FW:

[wsm-3]

---- Original Message 1 ----
From: [hidden email]
To: [hidden email]. net
Subject: K2  problems
Date: Sat, 30 Dec 2006 21:46:02 -0600

Hi

I finished assembling K2 # 5846 a few days ago and have a problem
that I need some help on.
After finishing the initial alignment I could hear signals on several
of the bands and had transmitter output. During the final alignment
the display started burning too bright. I found a solder bridge on
the J7 connector that was shorting the outputs of the 8 volt and
5 volt regulators together. This was causing both regulators to be
putting out 8 volts. I cleared this up and was proceedng with the
alignment when I notice that U6 on the control board felt warm and I
had lost voltage on most of the components on the RF board.
I turned the rig off for a couple of hours and when I tried to turn
it back on, it wouldn't power up. I checked F1 and it has 12.8
volts on both pins.
Anyone have any ideas?
Scott N5SM  




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[Don Wilhelm-3]

Scott,

The microprocessor (Control Board U6) chip will not stand a lot more than 5
volts without damage.  The application of 8 volts on the 5 volt rail could
have damaged any of the digital chips on the control board - those are U6,
U7 and U8.

Many devices on the RF board receive the power from the 8R and 8T lines -
and must have the RX or TX signal active from the microprocessor to apply
voltage to 8R or 8T (if the uP is bad, some power to the RF board will not
happen).

Make a quick check - power on and check the voltage out of the regulators
(5V and 8V), check power to U6 at pin 1 (should be 5 volts), then check the
RX output (U6 pin 28) which under normal conditions should be 5 volts during
receive (I expect you will find it at zero volts).

If RX is not 5 volts in the above test, obtain a new microprocessor (U6) and
while you are ordering replace U7 and U8 as well - they have been stressed
and if they are not bad now, they could fail later.

The other components on the Control board should have survived just fine
because they are analog devices and have higher voltage ratings whereas the
digital logic circuits can be damaged with voltages above 6 volts.

73,
Don W3FPR

> -----Original Message-----
>
> I finished assembling K2 # 5846 a few days ago and have a problem
> that I need some help on.
> After finishing the initial alignment I could hear signals on several
> of the bands and had transmitter output. During the final alignment
> the display started burning too bright. I found a solder bridge on
> the J7 connector that was shorting the outputs of the 8 volt and
> 5 volt regulators together. This was causing both regulators to be
> putting out 8 volts. I cleared this up and was proceedng with the
> alignment when I notice that U6 on the control board felt warm and I
> had lost voltage on most of the components on the RF board.
> I turned the rig off for a couple of hours and when I tried to turn
> it back on, it wouldn't power up. I checked F1 and it has 12.8
> volts on both pins.
> Anyone have any ideas?
> Scott N5SM
>

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