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Can no longer turn knob on KX170 to change radio frequency


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So yeah, it's a dinosaur of a radio, but it's my #2 backup and pretty trusty. Garmin 430W as #1. The problem started a few weeks ago when if I turned the knob to change radio frequency, it would not always "catch" if that makes sense to turn the dial. So I started to push in to help it catch. Seemed like that worked for a few flights, except now I have to push in so hard that I can barely turn it.

Is this something that can be fixed? The nav works fine. I saw this site: http://www.kx170b.com/ - but honestly, I'm not a fan of sending in the equipment and paying $250 either way even if it can't be fixed. That seems a little strange to me.

If anyone has any leads or a working spare after they upgraded their avionics, let me know. I want to keep it rather inexpensive, don't want to invest $1000+ in a TKM MX170C; the KX 170 works fine as a trusty backup and to grab ATIS every now and then.

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1 hour ago, AlexLev said:

So yeah, it's a dinosaur of a radio, but it's my #2 backup and pretty trusty. Garmin 430W as #1. The problem started a few weeks ago when if I turned the knob to change radio frequency, it would not always "catch" if that makes sense to turn the dial. So I started to push in to help it catch. Seemed like that worked for a few flights, except now I have to push in so hard that I can barely turn it.

Is this something that can be fixed? The nav works fine. I saw this site: http://www.kx170b.com/ - but honestly, I'm not a fan of sending in the equipment and paying $250 either way even if it can't be fixed. That seems a little strange to me.

If anyone has any leads or a working spare after they upgraded their avionics, let me know. I want to keep it rather inexpensive, don't want to invest $1000+ in a TKM MX170C; the KX 170 works fine as a trusty backup and to grab ATIS every now and then.

From the website you quoted:

** One serious problem is that of the COM kilohertz frequency selector dial jamming or slipping / skipping when the knob is turned. This is the end of the road for the KX170B. Your best option here would be to slide out the bad KX170B and slide in a good one.

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3 hours ago, AlexLev said:

So yeah, it's a dinosaur of a radio, but it's my #2 backup and pretty trusty. Garmin 430W as #1. The problem started a few weeks ago when if I turned the knob to change radio frequency, it would not always "catch" if that makes sense to turn the dial. So I started to push in to help it catch. Seemed like that worked for a few flights, except now I have to push in so hard that I can barely turn it.

Is this something that can be fixed? The nav works fine. I saw this site: http://www.kx170b.com/ - but honestly, I'm not a fan of sending in the equipment and paying $250 either way even if it can't be fixed. That seems a little strange to me.

If anyone has any leads or a working spare after they upgraded their avionics, let me know. I want to keep it rather inexpensive, don't want to invest $1000+ in a TKM MX170C; the KX 170 works fine as a trusty backup and to grab ATIS every now and then.

Same problem with a Narco... sent it in because it had broken 5 cent gears... not made of unobtanium.

They wanted some outrageous amount to fix it... (probably $50)

My radio stayed there while the Narco doors closed....

I eventually bought a new instrument panel... that came Complete, wrapped in an O.

 

don’t waste anymore dough on ancient technology... waste it on much newer technology....

See what the Grimm Reaper has reaped from some other poor plane... 

Do you know grimmy?  @Alan Fox he often has a bunch of radios ready to find new homes...

Best regards,

-a-

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I have taken that channel change mechanism apart and put it back together quite a few times. It is tricky to get all the gears phased right. You know it is right when all the number wheels advance correctly. There is about 10 ways to put it together wrong and only one that is correct. The gears are fairly robust, but over the years the switches and shafts get a lot of friction and if the faceplate gets a little loose they will bind and slip. A good cleaning and lubrication will almost always fix it and make it work like brand new. It requires taking the number wheels compleatly off and cleaning and lubing the switches and number drums separately until they all work smoothly then reassembling them.

Not a job for the impatient.

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9 hours ago, MikeOH said:

From the website you quoted:

** One serious problem is that of the COM kilohertz frequency selector dial jamming or slipping / skipping when the knob is turned. This is the end of the road for the KX170B. Your best option here would be to slide out the bad KX170B and slide in a good one.

On that same web site, it says, one of the things he does repairs to is: "COM MISC. (lubricate freq selectors, fix knobs, etc.)"

Is the Kilohertz frequency selector the outer knob that changes the number after the 120.xxx?  That's the one that's slipping. If so, then it does look like I am out of luck, unfortunately - according to the 40 page essay on that web site.

As far as newer technology goes, it's pretty pricey. I only use radio #2 to get ATIS sometime or talk to FSS, but the 430W has a monitoring feature so I don't even really need to use it to get ATIS. It's great as a backup, but hard to justify even spending 1K for something I hardly use.

Certainly if I had a second 430 in there, it could perhaps give some additional situational awareness, but $$$$$. Plus more knob turning and programming before departing. Haha.

Edited by AlexLev
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10 hours ago, AlexLev said:

Is this something that can be fixed? The nav works fine. I saw this site: http://www.kx170b.com/ - but honestly, I'm not a fan of sending in the equipment and paying $250 either way even if it can't be fixed. That seems a little strange to me.

That site is run by Gary Glassmeyer, an avionics tech/engineer who just repairs KX170's in retirement. He is a bit peculiar, but I sent him my radio and he fixed it. Works great. He does not just fix the radio, he tunes it as well.

