7 Segment TinyShield with Proto Terminal Tinyshield

[ahkub]

Hello all,
Today I came across something weird:
I can run the 7 Segment TinyShield with the Tinyduino board and the USB shield. Works well.
As soon as I plug the Proto Terminal Tinyshield in between USB shield and 7 segment shield, the IC below the two 7 segments becomes incredibly hot. The 7 segments do not light up.
When I take out the Proto Terminal shield, the 7 segment works perfectly again.

When I use the Proto Terminal shield for example with the 21 LED shield, it works well.
I have tried every combination with two 7 segment shields and two Proto Terminal shields. No success.

I will investigate and post, if I find the root cause.

Regards,
Alf

[ahkub]

This is really weird. If I set up my stack like this, the IC gets hot:
(bottom to top): Tinyduino, USB, Proto Terminal, 7 segment.

If I switch it around like this, it works.
(bottom to top): Tinyduino, Proto Terminal, USB, 7 segment.

Is this black magic? Or a pullup issue on the I2C lines A4 and A5?

Puzzled,
Alf