TK-830 troubles

ka7wnf · Post by **ka7wnf** » Tue Dec 21, 2004 5:26 pm

I have a TK-830 with the following problem. When first powered up the display is normal, with KCH-4 head. Shows the correct channel. After less than a second the display goes blank and only the backlight stays on. No transmit or receive. I swapped control heads and no change. I checked for voltages and everything looks normal. Any ideas? Bad CPU maybe? Thanks. Peter.

n5tbu · Post by **n5tbu** » Thu Dec 23, 2004 12:45 pm

Certain early models would lock up. Try putting it in the program mode bu powering up while holding the button just to the right og the channel selector,
program should then show..release the buttons and then turn off then on again.
mod

ka7wnf · Post by **ka7wnf** » Thu Dec 30, 2004 10:10 am

Thanks for the tip, but that didn't work either. It won't display anything.

n5tbu · Post by **n5tbu** » Thu Dec 30, 2004 10:24 am

Did it at least display program?

Wes · Post by **Wes** » Thu Dec 30, 2004 12:40 pm

On the 30 series mobiles, I have seen crazy things like this before, Usually reading and writing of the radio would fix it. Give this a try.....

Wes

ka7wnf · Post by **ka7wnf** » Sat Jan 01, 2005 4:10 pm

It won't display program, it won't read or write. I have had some of these that forgot their programming but this one has me stumped. It shows the proper channel for maybe a second when first powered up then goes blank. If I reboot it it won't show anything. If I leave it off for a awhile it will again show the channel but only for an instant. It will not show program even if I hold the buttons.

Boomer740 · Post by **Boomer740** » Sun Jan 02, 2005 1:07 am

Just a thought... is one of your front panel buttons stuck in the active (pressed) position?

Paul

ka7wnf · Post by **ka7wnf** » Sun Jan 02, 2005 12:34 pm

I swapped control heads. The problem persisted. It acts like the CPU just shuts down.

ka7wnf · Post by **ka7wnf** » Sun Jan 02, 2005 12:34 pm

I swapped control heads. The problem persisted. It acts like the CPU just shuts down.

n5tbu · Post by **n5tbu** » Mon Jan 03, 2005 3:21 pm

Now you need to pull out a scematic and check for regulated voltages,could be a shorted cap shutting down a regulater.
mod

ka7wnf · Post by **ka7wnf** » Mon Jan 03, 2005 8:29 pm

It does act like a shorted cap. Today I turned it on after being under my desk for a week. It came on and worked fine for several minutes before going into shutdown. It acts like when the cap is charging it's okay until it's charged then it shorts. I do have a schematic so I'll start looking.

n5tbu · Post by **n5tbu** » Fri Jan 07, 2005 10:17 pm

Let us know how the progress is going....
mod

ka7wnf · Post by **ka7wnf** » Thu Jan 27, 2005 3:36 pm

Fixed it! It was a bad cap in the control head. The spare head I used to check the radio had the same defect which steered me the wrong direction. (@#$^%%^!!!) C29 is a 22uf 16 volt electrolytic. It had leaked and corroded away the trace that goes from pin 4 of the 5 volt regulator to pin 72 in the CPU. I repaired the trace, replaced the cap and it works fine. Thanks for the advice. 73's.

n5tbu · Post by **n5tbu** » Thu Jan 27, 2005 10:12 pm

Glad you fixed it! We are gonna make a bench tech out of you yet!
Funny tho,it is almost always a bad cap...trouble is finding it!
I have lifted a many cap to try to find it,moto is the worst tho,for every cap they need in a circuit,they always put in 2 or 10 that weren't needed!
mod