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Author Topic: TS-520SE Freq drift on keyup  (Read 2116 times)
AB5CC
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Posts: 47




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« on: December 13, 2003, 11:00:24 PM »

I have a TS-520SE with the DG-5 and MC-50.  Most of the time, when I key up the frequency will jump exactly 100, 200 or 300 Hz.  If I press the key again, the frequency will go back to the correct frequency.  I know that the actual frequency is changing, not just the displayed frequency.  My friends have noticed it.  I have added a ground to the AF board and it made no difference.  Any ideas?


Thanks,

Kenneth
AB5CC
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N0RTU
Member

Posts: 27




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« Reply #1 on: January 04, 2004, 08:22:24 PM »

Hello Kenneth

I'm not a first class 520 tech, but what you are describing sounds familiar.
Although you don't specify what mode you are using when you notice the freq. change, I would look very carefully at  the power supply in the rig.
because there are several sections to the power supply, some high voltage, and some at lower levels, there is alot there that can cause problems.

If there is a filtering problem on any of the dc supplies (ripple or noise when loaded) I would clean this up before I went anywhere else.  filter caps would be highly suspect in rigs of this vintage.
Also,  making sure that all grounds are proper in the Oscillator sections (Local osc.) can cause what you are talking about.  I can't quite tell from your description, but if this freq. change occurs immediately at "key up" though, I'd look real hard at the power supplies.  I sudden drop or spike in voltage due to a sudden load on parts of the power supply  most certainly could cause your problem.

73
de
Mike
N0RTU
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KB9CRY
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Posts: 4283


WWW

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« Reply #2 on: February 18, 2004, 12:34:03 PM »

Go to this site which has tons of mods to various equipment.  Maybe your symptom is noted there.  Gd luck, Phil  KB9CRY

http://mods.dk/
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KC0NII
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Posts: 16




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« Reply #3 on: February 20, 2004, 08:33:31 AM »

Check that the 9V supply is being regulated on transmit.  Remove the top cover, in the center you will find the fixed channel/regulator board.  Near the front of the board you'll find the 9V output post marked "9".  Connect your voltmeter between that and the chassis ground.  It is staying at 9.00V when you transmit?
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