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Random avionics internals

Yes; they do look rough. However they could be punched. That used to be done for high volume (TVs and such) and was a bit of a fashion in the 1970s. I had some boards done that way back then. You get rough looking holes.

Shoreham EGKA, United Kingdom

I posted a bench test of the Lamar regulator here

Shoreham EGKA, United Kingdom

Another PS Engineering intercom / audio panel, from a similar era as the last one

The pots are made by Alps

From date codes it looks like 1996/97.

They appear to use analog switches (4066 type) for the signals and I think the purpose of the little Omron relay is to provide a signal path when power is lost.

Construction quality is good.

Shoreham EGKA, United Kingdom

Nice to see what is inside the PS engineering intercom, I ran ne of these for about twenty years and it was faultless, the only reason for changing is because of a major upgrade.

Yes; the construction is good. The only things I would criticise would be

  • no moisture protection, but virtually all of GA avionics is the same there – even a G1000 is completely open to the elements – but coating the PCB would help
  • vertical electrolytic capacitors are susceptible to vibration

Shoreham EGKA, United Kingdom

The Bose A20 headset of a colleague stopped working recently. First he started to hear the radio intermittently, touching the plug fixed it for a short while. But shortly, he couldn’t hear anything at all. Suspecting the cable or the plug, he called the dealer about spare parts. The only thing on offer is the complete cable/harness for which they charge 200 Euros. So I gave it a try myself first – he still can fork out 200 things for the cable any time if he wishes so.

Under the rubber covering the headphone plug is not metal, as in the cheapest audio plugs, but plastic (sorry about the bad picture):

That plastic core was broken, thereby severing the wires:

Luckily one can still see that only the green, blue and black wires are connected to the plug, so it was quite easy to solder a new connector (from my scrapbox) to the cable. Otherwise it would have been trial and error to find out which wires need to be connected. For some reason, Bose uses a shielded cable with 6 wires for connecting a plug with only three contacts…

Last Edited by what_next at 14 Jul 16:48
EDDS - Stuttgart

It always amazes me how high end Brands use plastic in really stupid places. Plastic will always degrade with sunlight/heat and it was probably not strong enough in any case! One can easily see from the photos above that the white plastic moulding had lots of air gaps which were filled by the black flexible outer coating.

A decent metal version of the above plug would probably cost a few pence more and guess what? They could probably sell a version of the same product with “Heavy Duty Professional Airline” plugs for another £ 20 and most people would pay for this as it is probably a “Giffin Good”……….(the higher the price, the more you sell) If one has spent £ 50K /100K /200K on a plane so what’s a few hundred pounds on a headset?

See above – perhaps that’s why the King KX175 radios lasted so long. Peter was a bit nasty about the best radio ever built a few days ago The KX175 only had two failure modes (1) the slider on the volume/potentiometer contacts degraded so the Audio was crackly or failed completely and (2) Electrolytic capacitors failed but only due to lack of flying!

These days the knob would fall off and it would be a USD 1,000 back to base fixed price repair!

United Kingdom

Neutrik phone plugs. One of Liechtenstein’s best products! They aren’t expensive and are very robust.

Andreas IOM

Apologies for knocking the KX175. I have just seen so many of them being repaired… I would however think they have plenty of other issues e.g. poor frequency stability. Every time I fly I hear some awful radio and most of them are these (or similar) very old sets. Maybe they can be repaired to as-new state but the expertise isn’t around to do it, especially when half the PCB is corroded.

The fixed price repairs on modern avionics are generally poor value, which is why a lot of people stick to the older (1990s) stuff which works fine for today’s IFR and can be repaired fully, off the books.

Shoreham EGKA, United Kingdom

Hi, somebody knows in what equipment the indicator KW-105G was used?
And where it can be bought cheap?

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