Component level repair to Hayward H series heater display board

[superuser]

I've got an H series heater, and more of the segments on the 3 digit LED display are dead than work. So, figured it'd be an easy task to pull the board and replace the 7 segment display module, but for the life of me I can't seem to match the part.

The numbers on the display are:
LA19209-46-01
116018 U

Anyone have any insight?

 

[ajw22]

@ogdento any ideas?

 

[ogdento]

i can't find anything with those numbers either... i thought an LA prefix might be a Rohm part but I can't find any evidence for it. It might take a little work but you should be able to find a replacement part.

besides the dimensions of the display itself and it's pinout, you'll have to know whether it's a "common anode" or "common cathode" display... there's a number of resources online that'll tell you how to do that with a multimeter.

 

[superuser]

Thanks for looking, it's definitely odd not to find what would seemingly be a common part.

Since it's being driven by a PIC16F73 in the 28 pin package, and there's the buttons plus the other LEDs on the board to drive, it could very well be serial. I'll pull the part and look to know for sure, but there may not be enough GPIO to run three digits in CA/CD mode plus the other stuff.

 

[ogdento]

ahh very nice, clearly you have an electronics background! it'd be interesting to see what you find... the non-serial 3 digit units usually need 12 gpio lines (1 for each segment, 1 for the common anode/cathode, a ground, and 3 to select the digit). i'm guessing the pic can run it all with a standard display... hoping rather, cuz then you'll have a much easier time finding a replacement

 

[superuser]

Just a hobbyist, honestly. Closest I got to having a real background in the field was a job right out of high school as a repair tech in a music store. That was 25 years ago though. I've always liked hardware, but my career took me in a software direction.

I still haven't yanked the board back out and pulled the display, but I hope to get at it this evening. We've been in this house a month now, been pretty busy with all of the maintenance, update and upgrade tasks.

 

[superuser]

Pulled the display module off the board and started probing. It's a common anode 2 digit display with a dedicated 1 perhaps? Not sure, can't get the leading digit to light up. But I'm assuming the Hayward can display 100+ deg, so they must be present. The pinout is different than typical, it's a 24 pin DIP but missing 5 pins (2, 3 and 22, 23, 24). Haven't been able to find a match to common modules, but I'm still looking. Once I get it fully figured out, if I have to cobble up a transposer board that's an option.

Emerson is multiplexing the pins for the discrete LEDs and the 7 segment display as well, with a few transistors on the board. All 5 LEDs share pins with the 7 segment module, strobing as necessary. With the module out of circuit I can get all 7 segments on digit 2 to light up, but only 3 of digit 3.

 

[superuser]

Replying to myself heh. Maybe someone else will need the info some day though.

Found the part! Numbers printed on the component totally do not match, but that made sense when I started searching Google Images for photos of the same board and found other numbers. Still don't know what the markings are intended to mean, but they don't match the manufacturer's part #.

It appears to be an Xlitx.com part #XL-TD504001. I haven't confirmed the measurements, but the pinout matches.

The next problem appears to be getting my hands on a single piece.

 

[superuser]

Circling back on this thread.

Couldn't get the OE part, so I picked a more off the shelf part to replace with. Ordered it from Mouser, got it earlier this week.

The swap was pretty easy, simply mapping the old pinout to the new. The button membrane was filthy and leaking horribly, possibly what led to the display's demise in the first place. The display window was cracked, so I just removed that portion and covered the entire membrane in a couple layers of packaging tape. Then I cleaned it all up with some alcohol, applied new contact adhesive, and put it back together. So while it may not be "new", it works perfectly. Rather than spend the hundreds of $ on a new display board, it cost about 8 bucks including shipping, and a little of my time to fix.

Oh, and it's now a green display instead of red. (Sorry for shaky pic)

 

[ogdento]

awesome job, it really pays to fix this stuff if you can!

 

[markayash]

Glad you fixed it.
Our world has become throw it away and buy a new one.
My dad had a TV shop years ago ( he is 90 now ) and use to have giant books of schematics of every TV made and would fix them.
Then he said it became cheaper ( parts and labor ) to throw them away and buy a new TV