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TK-830 troubles
Posted: Tue Dec 21, 2004 5:26 pm
by ka7wnf
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.
Posted: Thu Dec 23, 2004 12:45 pm
by n5tbu
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
830
Posted: Thu Dec 30, 2004 10:10 am
by ka7wnf
Thanks for the tip, but that didn't work either. It won't display anything.
Posted: Thu Dec 30, 2004 10:24 am
by n5tbu
Did it at least display program?
Posted: Thu Dec 30, 2004 12:40 pm
by Wes
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
830
Posted: Sat Jan 01, 2005 4:10 pm
by ka7wnf
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.
Posted: Sun Jan 02, 2005 1:07 am
by Boomer740
Just a thought... is one of your front panel buttons stuck in the active (pressed) position?
Paul
830
Posted: Sun Jan 02, 2005 12:34 pm
by ka7wnf
I swapped control heads. The problem persisted. It acts like the CPU just shuts down.
830
Posted: Sun Jan 02, 2005 12:34 pm
by ka7wnf
I swapped control heads. The problem persisted. It acts like the CPU just shuts down.
Posted: Mon Jan 03, 2005 3:21 pm
by n5tbu
Now you need to pull out a scematic and check for regulated voltages,could be a shorted cap shutting down a regulater.
mod
830
Posted: Mon Jan 03, 2005 8:29 pm
by ka7wnf
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.
Posted: Fri Jan 07, 2005 10:17 pm
by n5tbu
Let us know how the progress is going....
mod
830
Posted: Thu Jan 27, 2005 3:36 pm
by ka7wnf
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.
Posted: Thu Jan 27, 2005 10:12 pm
by n5tbu
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