… has escaped into the wild.
It is priceless for tracing stuff like excessive CMOS memory battery drain, due to a faulty TL084 op-amp which is a massively expensive chip:
If the TL084 input gets blown (possibly due to antistatic precautions not followed when changing the battery) the battery discharges via the 100k resistor, which reduces its life to some months.
Keeping a KLN94 working is priceless to most owners, who are facing a ~10k bill for upgrading to just about anything, and used units are not going to be about for ever since King are now reportedly refusing to repair them. It was discontinued in 2011.
It’s a bit strange because TL084 has a JFET input, so it shouldn’t be terribly susceptible to statics.
I expect you have a professional way of replacing surface mount components, but I discovered Chip Quik after I made a mess.
Simon
The best way, least likely to damage the PCB, of removing this type of chip, is to very carefully snip the legs where they enter the chip, with high quality cutters like this and then the chip falls off. Then, with a soldering iron, remove the legs, apply some flux and wipe the iron down the chip footprint to clean it all up, inspect for any track damage (should be none), apply more flux, position new chip, and solder it on. Re-inspect joints. 15 mins.
The desoldering tool method is quick but can damage the board.
I agree, Ultranomad, but the chip did have a low-Z input…
Hi Peter,
Have you replaced this chip before in your KLN94?
I just stumbled upon this thread when searching for Q’s about our Kln94 unit.
To summarize, we only replaced the internal battery some 4-5 months ago, only to discover the battery is flat again ( MSG showing low internal battery warning) plus unit is taking forever to initialize satellites and not showing current position!.
cheers
I haven’t but an avionics guy did, with my guidance. It is trivial to check with a voltmeter… with the KLN94 powered up, pin 7 of that chip (in the yellow box) must be the same voltage as the battery positive terminal. In the case I saw, pin 7 was about +10V and it was just as well that R73 is there otherwise it may have blown the input of the A-D converter which is inside the CPU, and replacing that would have been a big job (it has about 100 legs).
Strictly for anoraks 
I recently got the internal battery replaced by Mendelssohn and the unit is now not loading IFR procedures. There is a button sequence on start up which restores IFR capability (DB is valid), is there a link or page in the MM where this is explained?
