Help identify IR LED emitter / photodetector components on trackball - Page 1
Forum section: electronics / repair

author: cardiome
author_rank: Newbie
timestamp: February 01, 2024, 01:37:08 am
content: I could really use some help and guidance. I am trying to repair an old (ca. 2005) Trackball that is a critical part of an ultrasound imaging system in our Research-Lab).The emitter - detector pair of the X-axis positioning are perished (see photo) and the remaining Y-axis pair is still intact but has no identifying markings. The Y-axis cursor positioning is functional.I hope someone can identify the IR transmitter-receiver components or their equivalent for replacement (the tracks on the board are still intact).

author: cardiome
author_rank: Newbie
timestamp: February 01, 2024, 10:14:19 am
content: Bump

author: SeanB
author_rank: Super Contributor
timestamp: February 01, 2024, 10:22:58 am
content: Grab any other ball based mouse, and take the IR transmitter receiver from it. Not exactly many variants on them, so pretty much all use the same pinout, and the same height of emitter. And again tell people not to spill liquid on the trackball.

author: cardiome
author_rank: Newbie
timestamp: February 01, 2024, 10:36:39 am
content: Thanks for that (yes, the offender is on notice!)…The photodetector / receiver has what looks like 3 or 4 pins (see attached close up), making it more difficult (for me)

author: berke
author_rank: Frequent Contributor
timestamp: February 01, 2024, 11:19:39 am
content: The LED is easy, the tricky one is the detector.The detector seems to be a 4-SIP (single inline package with 4 leads.)Maybe HLC2701?Can you get a better close-up of the undamaged detector? And if you can measure the dimensions with a caliper it can help identify the part. Better pictures will help.

author: floobydust
author_rank: Super Contributor
timestamp: February 01, 2024, 06:57:00 pm
content: Can you give a clear pic of the front face of the receiver, and the slotted wheel. If you rest your hand on something, it stops motion blur when taking pictures.The LED emitter is odd, I've never seen one in a red package. It would narrow down a manufacturer. IR is clear or smoked gray, i.e popular LTE302https://www.eevblog.com/forum/projects/phototransistor-replacement-question/

author: Ian.M
author_rank: Super Contributor
timestamp: February 01, 2024, 07:23:53 pm
content: The PCB is carbonised. If you don't cut away the burnt area back to un-charred FR4, it will just burn up the new parts. As the PCB is so badly damaged, and the emitter and detector position are critical, this will be a PITA to rebuild accurately enough even after you find suitable parts.Have you tried to source a complete replacement trackball?

author: cardiome
author_rank: Newbie
timestamp: February 01, 2024, 09:13:20 pm
content: I will try my hand at getting better focused pix (using a microscopy camera or drink no coffee) and size the emitter-receiver as per above cogent (much appreciated) suggestions. Locating and aligning the emitter-receiver is somewhat critical and has to match the positioning of the slotted (spinning) wheel to correctly modulate the LED beam…Ian.M: Your PCB prognosis is rather discouraging (see attached top view) … sourcing a used trackball is a hefty pain ($200-$300)—

author: berke
author_rank: Frequent Contributor
timestamp: February 01, 2024, 10:52:01 pm
content: Eww, I kind of agree with Ian.M. That's some serious charring. You said the traces are intact but all that black tells me that the the epoxy binder turned to carbon. That's going to be somewhat conductive, the electrons won't be staying in their lanes. How the hell did that happen anyway? That takes significant power. Are you sure the rest of the machine is OK?Assuming you can find the proper RX/TX pair it should be repairable but it will need some improvisation. Maybe make a small PCB, glue it over the corner if it's mehcanically possible? If you can get a replacement for a couple hundred bucks might not be worth it. Also don't ultrasound machines cost an arm and a leg compared to which $300 is peanuts?

author: Ian.M
author_rank: Super Contributor
timestamp: February 01, 2024, 11:32:54 pm
content: Its not just the blackness, its the exposed weave of the glasscloth which indicates the epoxy has significantly shrunk so must be highly carbonised. First you need to establish accurate coordinates for the damaged pad centers, then its PCB repair time!See:https://youtu.be/7o4ZWlG6mmo?si=VpPCSt6lVA35l30y16:20 onwards for the structural repair.

author: cardiome
author_rank: Newbie
timestamp: February 03, 2024, 01:00:57 am
content: Berke: Per your comments and suggestion, attached are some additional (microscope) images that might help identify the emitter - detector (encoder) pair…

author: cardiome
author_rank: Newbie
timestamp: February 03, 2024, 01:02:42 am
content: Emitter - Detector Pair:

author: berke
author_rank: Frequent Contributor
timestamp: February 03, 2024, 08:36:41 am
content: Yep the pinout, shape and dimensions are consistent with the HLC2701: GND and VCC are in the middle and the quadrature outputs A and B are on the sides.The datasheet says "Mechanically and spectrally matched to SEP8506 and SEP8706 infrared emitting diodes", per the Digikey thumbnails SEP8506 is red while the other one is white.So your component pair seems to be HLC2701 (quadrature receiver) and SEP8506 (transmitter) both of which of course have zero stock.

author: Ian.M
author_rank: Super Contributor
timestamp: February 03, 2024, 09:06:39 am
content: Honeywell discontinued all their IR sensors and transmitters back in 2018.Jotrinclaim to have stock of both, and are more reputable than many Hong Kong / Shenzhen based obsolete component specialists.N.B. When tracing the burnt tracks, as long as you get power and ground to the right pins of the sensor, getting the quadrature outputs swapped wont cause any harm - it just reverses that axis. You probably need to get the sensor and IR position correct to better than 10% of the wheel slot width.