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Random avionics internals

KI266 remote DME indicator – a real vintage piece from c. 1976

The Positronic connectors – originally developed in the Apollo era and AFAIK for that programme (or similar)

Some milspec (-55C to +125C) ceramic package logic chips

What looks like moulded carbon resistors… these were not accurate (maybe 20%) and not stable, so the designer had to be competent. I don’t know that that large round module is – probably a transformer or an inductor, with a shield around it

The usual fluorescent / luminescent displays, and a significant investment ($10k+) in the diecast front panel

This shows the level of diligence in those days: a layout diagram on the inside of the covers

The strange thing is that for all the robust design etc, and the very nontrivial price which this would have sold for (probably 20x the parts cost), no attempt has been made to protect from moisture. Not even a conformal coating on the PCB. EDIT: they have applied a conformal coating on the “analog” PCB but not on the logic PCB…

Administrator
Shoreham EGKA, United Kingdom

Finally there is a very interesting thread for me! I wonder why did it take six pages until the old trusty GNS-430 appears here :-). I hope to see more interesting pictures coming. I should have some SR22 Avidyne internals documented at home, will try to post here later. It is nothing more than industrial PC.

LKHK, Czech Republic

Here is the well known King KA-33 / KA33 avionics fan, which is used all over GA to blow air into the back of the various boxes in the avionics stack

I got my hands on a scrap one. It was actually working but the fan unit was rubbing on something. Out of interest I contacted the maker of the fan unit itself

which is fairly obviously not an aviation product, but they are evidently one step ahead of the game, having been getting many enquiries from places like Angola, Jupiter, and maybe even Europe…

Of course it is delightful to be aware that the one they sell you for that outrageous price is ITAR compliant

Opening up the motor was fun. The case is made of soft steel; possibly mu-metal, and there was no evident way to get inside without damage:

The motor uses electronic commutation (no brushes; they use Hall effect sensors apparently) but the control “electronics” is the worst POS I have seen in GA:

In fact the whole construction is utter crap and I am astonished that (a) it ever got certified (well, I know the answer to that one) and (b) King/Honeywell put their name on it.

You can buy the complete unit on US Ebay for $150, in very good condition, but Euro-reg owners can’t take advantage of that (officially).

Administrator
Shoreham EGKA, United Kingdom

Good grief. The majority of electronics hobbyists wouldn’t build anything as awful as that board.

Andreas IOM

Yes; this might be the worst I have ever seen…

The fan unit is bought in by King and fitted into the rest of the module, which is some metalwork and a plastic moulding (the right-hand moulding below)

The fan is a cheap and nasty piece of crap, with a plastic impeller which just pushes onto the motor shaft

That was the “fault” with the one I got – the impeller slid along the shaft and started grinding itself against some screws. King buy the fan with a CofC issued against a QA system like ISO9000 which is bogus anyway because you can make any crap using documented procedures and you just issue the CofC at the end.

If this fan fails, you get random failures in the avionics. And most people will never notice the fan failure…

At $950, this is a snip for such high technology which played a prime role in getting America to the moon:

Administrator
Shoreham EGKA, United Kingdom

For 950 bucks you could buy about 100 graphic card cooling fans and spread them evenly across the back of your panel…

For 950 bucks you could buy about 100 graphic card cooling fans and spread them evenly across the back of your panel…

Yes, though I have had a 100% failure rate on PC fans… after a few years. They clog up with dust, bearings wear out, etc. One needs a more robust approach.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

You can buy the complete unit on US Ebay for $150, in very good condition, but Euro-reg owners can’t take advantage of that (officially).

manufacturer’s online shop

Why wouldn’t I get it, when ordering from their shop ?
OK, I might have to provide a US shipping address – so ?

...
EDM_, Germany

Yes, and a US credit card etc. These people seem to really dislike non US customers.

You also probably won’t get any traceability document with the new fan, and overhauling the ka-33 is outside pilot privileges

Administrator
Shoreham EGKA, United Kingdom

Here is the LAMAR voltage regulator which is common in GA

There are two PCBs inside. This is the main one, showing a real chinese spare garage workmanship

This is the other one, with some fuses and other bits

and this is what is on the bottom of the metal case – a pretty awful way of attaching the power resistor when this style should have been used

There is zero moisture protection, yet this is a crucial part of the electrical system. The adjustment trimpot is o-ring sealed but IME that seal won’t work long-term. When that goes, so will the bus voltage.

The circuit is a switching regulator (500Hz or so I think).

The dates codes of “5” are ambiguous; could be 1985, 1995, 2005… however the adjustment pot and the big resistor have a clear 1999 on it. I thus suspect it is 1995 or 2005 and probably the former.

Parts cost about $30. List price $419.

Administrator
Shoreham EGKA, United Kingdom
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