1240 Logic Analyser display problem


Kevin Wood G7BCS
 

Hi Guys,

I wonder if anyone has ever troubleshooted display issues with a 1240
Logic Analyser?

Symptoms are that I get a stable raster on the screen if brightness is
turned up but no display.

All power supply rails measure fine.

Both main and I/O processors seem to be going through their self tests
successfully and entering normal operation according to the LEDs on their
respective boards.

Display board gives HD sync output but no VD or luminance.
.
I've traced the VD output back to the MM5321 sync. generator IC on the
display board. It has a clock input, both power supply rails and the
vertical reset input is inactive (High). The horizontal outputs are
present but no vertical drive output.

I'm thinking the MM5321 is dead, but just wondered if anyone else has been
down this path before, or has any other suggestions?

Next question is where to find an MM5321. Littlediode have them at a
price, but any other ideas?

Thanks in advance,

Kevin


Phil Pemberton
 

On 13/06/11 00:01, Kevin Wood wrote:
I'm thinking the MM5321 is dead, but just wondered if anyone else has been
down this path before, or has any other suggestions?
Have you tried disconnecting the VSYNC pin from the 5321 chip (i.e. remove the chip if it's socketed) and then checking for a short-to-ground, or any output from the (now floating) pin?

Personally, I'd swap the thing for a CPLD or a board-o'-TTL, but that's only because I have copious stocks of both. A couple of TTL counters (HC4040?) and comparators should just about do it.

But that's just me. I'll go for the crazy solution if it saves a trip to Ye Olde Parts Shoppe... :)

--
Phil.
ygroups@...
http://www.philpem.me.uk/


Kevin Wood G7BCS
 

Have you tried disconnecting the VSYNC pin from the 5321 chip (i.e.
remove the chip if it's socketed) and then checking for a
short-to-ground, or any output from the (now floating) pin?
Ahh, good point. I should try that. It feeds the next stage through a 10k
resistor so unlikely it's being dragged down but you never know...

Personally, I'd swap the thing for a CPLD or a board-o'-TTL, but that's
only because I have copious stocks of both. A couple of TTL counters
(HC4040?) and comparators should just about do it.
Yep, the thought crossed my mind too. Actually, the H&V counters are
already on the board, thinking about it. Not sure I want to hack it about
that much though.

Kevin


Kevin Wood G7BCS
 

Well, a happy ending. Managed to source a new MM5321 sync. generator chip,
albeit rather pricey, but my 1240 is now back in working order.

Kevin


gwangju3 <gwangju3@...>
 

I hope you got it at Jameco for $3.75. If not sorry I didn't see this sooner.

Littlediode is outrageously priced.

--Victor

--- In TekScopes@..., "Kevin Wood" <mailinglists@...> wrote:

Well, a happy ending. Managed to source a new MM5321 sync. generator chip,
albeit rather pricey, but my 1240 is now back in working order.

Kevin