OLD KO PROPO TRANSMITER NOT TRANSMITTING!!!

[EXAEROCAR]

Hey guys, I need help!

I have an old KO PROPO Navigator (basically an EX-5) that powers up but doesn't transmit.

I have checked the crystal on another EX-5 and it is OK.

I do have an oscilloscope and am not a complete newbie to electronics, but my knowledge is limited when it comes to radios.

Any help will be awesome!!!!!

Tom

[scr8p]

are they the same band? 27..... 75.

[EXAEROCAR]

Yes 27 mz.

Pretty sure all of the early EX- series was 27.

Tom

[EXAEROCAR]

I wish it were that easy.

I've had the transmitter apart and checked everything that I know.

No loose wires, no craters in boards, no bad solder joints and no charcoal...

Also as I stated, the receiver works fine with another transmitter ( I have 8 of them), and the TX crystal works in another transmitter.

I need some real electronic help as in how to trouble shoot the electronics inside the transmitter.

Tom

[jwscab]

is this an AM or FM system?

where I would start is to check the board for any IC's that you can look up part numbers to to get a rough idea of the schematics

then, apply power to the board, and check that it goes to all the places the traces say it should go. The potentiometers that are the throttle and steering inputs should have three wires going to them, and on the middle terminal, they should measure a moving voltage as you move it through the range, the other two wires will be a high and a low voltage, MAYBE +5 and 0v, for instance, so checking out all three will tell you if the input controls are working.

then check the crystal circuit, you should seen a sine wave at approximately the frequency listed on the xtal on one of the pins, it might be very small, and it will shift in frequency with the probe loading.

beyond those basics, now you would have to dig into the modulation part of the radio, which is hard to explain through a message board with no idea of what is on the board.

[EXAEROCAR]

Thanks for the reply!

The old KO radios were all AM.

As for the trouble shooting info, that gives me a place to start.

Once again thanks!!!!!

Tom

[longboardnj]

KO PROPO radios gave me some trouble in the past and i junked them. seems like some of the old radios get lazy (dont want to work all the time) your best bet is to get full new radio gear . you can get am radio,rec,servo,the full combo on ebay for $30 - $40 just do that and save yourself the headache

[Jirka]

One possibility to do, since You don't seem to have nothing to lose, is to go through all potentiometers what You find. One by one check their current setting, turn them a few degrees back and forth afew times and try to get them to same position than they used to be. This might help to get corrosion and/or dust out from contact surfaces.

Jirka

[Lonestar]

KO PROPO radios gave me some trouble in the past and i junked them. seems like some of the old radios get lazy (dont want to work all the time) your best bet is to get full new radio gear . you can get am radio,rec,servo,the full combo on ebay for $30 - $40 just do that and save yourself the headache

this is rc10talk, man... not rc10b4.1rtrtalk...

[GoMachV]

this is rc10talk, man... not rc10b4.1rtrtalk...

Not to mention that this was the only pistol grip to ever sport a helm wheel!

[EXAEROCAR]

KO PROPO radios gave me some trouble in the past and i junked them. seems like some of the old radios get lazy (dont want to work all the time) your best bet is to get full new radio gear . you can get am radio,rec,servo,the full combo on ebay for $30 - $40 just do that and save yourself the headache

I understand what you are saying but, I am also a collector, therefore I want to restore this radio to working order.

Thanks anyway...

[EXAEROCAR]

One possibility to do, since You don't seem to have nothing to lose, is to go through all potentiometers what You find. One by one check their current setting, turn them a few degrees back and forth afew times and try to get them to same position than they used to be. This might help to get corrosion and/or dust out from contact surfaces.

Jirka

Checked and are OK, I think it has something to do with the transmitter itself...not sure.

[EXAEROCAR]

KO PROPO radios gave me some trouble in the past and i junked them. seems like some of the old radios get lazy (dont want to work all the time) your best bet is to get full new radio gear . you can get am radio,rec,servo,the full combo on ebay for $30 - $40 just do that and save yourself the headache

this is rc10talk, man... not rc10b4.1rtrtalk...

Right on Lonestar!!!!

[EXAEROCAR]

this is rc10talk, man... not rc10b4.1rtrtalk...

Not to mention that this was the only pistol grip to ever sport a helm wheel!

Sadly, I replaced it with a regular wheel somewhere in the 90's and don't know what i did with it...http://www.rc10talk.com/posting.php?mode=quote&f=78&p=292029#

[scr8p]

as joe pesci said in "my cousin vinny"........... i guess the f**kin' thing is broken.