KX 155 tso schematic ...

[CWB]

hey all ,

 

i am trying to find the schematic for the mentioned nav/comm tranceiver .

(owner/op manuals abound on the 'net)

the receiver breaks/trips the squelch without the reception of a signal ...

pressing the transmit button a couple of times usually clears the problem .

the problem becomes worse as the radio/cluster "heats up" .

the second KX 155 works ok .

 

many thanks in advance

[N601RX]

The repair manual is almost 600 pages, but here is the area you were asking about.  Notice that the PPT is fed back into the squelch circuit via CR 207

[carusoam]

Welcome to the MS community CWB.

Where else can you get Mooney support by like minded fellow pilots..?

Best regards,

-a-

[robert7467]

Dont know if this helps or if its even relevant, but I am installing a 430 and its not putting out a signal. The engineer told me to ground the 500ohm audio low pin. Havent tried that yet. I am also installing a kx165 just like the 155 except 24v and has glideslope. If you want I can email you the schematics that the engineer have me for you to cross reference. Also, you are not going to be able to see the numbers on the connector so print one off and use one as reference.

[robert7467]

Hmm. Was this already hooked up? Once you get the schematics, it wouldnt hurt to pull audio panel and radio out of the trays and check the resistance. I am in no way an expert, I am just doing my own install under the guidence of an avionics guru.

[CWB]

thanks for the welcome and thanks for the schematic excerpts ... they will help out ...

time to fire up the o'scope and soldering pencil .

 

@ robert :

i am not sure if the audio out on the 155/165 is a "balanced" type (think why the old telco stuff did not pick up noise and hum with lines miles long) .

grounding one side would create an "unbalanced" condition (think guitar or most headphones) .

this may cause "noise" pickup ... unless the output is low impedance (say , 8-200 ohms) .

ahhh ... if i had the manual ... i wouldn't need my crystal ball .

 

off to dig into the radio .

 

ps ... i'll PM you my email ... much appreciated .

[robert7467]

Schematics Sent to your inbox!

[CWB]

thanks for the information ...

i can't remember if i sent a "thank you" already !

too much "stuff" going on .

 

i have to get some things done before the fly-in at grygla, mn on sunday .

at least i think it is this sunday ...

[HRM]

pressing the transmit button a couple of times usually clears the problem .

the problem becomes worse as the radio/cluster "heats up" .

 

Your first item sounds like something is being 'charged' and needs a kickstart, the second one (obviously) speaks to an overheat problem.

 

Could be a cap, most likely electrolytic, that has dried out. Overheat could be a transistor. I'd set it up on a bench and try to reproduce the symptoms.

 

Now that you have the schematic you can just wave trace.

 

Please let us know what you find.

[CWB]

thanks for the tips HRM .

one of the nice things about where you are at is you get the best of both worlds ... texas and loisiana cooking !

 

another member here is going to graciously provide a more complete data set .

my plan of attack includes a thermos of tea and a bottle of aspirin .

 

i will post my findings once the fix has proven to be correct and stable .

 

heh ... the old loran radio (not used for a long time) is/was being used as a *placeholder" in the console ...

the NiCd back up battery decided to puke its guts out .

the electrolyte made an absolute mess of the pc boards ... it is now a worthless paperweight .

this is good though ... i am trying out  a new gps program that allows me to download the tiles from google (and other providers) and stash them on the HDD or flash drive .

the plan is to ultimately build an on-board comp that uses a "ublox" gps receiver module and has a touch-screen display .

(i could always purchase a gps unit complete , but where is the fun in that)

yeah ... add that project to the others ... including the GF making (more) noises about painting the house .

___ sigh ___

 

ps ... the fly-in at grygla is this coming weekend .

[Photon4]

On 8/19/2015 at 7:16 PM, robert7467 said:

Schematics Sent to your inbox!

Hi Robert7467,

I am an electronics engineer trying to help my friend fix his KX-155 radio.

I would be much obliged if you could please send me the schematics and any other tech data you may have for the KX-155 so that I can help fix the radio.

Thanks !