# Unicorn Hat HD missing pixels

**URL:** <https://forums.pimoroni.com/t/unicorn-hat-hd-missing-pixels/11251>\
**Category:** Support\
**Created:** [August 9, 2019, 1:51pm UTC](https://forums.pimoroni.com/t/unicorn-hat-hd-missing-pixels/11251 "2019-08-09T13:51:13Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![pwhitrow](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.pimoroni.com/pwhitrow/32/5741_2.png) [@pwhitrow](https://forums.pimoroni.com/u/pwhitrow)\
**Post date:** [August 9, 2019, 1:51pm UTC](https://forums.pimoroni.com/t/unicorn-hat-hd-missing-pixels/11251/1 "2019-08-09T13:51:13Z")

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Hello there!

I recently purchased a Unicorn Hat HD from yourselves (Order #PI321849). I’ve just got around to testing it by connecting to a Teensy 3.5. All red pixels are fine, all blue pixels are fine, but I have missing green pixels (see photos below).

Please advise as to how I can get a replacement.

many thanks,

Paul

 ![IMG_20190809_143730%20(Custom)](https://us1.discourse-cdn.com/flex016/uploads/pimoroni/original/2X/4/4a8b908d29f74d17a2d22ffd793032ef5bcaa5be.jpeg)

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**Author:** ![alphanumeric](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.pimoroni.com/alphanumeric/32/2729_2.png) [@alphanumeric](https://forums.pimoroni.com/u/alphanumeric)\
**Post date:** [August 9, 2019, 2:10pm UTC](https://forums.pimoroni.com/t/unicorn-hat-hd-missing-pixels/11251/2 "2019-08-09T14:10:13Z")

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If you haven’t already, try connecting all the grounds listed here

> **[Unicorn HAT HD at Raspberry Pi GPIO Pinout](https://pinout.xyz/pinout/unicorn_hat_hd#)**
>
> A matrix of 256 RGB LED pixels for the Raspberry Pi

All the ones with the black around the pin numbers.

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**Author:** ![alphanumeric](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.pimoroni.com/alphanumeric/32/2729_2.png) [@alphanumeric](https://forums.pimoroni.com/u/alphanumeric)\
**Post date:** [August 9, 2019, 3:39pm UTC](https://forums.pimoroni.com/t/unicorn-hat-hd-missing-pixels/11251/3 "2019-08-09T15:39:46Z")

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I have a couple of LED Shims, if I don’t ground pin 20 they don’t work. It had me doing some head scratching, until I went here.

> **[LED SHIM at Raspberry Pi GPIO Pinout](https://pinout.xyz/pinout/led_shim#)**
>
> 28 RGB LEDs

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<div class="post-metadata">

**Author:** ![pwhitrow](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.pimoroni.com/pwhitrow/32/5741_2.png) [@pwhitrow](https://forums.pimoroni.com/u/pwhitrow)\
**Post date:** [August 30, 2019, 1:44pm UTC](https://forums.pimoroni.com/t/unicorn-hat-hd-missing-pixels/11251/4 "2019-08-30T13:44:02Z")

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I’ll give that a try