KING KLN-90B TROUBLESHOOTING IDEAS..

RV-4 · #1 10-09-2018, 10:53 AM

Hello Gents

I have a vintage King KLN-90B installed in my RV-4 and I have a bit of a snag with it and was wondering if someone here familiar with these old GPS would have a clue on what could be the problem..

it looks like that it is no longer seeing the satellites or at least it doesn?t after 1/2 hrs and I?m getting a ??FLAG?? annunciation when in the NAV window.

I tried a different antenna, made sure the coax was good, enter a present position just to give it a head start in finding where it is etc...but it still doesn?t appear to see the satellites...

In the ??STA+1?? window where you see the satellites it is looking at all I get are ??00?? for SNR & ELV ... After 1/2 hr today I had 1 or 2 satellites that were showing some sort of SNR ( Sound to Noise ) and elevation but that was it...

Any idea what might be the problem??

I?m thinking that the internal memory battery is either dead or very weak and the GPS has to find where it is every time it boot up and it takes a long time.. Am I right on this...??

If so, how hard is it to replace the battery if someone has ever done it??

Thank you for any info you may provide.

Bruno
rv4@videotron.ca

lr172 · #2 10-09-2018, 11:18 AM

The battery is not that hard to replace, but it is soldered onto one of the boards and takes some work to get at it.

Not sure this is your issue. You can tell the 90 what day and time it is now. That is what the unit needs to find the satellites. If you do that and don't get reception in 5-10 minutes, I would guess that the battery is not the issue.

Your present position doesn't help the unit, without more data. In order to find the satellites, it needs to know, in addition to where your are, where in the sky they are and they are constantly moving. Having the present position does help speed up acquistion. The 90 has an internal almanac / table that tells it where they will be at every minute during every day of the month. There are new algorithms to do this, but the old ones are crude and slow and the 90 has slower processors. It will take the 90 a LONG time to find them with a bad date/time. I kinda of think that 30 minutes would be enough to find one satellite. Once it finds one, it grabs the date/time from it.

Larry

KRviator · #3 10-09-2018, 01:39 PM

Just wondering what antenna you're using? I have a -90B in my -9 (and quite like it) but it came with a GA35 antenna - and those are reported to have a known oscillatory failure mode.

The only other thing I could suggest, is to pull it and the antenna, and make a short pigtail to connect the antenna to the unit with power applied on your back deck to see if it works then. I was adamant I hadn't made a mistake with mine, but after not finding satellites in the plane, but it did at home made me double-check the coax, and sure enough, there was but one strand of the **** thing creating an intermittent short so it'd test OK when held 'just so' but fail in the 'as installed' position.

For a bad battery, I would think you'd get the "RCVR Hardware Error 0008" fault before you'd need to consider getting too deep into troubleshooting it.

jartlip · #4 10-09-2018, 03:57 PM

I also have the KLN-90B. Never seen that indication. Is the database up to date? Can you even update the database anymore? I know mine is expired.

RV-4 · #5 10-11-2018, 09:18 PM

Hello Gents

Sorry for the late reply but I've been busy flying the friendly sky at work..

I really do appreciate you guys taking the time to help me out in this.

Larry, as far as I can remember it is showing the right time and date but I would check next time at the hangar to make sure..

KR: My present antenna if my memory serve me right is a Comant 420..something and also tried it with a Garmin GA-56 I had in stock with no change.

Jim: The database is up to date as off yesterday and will update it with the new release first chance I get.

If you have more ideas, please let me know and I will report any new developpement

Thanks again

Bruno
rv4@videotron.ca

lr172 · #6 10-11-2018, 09:21 PM

Quote:

Originally Posted by RV-4

Larry, as far as I can remember it is showing the right time and date but I would check next time at the hangar to make sure..
rv4@videotron.ca[/email]

The battery really just keeps the date/time and present position at shutdown. If your observation is correct, the battery isn't your issue.

Larry

RV-4 · #7 10-12-2018, 11:05 PM

Hi Larry

I checked today and the Date& Time were accurate so as you say, the internal battery appears to be out of the equation..

I will put a battery charger on the a/c and turn the GPS ON and let it search for satellites for a long time and see if it can acquire them again..If not I guess it will become a boat ancher..

Thanks

Bruno