Whats inside a Rockwell Collins TPR-720 ATC Mode-S Transponder? Autopsy of failure and teardown.

Want to know what sort of electronics and computing power the average airliner has got? Well in this video I got my hands on this Air Traffic Control transponder which is fitted to many types of commercial aircraft such as the Boeing 737, 757,767 and the BAE146 amongst others. It would normally be fitted in the E&E bay (avionics bay) typically located under the cockpit. It was one of several avionics items that were on a pallet from an airline that was retiring some of their aircraft and these parts were from their engineering spares and / or pulls from scrap aircraft. I was told that the unit in particular is likely a unit that is faulty and had been deemed beyond economical repair however the pallet contained serviceable but yet obsolete items as well.
The unit was sealed in an antistatic bag with Rockwell Collins service centre warranty stickers on the rear of the unit and a protective cover was over the rear connectors which made me suspect this is in fact a repaired unit but obsolete / surplus to requirements. I bought it as a curiosity item and to possibly use the case for an electronics project and salvage any useful components as it only cost £9 plus postage.
I opened the bag and was immediately hit with a strong acrid electronic burning smell and I noticed there was damage to the corner. Maybe this was why it was deemed BER? Damaged in transit on return from repair? What was that smell? Who knows but there is no way of finding out.
So I decided to take it apart and see what had failed. Eventually I couldn't find anything amiss and the smell was really getting to me. So it looks like it's going to be a salvage item. The case is too flimsy to use once the electronics have been removed so I might even put it back on eBay and get more money than I paid for it.
Anyway it made for an interesting video.
Another youtuber did a teardown video of one of these (I suspect he bought his from the same seller) and he goes into more detail. The direct link to his video is here • Avionics teardown Coll...
The main cpu in this is an 80C196 which is a 16 bit microcontroller designed for embedded applications. It was commonly found on old printers, routers and was also popular for industrial use during the 80's and 90's. The 40 pin ceramic IDT chip is a 1k dual bus SRAM chip. There are also 3x 32k EEPROM chips containing the firmware; presumably the two near the microcontroller are the application EEPROMS and the single one is for the FPGA / ASIC. The Motorola chip I couldn't find any information on and the other 40 pin ceramic chip neither so I suspect these are custom ASICS. Lots of bodge wires too but these are probably hardware modifications added later. For software upgrades the EPROM chips would have to be unsoldered. In other avionics they are in sockets with a zip tie to fasten them down. Newer things are flash upgradable.
Please like and subscribe so I get an idea what viewers like. Seems most videos that are liked are stupid things like blowing speakers and destroying things. If that's what people like I'll find more stuff to destroy...
#avionics
#teardowns