ronaldlw]

For the RGB signals, when the board boots and the blinking cursor shows on the screen you should see 3.3V pulses on all of the _1 signals (red_1, green_1 and Blue_1) (assuming you have it set for white text), and nothing on the _0 signals. If you go into the SET-UP B or C screens there is bold text on the screen so you should then see pulses also on the _0 signals.

Also, the resistance measurement between the pairs of resistors (measured on the right side of each one) should be around 1.2k in each case. If it's much different than that then maybe pins are shorted or partially shorted.

Resistance between any one of the paired resistors and any other resistor pair should be multi-mega ohm (measuring on the right side of the resistors).

[ronaldlw]

As a final (hopefully) update on this.

TLDR: use quality flux that you're sure is good for electronics, preferably no-clean type so it shouldn't matter if you can't get it all cleaned up.

It ends up the flux that I was using is apparently conductive and slightly corrosive. Some of it got underneath the ESP-WROVER board on both of my VT-132 boards and so it would randomly start partially shorting out pins as it heated up and wicked to the outside edges where the pins are.

I had a hot air rework station in my amazon cart for quite awhile so I decided this was as good a reason as any to go ahead and pull the trigger on that. lol

(I also got some, hopefully, better flux!)

I used it to remove both boards and was able to get it nice and clean and now everything seems much better. So far...

Well, other than I did manage to melt the buzzer on one of them lol. oops.