His website explains what to look for to determine if your radio is fixable or not. For me, I discovered that the radio has two microswitches on each power knob. When that switch goes it is DOA. The switches, Honeywell (1SX74-T), are very hard to find, but I think Gary may have a stockpile of them. Anyway, he taped the old ones to the outside of my radio before he shipped it back and they were the problem. He also suggested I leave the radios on and use the avionics master switch to activate them and that would make the switches last longer than the usual life of a decade. Well, I don't have an avionics master switch and do not plan on keeping the radio past the next decade :P

My point is that as peculiar as he is, if you have an attachment to your radio (I do) he is on the up and up, just follow his instructions and you'll have your radio back like new in no time. Of course, something else could go wrong...

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7 minutes ago, HRM said:

That site is run by Gary Glassmeyer, an avionics tech/engineer who just repairs KX170's in retirement. He is a bit peculiar, but I sent him my radio and he fixed it. Works great. He does not just fix the radio, he tunes it as well.

His website explains what to look for to determine if your radio is fixable or not. For me, I discovered that the radio has two microswitches on each power knob. When that switch goes it is DOA. The switches, Honeywell (1SX74-T), are very hard to find, but I think Gary may have a stockpile of them. Anyway, he taped the old ones to the outside of my radio before he shipped it back and they were the problem. He also suggested I leave the radios on and use the avionics master switch to activate them and that would make the switches last longer than the usual life of a decade. Well, I don't have an avionics master switch and do not plan on keeping the radio past the next decade :P

My point is that as peculiar as he is, if you have an attachment to your radio (I do) he is on the up and up, just follow his instructions and you'll have your radio back like new in no time. Of course, something else could go wrong...

If I could send it to him for repair, without being charged a $300 bill for "testing" if it's unrepairable, I would. I'm just not clear if the above quote on his web site means my radio is not able to be fixed.

Edited by AlexLev
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5 hours ago, HRM said:

His website explains what to look for to determine if your radio is fixable or not. For me, I discovered that the radio has two microswitches on each power knob. When that switch goes it is DOA. The switches, Honeywell (1SX74-T), are very hard to find, but I think Gary may have a stockpile of them.

If it is the power switch, then a tad bit of solder on the B+ lead and the wire on the other side of the switch will bring the radio back to life and leave it on permanently.

If BK did not want you inside their radios, they should have made it harder than 4 phillips head screws is the way I see it.

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1 minute ago, Yetti said:

If BK did not want you inside their radios, they should have made it harder than 4 phillips head screws is the way I see it.

This radio design is almost 50 years old.

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1 hour ago, Yetti said:

It's possible that I still have some old Motorola and RCA keys needed to pull radios.  I wonder if the new one use the same keys

You mean like these?

I just happen to have my mayonnaise jar full of RF adapters in my desk and my old collection of radio keys was in it. These should fit most Motorola and GE radios. At least in 1980....

Keys.JPG

Edited by N201MKTurbo
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24 minutes ago, N201MKTurbo said:

You mean like these?

I just happen to have my mayonnaise jar full of RF adapters in my desk and my old collection of radio keys was in it. These should fit most Motorola and GE radios. At least in 1980....

Keys.JPG

those be the ones.  put me though college

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When my 170B's stopped tunning, an avionics shop told me a plastic gear had stripped teeth.  It sold me a brass gear for each radio which the hangar elves installed.  Those radios are still working well today, though the elves disavow all knowledge.

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Thanks, turns out mine is a 175b, the TSO'd version.

https://www.bevanrabell.com still seems to service them and talking to them on the phone was a good experience, they think it can be fixed ... since the numbers still turn normally they think the gears are fine.

However, a twist to the story is my closest friend had an MX170B in his basement the whole time. He said it's been in his basement for about 5 years now, but is letting me use it indefinitely. I may try it out, since it seems to be a straight swap...

However, I am not sure what paperwork may be required to swap the radios out? Anyone have any guidance here?

Edited by AlexLev
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10 minutes ago, AlexLev said:

However, I am not sure what paperwork may be required to swap the radios out? Anyone have any guidance here?

Just a pilot's log entry, i.e. "Removed KX175b SNxxxx, replaced with MX170B snyyyyy, no w&b change".

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4 minutes ago, neilpilot said:

Just a pilot's log entry, i.e. "Removed KX175b SNxxxx, replaced with MX170B snyyyyy, no w&b change".

Hehe, there is a one pound of extra useful load that I'll gain, which will have my useful load go from 899lbs to 900(!!). Do I need a shop to work up a W&B change?

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33 minutes ago, AlexLev said:

Thanks, turns out mine is a 175b, the TSO'd version.

https://www.bevanrabell.com still seems to service them and talking to them on the phone was a good experience, they think it can be fixed ... since the numbers still turn normally they think the gears are fine.

However, a twist to the story is my closest friend had an MX170B in his basement the whole time. He said it's been in his basement for about 5 years now, but is letting me use it indefinitely. I may try it out, since it seems to be a straight swap...

However, I am not sure what paperwork may be required to swap the radios out? Anyone have any guidance here?

Alex -- take it from someone who has been down the avionics repair path a few times, you could end up spending as much for a replacement new ICOM, Becker or other NavComs fixing an old KX-170B. Back before GPSs, the Bendix King 155 was going for $5000 plus installation so fixing a busted KX-170B for $300 made sense. There are a number of available new replacements for what a few repairs would cost. 

http://www.aircraftspruce.com/categories/wizard.html?sec=av&cat=comm&s=COM/Panel Transceivers Wizard&brand=becker,bendix,dynon,flightline,gar,icom,lynx,mgl,microair,ramiller,tkm,trig,valavionics,xcom&price=0-2500&35=174&36=176,178

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